Showing posts with label Atrial. Show all posts
Showing posts with label Atrial. Show all posts

Friday, March 14, 2014

Practice Essentials

Atrial fibrillation (AF) has strong associations with other cardiovascular diseases, such as heart failure, coronary artery disease (CAD), valvular heart disease, diabetes mellitus, and hypertension. It is characterized by an irregular and often rapid heartbeat. The exact mechanisms by which cardiovascular risk factors predispose to AF are not understood fully but are under intense investigation. Catecholamine excess, hemodynamic stress, atrial ischemia, atrial inflammation, metabolic stress, and neurohumoral cascade activation are all purported to promote AF.

Essential update: Bleeding complications less severe with dabigatran

In a meta-analysis of pooled patient-level data on more than 1000 patients who suffered major bleeding, this complication was generally less critical and more manageable in patients being treated with dabigatran than in those on warfarin therapy. For instance, in patients treated with dabigatran, the worst major bleeds tended to be gastrointestinal, while in those treated with warfarin, most of the worst bleeds were intracranial and therefore more difficult to treat.[1, 2]

The study's authors, Majeed et al, used data from the AF trial RE-LY and the venous thromboembolism – prevention trials RECOVER, RECOVER II, RE-MEDY, and RESONATE.

Compared with patients receiving warfarin, dabigatran-treated patients who experienced a major bleeding event tended to be older, with worse renal function, and were more often being treated concomitantly with a nonsteroidal anti-inflammatory agent, such as aspirin. More red blood cell transfusions, but less plasma, were required by dabigatran patients with major bleeds. These patients also spent less time in intensive care and had a lower mortality rate than the warfarin patients.

Signs and symptoms

The clinical presentation of AF spans the entire spectrum from asymptomatic AF with rapid ventricular response to cardiogenic shock or devastating cerebrovascular accident (CVA). Unstable patients requiring immediate direct current (DC) cardioversion include the following:

Patients with decompensated congestive heart failure (CHF)Patients with hypotensionPatients with uncontrolled angina/ischemia

Initial history and physical examination include the following:

Documentation of clinical type of AF (paroxysmal, persistent, or permanent)Assessment of type, duration, and frequency of symptomsAssessment of precipitating factors (eg, exertion, sleep, caffeine, alcohol use)Assessment of modes of termination (eg, vagal maneuvers)Documentation of prior use of antiarrhythmics and rate-controlling agentsAssessment of presence of underlying heart diseaseDocumentation of any previous surgical or percutaneous AF ablation proceduresAirway, breathing, and circulation (ABCs)Vital signs (particularly heart rate, blood pressure, respiratory rate, and oxygen saturation)Evaluation of head and neck, lungs, heart, abdomen, lower extremities, and nervous system

See Clinical Presentation for more detail.

Diagnosis

Findings from 12-lead electrocardiography (ECG) usually confirm the diagnosis of AF and include the following:

Typically irregular ventricular rateAbsence of discrete P waves, replaced by irregular, chaotic F waves, in the setting of irregular QRS complexesAberrantly conducted beats after long-short R-R cycles (ie, Ashman phenomenon)Heart rate (typically 110-140 beats/min, rarely >160-170 beats/min)PreexcitationLeft ventricular hypertrophyBundle-branch blockAcute or prior myocardial infarction (MI)

Transthoracic echocardiography (TTE) is helpful for the following applications:

To evaluate for valvular heart diseaseTo evaluate atrial and ventricular chamber and wall dimensionsTo estimate ventricular function and evaluate for ventricular thrombiTo estimate pulmonary systolic pressure (pulmonary hypertension)To evaluate for pericardial disease

Transesophageal echocardiography (TEE) is helpful for the following applications:

To evaluate for left atrial thrombus (particularly in the left atrial appendage)To guide cardioversion (if thrombus is seen, cardioversion should be delayed)

See Workup for more detail.

Management

The cornerstones of AF management are rate control and anticoagulation,[3] as well as rhythm control for those symptomatically limited by AF. The clinical decision to use a rhythm-control or a rate-control strategy requires integrated consideration of the following:

Degree of symptomsLikelihood of successful cardioversionPresence of comorbiditiesCandidacy for AF ablation

The 2006 American College of Cardiology (ACC)/American Heart Association (AHA)/European Society of Cardiology (ESC) guidelines on anticoagulation for patients with nonvalvular AF include the following[4] :

No risk factors: Aspirin 81-325 mg/day1 moderate risk factor: Aspirin 81-325 mg/day or warfarin (international normalized ratio [INR] 2-3)Any high-risk factor or >1 moderate-risk factor: Warfarin (INR 2-3)

Risk factors are as follows:

High-risk factors: Prior stroke or transient ischemic attack (TIA), systemic thromboembolismModerate-risk factors: Age >75 years, hypertension, heart failure, left ventricular function Risk factors of unknown significance: Female sex, age 65-74 years, coronary artery disease, thyrotoxicosis

New-onset AF:

ACC/AHA/ESC 2006 guidelines for new-onset AF include the following[4] :

An initial rate-control strategy is “reasonable” for asymptomatic or minimally symptomatic older patients with hypertension and comorbid cardiovascular disease For younger individuals, especially those without significant comorbid cardiovascular disease, an initial rhythm-control strategy may be better

Agents used for rate control in new-onset AF include the following:

DiltiazemMetoprololDigoxin (rarely as monotherapy)Amiodarone (mainly for patients who are intolerant of or unresponsive to other agents)

Anticoagulation is indicated as follows:

Patients with newly diagnosed AF and those awaiting electrical cardioversion can be started on intravenous (IV) heparin or low-molecular-weight heparin (LMWH) Concomitantly, patients can be started on warfarin in an inpatient setting while awaiting a therapeutic INR value (2-3)Oral direct thrombin inhibitors may present an alternative to warfarin in a higher-risk population with nonvalvular AF

Newer oral anticoagulants that have been approved by the US Food and Drug Administration (FDA) and may be considered as alternatives to warfarin include the following:

Dabigatran (direct thrombin inhibitor)Rivaroxaban (highly selective direct factor Xa inhibitor)Apixaban (factor Xa inhibitor)

Long-term management of AF:

Optimal long-term strategies for AF management should be based on a thoroughly integrated consideration of patient-specific factors and likelihood of success. Selection of an appropriate antithrombotic regimen should be balanced between the risk of stroke and the risk of bleeding. Factors that increase the risk of bleeding with warfarin therapy include the following:

History of bleeding (the strongest predictive risk factor)Age older than 75 yearsLiver or renal diseaseMalignancyThrombocytopenia or aspirin useHypertensionDiabetes mellitusAnemiaPrior strokeFall riskGenetic predispositionSupratherapeutic INR

Alternatives to warfarin:

If warfarin will not be used, adding clopidogrel to aspirin may be considered[5] Updated ACC/AHA/Heart Rhythm Society (HRS) guidelines on AF include a class Ib recommendation for dabigatran[6] for preventing stroke and systemic thromboembolism in patients with paroxysmal-to-permanent atrial fibrillation and risk factors for stroke or systemic embolization

Agents used for rate control include the following:

Oral beta-blockersNondihydropyridine calcium channel blockersDigoxinAmiodarone

Agents used for rhythm control include the following:

FlecainidePropafenoneDofetilideAmiodaroneDronedaroneSotalol

Catheter ablation performed in experienced centers is recommended in the 2011 update to the ACCF/AHA/HRS AF guidelines for the following indications[5] :

It is recommended as an alternative to pharmacologic therapy to prevent recurrent paroxysmal AF in significantly symptomatic patients with little or no structural heart disease or severe pulmonary disease[7] It is reasonable as a treatment for symptomatic persistent AFIt may be reasonable as a treatment for symptomatic paroxysmal AF in patients with some structural heart disease

See Treatment and Medication for more detail.

Image libraryClassification scheme for patients with atrial fibClassification scheme for patients with atrial fibrillation. NextBackground

Classification of atrial fibrillation (AF) begins with distinguishing a first detectable episode, irrespective of whether it is symptomatic or self-limited. Published guidelines from an American College of Cardiology (ACC)/American Heart Association (AHA)/European Society of Cardiology (ESC) committee of experts on the treatment of patients with atrial fibrillation recommend classification of AF into the following 3 patterns (also see the image below)[8] :

Paroxysmal AF – Episodes of AF that terminate spontaneously within 7 days (most episodes last less than 24 hours)Persistent AF - Episodes of AF that last more than 7 days and may require either pharmacologic or electrical intervention to terminate Permanent AF - AF that has persisted for more than 1 year, either because cardioversion has failed or because cardioversion has not been attemptedClassification scheme for patients with atrial fibClassification scheme for patients with atrial fibrillation.

