Emergent Management of Acute Aortic Dissection

Overview

Aortic dissection is the most common catastrophe of the aorta, 2-3 times more common than rupture of the abdominal aorta. When left untreated, about 33% of patients die within the first 24 hours, and 50% die within 48 hours. The 2-week mortality rate approaches 75% in patients with undiagnosed ascending aortic dissection.

The establishment of the International Registry of Acute Aortic Dissection in 1996, which gathers information from 24 centers in 11 countries, has helped in the development of an understanding of the complexity of aortic dissection.

Dissections of the thoracic aorta have been classified anatomically by 2 different methods. The more commonly used system is the Stanford classification, which is based on involvement of the ascending aorta and simplifies the DeBakey classification.

Go to Aortic Dissection for complete information on this topic.

Stanford classification

The Stanford classification divides dissections into 2 types, type A and type B. Type A involves the ascending aorta (DeBakey types I and II); type B does not (DeBakey type III).

This system helps to delineate treatment. Usually, type A dissections require surgery, while type B dissections may be managed medically under most conditions.

DeBakey classification

The DeBakey classification divides dissections into 3 types, as follows:

Type I involves the ascending aorta, aortic arch, and descending aortaType II is confined to the ascending aortaType III is confined to the descending aorta distal to the left subclavian artery

Type III dissections are further divided into IIIa and IIIb. Type IIIa refers to dissections that originate distal to the left subclavian artery but extend proximally and distally, mostly above the diaphragm.

Type IIIb refers to dissections that originate distal to the left subclavian artery, extend only distally, and may extend below the diaphragm.

Thoracic aortic dissections should be distinguished from aneurysms (ie, localized abnormal dilation of the aorta) and transections, which are caused most commonly by high-energy trauma.

NextPrehospital Care

Assure adequate breathing, maintain oxygenation, treat shock, and obtain useful historical information.

Establishing the diagnosis in the field is usually difficult or impossible, but certain salient features of aortic dissection may be observed. It is life threatening if not quickly recognized and treated.

Radio communication with the receiving hospital permits the medical control physician to direct care and select a capable destination hospital, while permitting the emergency department (ED) to mobilize appropriate resources.

In the rare event that the diagnosis can be made based on prehospital information, the physician directing prehospital care should request transport to a facility capable of operative treatment of an aortic dissection.

PreviousNextEmergency Department Care

The mortality rate of patients with aortic dissection is 1-2% per hour for the first 24-48 hours. Initial therapy should begin when the diagnosis is suspected. This includes 2 large-bore intravenous lines (IVs), oxygen, respiratory monitoring, and monitoring of cardiac rhythm, blood pressure, and urine output.

Clinically, the patient must be assessed frequently for hemodynamic compromise, mental status changes, neurologic or peripheral vascular changes, and development or progression of carotid, brachial, and femoral bruits.

Aggressive management of heart rate and blood pressure should be initiated.

Beta blockers should be given initially to reduce the rate of change of blood pressure (dP/dt) and the shear forces on the aortic wall.

The target heart rate should be 60-80 beats per minute.

The target systolic blood pressure should be 100-120 mm Hg.

End organ perfusion should be evaluated. Balancing the risks of dP/dt on the aortic wall versus the benefits of acceptable end organ perfusion may be a difficult clinical decision.

Retrograde cerebral perfusion may increase the protection of the central nervous system during the arrest period.

The mortality rate from aortic arch dissections is about 10-15%, with significant neurologic complications occurring in another 10% of patients. The mortality rate is influenced by the patient's clinical condition.

The American College of Radiology has established ACR Appropriateness Criteria for the diagnosis and treatment of suspected aortic dissection.[1]

Type A dissections

Urgent surgical intervention is required in type A dissections.

The area of the aorta with the intimal tear usually is resected and replaced with a Dacron graft.

The operative mortality rate is usually less than 10%, and serious complications are rare with ascending aortic dissections.

