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Biomedical subjects

E Braunwald

Publications and source records attributed to E Braunwald.

At least 361 records · Page 20Linked to original sources
PubMed1981

Demonstration of lateral and epicardial border zone salvage by flurbiprofen using an in vivo method for assessing myocardium at risk.

The purposes of this investigation were (1) to develop an in vivo method of determining the myocardium at risk after experimental coronary occlusion; (2) to define the spatial geometry of the salvageable ischemic border zone; an (3) to assess the ability of flurbiprofen, an antiinflammatory agent, to protect ischemic myocardium from necrosis. Twenty-two open-chest dogs underwent left anterior descending coronary artery occlusion and were randomized to treated (flurbiprofen 1 mg/kg i.v. at 30 minutes and 4 hours after occlusion; n = 11) or control (saline; n = 11) groups. Six hours after occlusion, methylene blue, 3 ml/lg, was injected into the left atrium, and immediately thereafter the hearts were removed and sliced transversely. Areas not perfused by methylene blue (area at risk [Ar]) were traced, planimetered, and compared to the area of necrosis (An) after incubation in triphenyltetrazolium chloride. The Ar for the two groups were similar (control 28.2 +/- 2.6%; treated 25.2 +/- 2.3% of total left ventricle; NS). In control dogs, An/Ar was 96.2 +/- 0.7%, with similar values for the epicardium and endocardium. In treated dogs, An/Ar was 66.9 +/- 8.9% (p < 0.001), with greater epicardial than endocardial salvage. Topographic superimposition of the An on the Ar showed that salvage occurred both on the epicardial and lateral aspects of the infarct. We conclude that (1) the in vivo methylene blue method of assessing myocardium at risk is useful in standardizing experimental infarct size; (2) flurbiprofen, administered 30 minutes and 4 hours after occlusion, is a potent agent for reducing infarct size; and (3) salvage of myocardium occurs both at the lateral and epicardial borders of the infarct in dogs treated with flurbiprofen.

Animals↗
PubMed1981

Effects and mechanism of action of aminophylline on cardiac function and regional blood flow distribution in conscious dogs.

The effects of aminophylline, 1 mg/kg/min infused intravenously for 10 minutes, were examined on left ventricular (LV) diameter, pressure, an indexes of myocardial contractility, as well as systemic, coronary and regional hemodynamics in conscious dogs. Aminophylline increased mean arterial pressure 12 +/- 2%, LV systolic pressure 8 +/- 1%, LV dP/dt 20 +/- 2%, velocity of myocardial fiber shortening 13 +/- 2% and heart rate 5 +/- 2%, and reduced LV end-diastolic diameter 2 +/- 0.5%. Vascular resistance rose in the systemic bed 13 +/- 5%, the coronary bed 26 +/- 3%, the mesenteric bed 26 +/- 5% and the iliac bed 36 +/- 4%, but did not rise in the renal bed. Both beta-adrenergic receptor blockade with propranolol and chronic treatment with reserpine attentuated but did not abolish the positive inotropic response induced by aminophylline. Alpha-adrenergic receptor blockade with phentolamine prevented aminophylline-induced vasoconstriction in the systemic, coronary, mesenteric and iliac beds. In contrast to the vasoconstriction with i.v. aminophylline, when the drug was infused directly into the iliac artery, it elicited marked iliac vasodilation. Thus, in the intact conscious dog, i.v. aminophylline, in a dose that had little effect on heart rate, increased LV contractility and reduced preload. The increase in contractility was dependent in part on intact beta-adrenergic nervous activity and endogenous catecholamine stores. The increase in systemic, coronary, iliac and mesenteric resistances involved alpha-adrenergic mechanisms. These actions appear to involve autonomic mechanisms, because the only direct effect of aminophylline on the iliac artery was marked vasodilation.

Adrenergic alpha-Antagonists↗
PubMed1981

Left ventricular diastolic pressure-volume relations in rats with healed myocardial infarction. Effects on systolic function.

