The purpose of these studies is to determine the efficacy and safety of augmenting blood flow to the ischemic myocardium. The rationale is that both endstage coronary disease and hypertrophic cardiomyopathy result in global or regional ischemia at rest which is severely exacerabated by any increase in cardiac work. The clinical manifestations are angina pectoris, fatigue and malignant forms of ventricular tachycardias. Over the past two years more than 60 dogs have had applications of one to two ameroid constrictors to the left anterior descending coronary artery and the circumflex coronary artery and an internal mammary artery (IMA) implanted into the zone(s) of ischemia. New efforts to develop a series of standard ameroid constrictors has been made so that closure times are reproducible at 30, 60 and 90 days. Previous data have demonstrated that: 1) an IMA implant is protective to the development of myocardial infarction; 2) all IMA implants remained open and collateralized to native vessels; and 3) blood flow through the IMA represented 15 - 20% of normal resting flow per gram of tissue. Extracardiac myocardial blood flow was augmented by catecholamine administration as determined by serial radioactive microsphere injections but not by the addition of an omental overlay. New data demonstrate that the entire left ventricle can be made slowly ischemic by two ameroid constrictors and be totally supported by two IMA implants. Studies performed at 9 or more months after the implants demonstrate: 1) complete closure of the native vessels of the left ventricle; 2) marginal aerobic metabolism at rest with evidence of ischemia as shown by increased coronary sinus lactate concentrations with minimal increase in heart rate; and 3) diminished left ventricular wall motion. These data suggest that dual internal mammary implants alone are insufficient to supply the metabolic requirements of the left ventricle of the dog and that collateral enrichment techniques, additional sources of blood supply must be sought to totally support the left ventricle under basal conditions and with exercise.