The development of more impermeable grafts, such as woven Dacron, collagen-impregnated Hemashield (Meadox Medicals, Oakland, NJ), aortic grafts, and gel-coated Carbo-Seal Ascending Aortic Prothesis (Sulzer CarboMedics, Austin, Tex), has greatly enhanced the surgical repair of thoracic aortic dissections.

With the introduction of profound hypothermic circulatory arrest and retrograde cerebral perfusion, the morbidity and mortality rates associated with this highly invasive surgery have decreased.

Dissections involving the arch are more complicated that those involving only the ascending aorta, because the innominate, carotid, and subclavian vessels branch from the arch. Deep hypothermic arrest usually is required. If the arrest time is less than 45 minutes, the incidence of central nervous system complications is less than 10%.

Aortic stent grafting is a challenging technique. It may prove feasible and has offered good results in a small series of patients. It may be a reasonable alternative in high-risk patients in the near future.

Type B dissections

The definitive treatment for type B dissections is less clear.

Uncomplicated distal dissections may be treated medically to control blood pressure. Distal dissections treated medically have a mortality rate that is the same as or lower than the mortality rate in patients who are treated surgically.

Surgery is reserved for distal dissections that are leaking, ruptured, or compromising blood flow to a vital organ.

Acute distal dissections in patients with Marfan syndrome usually are treated surgically.

Inability to control hypertension with medication is also an indication for surgery in patients with a distal thoracic aortic dissection.

Patients with a distal dissection are usually hypertensive, emphysematous, or older.

Long-term medical therapy involves a beta-adrenergic blocker combined with other antihypertensive medications. Avoid antihypertensives (eg, hydralazine, minoxidil) that produce a hyperdynamic response that would increase dP/dt (ie, alter the duration of P or T waves).

Survivors of surgical therapy also should receive beta-adrenergic blockers.

A series of patients with type B dissections demonstrated that aggressive use of distal perfusion, CSF drainage, and hypothermia with circulatory arrest improves early mortality and long-term survival rates.

Endovascular stenting remains an option for treatment of some type B dissections. Some studies recommend that patients with complicated acute type B dissections undergo endovascular stenting with the goal of covering the primary intimal tear.[2]

Definitive treatment

Definitive treatment involves segmental resection of the dissection, with interposition of a synthetic graft.

When thoracic dissections are associated with aortic valvular disease, replace the defective valve.

With combined reconstruction–valve replacement, the operative mortality rate is approximately 5%, with a late mortality rate of less than 10%.

Operative repair of the transverse aortic arch is technically difficult, with an operative mortality rate of 10% despite induction of hypothermic cardiocirculatory arrest.

Repair of the descending aorta is associated with a higher incidence of paraplegia than repair of other types of dissections because of interruption of segmental blood supply to the spinal cord.

The operative mortality rate is approximately 5%.

In a study by Mimoun et al of patients with Marfan syndrome who had acute aortic dissection, the patients were found to have a better event-free survival when there were no dissected portions of the aorta remaining after surgery.[3]

PreviousNextConsultations

Once a thoracic dissection is suspected, consult a thoracic surgeon. Because many patients with this disorder have concomitant medical illness, consult the patient's primary care provider to expedite preoperative preparation. Early consultation is encouraged when ordering further imaging studies if the patient requires rapid operative intervention.

Consult a radiologist prior to obtaining aortography.

PreviousNextInpatient Care

Patients with symptomatic dissection should undergo immediate repair, especially if it is leaking or expanding.

Symptomatic patients require admission to a center experienced in cardiopulmonary bypass and operative care.

Completely asymptomatic patients may have their repair performed electively but may require admission to expedite their evaluation or for preoperative stabilization of their condition.

Patients with chest pain should undergo serial echocardiograms (ECGs) and creatine kinase (CK) determinations if acute myocardial infarction (AMI) is indicated.

PreviousNextOutpatient Care

Follow-up examinations with radiologic studies are recommended at 3-month intervals for the first year and every 6 months for the next 2 years.