To determine the effects of healed myocardial infarction on the diastolic compliance of the left ventricle, we studied 36 rats 26 days after left coronary artery ligation. Peak cardiac output and stroke volume were measured under ether anesthesia during volume loading, and peak left ventricular developed pressure was determined during occlusion of the ascending aorta. During a slow infusion of saline into the potassium-arrested left ventricle, diastolic pressure and volume were measured continuously over the pressure range -5 to 30 mm Hg. Infarct size was determined by planimetry of serial sections taken from each heart at 1-mm intervals from apex to base. In rats with healed infarcts, left ventricular volume was increased in proportion to infarct size and the diastolic pressure-volume relationship was shifted so that at pressures below 2.5 mm Hg volume was increased, resulting in an increased ventricular compliance in this low pressure range. Above this pressure, the slopes of the pressure-volume curves were similar in rats with and without infarctions. Peak cardiac output and pressure-generating capacity were impaired in proportion to infarct size. This impairment of cardiac performance correlated with the infarct size-related increase in diastolic volume, which served to offset the reduction in flow generating capacity caused by systolic dysfunction, while contributing directly to the impairment of pressure generating capacity.

Animals↗
PubMed1981

Early recovery of regional performance in salvaged ischemic myocardium following coronary artery occlusion in the dog.

Although numerous agents have been shown experimentally to protect ischemic myocardium, a critical unanswered question is whether function is preserved in the salvaged tissue. Accordingly, 38 openchest dogs had measurements of percent segment length shortening (%SS) and velocity of segment length shortening either in midmyocardial or subepicardial and subendocardial ischemic segments before and after 60 min of left anterior descending coronary artery occlusion during 5 h of reperfusion; 10 additional dogs were subjected to 3 h of coronary occlusion followed by 72 h of reperfusion. 15 min after coronary artery occlusion, radiolabeled microspheres were injected into the left atrium for measurement of regional myocardial blood flow, and dogs were treated with 1 mg/kg i.v. (n = 23) of an anti-inflammatory drug, flurbiprofen or an equal volume of saline (n = 25). The ischemic myocardium-at-risk for necrosis was determined by injecting methylene blue dye into the left atrium with the coronary artery reoccluded at the end of the reperfusion period, slicing the left ventricle into thin transverse sections, and measuring the areas of each slice that were not perfused (pink unstained tissue) by methylene blue. The quantity of necrotic tissue in each transverse section was measured by planimetry after incubation of the slices in triphenyltetrazolium chloride, and by direct histological examination in dogs with 72 h of reperfusion. Regional myocardial blood flow of the ischemic segments between the ultrasonic dimension crystals was similar in treated (0.34+/-0.03 ml/min per g) and control dogs (0.35+/-0.03 ml/min per g). In saline-treated control dogs subjected to a l-h coronary occlusion, 17.9+/-1.8% of the myocardium-at-risk became necrotic but in flurbiprofen-treated dogs none of the tissue became necrotic. In saline-treated dogs passive lengthening of the previously ischemic segments persisted through 5 h of reperfusion in all three regions of myocardium after a 1-h coronary occlusion. In flurbiprofen-treated dogs regional function returned to normal within 5 min of reperfusion in both the subendocardium (%SS preocclusion = 17.2+/-2.0%; 5 min reperfusion = 17.8+/-3.1%; P = NS) and in the midmyocardium (%SS preocclusion = 17.8+/-2.2%; 5 min reperfusion = 17.9+/-2.3%; P = NS) and was not significantly different after 5 h of reperfusion from what it was before coronary occlusion. In the subepicardium of treated dogs regional function began to improve within 15 min of drug administration even during coronary occlusion. Regional function was not different from preocclusion values after either 5 min or 5 h of reperfusion (%SS preocclusion = 21.0+/-2.4%; 5 min reperfusion = 20.6+/-3.8%; P = NS). In dogs subjected to 3 h of coronary occlusion and 72 h of reperfusion, the administration of flurbiprofen was also associated with significantly smaller infarcts and a significantly more rapid rate of functional recovery than in control dogs.Thus, it appears that flurbiprofen not only decreased the quantity of necrosis in tissue made ischemic after coronary occlusion and then reperfused, but also allowed more rapid recovery of segmental function in ischemic but nonnecrotic tissue and in tissue with patchy necrosis; such recovery did not occur in equally ischemic myocardium in untreated control dogs. Earlier functional recovery of reversibly injured tissue following prolonged periods of ischemia is an additional important role for agents that protect ischemic myocardium from necrosis.

