Evaluation of the effects of systemic nitroglycerin on perfusion of ischemic myocardium in coronary heart disease assessed intraoperatively by antegrade blood flow through intact saphenous vein bypass grafts.

To evaluate systemic nitroglycerin (NTG) effects on reduced perfusion of ischemic myocardium in coronary disease, intravenous NTG actions on coronary circulatory dynamics were directly assessed intraoperatively during aortocoronary bypass surgery in 24 patients. Thus metered antegrade blood flow was measured through 56 separate intack saphenous vein bypass grafts to analyze NTG perfusion response in the obstructed native coronary artery (CA). In 34 bypassed CA with proximal luminal diameter narrowing greater than 50% to 90%, NTG reduced (p less than 0.01) graft flow (GF) 82 to 63 cc/min, thereby indicating that NTG dilated proximal stenoses with resultant increased CA flow. In 11 bypassed CA obstructed greater than 90% to 100% with well developed collaterals distally, NTG decreased (p less than 0.05) GF 64 to 53 cc/min, thus indicating enhanced collateral flow. In contrast, in 11 bypassed CA obstructions greater than 90% to 100% without collaterals, that NTG increased (p less than 0.02) GF 91 to 100 cc/min indicated NTG nonresponsiveness of the severely diseased CA. Thus systemic NTG improves perfusion to ischemic myocardium subserved by diseased coronaries with less than 90% stenosis or by greater than 90% obstructed vessels with substantial collaterals distally.

Incremental intravenous nitroglycerin for control of afterload during anesthesia in patients undergoing myocardial revascularization.

In 25 patients undergoing coronary artery bypass grafting hemodynamic measurements (including values obtained with Swan-Ganz catheterization in 21 of the patients) were made before and after administering a bolus injection of 64 or 96 mcg of nitroglycerin to relieve intraoperative hypertension. This pharmacological agent reduced afterload and preload without raising heart rate. The effect was apparent within 1-3 min and lasted 5-10 min. Untoward hypotension was not encountered in any instance. This intervention appears to be a safe approach to the treatment of intraoperative hypertension in patients with coronary artery disease.

Central vagal control of fentanyl-induced bradycardia during halothane anesthesia.

Six mongrel dogs were used to investigate the mechanism of action of fentanyl-induced bradycardia. With controlled acid-base balance and temperature, and under 1.0 to 1.2 percent endtidal halothane anesthesia, 5 and microgram/kg of IV fentanyl citrate were given sequentially 1 hour apart and heart rate (HR) followed for 60 minutes. A dose-related depression of HR followed both injections. One week later the same dogs were studied similarly, except that bilateral cervical vagotomies were performed before fentanyl was given. The decrease in HR was at most 10 percent of the decrease in HR observed in the innervated dogs. Serum fentanyl levels were comparable. The data indicate the majority of the chronotropic action of fentanyl involves vagal efferent impulses from the central nervous system.

Arterialization of the coronary veins in diffuse coronary arteriosclerosis.

Since the coronary veins and capillaries are not involved with arteriosclerotic disease the authors performed experimental, and afterwards, clinical total and selective coronary vein arterialization. Acute myocardial ischaemia created for instance by ligation of the anterior descending branch, was treated by an internal mammary artery to regional coronary vein anastomosis. In 21 patients the selective arterialization of the "Vena cordis magna" or of "Vena cordis media", and total arterialization of the coronary sinus was performed. The clinical improvement and follow-up studies seem to be promising in the treatment of patients with advanced diffuse heavy coronary arteriosclerosis. In acute myocardial ischaemia with coronarographically localized coronary occlusion, the aim of regional vein arterialization is to minimize the area of infarction.