Objective To explore the etiology and risk factors of mitral regurgitation in patients with bicuspid aortic valve (BAV).

Methods Data from 4 352 patients with BAV diagnosed by echocardiography from January 2011 to June 2016 in Zhongshan Hospital, Fudan University were retrospectively analyzed.

Results Among 4 352 BAV patients, 256(5.9%) had moderate-to-severe mitral regurgitation, including 195 (76.2%) male, 206 (80.5%) moderate-to-severe aortic valve dysfunction, and 15 (5.9%) combined with other congenital heart diseases. Among 256 mitral regurgitation patients, functional mitral regurgitation accounted for 61.7% (158/256), with age and moderate-to-severe aortic valve dysfunction as its independent risk factors (P < 0.001); organic mitral regurgitation accounted for 38.3% (98/256), with aortic root dilatation as its independent risk factor (P=0.012). Mitral valve prolapse (MVP) was the most prevalent cause of organic mitral regurgitation (63, 64.29%), among which 19.0% (12/63) were Barlow disease. The aortic root diameter and the proportion of anterior leaflet prolapse were greater in BAV-MVP patients with Barlow disease than those without Barlow disease (P < 0.05).

Conclusion The etiology of mitral regurgitation is complex among BAV patients. Functional mitral regurgitation is more prevalent and associated with age and aortic valve dysfunction. MVP was the main cause of organic mitral regurgitation, among which Barlow disease presented syndromic traits including anterior leaflet prolapse and aortic root dilatation.