Abstract
Cardioplegic protection during ischemic arrest is impaired in patients with serious coronary artery disease, resulting in large regional temperature gradients and impaired myocardial cooling. Recent data have suggested that the viscosity of cardioplegic solutions may affect their distribution beyond coronary artery stenosis. This study compared the effects of asanguineous and blood cardioplegic solutions on myocardial cooling in 26 such patients who underwent elective myocardial revascularization; 15 were subjected to blood cardioplegia and 11 to crystalloid cardioplegia. One litre of blood or asanguineous cardioplegic solution was infused into the aortic root at a constant infusion pressure. Samples for viscosity determination were taken from both cardioplegic solutions during their infusion. Regional myocardial temperature was measured distal to coronary artery obstructions following administration of the cardioplegic agent. Although the viscosity of the blood solution was 250% greater than the asanguineous solution, regional myocardial temperatures were not significantly different beyond the coronary artery stenosis. Regional temperature was reduced to less than 15 degrees C after infusion of the cardioplegic agent in regional myocardium with a normal coronary circulation. Marked temperature gradients were observed distal to a critical stenosis, with temperatures ranging between 18 degrees C and 20 degrees C for stenosis, and about 23 degrees C for obstruction. The authors conclude that the marked difference in viscosity between crystalloid and blood cardioplegic solutions does not significantly affect their distribution beyond a coronary artery stenosis.