After this, follow up annually.

PreviousNextTransfer

Symptomatic patients require care at a facility equipped to perform cardiopulmonary bypass with aortic and/or valvular repair.

Contact the receiving physician as soon as possible to transfer patients before their condition deteriorates.

Early airway management is indicated in the presence of hemoptysis or stridor.

If coronary insufficiency is suspected, nitrates may be used, but therapy with thrombolytic agents and aspirin should be avoided.

Patients should be monitored and accompanied by personnel capable of resuscitation.

If a prolonged ground transport time is anticipated, consider air transport.

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Carotid Artery Dissection

Background

Carotid artery dissection begins as a tear in one of the carotid arteries of the neck, which allows blood under arterial pressure to enter the wall of the artery and split its layers. The result is either an intramural hematoma or an aneurysmal dilatation, either of which can be a source of microemboli, with the latter also causing a mass effect on surrounding structures.

Carotid artery dissection is a significant cause of ischemic stroke in all age groups, but it occurs most frequently in the fifth decade of life and accounts for a much larger percentage of strokes in young patients.[1] Dissection of the internal carotid artery can occur intracranially or extracranially, with the latter being more frequent. Internal carotid artery dissection can be caused by major or minor trauma, or it can be spontaneous, in which case, genetic, familial, or heritable disorders are likely etiologies.

Although in practice, dissections are labeled spontaneous in the absence of major blunt or penetrating trauma,[2] when they are associated with minor mechanism trauma they may be caused or influenced by an underlying arteriopathy.[3] Patients can present in a variety of settings, such as a trauma bay with multiple traumatic injuries; a physician’s office with nonspecific head, neck, or face pain; or an emergency department (ED) with a partial Horner syndrome.

Sophisticated imaging techniques, which have improved over the past 2 decades, are required to confirm the presence of dissection. Most ischemic cerebral symptoms arise from thromboembolic events; therefore, early institution of antithrombotic treatment provides the best outcome.[4]

Once diagnosed and treated, patients with carotid artery dissection require regular follow-up and imaging studies of both carotid arteries because healing usually takes 3-6 months and the incidence of contralateral dissection is higher than in the general population. When the condition is diagnosed early, the prognosis is usually good. A high index of suspicion is required to make this difficult diagnosis.

For patient education resources, see the Stroke Center, as well as Worst Headache of Your Life, Transient Ischemic Attack (Mini-stroke), and Stroke.

NextPathophysiology

Although the cause of internal carotid artery dissection remains elusive, mechanical forces (eg, trauma, blunt injury, and stretching) and underlying arteriopathies (eg, Ehlers-Danlos syndrome IV and other connective tissue disorders and aberrations), either alone or in combination, account for most of the pathophysiology. It is widely accepted that carotid artery dissection is a multifactorial disease.[5]

Carotid artery dissection begins as a tear in the tunica intima or directly within the tunica media (possibly originating from the vasa vasorum).[1] The blood dissects along the artery to create an intramural hematoma that leads to a thrombus, which can narrow the carotid artery lumen and become a nidus for distal embolization (see the image below).[2]

Arterial dissection. (A) Tear and elevation of intima from wall of artery, resulting in luminal stenosis. Illustration shows stasis of flow in false lumen beneath elevated intima. This condition creates blind pouch that predisposes patient to thrombus formation. (B) Subadventitial dissection represents hemorrhage between media and adventitia. Artery may become dilated as result of thickening of arterial wall, with some degree of luminal narrowing. Elevation of intimal flap is not commonly associated with this type of dissection. Hemorrhage may extravasate through adventitia, resulting in pseudoaneurysm or fistula formation.

Sometimes, the dissection plane lies between the tunica media and the tunica adventitia, resulting in an aneurysmal outpouching of the arterial wall that may also become a source of distal emboli. Aneurysmal dilatation can also cause a mass effect on nearby structures such as sympathetic fibers and the lower cranial nerves.[1, 2] The dilatation resulting from an internal carotid artery dissection may be termed a true rather than a false aneurysm because the wall is composed of blood vessel elements.

