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Coronary artery bypass in 150 patients with angina has been accomplished with 225 IMA grafts and 85 saphenous vein grafts. There were 7 (4.7%) hospital deaths. Posterative catheterization in 85% of patients revealed that 9 (4.7%) IMA grafts and 11 (15%) vein graft had thrombosed. One-year catheterization in 32 patients (38 IMA grafts and 13 vein grafts) revealed no additional graft failures. The better patency of the IMA grafts appears to be related to their smaller size and therfore greater velocity of blood flow and freedom from intimal proliferation.

Enthusiasm for new therapeutic modalities frequently results in a ground swell of overuse, which recedes to leave a trough of negativism before a definitive level is established. In the case of CABG, the ground swell has become a 10-year flood tide, without an ebb, although ripples have marred the surface. It is generally agreed that suitable control populations are needed to determine the role of a therapy and that the best controls would arise from randomized prospective trials. At present, the best randomized trial is the VA study which has shown that operation does not enhance longevity for single vessel disease, but clearly does for left main coronary disease. In those individuals with two- and three-vessel disease, the VA study has not shown that surgical therapy is better than medical treatment. However, three other studies containing patients selected by the VA criteria indicate that operation provides significantly greater longevity for patients in these two categories. Acceptance of this position requires acknowlegement of the validity of the VA study and the comparison of extramural concurrent surgical series.

These data would suggest that hypothermia combined with potassium cardioplegia enhances protection of the ischemic myocardium over other available techniques. The ideal conduct of this myocardial protection is not yet apparent but certain aspects are worthy of emphasis. (1) With the onset of ischemia cardioplegia should be immediately induced to abolish contractile activity and conserve energy. An advantage of blood cardioplegia is that there is no ischemia or it is trivial priorto cardioplegia. (2) The greater the degree of myocardial cooling the better. Although a myocardial temperature of 20 degrees C can commonly be achieved with perfusion hypothermia and topical hypothermia, it is possible to reduce myocardial temperature to 10 degrees C or lower with these same modalities. Because perfusion hypothermia provides fairly uniform rapid myocardial cooling, this should be maximally utilized by cooling of the systemic perfusate to 20 degrees C and cooling the cardioplegic infusate to 4-10 degrees C. Cardiac hypothermia should be maintained with crushed ice made from electrolyte solution or irrigation of the pericardial sac with cold electrolyte solution. The greater the degree of systemic hypothermia the less tendency for the myocardium to warm. (3) The ideal concentration of potassium is unknown at this time with a range of 15-40 mEq/l having been utilized without apparent potassium injury. (4) The ideal composition of the vehicle may never be defined and may not be of great importance. Whole blood would appear to offer physiological and pragmatic advantages over asanguinous vehicles. (5) The safe duration of ischemia has been moderately well defined. 1 h is well tolerated in the dog using profound cardiac hypothermia, whereas 30-45 min with lesser degrees of hypothermia is acceptable. When the interval of ischemia is to be 2 or 3 h reinfusion of potassium every 20-30 min has proven safe both experimentally and clinically.