This classification schema pertains to cases that are not related to a reversible cause of AF (eg, thyrotoxicosis, electrolyte abnormalities, acute ethanol intoxication). Atrial fibrillation secondary to acute myocardial infarction, cardiac surgery, pericarditis, pulmonary embolism, or acute pulmonary disease is considered separately because, in these situations, AF is less likely to recur once the precipitating condition has been treated adequately and has resolved.

Paroxysmal AF

Atrial fibrillation is considered to be recurrent when a patient has 2 or more episodes. If recurrent AF terminates spontaneously, it is designated as paroxysmal.

Some patients with paroxysmal AF, typically younger patients, have been found to have distinct electrically active foci within their pulmonary veins. These patients generally have many atrial premature beats noted on Holter monitoring. Isolation or elimination of these foci can lead to elimination of the trigger for paroxysms of AF.

Paroxysmal AF may progress to permanent AF, and aggressive attempts to restore and maintain sinus rhythm may prevent comorbidities associated with AF.

Persistent AF

If recurrent AF is sustained, it is considered persistent, irrespective of whether the arrhythmia is terminated by either pharmacologic therapy or electrical cardioversion.

Persistent AF may be either the first presentation of AF or the result of recurrent episodes of paroxysmal AF. Patients with persistent AF also include those with longstanding AF in whom cardioversion has not been indicated or attempted, often leading to permanent AF.

Patients can also have AF as an arrhythmia secondary to cardiac disease that affects the atria (eg, congestive heart failure, hypertensive heart disease, rheumatic heart disease, coronary artery disease). These patients tend to be older, and AF is more likely to be persistent.

Persistent AF with an uncontrolled, rapid ventricular heart rate response can cause a dilated cardiomyopathy and can lead to electrical remodeling in the atria (atrial cardiomyopathy). Therapy, such as drugs or atrioventricular nodal ablation and permanent pacemaker implantation, to control the ventricular rate can improve left ventricular function and improve quality-of-life scores.

Permanent AF

Permanent AF is recognized as the accepted rhythm, and the main treatment goals are rate control and anticoagulation. While it is possible to reverse the progression from paroxysmal to persistent and to permanent, this task can be challenging.

Lone atrial fibrillation

In addition to the above schema, the term "lone atrial fibrillation" has been used to identify AF in younger patients without structural heart disease, who are at a lower risk for thromboembolism. The definition of lone AF remains controversial, but it generally refers to paroxysmal, persistent, or permanent AF in younger patients ([9]

PreviousNextPathophysiology

Atrial fibrillation (AF) shares strong associations with other cardiovascular diseases, such as heart failure, coronary artery disease (CAD), valvular heart disease, diabetes mellitus, and hypertension.[10] These factors have been termed upstream risk factors, but the relationship between comorbid cardiovascular disease and AF is incompletely understood and more complex than this terminology implies. The exact mechanisms by which cardiovascular risk factors predispose to AF are not understood fully but are under intense investigation. Catecholamine excess, hemodynamic stress, atrial ischemia, atrial inflammation, metabolic stress, and neurohumoral cascade activation are all purported to promote AF.

Because diabetes mellitus and obesity are increasing in prevalence and are associated with an elevated risk of AF, Fontes et al examined whether insulin resistance is an intermediate step for the development of AF. In a community-based cohort that included 279 patients who developed AF within 10 years of follow-up, no significant association was observed between insulin resistance and incident AF.[11]

Although the precise mechanisms that cause atrial fibrillation are incompletely understood, AF appears to require both an initiating event and a permissive atrial substrate. Significant recent discoveries have highlighted the importance of focal pulmonary vein triggers, but alternative and nonmutually exclusive mechanisms have also been evaluated. These mechanisms include multiple wavelets, mother waves, fixed or moving rotors, and macro-reentrant circuits. In a given patient, multiple mechanisms may coexist at any given time. The automatic focus theory and the multiple wavelet hypothesis appear to have the best supporting data.

Automatic focus

A focal origin of AF is supported by several experimental models showing that AF persists only in isolated regions of atrial myocardium. This theory has garnered considerable attention, as studies have demonstrated that a focal source of AF can be identified in humans and that isolation of this source can eliminate AF.

The pulmonary veins appear to be the most frequent source of these automatic foci, but other foci have been demonstrated in several areas throughout the atria. Cardiac muscle in the pulmonary veins appears to have active electrical properties that are similar, but not identical, to those of atrial myocytes. Heterogeneity of electrical conduction around the pulmonary veins is theorized to promote reentry and sustained AF. Thus, pulmonary vein automatic triggers may provide the initiating event, and heterogeneity of conduction may provide the sustaining conditions in many patients with AF.

Multiple wavelet

The multiple wavelet hypothesis proposes that fractionation of wave fronts propagating through the atria results in self-perpetuating "daughter wavelets." In this model, the number of wavelets is determined by the refractory period, conduction velocity, and mass of atrial tissue. Increased atrial mass, shortened atrial refractory period, and delayed intra-atrial conduction increase the number of wavelets and promote sustained AF. This model is supported by data from patients with paroxysmal AF demonstrating that widespread distribution of abnormal atrial electrograms predicts progression to persistent AF.[12] Intra-atrial conduction prolongation has also been shown to predict recurrence of AF.[13] Together, these data highlight the importance of atrial structural and electrical remodeling in the maintenance of AF—hence the phrase "atrial fibrillation begets atrial fibrillation."

PreviousNextEtiology

Atrial fibrillation (AF) is strongly associated with the following risk factors:

Hemodynamic stressAtrial ischemiaInflammationNoncardiovascular respiratory causesAlcohol and drug useEndocrine disordersNeurologic disordersGenetic factorsAdvancing ageHemodynamic stress

Increased intra-atrial pressure results in atrial electrical and structural remodeling and predisposes to AF. The most common causes of increased atrial pressure are mitral or tricuspid valve disease and left ventricular dysfunction. Systemic or pulmonary hypertension also commonly predisposes to atrial pressure overload, and intracardiac tumors or thrombi are rare causes.

Atrial ischemia

Coronary artery disease infrequently leads directly to atrial ischemia and AF. More commonly, severe ventricular ischemia leads to increased intra-atrial pressure and AF.

Inflammation

Myocarditis and pericarditis may be idiopathic or may occur in association with collagen vascular diseases; viral or bacterial infections; or cardiac, esophageal, or thoracic surgery.

Noncardiovascular respiratory causes

Pulmonary embolism, pneumonia, lung cancer, and hypothermia have been associated with AF.

Drug and alcohol use

Stimulants, alcohol, and cocaine can trigger AF. Acute or chronic alcohol use (ie, holiday or Saturday night heart, also known as alcohol-related cardiomyopathy) and illicit drug use (ie, stimulants, methamphetamines, cocaine) have been specifically found to be related to AF.

Endocrine disorders

Hyperthyroidism, diabetes, and pheochromocytoma have been associated with AF.

Neurologic disorders

Intracranial processes such as subarachnoid hemorrhage or stroke can precipitate AF.

Familial AF

A history of parental AF appears to confer increased likelihood of AF (and occasional family pedigrees of AF are associated with defined ion channel abnormalities, especially sodium channels).[14] One cohort study suggests that familial AF is associated with an increased risk of AF. This increase was not lessened by adjustment for genetic variants and other AF risk factors.[15]

Advancing age

AF is strongly age-dependent, affecting 4% of individuals older than 60 years and 8% of persons older than 80 years.

PreviousNextEpidemiology

Atrial fibrillation affects more than 2.2 million persons in the United States. AF is strongly age-dependent, affecting 4% of individuals older than 60 years and 8% of persons older than 80 years. Approximately 25% of individuals aged 40 years and older will develop AF during their lifetime.[16]

The prevalence of AF is 0.1% in persons younger than 55 years, 3.8% in persons 60 years or older, and 10% in persons 80 years or older. With the projected increase in the elderly population in the United States, the prevalence of AF is expected to more than double by the year 2050. AF is uncommon in childhood except after cardiac surgery.[17]

The incidence of AF is significantly higher in men than in women in all age groups. AF appears to be more common in whites than in blacks, with blacks have less than half the age-adjusted risk of developing AF.

