Sinus of Valsalva Aneurysm

Background

John Thurnam first described sinus of Valsalva aneurysm (SVA) in 1840. Hope further described it in 1939. SVA is usually referred to as a rare congenital anomaly. A congenital SVA is usually clinically silent but may vary from a mild, asymptomatic dilatation detected in routine 2-dimensional echocardiography to symptomatic presentations related to the compression of adjacent structures or intracardiac shunting caused by rupture of the SVA into the right side of the heart.[1] Approximately 65-85% of SVAs originate from the right sinus of Valsalva, while SVAs originating from noncoronary (10-30%) and left sinuses ([2]

NextPathophysiology

Congenital SVA is caused by a dilation, usually of a single sinus of Valsalva, from a separation between the aortic media and the annulus fibrosus. A deficiency of normal elastic tissue and abnormal development of the bulbus cordis have been associated with the development of SVA.[3] Other disease processes that involve the aortic root (eg, atherosclerotic aneurysms, syphilis, endocarditis, cystic medial necrosis, chest trauma) may also produce SVA, although this usually involves multiple sinuses. Rupture of the dilated sinus may lead to intracardiac shunting when a communication is established with the right atrium (Gerbode defect [10%]) or directly into the right ventricle (60-90%). Cardiac tamponade may occur if the rupture involves the pericardial space.[1]

PreviousNextEpidemiologyFrequencyUnited States

SVA was present in 0.09% of cadavers in a large autopsy series and ranged to 0.14-0.23% in a Western surgical series.[4] Two-dimensional echocardiography is likely to determine a higher incidence of SVA, although researchers note the incremental value of 3-dimensional echocardiography.[5]

International

SVA is more prevalent in Asian surgical series (0.46-3.5%) and correlates with more supracristal ventricular septal defects (~60%).[6]

Mortality/Morbidity

The true natural history of SVA is unclear. Clinical complications from SVA are often the initial presentation of SVA (see Complications).

Associated structural defects in congenital SVAs included supracristal or perimembranous ventricular septal defect (30-60%), bicuspid aortic valve (15-20%) and aortic regurgitation (44-50%). Approximately 10% of patients with Marfan syndrome have some form of SVA. Less commonly observed anomalies include pulmonary stenosis, coarctation, and atrial septal defects. Rupture of SVA (with progressive heart failure and left-to-right shunting or endocarditis) is the main cause of death and rarely occurs before age 20 years in congenital SVA. Race

Race differences in SVA are unclear, although a higher frequency was observed in the Asian surgical series.

Sex

Male-to-female ratio is 4:1, including frequencies of both ruptured and unruptured SVA.

AgeUnruptured SVA is usually asymptomatic and is often detected serendipitously by routine 2-dimensional echocardiography, even in patients older than 60 years. Most ruptured SVAs occur from puberty to age 30 years and are often diagnosed or presented clinically at this age.A retrospective review of an institutional database identified 86 patients who underwent SVA repair from 1956-2003 found the median age to be 45 years (range 5-80 y).[7] PreviousProceed to Clinical Presentation , Sinus of Valsalva Aneurysm

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Thoracic Aortic Aneurysm

Background

Aneurysmal degeneration can occur anywhere in the human aorta. By definition, an aneurysm is a localized or diffuse dilation of an artery with a diameter at least 50% greater than the normal size of the artery.

A blood vessel has 3 layers: the intima (inner layer made of endothelial cells), media (contains muscular elastic fibers), and adventitia (outer connective tissue). Aneurysms are either true or false. The wall of a true aneurysm involves all 3 layers, and the aneurysm is contained inside the endothelium. The wall of a false or pseudoaneurysm only involves the outer layer and is contained by the adventitia. An aortic dissection is formed by an intimal tear and is contained by the media; hence, it has a true lumen and a false lumen.

Most aortic aneurysms (AA) occur in the abdominal aorta; these are termed abdominal aortic aneurysms (AAA). Although most abdominal aortic aneurysms are asymptomatic at the time of diagnosis, the most common complication remains life-threatening rupture with hemorrhage.

Aneurysmal degeneration that occurs in the thoracic aorta is termed a thoracic aneurysm (TA). Aneurysms that coexist in both segments of the aorta (thoracic and abdominal) are termed thoracoabdominal aneurysms (TAA). Thoracic aneurysms and thoracoabdominal aneurysms are also at risk for rupture. A recent population-based study suggests an increasing prevalence of thoracic aortic aneurysms. Thoracic aortic aneurysms are subdivided into 3 groups depending on location: ascending aortic, aortic arch, and descending thoracic aneurysms or thoracoabdominal aneurysms. Aneurysms that involve the ascending aorta may extend as proximally as the aortic annulus and as distally as the innominate artery, whereas descending thoracic aneurysms begin beyond the left subclavian artery. Arch aneurysms are as the name implies.

Dissection is another condition that may affect the thoracic aorta. An intimal tear causes separation of the walls of the aorta. A false passage for blood develops between the layers of the aorta. This false lumen may extend into branches of the aorta in the chest or abdomen, causing malperfusion, ischemia, or occlusion with resultant complications. The dissection can also progress proximally, to involve the aortic sinus, aortic valve, and coronary arteries. Dissection can lead to aneurysmal change and early or late rupture. A chronic dissection is one that is diagnosed more than 2 weeks after the onset of symptoms. Dissection should not be termed dissecting aneurysm because it can occur with or without aneurysmal enlargement of the aorta.

The shape of an aortic aneurysm is either saccular or fusiform. A fusiform (or true) aneurysm has a uniform shape with a symmetrical dilatation that involves the entire circumference of the aortic wall. A saccular aneurysm is a localized outpouching of the aortic wall, and it is the shape of a pseudoaneurysm.

Treatment of abdominal aortic aneurysms, thoracoabdominal aneurysms, and thoracic aneurysms involves surgical repair in good-risk patients with aneurysms that have reached a size sufficient to warrant repair. Surgical repair may involve endovascular stent grafting (in suitable candidates) or traditional open surgical repair.

NextHistory of the Procedure

The development of treatment modalities for thoracic aneurysms followed successful treatment of abdominal aortic aneurysms. Estes' 1950 report revealed that the 3-y survival rate for patients with untreated abdominal aortic aneurysms was only 50%, with two thirds of deaths resulting from aneurysmal rupture.[1] Since then, increased attempts were made to devise methods of durable repair.

