Early detection of left ventricular dysfunction in patients with mitral regurgitation due to flail leaflet is still a challenge.

Lack of normal mitral leaflet apposition and abnormal pointing of the flail component into the left atrium (LA) during systole are typical features of mitral leaflet flail which generate haemodynamically relevant mitral regurgitation (MR). The most common reason for mitral leaflet flail is chord rupture. Rarely, severe prolapse with the leaflet tip bulging into the LA causing severe MR can also occur without chord rupture. The flow direction impacting the mitral leaflets and anatomical features of the leaflets in patients with mitral valve prolapse (MVP) may facilitate chord rupture. Rupture of the chord or papillary muscle is the major cause of acute severe MR due to mitral leaflet flail. Flail mitral leaflet is associated with significant risk of developing left ventricular (LV) dysfunction, atrial fibrillation, pulmonary hypertension, tricuspid regurgitation (TR), heart failure, and sudden death. 3 Although MVP has a higher prevalence in younger women, mitral leaflet flail often affects males .50 years of age. The aetiology of mitral leaflet flail is complex. Prolapsed myxomatous mitral valves show collagen and elastic tissue alterations, and in spontaneously ruptured mitral chords the myxomatous process often involves mitral chords and papillary muscles. In spontaneously ruptured chords, collagen types III and AB are often absent. Impaired mechanical properties due to collagen alterations and acid mucopolysaccharide accumulation in the mitral leaflets and chords may lead to spontaneous chord rupture. Myxoid chords are more extensible and weaker than normal chords and the failure resistance is more likely to be compromised in the chord than in the leaflet. Relevant fibrosis of the myxoid chords, particularly near their insertion into the leaflets, is also frequent and can contribute to the alteration of mechanical properties. Other aetiologies that can be implicated are bacterial endocarditis and mitral annular calcification. The chords of the posterior leaflet are shorter and thinner than those of the anterior mitral leaflet. Therefore, the posterior mitral leaflet is more vulnerable to stress. Being also more liable to myxomatous processes the posterior leaflet is more frequently the origin of mitral leaflet flail. Mitral leaflet flail appears to be predominantly characterized by independent P2 (55%) flail, followed by entire posterior leaflet flail (8%), P2,3 flail (7%), and A2 flail (7%). 1