In 10-15% of cases of AF, the disease occurs in the absence of comorbidities (lone atrial fibrillation). However, AF is often associated with other cardiovascular diseases, including hypertension; heart failure; diabetes-related heart disease; ischemic heart disease; and valvular, dilated, hypertrophic, restrictive, and congenital cardiomyopathies.[16] The Atherosclerosis Risk in Communities (ARIC) Study suggests reduced kidney function and presence of albuminuria are strongly associated with AF.[18]

The rate of ischemic stroke in patients with nonrheumatic AF averages 5% a year, which is somewhere between 2 and 7 times the rate of stroke in patients without AF. The risk of stroke is not due solely to AF; it increases substantially in the presence of other cardiovascular diseases.[19] The prevalence of stroke in patients younger than 60 years is less than 0.5%; however, in those older than 70 years, the prevalence doubles with each decade.[20] The attributable risk of stroke from AF is estimated to be 1.5% for those aged 50-59 years, and it approaches 30% for those aged 80-89 years. Women are at a higher risk of stroke due to AF than men and some have suggested this may be due to undertreatment with warfarin. However, one study of patients 65 years or older with recently diagnosed AF found warfarin use played no part in the increased risk of stroke among female patients.[21]

PreviousNextPrognosis

AF is associated with a 1.5- to 1.9-fold higher risk of death, which is in part due to the strong association between AF and thromboembolic events, according to data from the Framingham heart study.[22]

Medical therapies aimed at rhythm control offered no survival advantage over rate control and anticoagulation, according to the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial. The study addressed whether rate control and anticoagulation are sufficient goals for asymptomatic, elderly patients.[23]

Atrial fibrillation (AF) is associated with increased morbidity and mortality, in part due to the risk of thromboembolic disease, particularly stroke, in AF and in part due to its associated risk factors. Studies have shown that individuals in sinus rhythm live longer than individuals with AF. Disruption of normal atrial electromechanical function in AF leads to blood stasis. This, in turn, can lead to development of thrombus, most commonly in the left atrial appendage. Dislodgement or fragmentation of a clot can then lead to embolic phenomena, including stroke.

Development of AF predicts heart failure and is associated with a worse New York Heart Association Heart Failure classification. AF may also worsen heart failure in individuals who are dependent on the atrial component of the cardiac output. Those with hypertensive heart disease and those with valvular heart disease are particularly at high risk for developing heart failure when AF occurs. In addition, AF may cause tachycardia-mediated cardiomyopathy if adequate rate control is not established.

The risk of stroke from AF that lasts longer than 24 hours is a major concern and is usually addressed by prescribing a blood thinner (Coumadin or dabigatran). Prognostic score systems, such as CHADS2, appear to underestimate the risk of embolic stroke in patients older than 75 years; thus, some studies recommend treating all patients older than 75 years unless a compelling contraindication is noted.[24] The CHADS2 score predicts ischemic stroke not only for patients with a history of atrial fibrillation but also for patients without atrial fibrillation who have a history of coronary heart disease.[25] In the latter group, net benefit of prophylactic anticoagulation has yet to be established.

An analysis of the AFNET (Central Registry of the German Competence NETwork on Atrial Fibrillation) registry of 8847 patients with nonvalvular atrial fibrillation indicated that the CHA2 DS2 -VASc score is more sensitive than the CHADS2 score for risk stratification of thromboembolic events (ischemic stroke, transient ischemic attack [TIA], systemic embolism), particularly in patients at low or intermediate risk for stroke (CHADS2 score of 0 or 1)—who therefore do not require oral anticoagulation.[26, 27]

During a mean follow-up of 5 years, the investigators found 36.5% (144 of 395) of strokes or other thromboembolic events occurred in patients given a CHADS2 score of 0 or 1, groups in which there is no definitive recommendation for oral anticoagulation.[26, 27] However, CHA2 DS2 -VASc scoring—which adds age 65-74 years, vascular disease, and female sex as stroke risk factors to the CHADS2 score[27] —placed 30.3% of those classified as CHADS2 0 or 1 into CHA2 DS2 -VASc 1 or 2 and higher, groups in which oral anticoagulation is recommended.[26]

A post-hoc analysis of the ONTARGET and TREND studies, which evaluated the efficacy of treatment with ramipril plus telmisartan or telmisartan alone in reducing cardiovascular disease, used the Mini–Mental State Examination (MMSE) to measure the cognitive function of participants at baseline and after two and five years. Results show that AF is associated with an increased risk of cognitive decline, new dementia, loss of independence in performing activities of daily living and admission to long-term care facilities.[28]

Atrial fibrillation in association with acute myocardial infarction

AF is a common finding in patients presenting with an acute myocardial infarction. A meta-analysis pooled data from 43 studies and more than 278,800 patients.[29] The study found that AF in the setting of acute myocardial infarction was associated with 40% increase in mortality compared to patients in sinus rhythm with acute myocardial infarction. The causes of death were unclear, but may be related to triple anticoagulation therapy with aspirin, clopidogrel, and warfarin, or may be related to hemodynamic consequences associated with the loss of atrial contraction. Whether AF is a complication of myocardial infarction or a marker for myocardial infarction severity is unclear.

PreviousNextPatient Education

A study by van Diepen et al suggests that patients with heart failure or atrial fibrillation have a significantly higher risk of noncardiac postoperative mortality than patients with coronary artery disease; thus, patients and physicians should consider this risk, even if a minor procedure is planned.[30]

For excellent patient education resources, visit eMedicineHealth's Heart Center and Stroke Center. Also, see eMedicineHealth's patient education articles Atrial Fibrillation, Heart Rhythm Disorders, Stroke, and Supraventricular Tachycardia.

PreviousProceed to Clinical Presentation  Contributor Information and DisclosuresAuthor

Lawrence Rosenthal, MD, PhD, FACC, FHRS  Associate Professor of Medicine, Director, Section of Cardiac Pacing and Electrophysiology, Director of EP Fellowship Program, Division of Cardiovascular Disease, University of Massachusetts Memorial Medical Center
Lawrence Rosenthal, MD, PhD, FACC, FHRS is a member of the following medical societies: American College of Cardiology, American Heart Association, and Massachusetts Medical Society
Disclosure: Nothing to disclose.

Coauthor(s)

David D McManus, MD, ScM, FACC, FHRS,  Director, Atrial Fibrillation Program, Assistant Professor of Medicine and Quantitative Health Sciences, University of Massachusetts Medical School
Disclosure: Nothing to disclose.

Chief Editor

Jeffrey N Rottman, MD  Professor of Medicine and Pharmacology, Vanderbilt University School of Medicine; Chief, Department of Cardiology, Nashville Veterans Affairs Medical Center
Jeffrey N Rottman, MD is a member of the following medical societies: American Heart Association and North American Society of Pacing and Electrophysiology
Disclosure: Nothing to disclose.

Additional Contributors

Pierre Borczuk, MD Assistant Professor of Medicine, Harvard Medical School; Associate in Emergency Medicine, Massachusetts General Hospital

Pierre Borczuk, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

David FM Brown, MD Associate Professor, Division of Emergency Medicine, Harvard Medical School; Vice Chair, Department of Emergency Medicine, Massachusetts General Hospital

David FM Brown, MD is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Abraham G Kocheril, MD, FACC, FACP, FHRS Professor of Medicine, University of Illinois College of Medicine

Abraham G Kocheril, MD, FACC, FACP, FHRS is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, Cardiac Electrophysiology Society, Central Society for Clinical Research, Heart Failure Society of America, and Illinois State Medical Society

Disclosure: Nothing to disclose.

William Lober, MD, MS Associate Professor, Health Informatics and Global Health, Schools of Medicine, Nursing, and Public Health, University of Washington

Disclosure: Nothing to disclose.

