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Coronary circulation and myocardial oxygen consumption after extracorporeal circulation and after cardioplegic arrest
Insights
Hemodilution significantly increased coronary circulation and myocardial oxygen consumption, while blood perfusion decreased it. Cardioplegic arrest minimally impacted myocardial blood flow but reduced oxygen consumption.
Area of Science:
- Cardiovascular Physiology
- Cardiac Surgery
Background:
- Understanding the effects of hemodilution, blood perfusion, and cardioplegic arrest on cardiac function is crucial for managing patients with congenital heart defects.
- Limited literature exists on the specific impacts of these interventions on coronary circulation and myocardial oxygen consumption in this patient population.
Purpose of the Study:
- To investigate the influence of hemodilution, blood perfusion, and cardioplegic arrest on coronary circulation, myocardial oxygen consumption, and hemodynamic parameters.
- To compare the effects of these interventions in patients with slight congenital acyanotic cardiac malformation.
Main Methods:
- Coronary circulation measured using the argon-gas-technique.
- Three groups of patients studied: hemodilution, blood perfusion, and cardioplegic cardiac arrest.
- Hemodynamic parameters, cardiac index, coronary resistance, and oxygen saturation were monitored.
Main Results:
- Hemodilution (4.8% Hb fall) increased cardiac index by 8% and coronary circulation by 100%, decreasing coronary resistance due to vasodilation and reduced blood viscosity. Myocardial O2 consumption increased despite higher coronary-venous O2 saturation and reduced AVD O2.
- Blood perfusion led to no change in coronary circulation or resistance, but decreased myocardial O2 consumption by approximately 16%.
- Cardioplegic cardiac arrest resulted in no significant reduction in myocardial blood flow, but a 20% decrease in myocardial oxygen consumption.
Conclusions:
- Hemodilution significantly enhances coronary circulation and myocardial oxygen consumption, necessitating careful consideration in cardiac patients.
- Blood perfusion and cardioplegic arrest appear to reduce myocardial oxygen demand, with implications for surgical strategies.
- Contraindications for hemodilution perfusion and cardioplegic cardiac arrest are discussed based on these findings.
Abstract:
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.