Myocardial Temperatures in Clinical Cardioplegia

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Abstract
Intramyocardial temperature gradients developing during and following cold infusion cardioplegia were studied in patients operated upon for coronary and for valvular heart disease as a function of systemic blood- and ambient temperatures. Following cardioplegic infusion septal temperature fell more profoundly than that of the lateral and particularly the inferior wall of the left ventricle in both groups of patients. In those with multiple coronary heart disease and in the presence of grossly viable myocardium, distribution of cold within the left ventricle was not affected by the degree of coronary obstruction. The spontaneous septal rewarming rate was greater in coronary than in valvular heart diesease. The rate of temperature rise at any of the measuring sites depended upon the level of systemic blood temperature, on the removal of warm collateral blood from the cardiac cavities and particularly upon the presence or absence of cold pericardial irrigation. It is concluded that near homogeneous cooling of the heart only can be achieved and maintained in clinical cardioplegia when the influence of extracavitary and intracavitary heat sources is minimized. In prolonged clinical cardioplegia systemic blood temperature should be kept low, the cardiac cavities drained of collateral blood, topical cooling maintained and the heart shielded within the pericardium.

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