Clinico-morphologic integration in the surgical repair of atrioventricular septal defect with common atrioventricular junction

Atrioventricular septal defect with common atrioventricular junction has been successfully managed surgically for 50 years now. In this time, operative mortality has fallen from 60% to some 2-3% in the modern era. Despite this, almost 10% of these patients develop significant regurgitation of the left atrioventricular valve requiring re operation within ten years. This figure has not changed in this time. So although patients are surviving more than ever, their ultimate outlook, and potential quality of life has not changed despite major advances in other areas. In this thesis, I have gone back to first morphologic principles and examined why long-term valve failure has remained disconcertingly stagnant. The detailed morphology of the trifoliate left atrioventricular valve in atrioventricular septal defects was compared it to its bicuspid normal counterpart, the mitral valve. This latter structure is the "Gold Standard" that the surgically repaired valve should aspire to, with pliable leaflets that are supported with a well-organized subvalvar tension apparatus. Even after bicuspidization of the trifoliate valve in atrioventricular septal defects, this morphologic standard set by the mitral valve is never achieved. One reason for this lies in the so-called Zone of Apposition of the left atrioventricular valve, the area between the left side of the bridging leaflets in the trifoliate valve has both been described as a "cleft" or else a "commissure". This study demonstrates that, morphologically, it is neither, and closure of this Zone in order to bicuspidize the valve does not restore mitral anatomy. Furthermore, this Zone is highly variable in its morphology, and has poor subvalvar support compared to the mitral arrangement. Finally, the results of repair of atrioventricular septal defects at Great Ormond Street Hospital in the least 10 years were analysed, emphasising the notion that in this modem era, when surgical mortality has been overcome, we should integrate morphologic understanding wih surgical practice ...