Evaluation of procedure designed to enhance coronary collateral blood flow.

• The high incidence of coronary artery disease in man has prompted extensive research efforts in the direction of improving blood flow to the heart muscle. Attempts to achieve this goal have taken many forms and may be summarized as follows: (1) scarifying procedures designed to encourage the growth of new vascular channels into the heart from extracardiac sources; (2) retrograde perfusion of the myocardium via the coronary sinus; (3) direct surgical removal of the obstructing lesion in the coronary vessels with or without replacement of a segment of coronary arteries; (4) myocardial implantation of a large extracardiac artery; (5) ligation of an internal mammary artery; (6) combinations of one or more of the above procedures. Since (a) retrograde perfusion via the coronary sinus is only of temporary value, (b) internal mammary artery ligation does not divert blood to the myocardium, and (c) surgical removal of coronary thrombi and replacement of diseased vessel segments are still extremely difficult and hazardous, procedures involving the production of vascular adhesions between the heart and other tissues, or arterial implantations into the myocardium are currently in favor. Practically all of the methods described appear to increase the collateral circulation of the heart of the normal experimental animal. Whether they are equally effective in the arteriosclerotic heart remains to be demonstrated. In humans with coronary artery disease objective improve-