Most of these initial successful repairs involved the use of preserved aortic allografts, thus triggering the establishment of numerous aortic allograft banks. Simultaneously, Gross and colleagues successfully used allografts to treat complex thoracic aortic coarctations, including those with aneurysmal involvement.[2]

In 1951, Lam and Aram reported the resection of a descending thoracic aneurysm with allograft replacement.[3] Ascending aortic replacement required the development of cardiopulmonary bypass and was first performed in 1956 by Cooley and DeBakey.[4] They successfully replaced the ascending aorta with an aortic allograft. Successful replacement of the aortic arch, with its inherent risk of cerebral ischemia, was understandably more challenging and was not reported until 1957 by DeBakey et al.[5]

Although the use of aortic allografts as aortic replacement was widely accepted in the early 1950s, the search for synthetic substitutes was well underway. Dacron was introduced by DeBakey. By 1955, Deterling and Bhonslay believed that Dacron was the best material for aortic substitution.[6] Numerous types of intricately woven hemostatic grafts have since been developed and are now used much more extensively than their allograft counterparts. Such Dacron grafts are used to replace ascending, arch, thoracic, and thoracoabdominal aortic segments.

However, some patients required replacement of the aortic root, as well. Subsequently, combined operations that replaced the ascending aneurysm in conjunction with replacement of the aortic valve and reimplantation of the coronary arteries were performed by Bentall and De Bono in 1968, using a mechanical valve with a Dacron conduit.[7] Ross, in 1962, and Barratt-Boyes, in 1964, successfully implanted the aortic homograft in the orthotopic position.[8, 9] In 1985, Sievers reported the use of stentless porcine aortic roots.[10]

More recently, less invasive therapy for descending thoracic aortic aneurysm have been developed. Dake et al reported the first endovascular thoracic aortic repair in 1994.[11] In March 2005, the US Food and Drug Administration (FDA) approved the first thoracic aortic stent graft, the GORE TAG graft (W.L. Gore and Associates; Flagstaff, AZ).[12] Since 2005, 2 other devices have gained FDA approval: the Talent Thoracic endograft (Medtronic; Santa Rosa, CA) and the Cook TX2 endograft (Cook; Bloomington, IN). Several successive next-generation reiterations of all of these devices have also gained approval.

Given the relative acceptance of the indications for thoracic endografts as an alternative to open procedures in the treatment of uncomplicated diseases of the descending thoracic aorta, experienced users of the devices now use them "off-label" in increasingly more complex indications, including use via "hybrid-procedures" in the ascending aorta and aortic arch. However, little long-term data are available at this time to support use in this fashion.

PreviousNextProblem

Aneurysms are usually defined as a localized dilation of an arterial segment greater that 50% its normal diameter. Most aortic aneurysms occur in the infrarenal segment (95%). The average size for an infrarenal aorta is 2 cm; therefore, abdominal aortic aneurysms are usually defined by diameters greater than 3 cm.

The normal size for the thoracic and thoracoabdominal aorta is larger than that of the infrarenal aorta, and aneurysmal degeneration in these areas is defined accordingly. The average diameter of the mid-descending thoracic aorta is 26-28 mm, compared with 20-23 mm at the level of the celiac axis.

PreviousNextEpidemiologyFrequency

Although findings from autopsy series vary widely, the prevalence of aortic aneurysms probably exceeds 3-4% in individuals older than 65 years.

Death from aneurysmal rupture is one of the 15 leading causes of death in most series. The estimated incidence of thoracic aortic aneurysms is 6 cases per 100,000 person-years. In addition, the overall prevalence of aortic aneurysms has increased significantly in the last 30 years. This is partly due to an increase in diagnosis based on the widespread use of imaging techniques. However, the prevalence of fatal and nonfatal rupture has also increased, suggesting a true increase in prevalence. Population-based studies suggest an incidence of acute aortic dissection of 3.5 per 100,000 persons; an incidence of thoracic aortic rupture of 3.5 per 100,000 persons; and an incidence of abdominal aortic rupture of 9 per 100,000 persons. An aging population probably plays a significant role.

PreviousNextEtiology

Aneurysmal degeneration occurs more commonly in the aging population. Aging results in changes in collagen and elastin, which lead to weakening of the aortic wall and aneurysmal dilation. According to the law of Laplace, luminal dilation results in increased wall tension and the vicious cycle of progressive dilation and greater wall stress. Pathologic sequelae of the aging aorta include elastic fiber fragmentation and cystic medial necrosis. Arteriosclerotic (degenerative) disease is the most common cause of thoracic aneurysms.

A previous aortic dissection with a persistent false channel may produce aneurysmal dilation; such aneurysms are the second most common type. False aneurysms are more common in the descending aorta and arise from the extravasation of blood into a tenuous pocket contained by the aortic adventitia. Because of increasing wall stress, false aneurysms tend to enlarge over time.

Authorities strongly agree that genetics play a role in the formation of aortic aneurysms. Of first-degree relatives of patients with aortic aneurysms, 15% have an aneurysm. This appears especially true in first-degree relatives of female patients with aortic aneurysms. Thus, inherited disorders of connective tissue appear to contribute to the formation of aortic aneurysms.

Marfan syndrome is a potentially lethal connective-tissue disease characterized by skeletal, heart valve, and ocular abnormalities. Individuals with this disease are at risk for aneurysmal degeneration, especially in the thoracic aorta. Marfan syndrome is an autosomal dominant genetic condition that results in abnormal fibrillin, a structural protein found in the human aorta. Patients with Marfan syndrome may develop annuloaortic ectasia of the sinuses of Valsalva, commonly associated with aortic valvular insufficiency and aneurysmal dilation of the ascending aorta.

Type IV Ehlers-Danlos syndrome results in a deficiency in the production of type III collagen, and individuals with this disease may develop aneurysms in any portion of the aorta. Imbalances in the synthesis and degradation of structural proteins of the aorta have also been discovered, which may be inherited or spontaneous mutations.