Animals↗
PubMed1981

Efforts to limit the size of myocardial infarcts.

Throughout the last decade, multiple interventions have been shown to decrease myocardial ischemic injury and limit infarct size in animal models of acute myocardial infarction. Results of pilot studies have suggested that some of these interventions may also have beneficial effects in humans with evolving myocardial infarction. This review focuses on the rationale for limiting infarct size, efficacy of methods for estimating size of infarcts, and current clinical data on specific intervention therapy. No intervention has yet been proved sufficiently efficacious to warrant its routine clinical use. However, treatment with beta-adrenergic blockers, intravenous nitroglycerin, and hyaluronidase has been shown to affect one or more indexes of infarct size in patients with acute myocardial infarction. Large, randomized clinical trials of these and other promising interventions are underway and will provide data on whether infarct size can be limited in humans and whether residual cardiac function and patient prognosis can thereby be improved.

Adrenergic beta-Antagonists↗
PubMed1980

A trial of two strategies to modify the test-ordering behavior of medical residents.

We studied two methods to reduce the ordering of laboratory and radiologic tests by medical residents in their first postgraduate year. Dividing the residents into three groups, we compared the effect of concurrent chart review and discussion in one group with the effect of a moderate financial incentive for limited ordering of tests in a second group. The third group of residents served as a concurrent control, and data on the testing patterns of residents at the same hospital during the year before the study provided a retrospective control.

Boston↗
PubMed1980

Nifedipine therapy for coronary-artery spasm. Experience in 127 patients.

We report clinical experience with the coronary vasodilator nifedipine in 127 patients with symptoms of myocardial ischemia associated with electrocardiographic or angiographic evidence, or both, of coronary-artery spasm. In the majority of patients conventional antianginal therapy including nitrates and beta-adrenergic blockers failed, and in one third of the patients at least one episode of ventricular tachycardia developed during an attack of angina. Nifedipine (40 to 160 mg every 24 hours) significantly reduced the mean weekly rate of anginal attacks from 16 to two (P less than 0.001). Similar marked reductions in the nitroglycerin requirement were noted. In 63 per cent of the patients complete control of anginal attacks was achieved, and in 87 per cent the frequency of angina was reduced by at least 50 per cent. Nifedipine was generally well tolerated, with only 5 per cent of the patients requiring termination of the drug because of intolerable side effects. This experience with nifedipine suggests that it is a highly effective drug for the treatment of coronary-artery spasm and variant angina.

Adult↗
PubMed1980

Oral amrinone in refractory congestive heart failure.

The acute effects of an oral preparation of amrinone, a recently synthesized cardiotonic agent, were assessed noninvasively in nine patients who had advanced heart failure that persisted despite treatment with digitalis, diuretic drugs and afterload-reducing agents. All patients demonstrated an improvement in left ventricular ejection fraction determined by radionuclide ventriculography (20.3 +/- 2.8 to 30.8 +/- 4.8 percent [mean +/- standard error of the mean], p less than 0.005) after a single dose of amrinone. Initial effects were seen within 1 hour, with the peak effect occurring at 1 to 3 hours; persistent effects were demonstrable at 4 to 6 hours. No change in blood pressure, heart rate or rhythm was observed, and there was no clinical evidence of myocardial ischemia. Continued benefit was demonstrated by radionuclide ventriculography in two patients treated for 1 and 6 weeks, respectively, although two other patients experienced major side effects with the chronic administration of amrinone. Although orally administered amrinone shows promise as a potentially useful agent in the treatment of advanced heart failure, the safety of this drug remains to be established.

Aged↗
PubMed1980

Myocardial infarction in experimental hypertension in rats: mechanism of the reduction in blood pressure.

1. Haemodynamic changes during graded methoxamine infusion have been measured in 16 spontaneously hypertensive rats with healed myocardial infarction produced by left coronary artery ligation and in 15 hypertensive rats without infarction. 2. Arterial pressure of the hypertensive rats was reduced to levels within the normotensive range in animals with moderate and large myocardial infarctions. 3. The peripheral vascular response to methoxamine was similar in rats with and without infarction. 4. The reduction in blood pressure resulted from a combination of lower heart rate and inability to maintain stroke volume at hypertensive pressures.

