Passive infusion: a simple delivery method for retrograde cardioplegia

Some damage to the capillaries and increase in myocardial edema have been shown when retrograde cardioplegia perfusion pressure exceeds 40-50 mmHg, or possibly when it falls within this pressure interval. To avoid these complications, we designed a very simple delivery method for retrograde cardioplegia: passive continuous infusion by gravitational force alone. From August 2002 through April 2003, 147 patients undergoing elective coronary artery bypass surgery were randomly allocated into 2 groups. In both groups, isothermic blood cardioplegic solution was infused continuously in a retrograde fashion, after antegrade cardioplegic arrest. Group 1 (n=76) received retrograde infusion passively by gravitational force, while Group 2 (n=71) received retrograde infusion from a manually controlled pressure bag, with the pressure maintained at about 40 mmHg. Myocardial biopsy specimens were taken just before the aorta was declamped, and myocardial edema was scored upon histopathologic examination. Postoperative myocardial damage was evaluated with periodic measurements of CK-MB isoenzyme and cardiac troponin T levels. We recorded cardioplegic infusion pressures and rates, and the total amount of potassium administered. The mean cardioplegic infusion pressures and rates, total potassium levels, and cardioplegic solution amounts were significantly lower in Group 1 than Group 2. Histologic observations revealed significantly less myocardial edema in Group 1. There were no differences between groups in CK-MB isoenzyme or cardiac troponin T levels, mortality, or morbidity. Retrograde continuous infusion of isothermic blood cardioplegic solution by gravitational force alone appears to provide satisfactory myocardial protection and to eliminate the harmful effects of higher pressures upon the myocardium.