Atherosclerosis may play a role. Whether atherosclerosis contributes to the formation of an aneurysm or whether they occur concomitantly is not established. Other causes of aortic aneurysms are infection (ie, bacterial [mycotic or syphilitic]), arteritis (ie, giant cell, Takayasu, Kawasaki, Behçet), and trauma. Aortitis due to granulomatous disease is rare, but it can lead to the formation of aortic and, on occasion, pulmonary artery aneurysms. Aortitis caused by syphilis may cause destruction of the aortic media followed by aneurysmal dilation.

Traumatic dissection is a result of shearing from deceleration injury due to high speed motor vehicle accidents (MVA) or a fall from heights. The dissection occurs at a point of fixation, usually at the aortic isthmus (ie, at the ligamentum arteriosum, distal to the origin of the left subclavian artery), the ascending aorta, the aortic root, and the diaphragmatic hiatus.

The true etiology of aortic aneurysms is probably multifactorial, and the condition occurs in individuals with multiple risk factors. Risk factors include smoking, chronic obstructive pulmonary disease (COPD), hypertension, atherosclerosis, male gender, older age, high BMI, bicuspid or unicuspid aortic valves, genetic disorders, and family history. Aortic aneurysms are more common in men than in women and are more common in persons with COPD than in those without lung disease.

PreviousNextPathophysiology

The occurrence and expansion of an aneurysm in a given segment of the arterial tree probably involves local hemodynamic factors and factors intrinsic to the arterial segment itself.

The medial layer of the aorta is responsible for much of its tensile strength and elasticity. Multiple structural proteins comprise the normal medial layer of the human aorta. Of these, collagen and elastin are probably the most important. The elastin content of the ascending aorta is high and diminishes progressively in the descending thoracic and abdominal aorta. The infrarenal aorta has a relative paucity of elastin fibers in relation to collagen and compared with the thoracic aorta, possibly accounting for the increased frequency of aneurysms in this area. In addition, the activity and amount of specific enzymes is increased, which leads to the degradation of these structural proteins. Elastic fiber fragmentation and loss with degeneration of the media result in weakening of the aortic wall, loss of elasticity, and consequent dilation.

Hemodynamic factors probably play a role in the formation of aortic aneurysms. The human aorta is a relatively low-resistance circuit for circulating blood. The lower extremities have higher arterial resistance, and the repeated trauma of a reflected arterial wave on the distal aorta may injure a weakened aortic wall and contribute to aneurysmal degeneration. Systemic hypertension compounds the injury, accelerates the expansion of known aneurysms, and may contribute to their formation.

Hemodynamically, the coupling of aneurysmal dilation and increased wall stress is defined by the law of Laplace. Specifically, the law of Laplace states that the (arterial) wall tension is proportional to the pressure times the radius of the arterial conduit (T = P x R). As diameter increases, wall tension increases, which contributes to increasing diameter. As tension increases, risk of rupture increases. Increased pressure (systemic hypertension) and increased aneurysm size aggravate wall tension and therefore increase the risk of rupture.

Aneurysm formation is probably the result of multiple factors affecting that arterial segment and its local environment.

PreviousNextPresentation

Most patients with aortic aneurysms are asymptomatic at the time of discovery. Thoracic aneurysms are usually found incidentally after chest radiographs or other imaging studies. Abdominal aortic aneurysms may be discovered incidentally during imaging studies or a routine physical examination as a pulsatile abdominal mass.

The most common complication of abdominal aortic aneurysms is rupture with life-threatening hemorrhage manifesting as pain and hypotension. The triad of abdominal pain, hypotension, and a pulsatile abdominal mass is diagnostic of a ruptured abdominal aortic aneurysm, and emergent operation is warranted without delay for imaging studies.

Patients with a variant of abdominal aortic aneurysm may present with fever and a painful aneurysm with or without an obstructive uropathy. These patients may have an inflammatory aneurysm that can be treated with surgical repair.

Other presentations of abdominal aortic aneurysm include lower extremity ischemia, duodenal obstruction, ureteral obstruction, erosion into adjacent vertebral bodies, aortoenteric fistula (ie, GI bleed), or aortocaval fistula (caused by spontaneous rupture of aneurysm into the adjacent inferior vena cava [IVC]). Patients with aortocaval fistula present with abdominal pain, venous hypertension (ie, leg edema), hematuria, and high output cardiac failure.

Patients with thoracic aneurysms are often asymptomatic. Most patients are hypertensive but remain relatively asymptomatic until the aneurysm expands. Their most common presenting symptom is pain. Pain may be acute, implying impending rupture or dissection, or chronic, from compression or distension. The location of pain may indicate the area of aortic involvement, but this is not always the case. Ascending aortic aneurysms tend to cause anterior chest pain, while arch aneurysms more likely cause pain radiating to the neck. Descending thoracic aneurysms more likely cause back pain localized between the scapulae. When located at the level of the diaphragmatic hiatus, the pain occurs in the mid back and epigastric region.

Large ascending aortic aneurysms may cause superior vena cava obstruction manifesting as distended neck veins. Ascending aortic aneurysms also may develop aortic insufficiency, with widened pulse pressure or a diastolic murmur, and heart failure. Arch aneurysms may cause hoarseness, which results from stretching of the recurrent laryngeal nerves. Descending thoracic aneurysms and thoracoabdominal aneurysms may compress the trachea or bronchus and cause dyspnea, stridor, wheezing, or cough. Compression of the esophagus results in dysphagia. Erosion into surrounding structures may result in hemoptysis, hematemesis, or gastrointestinal bleeding. Erosion into the spine may cause back pain or instability. Spinal cord compression or thrombosis of spinal arteries may result in neurologic symptoms of paraparesis or paraplegia. Descending thoracic aneurysms may thrombose or embolize clot and atheromatous debris distally to visceral, renal, or lower extremities.

Patients who present with ecchymoses and petechiae may be particularly challenging because these signs probably indicate disseminated intravascular coagulation (DIC). The risk of significant perioperative bleeding is extremely high, and large amounts of blood and blood products must be available for resuscitative transfusion.

The most common complications of thoracic aortic aneurysms are acute rupture or dissection. Some patients present with tender or painful nonruptured aneurysms. Although debate continues, these patients are thought to be at increased risk for rupture and should undergo surgical repair on an emergent basis.

