Discussion
Acquired LV-RA communication is a rare condition, that results from endocarditis, blunt trauma, myocardial infarction, or complication of cardiac surgery (1-7). The most common cause of acquired LV-RA communication is previous cardiac surgery, such as aortic or mitral valve replacement (6,7). In valve replacement surgery, excessive debridement of annular calcification leads to paravalvular leakage, left ventricular rupture, or intracardiac shunts. However, TAP with a prosthetic ring is uncommon cause of this complication. In our case, although debridement of annular calcification at the posteromedial site was performed in the previous MVR, the location of the defect did not match that site. Anatomically, a septum between the LV and RA is created by a more apical displacement of the tricuspid annulus than the mitral valve, posterior to the membranous septum and separated from the interventricular part by the attachment line of the tricuspid valve (8). If the sutures for TAP are placed incorrectly on this atrioventricular membranous portion at the anteroseptal commissure, dehiscence of the prosthetic ring may occur, leading to LV-RA communication. An inadequate suture was presumed to be the main cause of the LV-RA communication in our case, because the annulus of the anteroseptal commissure was intact. Additionally, if excessive removal of the calcification of the mitral annulus leads to LV-RA communication, the defect should be more cephalad and rightward due to the difference in annulus levels between the mitral and tricuspid valves. Aggressive correction of a markedly dilated tricuspid annulus is speculated to be another factor contributing to this complication. This causes excessive tension at the suture sites, especially when a rigid prosthetic ring is used.
The defects are basically formed as a result of laceration of fragile tissue, by conditions such as endocarditis, myocardial infarction, or excessive decalcification; therefore, patch closure of the defect is recommended for surgical repair of LV-RA communication, with repair sutures placed outside the involved tissue. As the defect locates more cephalad in the case of excessive decalcification for MVR, stitches for closure are placed simply around the defect. However, in our case, as the lower margin of the defect was bordered by the annulus of the tricuspid valve, interrupted stiches for the caudal part were placed on the interventricular septum to avoid the conduction system. We had to resect the anterior edge of the prosthetic ring during this procedure, which interfered with defect closure.
Although surgical repair of the LV-RA communication is standard, it is technically risky and demanding, after the cardiac surgery. Some studies have reported using transcatheter repair for this (9), and this could be further developed using advanced three-dimensional diagnostic ware and by improving closure devices in the future.