PreviousNextEtiology

Causes of carotid artery dissection include the following:

Heritable connective-tissue disordersEhlers-Danlos syndrome type IVFibromuscular dysplasiaCystic medial necrosisMarfan syndromeAutosomal dominant polycystic kidney diseaseOsteogenesis imperfecta type IOral contraceptivesHypertensionNeck manipulation or strain - This can result from intentional manipulation or from other strain that may occur during sports activities, yoga, or even apparently minimal activity (eg, overhead painting) Blunt trauma from high impact and seemingly minor mechanisms of injuryPenetrating traumaWearing a 3-point restraint seat belt during a motor vehicle crashSmokingRespiratory tract infectionPreviousNextEpidemiology

The annual incidence of symptomatic spontaneous internal carotid artery dissection is 2.5-3 per 100,000.[1] The incidence of carotid artery dissection as a result of blunt injuries (mainly high-speed motor vehicle accidents) ranges from less than 1% to 3%.[6] The actual incidence may be higher; some dissections are asymptomatic or cause only minor transient symptoms and remain undiagnosed.

Age- and sex-related demographics

Internal carotid artery dissection is a common cause of ischemic stroke in patients younger than 50 years and accounts for as many as 25% of ischemic strokes in young and middle-aged patients.[1] The mean age for ischemic stroke secondary to internal carotid artery dissection from blunt traumatic injury is even younger: 35-38 years. Dissection of the intracranial part of the internal carotid artery is rare at any age, because the intracranial carotid artery is less mobile and the skull absorbs most of the force of trauma.

No significant gender-based difference in frequency exists for spontaneous internal carotid artery dissection, though there may be a slight male preponderance when traumatic causes of carotid artery dissection are taken into account.

PreviousNextPrognosis

In general, the prognosis depends on the severity of the initial ischemic injury and the extent of collateral circulation. Overall, the prognosis for spontaneous internal carotid artery dissection is favorable, with about 75% of patients making a good recovery.[1, 7] The reported mortality is less than 5%. Patients who have a dissection secondary to trauma have a much higher rate of mortality on discharge.

Morbidity from carotid artery dissection ranges in severity from transient focal deficits to permanent cerebral or retinal ischemic injury. More than one half of patients with spontaneous carotid artery dissection develop stroke,[1] although this may be delayed by hours or days. Rates of delayed stroke due to blunt-traumatic causes of carotid artery injury range from 3% in grade I injuries to 44% in grade IV injuries.[2]

In the setting of blunt trauma, 37-58% of patients have permanent neurologic deficits on discharge,[6] though early use of antithrombotic therapy has essentially eliminated ischemic events in asymptomatic patients with carotid artery dissection.[4, 8]

As in other causes of stroke in young adults, the functional outcome is generally good, and recurrence of cerebral ischemia and carotid artery dissection is rare.[5] The risk of recurrence is highest in the first month and then remains in the area of 1% per year for about a decade. Headache may persist, in some cases for years after the dissection.

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Vertebral Artery Dissection

Practice Essentials

Vertebral artery dissection (VAD) is a relatively rare but increasingly recognized cause of stroke in patients younger than 45 years. Although the term spontaneous VAD is used to describe cases that do not involve significant blunt or penetrating trauma as a precipitating factor, many patients with so-called spontaneous VAD have a history of trivial or minor injury involving some degree of cervical distortion.