PreviousNextIndications

Indications for surgery of thoracic aortic aneurysms are based on size or growth rate and symptoms. Because the risk of rupture is proportional to the diameter of the aneurysm, aneurysmal size is the criterion for elective surgical repair. Elefteriades published the natural history of thoracic aortic aneurysms and recommends elective repair of ascending aneurysms at 5.5 cm and descending aneurysms at 6.5 cm for patients without any familial disorders such as Marfan syndrome.[13, 14] These recommendations are based on the finding that the incidence of complications (rupture and dissection) exponentially increased when the size of the ascending aorta reached 6.0 cm (31% risk of complications) or when the size of the descending aorta reached 7.0 cm (43% risk).[15, 14] Patients with Marfan syndrome or familial aneurysms should undergo earlier repair, when the ascending aorta grows to 5.0 cm or the descending aorta grows to 6.0 cm.

In addition, relative aortic aneurysm size in relation to body surface area may be more important than absolute aortic size in predicting complications.[16] Using the aortic size index (ASI) of aortic diameter (in cm) divided by body surface area (m2), patients are stratified into 3 groups: ASI 2 are at low risk for rupture (4%/y), ASI 2.75-4.25 cm/m2 are at moderate risk (8%/y), and ASI >4.25cm/m2 are at high risk (20-25%/y).[16, 17]

Rapid expansion is also a surgical indication. Growth rates average 0.07 cm/y in the ascending aorta and 0.19 cm/y in the descending aorta.[14] A growth rate of 1 cm/y or faster is an indication for elective surgical repair.

Symptomatic patients should undergo aneurysm resection regardless of size. Acutely symptomatic patients require emergent operation. Emergent operation is indicated in the setting of acute rupture. Rupture of the ascending aorta may occur into the pericardium, resulting in acute tamponade. Rupture of the descending thoracic aorta may cause a left hemothorax.

Patients with acute aortic dissection of the ascending aorta require emergent operation. They may present with rupture, tamponade, acute aortic insufficiency, myocardial infarction, or end-organ ischemia. Acute dissection of the descending aorta does not require surgical intervention, unless complicated by rupture, malperfusion (eg, visceral, renal, neurologic, leg ischemia), progressive dissection, persistent recurrent pain, or failure of medical management.

Patients who undergo surgery for symptomatic aortic insufficiency or stenosis with an associated enlarged aneurysmal aorta should have concomitant aortic replacement if the aorta reaches 5 cm in diameter. Concomitant aortic replacement should be consider for patients with bicuspid aortic valves with an aorta >4.5 cm in diameter.

As one may imagine, the quality of data and level of evidence supporting these recommendations widely vary. Given this discrepancy and important subject matter, in 2010, a joint task force spearheaded by the American College of Cardiology Foundation and the American Heart Association, and composed of members of many professional societies specializing in treatment of diseases of the thoracic aorta, produced an Executive Summary detailing guidelines for diagnosis and management of this disease, which will be annually updated.[18]

Summary of indicationsAortic size Ascending aortic diameter ≥5.5 cm or twice the diameter of the normal contiguous aortaDescending aortic diameter ≥6.5 cmSubtract 0.5 cm from the cutoff measurement in the presence of Marfan syndrome, family history of aneurysm or connective tissue disorder, bicuspid aortic valve, aortic stenosis, dissection, patient undergoing another cardiac operation Growth rate ≥1 cm/ySymptomatic aneurysmTraumatic aortic ruptureAcute type B aortic dissection with associated rupture, leak, distal ischemiaPseudoaneurysmLarge saccular aneurysmMycotic aneurysmAortic coarctationBronchial compression by aneurysmAortobronchial or aortoesophageal fistulaPreviousNextRelevant Anatomy

Ascending aortic aneurysms occur as proximally as the aortic annulus and as distally as the innominate artery. They may compress or erode into the sternum and ribs, causing pain or fistula. They also may compress the superior vena cava or airway. When symptomatic by rupture or dissection, they may involve the pericardium, aortic valve, or coronary arteries. They may rupture into the pericardium, causing tamponade. They may dissect into the aortic valve, causing aortic insufficiency, or into the coronary arteries, causing myocardial infarction.

Aortic arch aneurysms involve the aorta where the innominate artery, left carotid, and left subclavian originate. They may compress the innominate vein or airway. They may stretch the left recurrent laryngeal nerve, causing hoarseness.

Descending thoracic aneurysms originate beyond the left subclavian artery and may extend into the abdomen. Thoracoabdominal aneurysms are stratified based on the Crawford classification. Type I involves the descending thoracic aorta from the left subclavian artery down to the abdominal aorta above the renal arteries. Type II extends from the left subclavian artery to the renal arteries and may continue distally to the aortic bifurcation. Type III begins at the mid-to-distal descending thoracic aorta and involves most of the abdominal aorta as far distal as the aortic bifurcation. Type IV extends from the upper abdominal aorta and all or none of the infrarenal aorta. Descending thoracic aneurysms and thoracoabdominal aneurysms may compress or erode into surrounding structures, including the trachea, bronchus, esophagus, vertebral body, and spinal column.

PreviousNextContraindications

Aneurysm surgery has no strict contraindications. The relative contraindications are individualized, based on the patient's ability to undergo extensive surgery (ie, the risk-to-benefit ratio). Patients at higher risk for morbidity and mortality include elderly persons and individuals with end-stage renal disease, respiratory insufficiency, cirrhosis, or other comorbid conditions. For descending thoracic aneurysms, endovascular stent grafting is less invasive and is an ideal alternative (with appropriate anatomic considerations) to open repair for patients at high risk for complications of open repair. Stent grafts are also a reasonable alternative (with the appropriate anatomy) to open repair in patients who are not at high risk for complications. Patients must understand that life-long follow-up is required and that long-term durability is unknown.

PreviousProceed to Workup , Thoracic Aortic Aneurysm

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Emergent Management of Abdominal Aortic Aneurysm Rupture

Introduction to AAA

The decision to treat an unruptured abdominal aortic aneurysm (AAA) is a complex one, based on operative risk, the risk of rupture, and the patient’s estimated life expectancy. Ruptured AAA is a life-threatening condition that requires emergent surgery. For other discussions on AAA, see Abdominal Aortic Aneurysm and Bedside Ultrasonography Evaluation of Abdominal Aortic Aneurysm.