Brian Olshansky, MD Professor of Medicine, Department of Internal Medicine, University of Iowa College of Medicine

Brian Olshansky, MD is a member of the following medical societies: American College of Cardiology, American Heart Association, Cardiac Electrophysiology Society, and Heart Rhythm Society

Disclosure: Guidant/Boston Scientific Honoraria Speaking and teaching; Medtronic Honoraria Speaking and teaching; Guidant/Boston Scientific Consulting fee Consulting

Gary Setnik, MD Chair, Department of Emergency Medicine, Mount Auburn Hospital; Assistant Professor, Division of Emergency Medicine, Harvard Medical School

Gary Setnik, MD is a member of the following medical societies: American College of Emergency Physicians, National Association of EMS Physicians, and Society for Academic Emergency Medicine

Disclosure: SironaHealth Salary Management position; South Middlesex EMS Consortium Salary Management position; ProceduresConsult.com Royalty Other

Ali A Sovari, MD, FACP Clinical and Research Fellow in Cardiovascular Medicine, Section of Cardiology, University of Illinois College of Medicine; Staff Physician and Hospitalist, St John Regional Medical Center, Cogent Healthcare, Inc

Ali A Sovari, MD, FACP is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, American Physiological Society, and Heart Rhythm Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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Vermes E, Tardif JC, Bourassa MG, Racine N, Levesque S, White M, et al. Enalapril decreases the incidence of atrial fibrillation in patients with left ventricular dysfunction: insight from the Studies Of Left Ventricular Dysfunction (SOLVD) trials. Circulation. Jun 17 2003;107(23):2926-31. [Medline].

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 PreviousNext Ventricular rate varies from 130-168 beats per minute. Rhythm is irregularly irregular. P waves are not discernible. Classification scheme for patients with atrial fibrillation. Patient management for newly diagnosed atrial fibrillation. Subtherapeutic INR: INR Antiarrhythmic drug algorithm for the medical management of sinus rhythm in patients with atrial fibrillation. The image on the right is a reconstructed 3-dimensional image of the left atrium in a patient undergoing atrial fibrillation ablation. The figure on the left was created with a mapping catheter using Endocardial Solutions mapping technology. It represents the endocardial shell of the left atrium and is used as the template during left atrial ablation procedures. Table 1. Risk Factors for Stroke in Patients with Nonvalvular Atrial FibrillationTable 2. Adjusted Stroke Rate in Patients with Nonvalvular Atrial Fibrillation not Treated with AnticoagulationTable 3. Recommendations for Antithrombotic Therapy in Patients with Nonvalvular Atrial FibrillationTable 1. Risk Factors for Stroke in Patients with Nonvalvular Atrial FibrillationRisk FactorsRelative RiskPrior stroke or TIA2.5History of hypertension1.6Heart failure and/or reduced left ventricular function1.4Advanced age1.4Diabetes1.7Coronary artery disease1.5Table 2. Adjusted Stroke Rate in Patients with Nonvalvular Atrial Fibrillation not Treated with AnticoagulationCHADS2 ScoreAdjusted Stroke Rate (%/y)01.912.824.035.948.5512.5618.2Table 3. Recommendations for Antithrombotic Therapy in Patients with Nonvalvular Atrial FibrillationRisk CategoryRecommended TherapyNo risk factorsAspirin 81-325 mg dailyOne moderate-risk factorAspirin 81-325 mg daily or warfarin (INR 2-3)Any high-risk factor or more than 1 moderate-risk factorWarfarin (INR 2-3)PreviousNext View Table List  Read more about Atrial Fibrillation on MedscapeRelated Reference Topics
Emergent Management of Atrial Flutter
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Medscape Reference © 2011 WebMD, LLC, Atrial Fibrillation

Monday, March 10, 2014

Overview of Multifocal Atrial Tachycardia

Multifocal atrial tachycardia (MAT) is a cardiac arrhythmia caused by multiple sites of competing atrial activity. It is characterized by an irregular atrial rate greater than 100 beats per minute (bpm). Atrial activity is well organized, with at least 3 morphologically distinct P waves, irregular P-P intervals, and an isoelectric baseline between the P waves.

Shine, Kastor and Yurchak first proposed this definition of MAT in 1968.[1] MAT has previously been described by terms such as chaotic atrial rhythm or tachycardia, chaotic atrial mechanism, and repetitive paroxysmal MAT.

Usually, treatment of the patient's underlying problem (eg, respiratory failure, sepsis, theophylline toxicity) takes therapeutic precedent. The condition is transient and resolves when the underlying condition improves.

For more information, see Atrial Tachycardia

NextPathophysiology of MAT

The mechanism of the arrhythmia has not been well defined. Delayed afterdepolarizations leading to triggered automaticity are postulated to result in the development of multifocal atrial tachycardia (MAT). The evidence that implicates this mechanism is mainly indirect and points to intracellular calcium overload by various mechanisms (eg, catecholamine excess, phosphodiesterase inhibition, acidosis, hypoxemia). Electrolyte imbalances associated with severe underlying illnesses can further potentiate the development of this arrhythmia. MAT most often is found in the elderly patient with decompensated chronic lung disease and should be thought of as a hypoxic complication of underlying heart conduction pathology. However, other underlying causes may be present, such as heart failure, sepsis, or methylxanthine toxicity. The effect of MAT on the heart’s conduction system may or may not lead to hemodynamic instability.

PreviousNextEtiology of MAT

Causes of multifocal atrial tachycardia (MAT) are mainly related to underlying illnesses. The following common underlying illnesses are associated with this arrhythmia:

Decompensated chronic lung diseaseCoronary artery diseaseHeart failureValvular heart diseaseDiabetes mellitusHypokalemiaHypomagnesemiaAzotemiaPostoperative statePulmonary embolism PneumoniaSepsisMethylxanthine toxicityPreviousNextEpidemiology of MAT

Multifocal atrial tachycardia (MAT) is a relatively infrequent arrhythmia, with a prevalence rate of 0.05-0.32% in patients who are hospitalized. It is predominantly observed in males and in older patients—in particular, elderly patients with multiple medical problems. The average age of patients from 9 studies was 72 years.

Patients with MAT frequently have significant comorbidities, especially chronic obstructive pulmonary disease (COPD) and respiratory failure, and are often treated in ICUs. Consequently, a high mortality rate (ie, up to 45%) is associated with this arrhythmia, although it is not a direct consequence of the rhythm abnormality.

MAT is seldom life threatening. The overall clinical picture and symptoms improve when the underlying condition is addressed and MAT is controlled. Morbidity is difficult to quantify because the underlying disease is the primary determinant of complications.

PreviousNextClinical PresentationPatient history

Patients may complain of a variety of symptoms, or more rarely, the disease may be asymptomatic. The most common complaints include the following:

PalpitationsShortness of breathChest painLightheadednessSyncopal episode

These symptoms may be transient.

Physical examination

Physical examination findings are typically related to the underlying disease process and are not specific for MAT. The pulse is rapid and irregular,[2] and the first heart sound may be variable. The physical examination is not typically sufficient to differentiate multifocal atrial tachycardia from atrial fibrillation. Respiratory adventitial sounds often are prominent.

Depending upon comorbid conditions or general health status, the patient may be hemodynamically unstable. However, determining whether this is due to the underlying condition or the dysrhythmia may be difficult.

Complications

Potential acute complications of MAT include the following:

Atrial thrombi with embolization and subsequent strokeMyocardial infarction from incongruous myocardial supply and demandPulmonary emboliUnderlying disorders

COPD is the most common underlying disease process, seen in approximately 60% of MAT cases. MAT is commonly precipitated by exacerbation of COPD, sometimes due to infection or cardiac decompensation. Increasing hypoxemia with respiratory acidosis and advanced disease also leads to increased bronchodilator usage, thereby increasing catecholamine levels, which may contribute to development of MAT.

Patients with MAT frequently have cardiac diseases, mainly coronary artery disease and valvular heart diseases, often in conjunction with COPD. Heart failure is often present when the diagnosis of MAT is first made.

In various series, 24% of patients with MAT were found to have diabetes mellitus. Fourteen percent had hypokalemia, and 14% had azotemia. Twenty-eight percent of patients with MAT were recovering from major surgery, while others had postoperative infections, sepsis, pulmonary embolism, and heart failure.

The link between pulmonary embolism and MAT is weak (ie, 6-14% of such patients have been said to have MAT), but the methods of diagnosing pulmonary embolism have not been well documented.

Experimental evidence demonstrates that IV cocaine use may lead to the development of MAT.

PreviousNextDifferential Diagnosis

The differential diagnosis of MAT includes atrial fibrillation and atrial flutter. Clear differentiation of multifocal atrial tachycardia (MAT) from atrial fibrillation is very important because the treatment of atrial fibrillation differs from that of MAT. MAT with aberration or preexisting bundle branch block may be misinterpreted as ventricular tachycardia. MAT must also be differentiated from other tachyarrhythmias, both narrow-complex and wide-complex, including sinus tachycardia with frequent premature atrial contractions (PACs).

