Importance of retrograde coronary flow in the prediction of experimental myocardial infarct size.

The relationship between myocardial infarct size (measured by a histochemical stain) and coronary collateral blood flow (measured via retrograde flow and by use of radioactive microspheres) was studied in anesthetized dogs with high, moderate and low retrograde flows undergoing a 2-hour occlusion and 30-min reperfusion of the left anterior descending coronary artery. The results demonstrate that experimental myocardial infarct size is closely related to native coronary collateral blood flow, and the large variability in collateral perfusion amongst dogs is a source of variability in the mass of myocardium undergoing irreversible damage following acute coronary occlusion. Results also demonstrate that the variability in experimental infarct size can be reduced and ultimate infarct size predicted prior to irreversible tissue injury by initial measurement of retrograde coronary blood flow.

Comparative actions of dihydropyridine slow channel calcium blocking agents in conscious dogs: alterations in baroreflex sensitivity.

The effects of five dihydropyridine slow channel calcium blocking agents, nifedipine, nitrendipine, FR 34235, niludipine and nisoldipine were compared to those of the peripheral vasodilator hydralazine on the reflex bradycardia and tachycardia after abrupt increases and decreases in arterial pressure in conscious dogs. On alternate days, the baroreflex was elicited during control conditions (drug vehicle) and/or after low (2.5 micrograms/kg/min) or high (5.

Comparative actions of dihydropyridine slow channel calcium blocking agents in conscious dogs: systemic and coronary hemodynamics with and without combined beta adrenergic blockade.

The cardiovascular effects of the dihydropyridine slow channel calcium blocking agents, nifedipine, nitrendipine, FR 34235, niludipine and nisoldipine were compared to the vasodilator, hydralazine, in conscious, instrumented dogs before and after propranolol (2 mg/kg i.v.).

The slow-channel calcium blocking agent, nitrendipine, and coronary collateral blood flow.

The effects of a new dihydropyridine slow-channel calcium blocking agent, nitrendipine, on hemodynamics and myocardial blood flow in normal and ischemic areas distal to either an acute or chronic coronary artery occlusion were studied in anesthetized dogs. Nitrendipine produced significant and dose-related decreases in mean aortic blood pressure and increases in flow through the nonobstructed coronary artery. In acute coronary artery occlusion experiments, only small changes in perfusion of the ischemic zone were observed following nitrendipine.

Subendocardial versus transmural myocardial infarction: relationship to the collateral circulation in canine and porcine hearts.

In the present study, the relationship between transmural perfusion gradients and myocardial infarct size and distribution in canine and porcine hearts was characterized. Anesthetized pigs (N = 6) and dogs (N = 7) underwent a 2-h occlusion and 5-h reperfusion of the distal third of the left anterior descending coronary artery. The area at risk for infarction and ultimate infarct size were determined by fluorescein dye infused intracoronary and nitro blue tetrazolium stain, respectively.

Effects of vertebral column distraction in the monkey.

Experiments were performed to assess the effects of vertebral column distraction on evoked potential responses from multiple recording sites along the conducting pathway in the monkey, and on concurrent blood flows, measured with the radioactive microsphere technique, along the axis of the central nervous system. Linear distractive loads were applied until the amplitude of the evoked response was significantly reduced. In four monkeys, the loads (100 to 150 lb) were sustained, whereas in two monkeys the forces (80 to 110 lb) were relaxed.

Myocardial perfusion distal to an acute or chronic coronary artery occlusion: effects of diltiazem and nifedipine.

The effect of two slow channel calcium antagonists, diltiazem and nifedipine, on perfusion of normal and ischemic myocardium was studied in anesthetized dogs with acute or chronic (ameroid constrictor) left anterior descending coronary artery occlusion. Diltiazem (15 and 30 micrograms/mkg/min i.v.

Beneficial effects of the dihydropyridine calcium antagonist, FR 34235, in a chronic coronary occlusion model.

Administration of FR 34235 reduced aortic blood pressure and increased cardiac output in anesthetized dogs with an ameroid-induced coronary artery occlusion. Following FR 34235, there was an increase in perfusion within normal myocardium and ischemic subepicardium. Ischemic zone flow to subepicardium and subendocardium were both significantly increased when aortic pressure was held at control levels.

Determination of experimental myocardial infarct size.

Myocardial infarction was produced in anesthetized dogs by a 2-hr occlusion and 30-min reperfusion of the left anterior descending cornary artery. A balloon-reservoir perfusion system was used for reperfusion and delineation of perfusion bed size (area at risk) with Patent blue dye. Infarct mass was determined by a histochemical staining technique with triphenyl tetrazolium chloride.

Redistribution of myocardial blood flow distal to a dynamic coronary arterial stenosis by sympathomimetic amines: comparison of dopamine, dobutamine and isoproterenol.

The effects of dopamine, dobutamine and isoproterenol on coronary hemodynamics, severity of stenosis, distal bed resistance and transmural myocardial perfusion gradients with radioactive microspheres were studied in dogs with a mild obstruction of the left circumflex coronary artery anesthetized with morphine-chloralose. Changes in transmural blood flow were related to the ratio of the diastolic aortic pressure-time index to tension-time index (DPTI/TTI) and the ratio of the distal diastolic coronary pressure-time index to tension-time index (DDPTI/TTI). At doses of 5 microgram/kg per min, dopamine had no significant effect on DPTI/TTI, DDPTI/TTI or endocardial/epicardial flow ratio; however, dobutamine produced a slight decrease in this flow ratio and in DDPTI/TTI.