History of the procedure

Vesalius described the first AAA in the 16th century. Before the development of a surgical intervention for the process, attempts at medical management failed. The initial attempts at surgical control used ligation of the aorta, with the expected consequences.

In 1923, Matas performed the first successful aortic ligation on a patient. Attempts were made to induce thrombosis by inserting intraluminal wires. In 1948, Rea wrapped reactive cellophane around the aneurysm in order to induce fibrosis and limit expansion. This technique was used on Albert Einstein in 1949, and he survived 6 years before succumbing to rupture. In 1951, Charles Dubost performed the first AAA repair using a homograft.

Prior to this, aortic aneurysms were treated using a variety of methods, including ligation, intraluminal wiring, and cellophane wrapping. Unfortunately, early homografts became aneurysmal because of preservation techniques. In 1953, Blakemore and Voorhees repaired a ruptured AAA using a Vinyon-N graft (ie, nylon). Later, these grafts were replaced by Dacron and GORE-TEX (ie, polytetrafluoroethylene [PTFE]) fabrics. The final advance was abandonment of silk sutures, which degenerate, in favor of braided Dacron, polyethylene, and PTFE (ie, GORE-TEX) sutures, all of which retain tensile strength.

Postoperative surgical mortality rates initially remained high (>25%) because the aneurysm sac generally was excised. Nearly simultaneously in 1962, Javid and Creech reported the technique of endoaneurysmorrhaphy (see the images below). This advancement dramatically reduced mortality. Today, operative mortality rates range from 1.8-5%.

Aneurysm with retroperitoneal fibrosis and adhesion of the duodenum and fibrosis. Endoaneurysmorrhaphy.

In the late 1980s, Parodi et al described endovascular repair using a large Palmaz stent and unilateral aortofemoral and femorofemoral crossover Dacron grafts.[1] Currently, many devices are used for the endovascular treatment of AAA (see the image below).

Endovascular grafts. NextEpidemiologyUnited States statistics

Ruptured abdominal aortic aneurysm (AAA) causes an estimated 15,000 deaths per year. The frequency of rupture is 4.4 cases per 100,000 persons. The reported incidence of rupture varies from 1-21 cases per 100,000 person-years.

International statistics

The frequency of rupture is 6.9 cases per 100,000 persons in Sweden, 4.8 cases per 100,000 persons in Finland, and 13 cases per 100,000 persons in the United Kingdom.

PreviousNextPrognosis

The prognosis is guarded in patients who suffer AAA rupture prehospital. More than 50% do not survive to the ED; of those who do, survival rate drops by about 1% per minute. However, survival rate is good in the subset of patients who are not in severe shock and who receive timely, expert surgical intervention.

In 1988, 40,000 surgical reconstructions for abdominal aortic aneurysm (AAA) were performed in the US, with substantial mortality differences between elective versus emergency operations. As elective aneurysm repair has a mortality rate drastically lower than that associated with rupture, the emphasis must be on early detection and repair free from complications.

The long-term prognosis is related to associated comorbidities. Long-term survival is shortened by chronic heart failure and chronic obstructive pulmonary disease. Rupture of associated thoracic aneurysms is also an important cause of late death. Overall, AAA repair is very durable, with few long-term complications ([2, 3]

PreviousNextPathophysiology

Aneurysm diameter is an important risk factor for rupture. In general, abdominal aortic aneurysms (AAAs) gradually enlarge (0.2-0.8 mm/y) and eventually rupture. Hemodynamics play an important role. Areas of high stress have been found in AAAs and appear to correlate with the site of rupture. Computer-generated geometric factors have demonstrated that aneurysm volume is a better predictor of areas of peak wall stress than aneurysm diameter. This may have implications in determining which AAAs require surgical repair.

AAA rupture is believed to occur when the mechanical stress acting on the wall exceeds the strength of the wall tissue. Wall tension can be calculated using the Laplace Law for wall tension: P × R/W, where P = mean arterial pressure (MAP), R = radius of the vessel, and W = wall thickness of the vessel.

AAA wall tension is a significant predictor of pending rupture. The actual tension in the AAA wall appears to be a more sensitive predictor of rupture than aneurysm diameter alone. For these reasons, the clinician may wish to achieve acute blood pressure control in patients with AAA and elevated blood pressure.

PreviousNextClinical Presentation

Persons with abdominal aortic aneurysms (AAAs) that have ruptured may present in many ways. The most typical manifestation of rupture is abdominal or back pain with a pulsatile abdominal mass. However, the symptoms may be vague, and the abdominal mass may be missed. Symptoms may include groin pain, syncope, paralysis, or flank mass. The diagnosis may be confused with renal calculus, diverticulitis, incarcerated hernia, or lumbar spine disease.

Transient hypotension should prompt consideration of rupture because this finding can progress to frank shock over a period of hours. Temporary loss of consciousness is also a potential symptom of rupture.

Patients with a ruptured AAA may present in frank shock as evidenced by cyanosis, mottling, altered mental status, tachycardia, and hypotension. At least 65% of patients with ruptured AAA die from sudden cardiovascular collapse before arriving at a hospital.

It is important to note progressive symptoms (eg, abdominal or back pain, vomiting, syncope, claudication). These should alert the clinician to the possibility of expansion with imminent rupture.

Peripheral emboli and claudication

Atheroemboli from small AAAs produce livedo reticularis of the feet or blue toe syndrome (see the image below). Occasionally, small AAAs thrombose, producing acute claudication.

Atheroemboli from small abdominal aortic aneurysms produce livedo reticularis of the feet (ie, blue toe syndrome). Aortocaval fistulae

AAAs may rupture into the vena cava, producing large arteriovenous fistulae. In this case, symptoms include tachycardia, congestive heart failure (CHF), leg swelling, abdominal thrill, machinery-type abdominal bruit, renal failure, and peripheral ischemia.

Aortoduodenal fistulae

Finally, an AAA may rupture into the fourth portion of the duodenum. These patients may present with a herald upper gastrointestinal bleed followed by an exsanguinating hemorrhage.