PreviousNextElectrocardiography

The diagnosis of multifocal MAT is confirmed with an ECG that displays the following features (see the image below):

Irregular ventricular rate greater than 100 bpmOrganized and discrete P waves with at least 3 different morphologies in the same electrocardiographic leadIrregular PP, PR, and RR intervals with an isoelectric baseline between the P wavesECG showing multifocal atrial tachycardia (MAT). ECG showing multifocal atrial tachycardia (MAT).

Some authors have suggested that patients who have a heart rate less than 100 bpm but who satisfy all other criteria (including the clinical profile commonly observed with MAT) be considered to have multifocal atrial rhythm, or multifocal atrial bradycardia if the rate is less than 60 bpm. There is controversy about whether this condition should be referred to as a MAT variant or a wandering atrial pacemaker, although patients with wandering atrial pacemaker usually do not have serious underlying illnesses.

The requirement that 3 different P waves should exist has been applied since early descriptions of the arrhythmia were recorded, but whether this should be interpreted as 2 ectopic P waves and 1 sinus P wave or 3 ectopic P waves has been a matter of controversy. The consensus favors a minimum of 3 different waveforms in addition to sinus P waves.

Baseline noise on the ECG can mimic atrial fibrillation and can obscure differences in P wave morphology. Conversely, coarse atrial fibrillation on short recordings may appear to show discrete P waves prior to each QRS complex. Longer ECG recordings are therefore useful.

PreviousNextLaboratory Studies

Laboratory testing mainly consists of the following:

Serum chemistry panel to exclude electrolyte disordersBlood hemoglobin level and RBC counts to seek evidence of anemiaArterial blood gases to define pulmonary status

Any further testing depends on the underlying disease process (eg, cardiac biomarkers in patients with coronary artery disease, or a theophylline level if patient has been prescribed, or has access to, this medication).

PreviousNextOther Tests

Consider a portable anteroposterior (AP) chest radiograph to evaluate for pulmonary and cardiac findings, particularly in the unstable patient. All patients should be placed on pulse oximetry and a cardiac monitor.

PreviousNextTreatment of MATPrehospital care

The following measures should be taken in the prehospital setting:

Assess for pulmonary causes that may be causing the arrhythmiaStabilize the acute situation as necessaryProvide oxygen, cardiac monitoring, and pulse oximetryEstablish IV access without delaying transportCollect medications that the patient may be taking or may have access toEmergency department care

Rapidly assess and stabilize the ABCs while providing simultaneous treatment. An upright sitting position usually is most appropriate. Obtain IV access with a large-bore catheter and give isotonic sodium chloride solution at a to-keep-open (TKO) rate.

Administer oxygen to maintain the saturation greater than 90%, but avoid excessive oxygen in patients with known significant chronic obstructive pulmonary disease (COPD). This will avoid the theoretical problem of removing the hypoxic drive for ventilation, which can result in increased carbon dioxide retention.

The need for tracheal intubation is dictated by the standard clinical indications.

Establish cardiac monitor, blood pressure monitor, and pulse oximetry.

Assess for and treat the underlying cardiopulmonary process, theophylline toxicity, or metabolic abnormality. Administer bronchodilators and oxygen for treatment of decompensated COPD; activated charcoal and/or charcoal hemoperfusion is the therapy for theophylline toxicity. When magnesium sulfate is administered to correct hypokalemia, most patients convert to normal sinus rhythm. Avoid sedatives.

Treatment and/or reversal of the precipitating cause may be all that is required for patients with multifocal atrial tachycardia (MAT); however, the arrhythmia may recur if the underlying condition worsens. Moreover, treatment of underlying diseases may sometimes have arrhythmia-promoting effects; for example, theophylline and beta-agonist drugs used in patients with COPD produce an increased catecholamine state. These therapies should be used judiciously.

Calcium channel blockers

Diltiazem[3] and verapamil[4, 5, 6, 7, 8, 9] decrease the atrial activity and slow atrioventricular (AV) nodal conduction, thereby decreasing ventricular rate, but they do not return all patients to normal sinus rhythm. Transient hypotension is the most common adverse effect, which may often be avoided by pretreating the patient with 1 g of intravenous calcium gluconate (10 mL of 10% calcium gluconate).

Diltiazem may be used as a 20-45 mg intravenous bolus and then as a 10-25 mg/h continuous infusion. Verapamil may worsen hypoxemia by negating the hypoxic pulmonary vasoconstriction in underventilated alveoli; this is usually not clinically significant.

Beta-blockers

More patients convert to a normal sinus rhythm when treated with beta-blockers. However, the use of beta-blockers is limited by transient hypotension and by bronchospastic adverse effects, since lung disease is commonly associated with MAT.

Metoprolol[6, 8, 10, 11, 12] has been used to lower the ventricular rate. Both oral and intravenous dosage forms have been used. The oral dosage is 25 mg q6h until the desired effects are obtained. Intravenous bolus dosing has been administered to as much as 15 mg over 10 minutes.

Although no controlled studies have evaluated the use of short-acting beta-blockers in treatment of MAT, esmolol can also be used to control the ventricular rate as an intravenous infusion. It has a very short half-life and can be terminated quickly in the event of an adverse reaction.

Magnesium

In a small number of patients, high-dose magnesium[6, 13, 14, 15, 16] causes a significant decrease in the patient's heart rate and conversion to normal sinus rhythm. The dosage is 2 g intravenously over 1 minute, followed by 2 g/h infusion over 5 hours.

Antiarrhythmics

Amiodarone[17, 18, 19] (300 mg PO tid or 450-1500 mg IV over 2-24 h) has been used and has been reported to be associated with conversion to normal sinus rhythm. The success rate was 40% at 3 days with oral dosing and 75% on day 1 with intravenous dosing; however, this has been evaluated in a very small number of patients. Recent data support the use of amiodarone prophylactically postoperatively in patients with COPD. Case reports have also supported the use of ibutilide[20] and flecainide[21] for cardioversion.

Digitalis

Despite the urge to use digoxin, it has not been found to be effective in controlling the ventricular rate or restoring normal sinus rhythm. Digoxin promotes afterdepolarizations, which may promote the arrhythmia. Ventricular arrhythmias, AV block, and death have been reported when excessive digoxin has been administered to patients who were incorrectly diagnosed with atrial fibrillation.

Cardioversion

Cardioversion is contraindicated in MAT. Due to the multiple atrial foci, direct current (DC) cardioversion is not effective in restoring normal sinus rhythm and can precipitate more dangerous arrhythmias.

Surgical care

In patients who have persistent and recurrent episodes of MAT and problems with rate control, the AV node may be ablated using radiofrequency energy and a permanent pacemaker implanted.[22] This approach should be considered both for symptomatic and hemodynamic improvement and to prevent the development of tachycardia-mediated cardiomyopathy.

Consultations

A cardiologist may be of assistance with ECG interpretation and may be available for consultation if antiarrhythmic therapy is being considered.

Inpatient care

Most patients with MAT require admission to further manage their underlying cardiopulmonary diseases. These patients frequently are admitted to a monitored bed; however, the clinical scenario and the hemodynamic stability of the patient dictate disposition.

Further outpatient care

Patients who convert to normal sinus rhythm after treatment and stabilization of the underlying process or provision of specific antiarrhythmic therapy may be cautiously considered for discharge. In order to be discharged, the patient must be back to baseline condition, have no complicating factors, be able to accomplish activities of daily living, and be available for close follow-up care.

Deterrence/prevention

The best means of prevention of MAT is prevention of respiratory failure plus careful monitoring of all electrolyte disorders, namely, hypokalemia, hypomagnesemia, and drug therapy (mainly digoxin toxicity). In patients receiving theophylline, careful monitoring of drug levels is important in order to avoid toxicity.

Patient education

Education about the causes of this arrhythmia may be beneficial. In the case of a pulmonary source, education about prevention and recognition of developing pulmonary conditions may be helpful. In the case of MAT related to medication use, education regarding the correct use and how to monitor such medications should be considered.

Previous, Multifocal Atrial Tachycardia

Saturday, March 1, 2014

Background

Atrial myxomas are the most common primary heart tumors. Because of nonspecific symptoms, early diagnosis may be a challenge. Left atrial myxoma may or may not produce characteristic findings on auscultation. Two-dimensional echocardiography is the diagnostic procedure of choice. Most atrial myxomas are benign and can be removed by surgical resection.

