Coronary sinus pressure and arterial venting do not affect retrograde cardioplegia distribution.

Retrograde techniques for the administration of cardioplegia solutions are of interest because of their relative practical convenience, and because of the possibility that they provide better delivery to myocardial regions jeopardized by coronary stenosis than can be achieved with traditional antegrade techniques. This study was designed to test the following three hypotheses about how the distribution of cardioplegia by retrograde techniques might be optimized: (1) venting an occluded coronary artery improves the distribution of cardioplegia to the myocardial region originally supplied by it; (2) increasing the coronary sinus perfusion pressure makes the distribution of cardioplegia through the myocardium more uniform; and (3) increasing the driving pressure, as achieved by increasing the coronary sinus perfusion pressure or occluding a left coronary artery, improves the distribution of flow to the right ventricular free wall and interventricular septum. Tracer microspheres infused retrogradely with cardioplegia solution into canine hearts in vitro showed that the distribution of flow through the coronary sinus is consistently and significantly nonuniform, and is not significantly altered by coronary arterial occlusion and venting, or by increases in coronary sinus perfusion pressure.