PreviousNextIndications

Even patients who do not have symptoms from their abdominal aortic aneurysms (AAAs) may eventually require surgical intervention because the result of medical management in this population is a mortality rate of 100% over time due to rupture. In addition, these patients have a high likelihood of limb loss from peripheral embolization.

The decision to treat an unruptured abdominal aortic aneurysm (AAA) is based on operative risk, the risk of rupture, and the patient’s estimated life expectancy. In 2003, the Society for Vascular Surgery (SVS) published a series of guidelines for the treatment of AAAs based on these principles.[4] The operative risk is based on patients’ comorbidities and hospital factors.

Abdominal ultrasonography can provide a preliminary determination of aneurysm presence, size, and extent. Rupture risk is in part indicated by the size of the aneurysm (see Table 1, below).

Table 1. Abdominal Aortic Aneurysm Size and Estimated Annual Risk of Rupture (Open Table in a new window)

AAA Diameter (cm) Rupture Risk (%/y) 04-50.5-55-63-156-710-207-820-40>830-50

In addition to aneurysm diameter, risk of rupture is also an expression of sex, aneurysm expansion rate, family history, and chronic obstructive pulmonary disease (COPD) (see Table 2, below).

Table 2. Risk of Abdominal Aortic Aneurysm Rupture (Open Table in a new window)

Low Risk Average Risk High Risk Diameter5-6 cm>6 cmExpansion0.3-0.6 cm/y>0.6 cm/ySmoking/COPDNone, mildModerateSevere/steroidsFamily historyNo relativesOne relativeNumerous relativesHypertensionNormal blood pressureControlledPoorly controlledShapeFusiformSaccularVery eccentricWall stressLow (35 N/cm2Medium (40 N/cm2High (45 N/cm2)Sex...MaleFemale

The operative risk (see Table 3, below) is based on patients’ comorbidities and hospital factors. Patient characteristics, including age, sex, renal function, and cardiopulmonary disease are perhaps the most important. However, lower-volume hospitals and surgeons are associated with higher mortality.[5]

Table 3. Operative Mortality Risk of Open Repair of Abdominal Aortic Aneurysm (Open Table in a new window)

Lowest RiskModerate RiskHigh RiskAge Age 70-80 yAge 80 yPhysically activeActiveInactive, poor staminaNo clinically overt cardiac diseaseStable coronary disease; remote MI;

LVEF >35%

Significant coronary disease; recent MI;

frequent angina; CHF; LVEF
No significant comorbiditiesMild COPDLimiting COPD; dyspnea at rest; O2

dependency; FEV1
...Creatinine 2.0-3.0 mg/dL...Normal anatomyAdverse anatomy or AAA

characteristics

Creatinine >3 mg/dLNo adverse AAA characteristics...Liver disease (↑ PT; albumin Anticipated operative mortality, 1%-3%Anticipated operative mortality, 3%-7%Anticipated operative mortality, at least

5%-10%; each comorbid condition

adds ~3%-5%

mortality risk

CHF – chronic heart failure; COPD – chronic obstructive pulmonary disease; LVEF – left ventricular ejection fraction; MI – myocardial infarction; PT – prothrombin time

With AAAs smaller than 5.5 cm, elective repair has not been shown to improve survival.[6]

Prospective studies have concluded that following aneurysms larger than 5.5 cm with serial ultrasounds or CT scans is safe. A slightly higher rupture rate in women exists, and this threshold may be lower.

Thus, the decision to repair an AAA is a complex one in which the patient must play an important role. In some very elderly patients or patients with limited life expectancy, aneurysm repair may not be appropriate. In these patients, the consequences of rupture should be frankly discussed. If rupture occurs, no intervention should be performed.

PreviousNextContraindications

Contraindications for operative intervention of abdominal aortic aneurysms (AAAs) include severe chronic obstructive pulmonary disease (COPD), severe cardiac disease, active infection, and medical problems that preclude operative intervention. These patients may benefit best from endovascular stenting of the aneurysm.

In many patients, the decision to operate is a balance between risks and benefits. In an elderly patient (>80 y) with significant comorbidities, surgical repair may not be indicated. However, the decision to intervene should not be based on age alone, even with rupture. The decision is best based on the patient's overall physical status, including a positive attitude toward the surgery.

Patients with known cancer that has an indolent course (eg, prostate cancer) may merit aneurysm repair if their estimated survival is 2 years or longer.

PreviousNextWorkupLaboratory studies

A complete blood count with differential is used to assess transfusion requirements and the possibility of infection. A metabolic panel (including kidney and liver function tests) is indicated for ascertaining the integrity of renal and hepatic function, in order to assess operative risk and guide postoperative management.

Type and crossmatch blood to prepare for the possibility of transfusion, including clotting factors and platelets.

Because synthetic material is used in the intervention, assess and eliminate potential foci of infection preoperatively by urinalysis.

Assessment of pulmonary function is part of the preoperative workup, to determine operative risk and postoperative care. Patients who can climb a flight of stairs without excessive shortness of breath generally do well. If the patient's pulmonary status is in question, blood gas measurement and pulmonary function tests are helpful.

Chest radiography

Chest radiography is used to gain a preliminary assessment of the status of the heart and lungs. Concurrent pulmonary or cardiac disease may need to be addressed prior to treating the aneurysm.

Computed tomography

Preoperative CT scanning helps more clearly define the anatomy of the aneurysm and other intra-abdominal pathologies. Nonenhanced CT scanning is used to size aneurysms.[7] Although sizing the aneurysm is important, the anatomic relationships important to surgery are also determined. These include the location of the renal arteries, length of the aortic neck, condition of the iliac arteries, and anatomic variants such as a retroaortic left renal vein or horseshoe kidney.

Enhanced spiral CT scanning of the abdomen and pelvis with multiplanar reconstruction and CT angiography is the test of choice for preoperative evaluation for open and endovascular repair (see the image below).

Enhanced spiral CT scans with multiplanar reconstruction and a CT angiogram.

Of AAA cases, 10-20% have focal outpouchings or blebs visible on CT scans that are thought to contribute to the potential for rupture. The wall of the aneurysm becomes laminated with thrombus as the blebs enlarge. This can give the appearance of a relatively normal intraluminal diameter in spite of a large extraluminal size.