Essential update: Long-term benefit from endovascular therapy for vertebral artery dissection

In a study of 73 patients treated for VAD with endovascular internal trapping, stable and durable results were demonstrated over a mean follow-up of 55.6 months. Recanalization was rare and observed only in 2 patients with ruptured VAD, both within 3 months after initial treatment without rupture. Cranial nerve paresis was observed in 8.21% of patients, perforating ischemia was seen in 9.59%, and spinal cord infarction was seen in 2.74%. Patient ratings of quality of life were good.[6]

Signs and symptoms

The typical patient with VAD is a young person who experiences severe occipital headache and posterior nuchal pain following a head or neck injury and subsequently develops focal neurologic signs attributable to ischemia of the brainstem or cerebellum. The focal signs may not appear until after a latent period lasting as long as 3 days, however, and delays of weeks and years also have been reported. Many patients present only at the onset of neurologic symptoms.

When neurologic dysfunction does occur, patients most commonly report symptoms attributable to lateral medullary dysfunction (ie, Wallenberg syndrome). Patient history may include the following:

Ipsilateral facial dysesthesia (pain and numbness)[7] - Most common symptom Dysarthria or hoarseness (cranial nerves [CN] IX and X)Contralateral loss of pain and temperature sensation in the trunk and limbsIpsilateral loss of taste (nucleus and tractus solitarius)HiccupsVertigo[7] Nausea and vomitingDiplopia or oscillopsia (image movement experienced with head motion)Dysphagia (CN IX and X)DisequilibriumUnilateral hearing loss[8]

Rarely, patients may manifest the following symptoms of a medial medullary syndrome:

Contralateral weakness or paralysis (pyramidal tract)Contralateral numbness (medial lemniscus)

Depending upon which areas of the brainstem or cerebellum are experiencing ischemia, the following signs may be present:

Limb or truncal ataxiaNystagmus[9] Ipsilateral Horner syndrome[4] Ipsilateral hypogeusia or ageusia (ie, diminished or absent sense of taste)Ipsilateral impairment of fine touch and proprioceptionContralateral impairment of pain and thermal sensation in the extremities (ie, spinothalamic tract)Lateral medullary syndrome[10]

Cerebellar findings may include the following:

NystagmusMedial medullary syndromeTongue deviation to the side of the lesion (impairment of CN XII)Contralateral hemiparesisIpsilateral impairment of fine touch and proprioception (nucleus gracilis)Internuclear ophthalmoplegia (lesion of the medial longitudinal fasciculus)

See Clinical Presentation for more detail.

Diagnosis

Imaging studies in patients with suspected VAD may include the following:

Computed tomography – Identifies subarachnoid hemorrhage[9] Four-vessel cerebral angiography[11] – Once the criterion standard for diagnosis, now largely supplanted by noninvasive techniques Magnetic resonance imaging[5, 12, 11, 13, 14] – Detects both the intramural thrombus and intimal flap that are characteristic of VAD[11] ; hyperintensity of the vessel wall seen on T1-weighted axial images is considered by some to be pathognomonic of VAD Magnetic resonance angiography[5, 12, 15, 13, 14] – Can identify a pseudolumen and aneurysmal dilation of the artery[11] Vascular duplex scanning – Demonstrates abnormal flow in 95% of patients with VAD,[5] but shows signs specific to VAD (eg, segmental dilation of the vessel, eccentric channel) in only 20% Transcranial Doppler – Approximately 75% sensitive to the flow abnormalities seen in VAD; useful also in detecting high-intensity signals (HITS), which are characteristic of microemboli propagating distally as a result of the dissection

Because VAD occurs in young, generally healthy individuals, laboratory evaluation is directed toward establishing baseline parameters in anticipation of anticoagulant therapy, as follows:

Prothrombin time (PT) with international normalized ratio (INR)Activated partial thromboplastin time (aPTT)

In addition, elevation of the erythrocyte sedimentation rate (ESR) may suggest vasculitis involving the cerebrovascular circulation.

See Workup for more detail.

Management

Acute management of proven or suspected spontaneous VAD is as follows[16] :

Anticoagulants and antiplatelet agents are the drugs of choice to prevent thromboembolic disordersMore potent agents (eg, intra-arterial thrombolytics) have been used in selected cases

See Treatment and Medication for more detail.

