The long-term effects of cold potassium cardioplegic arrest was examined in 40 patients who underwent myocardial revascularization. Comparisons between resting ejection fraction (EF), end diastolic volume (EDV), and segmental wall motion were made between the preoperative and postoperative catheterization (mean postoperative recatheterization, 6 months). A 2.93 graft per patient ratio was found in this group of patients, with 108/117 grafts visualized at the time of recatheterization. The EF was 60% ± 3% before surgery and 62% + 3% after surgery. A correlation coefficient of 0.91 was determined for the entire series. The EDV was 151 i 16 cc before coronary artery bypass graft (CABG) and was unchanged post CABG at an end diastolic volume of 137 ± 15 cc. Analysis of preoperative wall motion of 33 patients demonstrated 111 depressed segments, 68 normal, and 52 hypercontractile; at recatheterization, there were 100 depressed, 66 normal, and 65 hypercontractile segments. Although there was essentially no deterioration of myocardial function for 37 out of 40 patients, three demonstrated a reduction in EF, the largest reduction being 15%. These three patients had a cardioplegic arrest time greater than 70 minutes. An inverse relationship between percnt change in EF and the length of cardioplegic arrest was observed, with an r value of - 0.57 (p < 0.01). These data suggest that prolonged cardioplegic arrest times may be associated with mild dysfunction. Cold potassium cardioplegic arrest up to 70 minutes was associated with no change in EF, EDV, or wall motion in this series of patients.