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

Effect of ischemia on ventricular contractility in patients with coronary artery disease

The constant of elastance (E-MAX) is determined by measuring continuous left ventricular pressure and volume changes during the cardiac cycle. To evaluate the effect of myocardial ischemia on contractility, E-MAX was measured from serial pressure volume loops at baseline, with atrial pacing-induced ischemia, and after the administration of intravenous nitroglycerin with repeat pacing. Ten patients undergoing cardiac catheterization for presumed coronary artery disease were evaluated by this method. The severity of the coronary artery disease was graded angiographically by using the Gensini coronary score. In 8 of the 10 patients there was a significant decrease in E-MAX during atrial pacing (P less than .05). With the administration of nitroglycerin there was an attenuation of the ischemic effect previously noted with pacing. In 3 of the 10 patients administration of nitroglycerin produced a further decrease in E-MAX with ischemia. All 3 patients had a significantly lower Gensini coronary score with a well-developed, visible coronary collateral network. The authors' results indicate that continuous pressure volume loop analysis is possible using the nuclear stethoscope. Significant ischemic changes are seen with atrial pacing, which are relieved by the administration of nitroglycerin, except in the presence of coronary collaterals.

Pharmacology and clinical pharmacology of organic nitrates

Current concepts and future aspects of pharmacological interventions in the treatment of coronary heart disease have been compiled. Especially new insights in the pathophysiology of coronary heart disease e.g. the dynamic pathology of coronary atherosclerosis, possible role of endothelin in vasospasm, as well as new pharmacodynamic and pharmacokinetic aspects of organic nitrates are discussed. Also the role of sympathetic nervous system as a pivotal question in pathophysiology and clinical pharmacology in the treatment of angina pectoris has been considered.

Vasodilator drug effects on internal mammary artery and saphenous vein grafts

The internal mammary artery is a dynamic conduit used for myocardial revascularization in which potential exists for spasm as well as for vasodilation. This study investigated vasodilator drug effects on the mammary artery using nitroprusside and nitroglycerin in vitro to measure the inhibition of contraction of human internal mammary artery and in vivo to examine blood flow through a canine mammary artery. In the in vitro study, ring segments of human internal mammary arteries were suspended on strain gauges in muscle baths containing 37 degrees C Krebs solution for measurement of isometric tension in vitro. Arterial contraction was stimulated with 70 mM potassium and 10 microM norepinephrine, and inhibition of contraction by vasodilators was measured. Nitroprusside was more potent and effective than was nitroglycerin in inhibiting potassium and norepinephrine contraction. The in vivo study utilized a canine (n = 8) right heart bypass preparation that allowed precise control of cardiac output, blood pressure and heart rate, which were maintained constant. The internal mammary artery graft and the saphenous vein graft perfused the same coronary artery bed. Electromagnetic flow probes measured graft flow (with the other graft occluded) before and after 15 min of drug infusion (1 microgram/kg per min). Nitroglycerin significantly increased mammary artery flow 36 +/- 13%, whereas nitroprusside significantly decreased it 12 +/- 2%. Saphenous vein grafts responded differently; graft blood flow decreased with nitroglycerin and increased with nitroprusside. Thus, although nitroprusside was more effective than nitroglycerin in inhibiting mammary artery contraction in vitro, it decreased internal mammary artery graft flow measured in vivo. Nitroglycerin had the opposite effect, increasing mammary graft flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of combined nitroglycerin and dobutamine infusion in left ventricular dysfunction

The immediate therapy of severe left ventricular (LV) failure after acute myocardial infarction (AMI) frequently requires simultaneous preload reduction, pump output augmentation, and maintenance of systemic blood pressure. Therefore the effects of intravenous nitroglycerin (NG) and dobutamine (DB) were evaluated in 12 patients with severe LV failure following AMI. Nitroglycerin achieved salutary lowering of abnormally elevated LV filling pressure (23 to 14 mm Hg, p less than 0.001) while DB markedly augmented LV pump function (cardiac index rose from 1.7 to 2.5 L/min/m2, p less than 0.005). Notably, the combined infusion of NG + DB simultaneously decreased preload (LV filling pressure 23 to 14 mm Hg, p less than 0.001) and markedly enhanced LV pump performance (cardiac index increased from 1.7 to 2.4 L/min/m2, p less than 0.001). Minor decline in mean systemic blood pressure with NG (72 to 66 mm Hg, p less than 0.05) was rapidly reversed by DB addition (69 mm Hg, p greater than 0.05). Both agents were well tolerated without clinical or ECG evidence of myocardial ischemia or dysrhythmias. Thus the principally venodilator effects of NG minimize systemic hypotension while salutary augmentation of cardiac function in AMI with LV failure is achieved by NG + DB.

Effects of diltiazem-induced calcium blockade upon exercise capacity in effort angina due to chronic coronary artery disease

Few data are available regarding the effects of calcium blockade upon exercise tolerance in patients with stable effort angina due to coronary artery disease (CAD). Therefore we compared the effects of the calcium blocking agent, diltiazem (D), to placebo (P) in 12 patients with chronic effort angina and catheterization documented fixed CAD. The 8-week total protocol consisted of a 1-week baseline period followed by the double-blind randomized crossover alternate 1-week administration of P and D in doses of 120, 180, and 240 mg. Maximal exercise tests (MET) were performed at the end of each 1-week period, while rest radionuclide ventriculography (RVG) was obtained during 240 mg D and corresponding crossover P. Resting heart rate decreased from baseline and initial P at D doses of 60 and 240 mg, but not from P during crossover period. No changes were observed at any dose of D either at rest or during MET in systolic blood pressure or rate . pressure double product. D at 240 mg, but not lower doses, increased MET duration (437 vs 490 seconds, p less than 0.01) and time to angina (383 vs 441 seconds, p less than 0.01). Ejection fraction by RVG was greater with D than P (0.54 vs 0.50, p less than 0.05). Thus these data indicate that calcium blockade with diltiazem provides antianginal efficacy by reducing myocardial oxygen demand, and increases exercise tolerance without depression of myocardial performance in effort angina patients with fixed chronic CAD.