Flail refers to the disorganized, unpredictable, haphazard movement of a leaflet of one of the heart valves.
The mitral valve is quite often involved in disease processes, which cause a leaflet of the valve to rupture and become flail as a result of not having proper support of the chordae tendineae (see figures 116, 118, 119, 104b).
Some of these diseases include myxomatous degeneration, myocardial infarction, infection, trauma, genetic, and congenital defects.