NextPathophysiology

Myxomas account for 40-50% of primary cardiac tumors. Approximately 90% are solitary and pedunculated, and 75-85% occur in the left atrial cavity. Up to 25% of cases are found in the right atrium. Most cases are sporadic. Approximately 10% are familial and are transmitted in an autosomal dominant mode. Multiple tumors occur in approximately 50% of familial cases and are more frequently located in the ventricle (13% vs 2% in sporadic cases).

Myxomas are polypoid, round, or oval. They are gelatinous with a smooth or lobulated surface and usually are white, yellowish, or brown. The most common site of attachment is at the border of the fossa ovalis in the left atrium, although myxomas can also originate from the posterior atrial wall, the anterior atrial wall, or the atrial appendage. The mobility of the tumor depends upon the extent of attachment to the interatrial septum and the length of the stalk.

Although atrial myxomas are typically benign, local recurrence due to inadequate resection or malignant change has been reported. Occasionally, atrial myxomas recur at a distant site because of intravascular tumor embolization. The risk of recurrence is higher in the familial myxoma syndrome.[1]

Symptoms from a cardiac myxoma are more pronounced when the myxomas are left-sided, racemosus, and over 5 cm in diameter.[2] Symptoms are produced by mechanical interference with cardiac function or embolization. Being intravascular and friable, myxomas account for most cases of tumor embolism. Embolism occurs in about 30-40% of patients. The site of embolism is dependent upon the location (left or right atrium) and the presence of an intracardiac shunt.

Jong-Won Ha and associates reported a more frequent occurrence of systemic embolism in polypoid tumors as compared to round (58% vs 0%).[3] Also, polypoid tumors more frequently prolapse into the ventricle. Prolapse of a tumor through the mitral or tricuspid valve may result in the destruction of the annulus or valve leaflets. In one study, 19% of the patients had atrial fibrillation associated with large atrial myxoma. Left atrial myxomas produce symptoms when they reach about 70 g. Right atrial myxomas grow to approximately twice this size before becoming symptomatic. Tumors vary widely in size, ranging from 1-15 cm in diameter. Rate of growth is not exactly known. In one case report, right atrial myxoma had a growth rate of 1.36 X 0.03 cm/mo. The myxomas are vascular tumors and may be neovascularized by a branch of a coronary artery.[4] Recently, a case of hemorrhage in a left atrial myxoma was reported.[5]

Myxomas have been demonstrated to produce numerous growth factors and cytokines, including vascular endothelial growth factor, resulting in angiogenesis and tumor growth and an increased expression of the inflammatory cytokine, interleukin-6.[6, 7, 8]

PreviousNextEpidemiologyFrequencyUnited States

Based upon the data of 22 large autopsy series, the prevalence of primary cardiac tumors is approximately 0.02% (200 tumors per million autopsies). About 75% of primary tumors are benign, and 50% of benign tumors are myxomas, resulting in 75 cases of myxoma per million autopsies.

International

Surgical incidence in the Republic of Ireland from 1977-1991 was 0.50 atrial myxomas per million population per year.

Mortality/MorbiditySudden death may occur in 15% patients with atrial myxoma. Death is typically caused by coronary or systemic embolization or by obstruction of blood flow at the mitral or tricuspid valve. Morbidity is related to symptoms produced by tumor embolism, heart failure, mechanical valvular obstruction, and various constitutional symptoms. SexApproximately 75% of sporadic myxomas occur in females. In a series of 66 cardiac myxomas, the female-to-male ratio was 2.7:1.[9] Female sex predominance is less pronounced in familial atrial myxomas.AgeMyxomas have been reported in patients aged 3-83 years.The mean age for sporadic cases is 56 years. In a retrospective review of 171 patients from India, the mean age of presentation was 37.1 years. Most of these patients were symptomatic; dyspnea was the most common symptom.[10] The mean age for familial cases is 25 years.PreviousProceed to Clinical Presentation , Atrial Myxoma

Thursday, January 23, 2014

Practice Essentials

Atrial tachycardia is a supraventricular tachycardia (SVT) that does not require the atrioventricular (AV) junction, accessory pathways, or ventricular tissue for its initiation and maintenance. It occurs in persons with normal hearts and in those with structurally abnormal hearts, including individuals with congenital heart disease (particularly after surgery for repair or correction of congenital or valvular heart disease).

In patients with structurally normal hearts, atrial tachycardia is associated with a low mortality rate. Patients with underlying structural heart disease, congenital heart disease, or lung disease are less likely to be able to tolerate this rhythm disturbance.

Essential updates: Distinguishing between left- and right-sided atrial tachycardia

Patterns derived from combining pulmonary artery, right atrial, and coronary sinus potentials can be used to distinguish between left- and right-sided atrial tachycardia, according to a study by Hirai et al. Using sequences obtained using electrode and ablation catheters, the investigators were able to predict the presence of left-sided atrial tachycardia with 90% accuracy, as well as a sensitivity and specificity of 78% and 100%, respectively.[1]

Signs and symptoms

Manifestations of atrial tachycardia include the following:

Rapid pulse rate: In most atrial tachycardias, the rapid pulse is regular; it may be irregular in rapid atrial tachycardias with variable AV conduction and in multifocal atrial tachycardia (MAT) Episodic or paroxysmal occurrenceSudden onset of palpitationsContinuous, sustained, or repetitive tachycardia: If atrial tachycardia is due to enhanced automaticityWarm-up phenomenon: Tachycardia gradually speeds up soon after onset (may be clinically inapparent)Dyspnea, dizziness, lightheadedness, fatigue, or chest pressure: In tachycardic episodes accompanied by palpitationsSyncope: With rapid rate and severe hypotensionHeart-failure symptoms and reduced effort tolerance: Early manifestations of tachycardia-induced cardiomyopathy in patients with frequent or incessant tachycardia

In patients with MAT, the history may disclose an underlying illness that is causing the tachycardia. Such illnesses include pulmonary, cardiac, metabolic, and endocrinopathic disorders. Chronic obstructive pulmonary disease (COPD) is the most common underlying disease process (60%) in MAT.

Reentrant atrial tachycardia is not uncommon in patients with a history of a surgically repaired atrial septal defect. The scar tissue in the atrium may give rise to the formation of a reentrant circuit.

On physical examination, the primary abnormal finding is a rapid pulse rate. The rate is usually regular, but it may be irregular in rapid atrial tachycardias with variable AV conduction and in MAT. Blood pressure may be low in patients presenting with fatigue, lightheadedness, or presyncope.

See Clinical Presentation for more detail.

Diagnosis

Workup for atrial tachycardia can employ the following diagnostic tools:

12-lead electrocardiography: To help identify, locate, and differentiate atrial tachycardiaHolter monitoring: To analyze the onset and termination of atrial tachycardia, identify the AV conduction block during the episode, and correlate the symptoms to atrial tachycardia Endocardial mapping: To localize atrial tachycardia

The following laboratory studies may be indicated to exclude systemic causes of sinus tachycardia:

Serum chemistry: To exclude electrolyte disordersBlood hemoglobin level and red blood cell (RBC) counts: To seek evidence of anemiaArterial blood gas level: To define pulmonary statusSerum digoxin assay: When digitalis intoxication is suspected

The following imaging studies can be useful in the evaluation of patients with atrial tachycardia:

Chest radiography: In patients with tachycardia-induced cardiomyopathy or complex congenital heart diseaseComputed tomography (CT) scanning: To exclude pulmonary embolism, assess the anatomy of pulmonary veins, and provide images prior to ablative procedure Echocardiography: To rule out structural heart disease and assess left atrial size, pulmonary arterial pressure, left ventricular function, and pericardial pathology

See Workup for more detail.

Management

The primary treatment during a bout of atrial tachycardia is considered to be rate control using AV nodal blocking agents (eg, beta blockers, calcium channel blockers). Antiarrhythmic drugs can prevent recurrences and may be required; a calcium channel blocker or beta blocker also may be required in combination therapy. Specific antiarrhythmic therapies include the following:

Atrial tachycardia from triggered activity: Verapamil, beta blockers, and adenosineAtrial tachycardia from enhanced automaticity: Beta blockers, but overall success rates are lowRefractory recurrent atrial tachycardia: Class Ic antiarrhythmic drugsMaintenance of sinus rhythm: Class III antiarrhythmic drugs

Nonpharmacologic therapies for atrial tachycardia include the following:

Cardioversion: For patients in whom the rhythm is not well-tolerated hemodynamically and in whom rate-control drugs are ineffective or contraindicated Radiofrequency catheter ablation: For symptomatic, medically refractory patients[2, 3] Surgical ablation: For patients with complex congenital heart disease

Multifocal atrial tachycardia

Treatment of MAT involves treatment and/or reversal of the precipitating cause. Therapy also may include the following:

Calcium channel blockers: Used as the first line of treatmentMagnesium sulfate: When administered to correct hypokalemia, most patients convert to normal sinus rhythm (NSR)Beta blockersAntiarrhythmics

In very rare cases, when MAT is persistent and refractory, AV junctional radiofrequency ablation and permanent pacemaker implantation should be considered. Such treatment can provide symptomatic and hemodynamic improvement and prevent the development of tachycardia-mediated cardiomyopathy.[4]

See Treatment and Medication for more detail.