Animals↗
PubMed1980

Autoradiographic method for measuring the ischemic myocardium at risk: effects of verapamil on infarct size aftr experimental coronary artery occlusion.

Investigation of the efficacy of pharmacologic agents affecting myocardial infarct size after coronary artery occlusion is complicated by the variability of collateral flow among experimental animals which results in variability of infarct size. To overcome this difficulty, we developed an autoradiographic method to delineate the ischemic area at risk of necrosis after coronary artery occlusion and we invetigated the potential protective effect of a calcium antagonist verapamil. The left anterior descending coronary arteries of 25 barbiturate-anesthetized dogs were occluded. Thirty minutes later, highly radioactive human albumin microspheres labeled with 99mTc were injected into the left atrium. One hour after coronary artery occlusion, dogs were randomized to control or treated groups; the latter received a 0.2 mg/kg loading dose and 0.6 mg/kg per hr maintenance dose of verapamil intravenously. Eight hours after coronary artery occlusion, the dogs were killed, the hearts were excised, and the left ventricle was sectioned parallel to the atrioventricular groove; infarct size was determined planimetrically after incubation in triphenyl tetrazolium chloride. The slices were then exposed to high-speed x-ray film with image-enhancing screens. The percentage of left ventricle that was ischemic, as determined by planimetry of autoradiographs, was similar in treated and control animals (36.6 +/- 2.0% compared to 37.3 +/- 2.8%, respectively). Of the ischemic area, 92.0 +/- 4.3% was infarcted in control animals and 70.5 +/- 5.1% was infarcted in treated animals (P < 0.01). Thus, this autoradiographic method using 99mTc-labeled human albumin microspheres is useful in delineating the area of ischemia after coronary artery occlusion and in evaluating the efficacy of pharmacologic agents designed to protect ischemic myocardium. Verapamil, administered 1 hr after coronary artery occlusion, is effective in limiting infarct size.

Albumins↗
PubMed1980

Prolonged derangements of canine myocardial purine metabolism after a brief coronary artery occlusion not associated with anatomic evidence of necrosis.

Changes in myocardial purine metabolism were studied after temporary coronary artery occlusion and subsequent reperfusion in the dog. Sequential myocardial biopsies were performed to allow for measurements of ATP, adenine nucleotide, nucleoside, and base concentrations after 15 min of ischemia, and after 90 min and 72 hr of reperfusion following this period of ischemia. Control, nonischemic sites were also sampled. After 15 min of coronary occlusion, subendocardial ATP concentrations (reported in nmol/mg of protein; mean +/- SEM) were depressed in the ischemic zone at 19.9 +/- 3.5 compared to 38.1 +/- 2.8 in the nonischemic zone (P < 0.001). Subepicardial ATP concentrations also were depressed at 27.0 +/- 2.2 in ischemic sites compared to subepicardial nonischemic sites (40.0 +/- 4.0, P < 0.005). After 90 min of reperfusion ATP concentrations remained depressed in the previously ischemic subendocardium 26.8 +/- 4.2 (P < 0.025 vs. nonischemic sites). After 72 hr of reperfusion, ATP was still depressed in the previously ischemic subendocardium at 29.2 +/- 2.5 (P < 0.025 vs. nonischemic) and subepicardium (27.9 +/- 3.3, P < 0.05 vs. nonischemic). Total purines were determined as the sum of ATP, ADP, AMP, adenosine, inosine, and hypoxanthine. After 15 min of occlusion, the total purine pool in the ischemic subendocardium tended towards being lower than in the nonischemic zone (42.0 +/- 5.9 vs. 53.8 +/- 5.2, not significant) but in the ischemic subepicardium the total purine pool was similar to that in the nonischemic zone. After 90 min of reperfusion the previously ischemic subendocardial purine pool was reduced compared to the nonischemic zone (39.0 +/- 4.8, P < 0.025). Total purines were also depleted in both the subendocardium and subepicardium of previously ischemic zones after 72 hr of reperfusion (44.5 +/- 2.9 and 40.0 +/- 4.4, respectively, P < 0.05). Histologic analysis of the previously ischemic tissue revealed no evidence of necrosis. Therefore, brief temporary coronary artery occlusions not associated with anatomic evidence of necrosis may result in prolonged abnormalities of ATP concentration and significant depletion of the total purine pool.

Adenosine Diphosphate↗