Coronary sinus retroperfusion: can forward progress still be achieved by using a backward technique?

T I n this month’s edition of the Journal, Syeda and colleagues report the results of a meta-analysis performed on randomized experimental trials to assess the efficacy of coronary sinus retroperfusion by using intermittent coronary sinus occlusion (ICSO) and synchronized retroperfusion (SRP) to salvage acutely ischemic myocardium. In the ICSO technique a balloon-tipped catheter is positioned just beyond the orifice of the coronary sinus, similar to the placement of a retrograde coronary sinus cardioplegia catheter. The catheter is connected to a pneumatic pump that automatically inflates and deflates the balloon according to a preset cycle. A cycle of 10 seconds of inflation and 4 seconds of deflation was found to be the optimal period to limit the increase of pressure in the coronary sinus. This allows for sufficient drainage of coronary venous blood and avoids the complications of hemorrhage, edema, thrombosis, and arrhythmias observed with prolonged increase of coronary sinus pressure. This ability to limit peak coronary sinus pressure led to the term pressure-controlled intermittent coronary sinus occlusion (PICSO). The sudden occlusion of a coronary artery results in a significant decrease in coronary sinus pressure. By increasing coronary sinus pressure, PICSO redistributes coronary venous flow to jeopardized areas of the myocardium distal to an arterial occlusion. The intermittent inflation-deflation cycle also enhances the washout of toxic metabolites that form during periods of coronary occlusion and ischemia. In contrast to PICSO, which displaces existing coronary venous blood, SRP actively pumps arterial blood retrograde through the coronary sinus. In this technique a catheter is placed in the femoral artery, and arterial blood is withdrawn and pumped into the coronary venous system during diastole through a catheter positioned into the coronary sinus. The meta-analysis by Syeda and colleagues of 7 experimental studies in which PICSO was performed during an acute coronary occlusion revealed a 29% reduction in infarct size (P .001), which increased to 39% when PICSO was combined with SRP. Our experimental studies, performed in a porcine model of acute coronary occlusion with reperfusion on cardiopulmonary bypass and cardioplegic arrest similar to urgent-emergency coronary artery bypass graft (CABG) surgery, support these favorable effects of PICSO in salvaging ischemic myocardium. PICSO enhanced the distribution of antegrade cardioplegia, improved regional wall motion and global left ventricular function, decreased tissue acidosis, and decreased infarct size. When combined with percutaneous bypass and intra-aortic balloon pump (IABP) support in the same model, PICSO resulted in more complete reversal of ischemic damage than was observed from each individual modality alone. Mohl and coworkers showed that PICSO could be used clinically when they applied this technique in 15 patients undergoing multivessel CABG for 60 minutes during the reperfusion period. PICSO resulted in a significant improvement in regional wall motion in segments that were previously