Coronary circulation and myocardial oxygen consumption after extracorporeal circulation and after cardioplegic arrest.

The influence of haemodilution or of blood perfusion on the coronary circulation, myocardial oxygen consumption and on haemodynamic parameters was examined in two comparable groups of patients with slight congenital acyanotic cardiac malformation without indications of myocardial damage. In a third group of patients similar data were collected before and after artificial cardiac arrest by cardioplegic solutions. No findings concerning this question could be found in the literature. Coronary circulation was measured by the argon-gas-technique of Bretschneider et al. A fall in haemoglobin of 4.8% caused by haemodilution resulted in the first group in an increase in the cardiac index of about 8% and an increase in the coronary circulation of about 100% over the initial value with a simultaneous decrease in the coronary resistance due to coronary dilatation and reduction in blood viscosity. The myocardial O2 consumption was raised in spite of an increase in the coronary-venous O2 saturation and a clear reduction in the AVD O2. In contrast, the patients in the blood perfusion group showed no change in the coronary circulation and coronary resistance although a decrease of the myocardial O2 consumption was observed. The cardiac index fell to about 16% in these patients. After cardioplegic cardiac arrest there was no significant reduction in myocardial blood flow except for a decrease of myocardial oxygen consumption of about 20% The results are discussed and cantra-indications of haemodilution perfusion and cardioplegic cardiac arrest mentioned.