Image LibraryThis 12-lead electrocardiogram demonstrates an atrThis 12-lead electrocardiogram demonstrates an atrial tachycardia at a rate of approximately 150 beats per minute. Note that the negative P waves in leads III and aVF (upright arrows) are different from the sinus beats (downward arrows). The RP interval exceeds the PR interval during the tachycardia. Note also that the tachycardia persists despite the atrioventricular block. NextBackground

Atrial tachycardia is defined as a supraventricular tachycardia (SVT) that does not require the atrioventricular (AV) junction, accessory pathways, or ventricular tissue for its initiation and maintenance. Atrial tachycardia can be observed in persons with normal hearts and in those with structurally abnormal hearts, including those with congenital heart disease and particularly after surgery for repair or correction of congenital or valvular heart disease.

In adults, tachycardia is usually defined as a heart rate more than 100 beats per minute (bpm). In children, the definition of tachycardia varies because the normal heart rate is age dependent, as follows:[5, 6]

Age 1-2 days: 123-159 bpmAge 3-6 days: 129-166 bpmAge 1-3 weeks: 107-182 bpmAge 1-2 months: 121-179 bpmAge 3-5 months: 106-186 bpmAge 6-11 months: 109-169 bpmAge 1-2 years: 89-151 bpmAge 3-4 years: 73-137 bpmAge 5-7 years: 65-133 bpmAge 8-11 years: 62-130 bpmAge 12-15 years: 60-119 bpm

As in most SVTs, the electrocardiogram (ECG) typically shows a narrow QRS complex tachycardia (unless bundle branch block aberration occurs). Heart rates are highly variable, with a range of 100-250 bpm. The atrial rhythm is usually regular. (See the image below.)

This 12-lead electrocardiogram demonstrates an atrThis 12-lead electrocardiogram demonstrates an atrial tachycardia at a rate of approximately 150 beats per minute. Note that the negative P waves in leads III and aVF (upright arrows) are different from the sinus beats (downward arrows). The RP interval exceeds the PR interval during the tachycardia. Note also that the tachycardia persists despite the atrioventricular block.

The conducted ventricular rhythm is also usually regular. It may become irregular, however, especially at higher atrial rates, because of variable conduction through the AV node, thus producing conduction patterns such as 2:1, 4:1, a combination of those, or Wenckebach AV block.

The P wave morphology on the ECG may give clues to the site of origin and mechanism of the atrial tachycardia. In the case of a focal tachycardia, the P wave morphology and axis depend on the location in the atrium from which the tachycardia originates. In the case of macroreentrant circuits, the P wave morphology and axis depend on activation patterns (see Workup).

Multifocal atrial tachycardia (MAT) is an arrhythmia with an irregular atrial rate greater than 100 bpm. Atrial activity is well organized, with at least 3 morphologically distinct P waves, irregular P-P intervals, and an isoelectric baseline between the P waves.[7] Multifocal atrial tachycardia has previously been described by names such as chaotic atrial rhythm or tachycardia, chaotic atrial mechanism, and repetitive paroxysmal MAT. Go to Multifocal Atrial Tachycardia for more complete information on this topic.

Classification methods

A number of methods are used to classify atrial tachycardia. Classification in terms of origin can be based on endocardial activation mapping data, pathophysiologic mechanisms, and anatomy.

On the basis of endocardial activation, atrial tachycardia may be divided into the following 2 groups (see Presentation):

Focal atrial tachycardia: Arises from a localized area in the atria such as the crista terminalis, pulmonary veins, ostium of the coronary sinus, or intra-atrial septum. Reentrant atrial tachycardias: Usually macroreentrant; reentrant atrial tachycardias most commonly occur in persons with either structural or complex heart disease, particularly after surgery involving atrial incisions or scarring Other methods of classification are as follows:Pathophysiologic mechanisms: Atrial tachycardia can be classified as the result of enhanced automaticity, triggered activity, or reentry (see Pathophysiology) Anatomy: Classification of atrial tachycardia can be based on the location of the arrhythmogenic focus (see Anatomy)Diagnosis and treatment

A 12-lead ECG is an important tool to help identify, locate, and differentiate atrial tachycardia. Laboratory studies may be indicated to exclude systemic disorders that may be causing the tachycardia. Electrophysiologic study may be required. (See Workup.)

The primary treatment during a bout of atrial tachycardia is considered to be rate control using AV nodal blocking agents, such as beta blockers or calcium channel blockers (see Treatment and Medication). Cardioversion should be considered for any patient in whom the rhythm is not tolerated well hemodynamically and in whom rate control drugs are ineffective or contraindicated.

Radiofrequency catheter ablation for atrial tachycardia has become a highly successful and effective treatment option for symptomatic patients whose condition is refractory to medical therapy or who do not desire long-term antiarrhythmic therapy. It can cure macroreentrant and focal forms of atrial tachycardia. (See Treatment.)[8, 9]

PreviousNextAnatomy

Atrial tachycardia can have a right or left atrial origin. Some atrial tachycardias actually originate outside the usual anatomic boundaries of the atria, in areas such as the superior vena cava, pulmonary veins, and vein of Marshall, where fingers of atrial myocardium extend into these locations. Rare locations, such as the noncoronary aortic cusp[2] and hepatic veins, have been described, as well. (See the video below.)

Propagation map of right atrial tachycardia originating from the right atrial appendage obtained with non-contact mapping using EnSite mapping system.

A number of aspects of the atrial anatomy can contribute to the substrate for arrhythmia. The orifices of the vena cava, pulmonary veins, coronary sinus, atrial septum, and mitral and tricuspid annuli are potential anatomic boundaries for reentrant circuits.

Anisotropic conduction in the atria due to complex fiber orientation may create the zone of slow conduction. Certain atrial tissues, such as the crista terminalis and pulmonary veins, are common sites for automaticity or triggered activity. Additionally, disease processes or age-related degeneration of the atria may give rise to the arrhythmogenic substrate.

Abnormalities that have been reported at the sites of atrial tachycardia origin include the following[1] :

Extensive myocardial fibrosisMyocyte hypertrophyEndocardial fibrosisMononuclear cell infiltrationMesenchymal cell proliferationIslets of fatty tissueThinningBlebs PreviousNext, Atrial Tachycardia

Tuesday, December 24, 2013

Practice Essentials

Atrial flutter is a cardiac arrhythmia characterized by atrial rates of 240-400 beats/min and some degree of atrioventricular (AV) node conduction block. For the most part, morbidity and mortality are due to complications of rate (eg, syncope and congestive heart failure [CHF]).

Essential update: Catheter ablation successfully treats scar-related atypical atrial flutter

With the aid of a combination of high-density activation and entrainment mapping, catheter ablation can be successfully used to treat scar-related atypical atrial flutter or atrial tachycardia, according to a report by Coffey et al.[1] The retrospective investigation also found that the highest rates of acute and long-term recurrences of atrial tachycardia were in patients with the septal form of the condition.

The study involved 91 consecutive patients with a total of 171 atrial tachycardias.[1] Irrigated radiofrequency ablation (RFA) of constrained areas along the circuit produced acute success rates of 97% for patients with nonseptal atrial tachycardia and 77% and those with septal atrial tachycardia. Long-term success rates were 82% for patients with nonseptal atrial tachycardia and 67% for those with at least 1 septal atrial tachycardia.

In patients whose atrial tachycardia was associated with previous catheter ablation, cardiac surgery or a maze procedure, or idiopathic atrial scarring, the long-term success rates were 75%, 88%, and 57%, respectively.[1]

Signs and symptoms

Signs and symptoms in patients with atrial flutter typically reflect decreased cardiac output as a result of the rapid ventricular rate. Typical symptoms include the following:

PalpitationsFatigue or poor exercise toleranceMild dyspneaPresyncope

Less common symptoms include angina, profound dyspnea, or syncope. Tachycardia may or may not be present, depending on the degree of AV block associated with the atrial flutter activity.

