Coronary flow obstruction in percutaneous aortic valve replacement. An in vitro study.

OBJECTIVE Coronary flow obstruction is a serious complication reported in percutaneous aortic valve replacement. In an in vitro study of porcine hearts, the effects of valved stent implantation on coronary artery flow were studied with the native valve's leaflets intact and excised. METHODS The right and left main coronary arteries of porcine hearts were dissected 20mm distal to the aortic root and directed into lengths of latex tubing leading to collection flasks. The ascending aorta was cut proximal to the brachiocephalic trunk, cannulated, and attached to a constant-head water supply. After steady flow was achieved, the flow rate from each coronary artery was measured. In Group A (n=10), a tubular pericardial valve sutured into a cylindrical, cobalt-nickel stent was deployed orthotopically using a valvuloplasty balloon catheter. In Group B (n=10), the native leaflets were removed before similar valve deployment. Coronary flow measurements were repeated post-implantation. RESULTS In Group A, valve implantation resulted in a significant decrease in both left and right coronary flows. In Group B, no significant change in either right or left coronary flow was found after valve placement. CONCLUSION Implantation of a percutaneous valved stent in the orthotopic position with the native valve in place causes coronary ostial obstruction. This problem highlights the need for modified stents that are designed for implantation in patients with non-retracted, fibrotic, or calcified leaflets.