Aortic Involvement in Patients With a Bicuspid Aortic Valve
The following are 10 points to remember about aortic involvement in patients with a bicuspid aortic valve (BAV):
1. BAV occurs in 0.5-1.4% of the general population and is one of the most common conditions associated with a dilated ascending aorta; in one series, 20% of patients with a dilated aorta on echocardiogram were found to have a concomitant BAV.
2. BAV can occur with other associated and congenital abnormalities, and a workup for these abnormalities should be considered, which includes coarctation of the aorta, Shone’s complex, Turner syndrome, sinus of Valsalva aneurysm, and familial thoracic aorta aneurysm/dissection syndromes.
3. BAV is a risk factor for aortic dissection, and may be present in up to 7-15% of those who present with an acute aortic dissection and up to 28% in those <40 years of age with acute dissection.
4. Ascending aortic dilation occurs in up to 50% of patients with BAV and appears to occur irrespective of the degree of valvular dysfunction.
5. Aortic dilation associated with BAV tends to involve the proximal to mid ascending aorta most prominently. This area may not be fully assessed on echocardiography, and additional imaging studies may be necessary (computed tomography or magnetic resonance imaging).
6. The aortic wall in patients with BAV exhibits reduced elasticity and distensibility compared with normal controls. Histologically, BAV-associated aneurysms have increased apoptosis, more elastic fragmentation, and increased levels of matrix metalloproteinase-2 compared to aneurysms associated with three leaflet aortic valves. Altered transforming growth factor-B signaling may play a role in BAV-associated aneurysm formation, but this is not yet proven.
7. BAV and BAV with associated aneurysm can occur in families, and up to 9% of first-degree relatives of patients with BAV may also have a BAV. The inheritance pattern is likely autosomal dominant with variable expressivity and reduced penetrance. Screening of first-degree relatives for BAV and aneurysm is therefore important and recommended in recent American College of Cardiology Foundation/American Heart Association guidelines.
8. Current consensus opinion recommends replacing the aortic root/ascending aorta in patients with a BAV if the aorta is >5.0 cm or exhibits a growth rate of >0.5 cm/year (≥4.5 cm if AVR is planned for valve dysfunction). Smaller size cutoffs should be considered in patients with small body habitus, as relative aortic size may be an important risk factor for aortic dissection.
9. Patients who undergo isolated AVR for BAV dysfunction without concomitant aortic intervention should have surveillance of the aortic root and ascending aorta, as late aortic dilation does occur.
10. Medical therapy for BAV-associated aneurysm should be considered at aortic size >4.0 cm. Beta-blockers are recommended (Class IIa recommendation). If hypertension is present, an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker can be considered. Lifestyle modifications, such as eliminating high-intensity weight lifting and avoidance of competitive sports when the aorta is >4.5 cm, are also recommended.
Keywords: Heart Valve Diseases, Matrix Metalloproteinase 2, Hypertension, United States, Echocardiography
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