The Trileaflet Mitral Valve.

With the advent of 3-dimensional echocardiography, visualization of the mitral valve has greatly improved. Recently, there has been an increase in reporting of a distinct entity called the "trileaflet mitral valve" using 3-dimensional echocardiography. It is controversial whether this is a new entity or an improved visualization of isolated mitral valve clefts or trifoliate left atrioventricular valve in the setting of an atrioventricular septal defect (AVSD) with intact septum. We present a case of a trifoliate valve, interpreting our findings based on a systematic review of previous publication on trileaflet mitral valves, isolated clefts in the mural (posterior) leaflet of the mitral valve, and trifoliate left atrioventricular valves with AVSD and intact septal structures. We describe the latter entity as a left atrioventricular valve because it never achieves the features of a normal mitral valve. We compare the features of isolated clefts of the mural leaflet of the mitral valve with trifoliate left atrioventricular valve found in the setting of AVSDs with intact septal structures to illustrate the current controversy regarding these conditions. In conclusion, our review suggested the reported trileaflet left atrioventricular valves is likely a misnomer because of a lack of consideration of embryologic development and nomenclature, rather than a greater appreciation and identification of a new distinct disease entity.