Selective Retrograde Venous Revascularization of the Myocardium when PCI or CABG Is Impossible: Investigation in a Porcine Model

Abstract

We investigated the possibility of nourishing the myocardium through selective retrograde coronary venous bypass grafting (CVBG) with an off-pump technique and evaluated various methods of monitoring the physiological effects of this procedure. In a porcine model, the left internal mammary artery (LIMA) was anastomosed to the left anterior descending coronary vein (LAD vein) in an off-pump procedure. The LAD vein was ligated proximal to the anastomosis. The LAD artery was ligated proximally. The physiological effects were monitored using microdialysis, tissue oxygen tension, blood flow in LIMA, blood samples, and hemodynamic and histological analyses. As controls, 5 pigs underwent surgery involving only LAD artery ligation without CVBG. CVBG with LAD ligation was performed in 16 pigs; 12 survived CVBG and were monitored for 2-2.5 hours while in sinus rhythm, a 75% salvage rate after an otherwise lethal LAD artery occlusion. Immediately after LAD artery ligation, the anterior wall of the left ventricle became cyanotic and hypokinetic. Over time it regained color and contractility as flow in the LIMA increased. Microdialysis showed a significant increase in lactate. Initially tissue oxygen tension decreased, but with time some recovery was seen. Cardiac troponin T was elevated. Histological analysis showed ischemic changes. In control pigs, microdialysis was performed for 1.5 hours up to LAD artery ligation, after which all pigs died in ventricular fibrillation arrest. No increase in lactate was observed. These results indicate that after LAD artery occlusion, CVBG can nourish the myocardium to a certain extent and prevent death in the majority of cases, although varying degrees of ischemia remain.