Regional myocardial protection by retrograde coronary sinus infusion of cardioplegic solution

Antegrade administration of a cardioplegic solution in the presence of a coronary artery stenosis may lead to the heterogeneous distribution of the agent and poor myocardial cooling distal to a vessel stenosis. To determine the effects of retrograde coronary sinus infusion of cardioplegic solution, coronary stenosis was created in the canine preparation by occluding the left circumflex artery (LCx) during cardioplegic arrest. Left ventricular global and regional function (assessed by sonomicrometry and solid-state micrometers) were studied after 60 min of ischemic arrest. Three groups (all n = 7) were studied: group I (control), cardioplegic solution infused via the aortic root without LCx occlusion; group II, same as group I except with LCx occlusion; group III, retrograde coronary sinus infusion of cardioplegic solution with LCx occlusion. Heart rate was controlled by atrial pacing. Statistically significant differences in global function between the three groups were seen at low filling pressures but were not seen during volume challenge. However, the recovery ratio of regional function in the LCx area at a left atrial pressure of 5 mm Hg in group II was 77.2% (% shortening) and 48.5% (segment work), which was significantly less (p < .01) than recovery in group 1 (111.7% and 75.9%) and group III (108.3% and 81.5%). These differences persisted during volume loading, to a mean left atrial pressure of 15 mm Hg. Regional compliance in group II was also significantly (p < .01) depressed after cardioplegic arrest but was well preserved in groups I and III. Myocardial temperature in the LCx region was higher in group II than in groups I and III throughout cardioplegic arrest (p < .01). We conclude that retrograde infusion of cardioplegic solution improves myocardial protection distal to a critical coronary occlusion.