Physical findings include the following:

The heart rate is often approximately 150 beats/min because of a 2:1 AV blockThe pulse may be regular or slightly irregularHypotension is possible, but normal blood pressure is more commonly observed

Other points in the physical examination are as follows:

Palpate the neck and thyroid gland for goiterEvaluate the neck for jugular venous distentionAuscultate the lungs for rales or cracklesAuscultate the heart for extra heart sounds and murmursPalpate the point of maximum impulse on the chest wallAssess the lower extremities for edema or impaired perfusion

If embolization has occurred from intermittent atrial flutter, findings are related to brain or peripheral vascular involvement. Other complications of atrial flutter may include the following:

CHFSevere bradycardiaMyocardial rate–related ischemia

See Presentation for more detail.

Diagnosis

The following techniques aid in the diagnosis of atrial flutter:

ECG – This is an essential diagnostic modality for this conditionVagal maneuvers – These can be helpful in determining the underlying atrial rhythm if flutter waves are not seen wellAdenosine – This can be helpful in the diagnosis of atrial flutter by transiently blocking the AV nodeExercise testing – This can be utilized to identify exercise-induced atrial fibrillation and to evaluate ischemic heart disease Holter monitor – This can be used to help identify arrhythmias in patients with nonspecific symptoms, to identify triggers, and to detect associated atrial arrhythmias

Transthoracic echocardiography (TTE) is the preferred modality for evaluating atrial flutter. It can evaluate right and left atrial size, as well as the size and function of the right and left ventricles, and this information facilitates diagnosis of valvular heart disease, left ventricular hypertrophy (LVH), and pericardial disease.

See Workup for more detail.

Management

General treatment goals for symptomatic atrial flutter are similar to those for atrial fibrillation. They include the following:

Control of ventricular rate – This can be achieved with drugs that block the AV node; intravenous (IV) calcium channel blockers (eg, verapamil and diltiazem) or beta blockers can be used, followed by initiation of oral agents Restoration of sinus rhythm – This can be done by means of electrical or pharmacologic cardioversion or RFA; successful ablation reduces or eliminates the need for long-term anticoagulation and antiarrhythmic medications Prevention of recurrent episodes or decrease in their frequency or duration – In general, the use of antiarrhythmic drugs in atrial flutter is similar to that in atrial fibrillation Prevention of thromboembolic complications – Adequate anticoagulation, as recommended by the American College of Chest Physicians, has been shown to decrease thromboembolic complications in patients with chronic atrial flutter and in patients undergoing cardioversion Minimization of adverse effects from therapy – Because atrial flutter is a nonfatal arrhythmia, carefully assess the risks and benefits of drug therapy, especially with antiarrhythmic agents

See Treatment and Medication for more detail.

Image libraryAnatomy of classic counterclockwise atrial flutterAnatomy of classic counterclockwise atrial flutter. This demonstrates oblique view of right atrium and shows some crucial structures. Isthmus of tissue responsible for atrial flutter is seen anterior to coronary sinus orifice. Eustachian ridge is part of crista terminalis that separates roughened part of right atrium from smooth septal part of right atrium. NextBackground

Atrial flutter is a cardiac arrhythmia characterized by atrial rates of 240-400 beats/min, usually with some degree of atrioventricular (AV) node conduction block. In the most common form of atrial flutter (type I atrial flutter), electrocardiography (ECG) demonstrates a negative sawtooth pattern in leads II, III, and aVF.

Type I (typical or classic) atrial flutter involves a single reentrant circuit with circus activation in the right atrium around the tricuspid valve annulus. The circuit most often travels in a counterclockwise direction. Type II (atypical) atrial flutter follows a different circuit; it may involve the right or the left atrium. (See Pathophysiology.)

Atrial flutter is associated with a variety of cardiac disorders. In most studies, approximately 60% of patients with atrial flutter have coronary artery disease (CAD) or hypertensive heart disease; 30% have no underlying cardiac disease. Uncommon forms of atrial flutter have been noted during long-term follow-up in as many as 26% of patients with surgical correction of congenital cardiac anomalies. (See Etiology.)

Symptoms in patients with atrial flutter typically reflect decreased cardiac output as a result of the rapid ventricular rate. The most common symptom is palpitations. Other symptoms include fatigue, dyspnea, and chest pain. (See Presentation.) ECG is essential in making the diagnosis. Transthoracic echocardiography (TTE) is the preferred modality for evaluating atrial flutter. (See Workup.)

Intervening to control the ventricular response rate or to return the patient to sinus rhythm is important. Consider immediate electrical cardioversion for patients who are hemodynamically unstable. Consider catheter-based ablation as first-line therapy in patients with type I typical atrial flutter if they are reasonable candidates. Ablation is usually done as an elective procedure; however, it can also be done when the patient is in atrial flutter. (See Treatment.)

Atrial flutter is similar to atrial fibrillation in many respects (eg, underlying disease, predisposing factors, complications, and medical management), and some patients have both atrial flutter and atrial fibrillation. However, the underlying mechanism of atrial flutter makes this arrhythmia amenable to cure with percutaneous catheter-based techniques.

PreviousNextPathophysiology

In humans, the most common form of atrial flutter (type I) involves a single reentrant circuit with circus activation in the right atrium around the tricuspid valve annulus (most often in a counterclockwise direction), with an area of slow conduction located between the tricuspid valve annulus and the coronary sinus ostium (subeustachian isthmus). A 3-dimensional electroanatomic map of type I atrial flutter is shown in the video below.

3-Dimensional electroanatomic map of type I atrial flutter. Colors progress from blue to red to white and represent relative conduction time in right atrium (early to late). Ablation line (red dots) has been created on tricuspid ridge extending to inferior vena cava. This interrupts flutter circuit. RAA = right atrial appendage; CSO = coronary sinus os; IVC = inferior vena cava; TV = tricuspid valve annulus.

Animal models have been used to demonstrate that an anatomic block (surgically created) or a functional block of conduction between the superior vena cava and the inferior vena cava, similar to the crista terminalis in the human right atrium, is key to initiating and maintaining the arrhythmia.

The crista terminalis acts as another anatomic conduction barrier, similar to the line of conduction block between the 2 venae cavae required in the animal model. The orifices of both venae cavae, the eustachian ridge, the coronary sinus orifice, and the tricuspid annulus complete the barrier for the reentry circuit (see the image below). Type I atrial flutter is often referred to as isthmus-dependent flutter. Usually, the rhythm is due to reentry, there is an excitable gap, and the rhythm can be entrained.

Anatomy of classic counterclockwise atrial flutterAnatomy of classic counterclockwise atrial flutter. This demonstrates oblique view of right atrium and shows some crucial structures. Isthmus of tissue responsible for atrial flutter is seen anterior to coronary sinus orifice. Eustachian ridge is part of crista terminalis that separates roughened part of right atrium from smooth septal part of right atrium.

Type I counterclockwise atrial flutter has caudocranial activation (ie, activation counterclockwise around the tricuspid valve annulus when viewed in the left antero-oblique fluoroscopic view) of the atrial septum (see the image below).

Type I counterclockwise atrial flutter. This 3-dimType I counterclockwise atrial flutter. This 3-dimensional electroanatomic map of tricuspid valve and right atrium shows activation pattern displayed in color format. Red is early and blue is late, relative to fixed point in time. Activation travels in counterclockwise direction.

Type I atrial flutter can also have the opposite activation sequence (ie, clockwise activation around the tricuspid valve annulus). Clockwise atrial flutter is much less common. When the electric activity moves in a clockwise direction, the ECG will show positive flutter waves in leads II, III, and aVF and may appear somewhat sinusoidal. This arrhythmia is still considered type I, isthmus-dependent flutter; it is usually called reverse typical atrial flutter.

Type II (atypical) atrial flutters are less extensively studied and electroanatomically characterized. Atypical atrial flutters may originate from the right atrium, as a result of surgical scars (ie, incisional reentry), or from the left atrium, specifically the pulmonary veins (ie, focal reentry) or mitral annulus (see the image below). Left atrial flutter is common after incomplete left atrial linear ablation procedures (for atrial fibrillation). Thus, tricuspid isthmus dependency is not a prerequisite for type II atrial flutter.

Atypical left atrial flutter. Atypical left atrial flutter. PreviousNext, Atrial Flutter