Aortic Dilatation in Patients With Bicuspid Aortic Valve

Perspective:

Bicuspid aortic valve is the most common congenital heart defect in adults, affecting 1.3% of the population worldwide, and is responsible for more deaths and complications than the combined effects of all the other congenital heart defects. Aortic stenosis and regurgitation are the most common complications of a bicuspid aortic valve, but dilatation of any or all segments of the proximal aorta from the aortic root to the aortic arch, called bicuspid aortopathy, is present in approximately 50% of affected people. The following are 10 highlights from this review:

1. A bicuspid aortic valve typically comprises two leaflets of unequal size. The most common pattern involves fusion of the right and left cusps, resulting in an anterior–posterior leaflet orientation (typical pattern); followed by fusion of the right and noncoronary cusps, resulting in right–left leaflet orientation (atypical pattern). The least common pattern involves fusion of the left and noncoronary cusps. In rare cases, leaflets are symmetrical or there is no raphe.

2. The patterns of aortic involvement can be classified into three types:

  1. Type 1, the most common type, involves dilation of the tubular ascending aorta (particularly along its convexity), accompanied by varying degrees of dilation of the aortic root (the aortic sinuses, aortic valve, and coronary ostia). This type has been associated with an older age at diagnosis (>50 years), aortic valve stenosis, and a right-left fusion pattern.

  2. Type 2 involves isolated involvement of the tubular ascending aorta (with relative sparing of the aortic root), frequently extending into the transverse aortic arch, and has been associated with the presence of the right–noncoronary fusion pattern.

  3. Type 3, also called the root phenotype, involves isolated dilation of the aortic root. This rare type has been associated with a younger age at diagnosis (<40 years), male sex, and aortic regurgitation; and has been proposed to be the form of bicuspid aortopathy most likely to be associated with a genetic cause.

3. The development of bicuspid aortopathy has been attributed to both genetic and hemodynamic bases. Although the relative contributions are debatable, both factors probably are operative.

4. Patients with bicuspid aortopathy are at risk of aneurysm formation and aortic dissection:

  1. The growth rate of the aorta ranges from 0.2 to 1.9 mm/year. Larger aortic diameter at baseline appears to be a predictor of more rapid growth.

  2. Contemporary series suggest a relatively low rate of aortic dissection (0.03–0.1/patient-year; age-adjusted relative risk ~8.4), probably reflecting current practices of serial surveillance and intervention. Risks are higher among older patients and in the setting of a known aortic aneurysm (no dissections observed among patients with an aorta diameter <45 mm).

5. The initial diagnosis of bicuspid aortopathy usually is made with transthoracic echocardiography (TTE). If the mid-distal ascending aorta and arch are not visualized along with the aortic root, then computed tomography (CT), magnetic resonance imaging (MRI), or transesophageal echocardiography should be considered.

6. Risk factors for aortic dilation, particularly smoking and hypertension, should be aggressively addressed.

7. Beta-adrenergic blockers, angiotensin-converting-enzyme inhibitors, and angiotensin-receptor blockers are antihypertensive agents of choice. (Beta-blockers have the theoretical advantage of reducing aortic wall shear stress, and angiotensin-receptor blockers have been shown to reduce the rate of aortic growth in patients with Marfan’s syndrome.)

8. Imaging and intervention are recommended as follows for patients with bicuspid aortic valve and no current indication for valve surgery, based on aortic diameter on TTE:

  1. Aortic root or an ascending aorta diameter <40 mm: Serial echocardiographic screening. Consider baseline CT or MRI scan.

  2. Aortic root or an ascending aorta with diameter 40–44 mm: Baseline CT or MRI scan and yearly surveillance with echo, CT, or MRI. Consider surgery if rapid progression (≥5 mm/year).

  3. Aortic root or ascending aorta diameter 45–49 mm: Consider surgery if there are high-risk features (family history of aortic dissection, rupture, or sudden death; growth rate ≥5 mm/year). For short stature, consider surgery if ratio of aortic area to body height >10 cm2/m. Tailor surgical approach based on aortopathy pattern, perioperative risk, and surgeon and center experience.

  4. Aortic root or ascending aorta diameter 50–55 mm: Consider surgery. Tailor surgical approach based on aortopathy pattern, perioperative risk, and surgeon and center experience.

9. Imaging and intervention are recommended as follows for patients with bicuspid aortic valve and a current indication for valve surgery, based on aortic diameter on TTE:

  1. Aortic root or an ascending aorta diameter <40 mm: Isolated aortic valve surgery and yearly surveillance with echo, CT, or MRI.

  2. Aortic root or an ascending aorta with diameter 40–44 mm: Isolated aortic valve surgery and yearly surveillance with echo, CT, or MRI.

  3. Aortic root or ascending aorta diameter 45–55 mm: Tailored surgical approach based on aortopathy pattern, perioperative risk, and surgeon and center experience, anticipated anticoagulation therapy, and patient preference. Options for the above include aortic valve replacement with supracoronary ascending aorta graft repair, hemiarch, or total arch repair; aortic valve repair; valve-sparing root repair; or valved conduit (Bentall procedure).

10. There are special patient populations with bicuspid aortic valve who deserve additional attention, including:

  1. Pregnant women with a bicuspid aortic valve and aortic dilatation are at increased risk for complications. In general, women with a bicuspid aortic valve and aortic diameter >45 mm should be advised against pregnancy.

  2. Athletes (with or without valve disease) with dilated aortic root or ascending aorta (diameter ≥45 mm) should be advised to participate only in low-intensity competitive sports.

  3. First-degree relatives of patients with a bicuspid aortic valve should be screened for the presence of a bicuspid aortic valve and asymptomatic aortic disease.

Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Noninvasive Imaging, Congenital Heart Disease, CHD & Pediatrics and Imaging, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Angiotensin Receptor Antagonists, Heart Defects, Congenital, Tomography, X-Ray Computed, Magnetic Resonance Imaging, Echocardiography


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