Magnetic resonance angiography

Magnetic resonance angiography (MRA) is quickly replacing the traditional angiographic assessment of aneurysms. The study provides excellent anatomical definition and 3-dimensional assessment of the problem. Gadolinium-enhanced MRA can provide excellent images, even though regional variations in quality are reported.

Conventional angiography

Angiography remains the criterion standard for the diagnosis of AAA, and it is indicated in the presence of associated renal or visceral involvement, peripheral occlusive disease, or aneurysmal disease. Angiography is also essential with any renal abnormality (eg, horseshoe kidney, pelvic kidney). (See the image below.)

Angiography is used to diagnose the renal area. In this instance, an endoleak represented continued pressurization of the sac. Echocardiography

Because of the fluid shift involved during the operative repair of AAA, cardiac function should be assessed using echocardiography. By ascertaining the ejection fraction of the patient, the operative intervention can be planned and cardiac protective measures can be instituted as needed. This study is particularly indicated in patients with a history of CHF or known cardiac enlargement.

Pulmonary assessment

Assessment of pulmonary function is of paramount importance in these patients. Because surgical intervention requires an abdominal incision, preoperative assessment of the patient's pulmonary status allows for tailored postoperative care.

Cardiac assessment

Assess cardiac status in all patients with vascular disease. If one vascular bed is involved with an atherosclerotic process, then consider that others also may be involved. Electrocardiography findings provide a baseline assessment of cardiac rhythm and old disease processes.

A stress test can be performed to uncover unsuspected cardiac ischemia. Significant coronary disease may need to be addressed before the AAA can be repaired.

PreviousNextTreatment & Management

Abdominal aortic aneurysms (AAAs) are typically repaired by an operative intervention. The possible approaches are the traditional open laparotomy, newer minimally invasive methodologies, or by the placement of endovascular stents.

Preoperative details

Preoperatively, obtain a careful history and perform a physical examination and laboratory assessment. These basic assessments provide the information for estimating perioperative risk and life expectancy after the proposed procedure.

Carefully consider whether the patient's current quality of life is sufficient to justify the operative intervention. In the case of elderly persons who may be debilitated or may have mental deterioration, this decision is made in conjunction with the patient and family.

Once the decision is made, identify comorbidities and risk factors that increase the operative risk or decrease survival. Ascertain the patient's activity level, stamina, and stability of health. Perform a thorough cardiac assessment tailored to the patient's history, symptoms, and results from preliminary screening tests such as the electrocardiogram and stress test.

Because COPD is an independent predictor of operative mortality, assess lung function by performing a room-air arterial blood gas measurement and pulmonary function tests. In patients with abnormal test results, preoperative intervention in the form of bronchodilators and pulmonary toilet often can reduce operative risks and postoperative complications.

Preoperative intravenous antibiotics (usually a cephalosporin) are administered to reduce the risk of infection. Arranging for appropriate intravenous accesses to accommodate blood loss, arterial pressure monitoring through an arterial line, and Foley catheter placement to monitor urine output are routine preparations for surgery.

For patients at high risk because of cardiac compromise, a Swan-Ganz catheter is placed to assist with cardiac monitoring and volume assessment. Transesophageal echocardiography can be useful to monitor ventricular volume and cardiac wall motion and to provide a guide with respect to fluid replacement and pressor use.

Prepare for blood replacement. The patient should have blood available for transfusion. Intraoperative Cell Saver use and preoperative autologous blood donation have become popular.

Maintain a normal body temperature during the operative intervention to prevent coagulopathy and maintain normal metabolic function. To prevent hypothermia, place a recirculating, warm forced-air blanket on the patient and warm any intravenous fluids and blood before administration.

In summary, the following are standard preoperatively:

Type and crossmatch bloodAdminister prophylactic antibiotics (cefazolin, 1 g intravenous piggyback)Insert a Foley catheterEstablish large-bore intravenous accessMonitor central venous pressure or establish Swan-Ganz catheterization (if indicated)Prepare the skin from the nipples to the mid thighAdminister general anesthesia (with or without epidural anesthesia)Cell Saver use has become popularInsert a nasogastric tubeIntraoperative details

The aorta may be approached either transabdominally or through the retroperitoneal space. Approach juxtarenal and suprarenal aortic aneurysms from the left retroperitoneal space.

Self-retaining retractors are used. Keep the bowel warm and, if possible, not exteriorized. The abdomen is explored for abnormalities (eg, gallstones, associated intestinal or pancreatic malignancy).

Depending on the patient's anatomy, the aorta can be reconstructed with a tube graft, an aortic iliac bifurcation graft, or an aortofemoral bypass.

For proximal infrarenal control, first identify the left renal vein. Occasionally (

Regarding pelvic outflow, in most instances, the inferior mesenteric artery is sacrificed. Therefore, to prevent colon ischemia, make every attempt to restore at least one hypogastric (internal iliac) artery perfusion. If the hypogastric arteries are sacrificed (associated aneurysms), reimplant the inferior mesenteric artery.

For supraceliac aortic control, first divide the ligaments to the left lateral segment of the liver and then retract the segment. The crura of the diaphragm are separated, and the aorta is bluntly dissected. Supraceliac control is recommended for inflammatory aneurysms.

The aorta is reconstructed from within using PTFE or Dacron. The aneurysm sac is closed, and the graft is put into the duodenum to prevent erosion.

Special considerations

Inflammatory aneurysms require supraceliac control, minimal dissection of the duodenum, and balloon occlusion of the iliac arteries. In patients with inflammatory aneurysms or large iliac artery aneurysms, identify the ureters; occasionally, ureteral stents are recommended in patients with inflammatory aneurysms.

Prevention of distal embolization

The patient is heparinized (5000 U intravenously) prior to aortic cross-clamping. If significant intraluminal debris, juxtarenal thrombus, or prior peripheral embolization is present, the distal arteries are clamped first, followed by aortic clamping.

Before restoring lower extremity blood flow, both forward flow (aortic) and back flow (iliac) are allowed to remove debris. The graft is also irrigated to flush out debris.

The colon is inspected prior to closure, and the femoral arteries are palpated. Before the patient leaves the operating room, determine lower extremity circulation. If a clot was dislodged at the time of aortic clamping, it can be removed with a Fogarty embolectomy catheter. Heparin reversal is not usually required.