Image libraryA, Dissection of the left vertebral artery secondary to guidewire injury. B, Complete resolution occurred in 6 months with only aspirin and clopidogrel (Plavix; Bristol-Myers Squibb/Sanofi Pharmaceuticals Partnership, Bridgewater, NJ) therapy. NextBackground

Vertebral artery dissection (VAD) is an increasingly recognized cause of stroke in patients younger than 45 years.[1, 2, 3, 4] Although its pathophysiology and treatment closely resemble that of its sister condition, carotid artery dissection (CAD), the clinical presentation, etiology, and epidemiological profile of VADs are unique. In particular, advances in imaging have contributed to growing awareness of this entity.[5]

PreviousNextPathophysiology

An expanding hematoma in the vessel wall is the root lesion in VAD. This intramural hematoma can arise spontaneously or as a secondary result of minor trauma, through hemorrhage of the vasa vasorum within the media of the vessel. It also can be introduced through an intimal flap that develops at the level of the inner lumen of the vessel. Major trauma is also an increasingly recognized cause of VAD.[17]

This intramural hemorrhage can evolve in a variety of ways, resulting in any of the following consequences:

The hematoma may seal off and, if sufficiently small, remain largely asymptomatic.If the dissection is subintimal, the expanding hematoma may partially or completely occlude the vertebral artery or one of its branches. Extensive dissections (those that extend intracranially and involve the basilar artery) result in infarctions of the brainstem, cerebellum or, rarely, the spinal cord. Subintimal dissections also may rupture back into the vertebral artery, thus creating a false lumen (pseudolumen). Subadventitial dissections tend to cause pseudoaneurysmal dilation of the vertebral artery, which may compress adjacent neurologic structures. These subadventitial dissections are prone to rupture through the adventitia, resulting in subarachnoid hemorrhage. In an autopsy series of more than 100 patients with subarachnoid hemorrhage, 5% of the hemorrhages were deemed the result of VAD. The intimal disruption and low flow states that arise in VAD create a thrombogenic milieu in which emboli may form and propagate distally. This results in transient ischemia or infarction.

An understanding of the anatomy of the vertebral artery is helpful. The course of the vertebral artery usually is divided into 4 sections as follows:

Segment I runs from its takeoff at the first branch of the subclavian artery to the transverse foramina of cervical vertebra C5 or C6. Segment II runs entirely within the transverse foramina of C5/C6 to C2.Segment III, a tortuous segment, begins at the transverse foramen of C2, runs posterolaterally to loop around the posterior arch of C1, and passes subsequently between the atlas and the occiput. This segment is encased in muscles, nerves, and the atlanto-occipital membrane. Segment IV, the intracranial segment, begins as it pierces the dura at the foramen magnum and continues until the junction of the pons and medulla, where the vertebral arteries merge to join the larger proximal basilar trunk.

Spontaneous dissection of the vertebral artery usually occurs in the tortuous distal extracranial segment (segment III) but may extend into the intracranial portion or segment IV.

PreviousNextEpidemiologyFrequencyUnited States

Dissections of the extracranial cervical arteries are relatively rare. The combined incidence of both VAD and CAD is estimated to be 2.6 per 100,000. However, cervical dissections are the underlying etiology in as many as 20% of the ischemic strokes presenting in younger patients aged 30-45 years. Among all extracranial cervical artery dissections, CAD is 3-5 times more common than VAD.[7]

Mortality/MorbidityVertebral artery dissection (VAD) has been associated with a 10% mortality rate in the acute phase. Death is the result of extensive intracranial dissection, brainstem infarction, or subarachnoid hemorrhage.[10] Those who survive the initial crisis do remarkably well, with long-term sequelae rare.Sex

The female-to-male ratio is 3:1.

Age

In contrast to atherothrombotic disease of the vertebrobasilar circulation, VAD occurs in a much younger population. The average age is 40 years; the average age of a patient with CAD is closer to 47 years.[12]

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