A comparison of retrograde cardioplegia versus antegrade cardioplegia in the presence of coronary artery obstruction.

Cardioplegic protection is limited by nonhomogeneous distribution of solutions distal to coronary artery obstructions. Using temperature mapping and sonomicrometry crystals implanted in the distributions of the left anterior descending (LAD) and circumflex coronary arteries, we studied the effects of blood cardioplegia delivery through the aortic root versus the coronary sinus in 10 dogs with a temporarily occluded LAD. All dogs were placed on cardiopulmonary bypass and cooled to 28 degrees C; the aorta was cross-clamped for two hours with the LAD occluded. Group 1 (N = 5) had cold (4 degrees C) potassium chloride cardioplegia (20 mEq per liter of KCl) administered through the aortic root at 20-minute intervals; Group 2 (N = 5) had the same solution infused through the coronary sinus by a balloon catheter. After two hours, the LAD snare was released and the dogs were weaned from bypass. Aortic root cardioplegia resulted in very poor cooling distal to the coronary obstruction with very poor systolic function and loss of diastolic compliance. In contrast, coronary sinus cardioplegia resulted in normal cooling distal to the coronary obstruction and complete return of systolic and diastolic functions following the experimental procedure. We conclude that cardioplegia administered through the coronary sinus offers superior cooling distal to coronary artery obstructions while preserving myocardial function in all areas. In contrast, delivery of cardioplegia through the aortic root causes severe depression in the myocardium distal to obstructions.