PreviousNextPostoperative Details

Fluid shifts are common following aortic surgery. Fluid requirements may be high in the first 12 hours, depending on the amount of blood loss and fluid resuscitation in the operating room. Monitor the patient in the surgical intensive care unit for hemodynamic stability, bleeding, urine output, and peripheral pulses. A postoperative electrocardiogram and chest radiograph are needed. Prophylactic antibiotics (eg, cefazolin at 1 g) are administered for 24 hours.

The patient is seen in 1-2 weeks for suture or skin staple removal, then yearly thereafter.

PreviousNextPatient Education

For patient education information, see the Circulatory Problems Center and Cholesterol Center, as well as Aortic Aneurysm, High Cholesterol, and Cholesterol FAQs.

PreviousNextComplications

The following are potential complications of abdominal aortic aneurysms:

Death - 1.8-5% if elective and 50% if rupturedPneumonia - 5%Myocardial infarction - 2-5%Groin infection - Less than 5%Graft infection - Less than 1%Colon ischemia - Less than 1% if elective and 15-20% if rupturedRenal failure related to preoperative creatinine level, intraoperative cholesterol embolization, and hypotensionIncisional hernia - 10-20%Bowel obstructionAmputation from major arterial occlusionBlue toe syndrome and cholesterol embolization to feetImpotence in males - Erectile dysfunction and retrograde ejaculation (>30%)Paresthesias in thighs from femoral exposure (rare)Lymphocele in groin - Approximately 2%Late graft enteric fistulaPreviousNextEndovascular Stent Grafts

Endovascular stent grafts for the treatment of abdominal aortic aneurysm (AAA) are a less invasive form of treatment. Patients are discharged 1-2 days following surgery. The graft is placed through 2 small incisions. In September 2000, 2 grafts were approved by the US Food and Drug Administration (FDA). Since then, several more devices have received FDA approval.[8] Recently, the FDA has recommended careful follow-up because of persistent endoleaks and late ruptures.

In some instances, endoleaks represent continued pressurization of the sac (see image below). Aneurysm sacs may also demonstrate elevated pressure despite the absence of a demonstrable endoleak. This has been described as "endotension."

Persistently elevated aneurysm sac pressure, whether secondary to endoleak or endotension, is worrisome because it may progress to AAA rupture. Early data demonstrated a need for secondary interventions, via endovascular techniques, in as many as 10% of patients per year following endovascular aneurysm repair, compared with 2% in the first 5 years for open repair. Improvement has been made in the rate of secondary interventions following endovascular repair, but long-term durability has yet to be determined.

Angiography is used to diagnose the renal area. In this instance, an endoleak represented continued pressurization of the sac.

Informing the patient about these potential problems is important prior to implanting these grafts. In addition, patients with endografts require follow-up evaluation with serial CT scanning on a schedule that demands more office visits than are required for patients who receive conventional grafts.

Currently, endovascular repair is advocated for patients at increased risk for open aneurysm repair, but until results from randomized controlled trials are available, patient preference is the strongest determinant in deciding between endovascular and open aneurysm repair.

Previous, Emergent Management of Abdominal Aortic Aneurysm Rupture

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Thoracic Aneurysm

Background

Thoracic aortic aneurysm (TAA) is a life-threatening condition that causes significant short- and long-term mortality due to rupture and dissection. Aneurysm is defined as dilatation of the aorta of greater than 150% of its normal diameter for a given segment. For the thoracic aorta, a diameter greater than 3.5 cm is generally considered dilated, whereas greater than 4.5 cm would be considered aneurysmal.

Aneurysms may affect one or more segments of the thoracic aorta, including the ascending aorta, the arch, and the descending thoracic aorta. As many as 25% of patients with TAA also have an abdominal aortic aneurysm. Thoracic aortic aneurysm most commonly results from degeneration of the media of the aortic wall as well as from local hemodynamic forces.

Descending thoracic aortic aneurysm with mural thrombus at the level of the left atrium. NextPathophysiology

Degenerative changes in the wall of the aorta lead to cystic medial necrosis. This causes damage to collagen and elastin, loss of smooth muscle cells, and increased amounts of basophilic ground substance in the medial (elastic) layer of the aorta. The ascending thoracic aorta is generally most affected by cystic medial necrosis, whereas a descending thoracic aneurysm is primarily a consequence of atherosclerosis.

In Marfan syndrome, abnormalities of the gene encoding for the synthesis of fibrillin have been implicated in the predisposition to form aneurysms. Mutations in the gene responsible for this structural lipoprotein found in the aortic wall have been found in patients who do not have Marfan syndrome but have aneurysms.

As many as 75% of patients with a bicuspid aortic valve have shown evidence for cystic medial necrosis, which may be because of inadequate fibrillin production. Other inherited forms of medial degeneration have been associated with defects in the genes for fibrillin and are associated with higher rates of thoracic aortic aneurysm (TAA).

Weakening of the aortic wall is compounded by increased shear stress, especially in the ascending aorta. This segment of the aorta is most exposed to the pressure of each cardiac systole (dP/dt) as well as the dynamic heart motion transmitted from each cardiac cycle. As local wall weakness causes dilatation of the aorta, wall tension increases (described by the Laplace law (T=PR), where wall tension equals the radius of a cylinder multiplied by the pressure within it). Small tears in the intimal (innermost) layer of the aorta can permit blood to penetrate the medial layer, leading to aortic dissection.

PreviousNextEpidemiologyFrequencyUnited States

The incidence of aortic aneurysm is 5.9 cases per 100,000 person-years.[1]

Mortality/Morbidity

The cumulative risk of rupturing a thoracic aortic aneurysm (TAA) is related to aneurysm diameter. In a recent series of 133 patients with TAA, risk of rupture at 5 years was 0% for diameter less than 4 cm, 16% for diameter 4-5.9 cm, and 31% for aneurysms greater than 6 cm in diameter.[2]

Race

Thoracic aortic aneurysm is most common among whites.

Sex

Men are affected 2-4 times more frequently than women.

Age

The mean patient age at diagnosis is 60-65 years.

PreviousProceed to Clinical Presentation , Thoracic Aneurysm

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