Flail mitral leaflet (FML) is a common complication of mitral valve prolapse, often leading to severe mitral regurgitation (MR) and left ventricular dysfunction. In the absence of timely surgical correction, survival is significantly impaired. Early recognition of FML and identification of risk factors is important because early intervention increases the chances of survival.

We studied 123 patients undergoing mitral valve surgery for severe MR caused by myxomatous disease. Chart review, echocardiography, and tensile testing were performed.

Thirty-eight patients had FML, and 85 patients had non-flail mitral leaflet (non-FML). Patients with FML were younger (53.7 ± 1.8 vs 59.3 ± 1.4 years, P = .02), had more severe MR (3.89 ± 0.04 vs 3.76 ± 0.04, P = .02), were less likely to be in New York Heart Association class III or IV heart failure (5% vs 20%, P = .037), and were less likely to have bileaflet mitral valve prolapse (5% vs 38%, P <.001) than non-FML patients. Valve tissue from patients with FML had less stiff chordae (23.5 ± 3.6 vs 59.1 ± 11.7 Mpa, P = .006) that tended to have a lower failure stress (3.8 ± 0.9 vs 9.6 ± 2.2 Mpa, P = .07) and had more extensible leaflets (56.4% ± 7.9% vs 42.9% ± 2.7% strain, P = .04) compared with that of non-FML patients.

The development of FML may result from intrinsic tissue abnormalities and is associated with a distinct subset of the myxomatous population. Identification of such clinical characteristics in this population and knowledge of an implicit mechanical abnormality of valve tissue may further the argument for early surgical correction.