Comparison of distribution beyond coronary stenoses of blood and asanguineous cardioplegic solutions

Abstract

In seven dogs on cardiopulmonary bypass, a critical stenosis (75% to 90%) of the left anterior descending coronary artery (LAD) was produced. Alternate 250 ml/min infusions of asanguineous and blood cardioplegic (4 degrees C) solutions were made for 3 to 5 minutes. Poststenotic flow (flowmeter), intramyocardial temperature, and aortic pressure were measured. During cardioplegic infusions of 250 ml/min, aortic pressure was 34 +/- 4 mm Hg higher with blood cardioplegia than with asanguineous cardioplegia (82 +/- 7 versus 48 +/- 8 mm Hg). Poststenotic cardioplegic flow was 39% +/- 9% higher (29 +/- 5 versus 18 +/- 5 ml/min) with blood cardioplegia. Consequently, blood cardioplegia resulted in more rapid arrest (20 +/- 2 versus 45 +/- 5 seconds) and lower myocardial temperature (6 degrees +/- 1 degree C) in the region of LAD blood supply; posterior ventricular myocardial cooling was similar (unobstructed vessels) with both solutions. These data show that the reduced viscosity of asanguineous cardioplegia compared to blood cardioplegia results in lower aortic pressure. Consequently, the higher aortic pressure with blood cardioplegia results in superior cardioplegic delivery beyond obstructed coronaries and better myocardial cooling. We conclude that the decreased viscosity of 4 degrees C asanguineous cardioplegia causes diversion of cardioplegic solution from the obstructed to the normal coronary bed.