Haemodynamic and thermographic signs of intramyocardial venous outflow redistribution induced by coronary sinus occlusion in the canine heart.

Short occlusions of the coronary sinus (CS) were performed in open chest dogs in order to study the clinico-physiologic aspects of changes induced by this manoeuvre both in intracoronary pressure distribution and myocardial blood supply. It was found that when mean CS blood flow (EM flowmeter) was plotted against mean CS pressure during the gradual blockade of the CS outflow, a perfectly linear relation could be established between these variables beyond the physiologic CS pressure range (greater than 10 mmHg). Inotropic stimulation (adrenaline administration), without affecting its basic characteristics, shifted this line to higher pressure-flow ranges. On occluding the sinus, intracoronary arterial pressure distal to the ligated LAD branch also increases, but to a lesser degree than CS outflow pressure; within the ischaemic zone this results in a complete reversal of the arteriovenous pressure gradient during a considerable part of the cardiac cycle. Blood supply to the non-ischaemic heart was estimated with the aid of the computerized thermographic method developed by the authors. It was demonstrated that cardiac heat emission reflecting changes in subepicardial blood flow is singularly little affected by CS occlusion. From all these findings it is evident that occlusion of the CS involves a drastic coronary outflow redistribution but not a drastic inflow reduction in the heart. The results were interpreted in terms of newly developed cardiosurgical procedures aimed at to preserve myocardial viability, and it was concluded that the occurrence of adverse coronary actions offsetting the potential benefits of these procedures is of very low probability.