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Biomedical subjects

M R Platt

Publications and source records attributed to M R Platt.

At least 37 records · Page 2Linked to original sources
PubMed1978

Unstable angina pectoris: a randomized study of patients treated medically and surgically.

Fifty patients with the clinical syndrome of unstable angina pectoris were evaluated. Twenty-seven were randomized into medical or surgical treatment groups and subsequently followed up. The results of the study reveal that: (1) there is approximately a 16 percent incidence rate of significant left main coronary artery disease in patients with this entity at our institution; (2) 10 percent of patients do not have angiographically significant coronary artery disease; (3) pain relief is better in the surgically treated patients, but the 1 1/2 year survival rate is not significantly different between the groups; (4) 50 percent of the medically treated patients again had the syndrome of unstable angina pectoris in the initial few months of the follow-up period; (5) the operative and late postoperative mortality rate in patients presenting with unstable angina pectoris and left main coronary artery disease in this small group of patients was 43 percent; and (6) four of six patients with this syndrome whose condition was deemed inoperable and who were not randomized died within the subsequent few months.

Angina Pectoris↗
PubMed1977

Serum myoglobin level as diagnostic test in patients with acute myocardial infarction.

Serum myoglobin levels were measured in normal subjects and patients by means of a newly developed radioimmunoassay. Myoglobin was identified in all of 135 sera from normal adults and ranged between 6 and 85 ng/ml (mean +/- SE 31 +/- 1.3). Raised myoglobin levels were present in 62 of 64 patients with documented acute myocardial infarction, the mean serum concentration being 528 +/- 76 ng/ml. Serial determinations in 46 patients with acute infarct showed that maximum values usually occurred within 4 hours after admission. In 19 of 42 cases, raised myoglobin levels preceded the rise in creatine kinase (CK) values; in the remaining patients, both serum myoglobin and creatine kinase were increased on admission. Only 2 of an additional 44 patients admitted with chest pain but without subsequent electrocardiographic, enzyme, or technetium-99m stannous pyrophosphate myocardial scintigraphic evidence of acute myocardial infarction had raised myoglobin levels; the mean value for this group was within the normal range (44 +/- 6 ng/ml). Serum myoglobin values also were normal in patients with congestive heart failure without acute myocardial infarction, and in patients after moderate exercise and cardiac catheterisation. Trasient myoglobinaemia appears to be one of the earliest laboratory abnormalities occurring in acute myocardial infarction and, therefore, should prove useful as a diagnostic aid in patients.

Acute Disease↗
PubMed1977

Primary pulmonary sporotrichosis.

A 34-year-old alcoholic and drug addict developed cavitary pulmonary sporotrichosis that progressed slowly during 6 years. Pulmonary resection and pre- and postoperative therapy with amphotericin B were associated with prompt clinical improvement with no evidence of relapse during a 2-year follow-up. Histologic examination of lung revealed granulomatous inflammation with organisms consistent with Sporothrix schenckii, and interstitial talc (magnesium silicate) granulomas. The latter finding was consistent with the history of intravenous drug abuse. Although the presence of silicates in lung enhances the pathogenicity of some microorganisms, the relation of these findings to the pathogenesis of sporotrichosis in our patient is unclear.

Adult↗
PubMed1976

Effect of hypertonic mannitol and intraaortic counterpulsation on regional myocardial blood flow and ventricular performance in dogs during myocardial ischemia.

Studies were performed to determine if intervention with hypertonic mannitol and intraaortic balloon counterpulsation increases regional myocardial blood flow during acute myocardial ischemia. Anesthetized dogs on right heart bypass were studied. Heart rate was kept constant by atrial pacing. Myocardial ischemia was provided by ligating the proximal left anterior descending coronary artery for 12 minute periods. Infusion of hypertonic mannitol begun immediately after ligation increased coronary blood flow to the ischemic area by 36 +/- 9.0% (standard error) (P less than 0.01) and to the nonischemic left ventricle by 21 +/- 8.8% (P less than 0.05) as compared with flow in the same regions during the control coronary ligation. Intraaortic balloon counterpulsation begun immediately after ligation increased regional coronary flow to the ischemic region by 20 +/- 8.4% (P less than 0.05) but did not significantly alter flow to the nonischemic left ventricle as compared with levels during the control ligation. Combined intraaortic counterpulsation and hypertonic mannitol increased coronary flow to the ischemic region by 46 +/- 13% (P less than 0.02) and to the nonischemic left ventricle by 59 +/- 22% (P less than 0.05) as compared with flow during occlusion of the left anterior descending artery with mannitol alone. The data demonstrate that both hypertonic mannitol and intraaortic counterpulsation increase left ventricular ischemic regional flow and that combined hypertonic mannitol and intraaortic balloon counterpulsation provide a greater increase in regional coronary blood flow to both the ischemic and nonischemic regions of the left ventricle than mannitol alone.

Acute Disease↗
PubMed1976

Technetium stannous pyrophosphate myocardial scintigrams in the recognition of myocardial infarction in patients undergoing coronary artery revascularization.

Myocardial imaging using technetium 99m stannous pyrophosphate (99mTc-PYP) has been utilized preoperatively and three to five days postoperatively to detect myocardial infarction in 48 patients undergoing aortocoronary bypass grafting, including 7 having valve replacement (5 aortic, 2 mitral) in addition to revascularization. In the total group of patients operated on there were 3 deaths (6%). Preoperatively, 26 patients had unstable angina and 10 had severe left main coronary artery disease. Eleven of the 48 (23%) were women. ECG and enzyme-proved infarctions occurred in 6 of the 48 patients (12%), but the addition of 99mTc-PYP myocardial imaging demonstrated scintigraphic evidence of infarction in 15 patients (31%), including 2 who died in the operating room. The 99mTc-PYP myocardial imaging technique, which has proved safe, simple, and relatively inexpensive in these patients, suggests that the incidence of infarction after coronary bypass operations is somewhat higher than has been previously recognized from just ECG and enzyme changes. This technique also has been of value in helping to exclude myocardial infarction in difficult clinical situations such as postoperative arrhythmias and the postpericardiotomy syndrome.

Adult↗
PubMed1976

Unstable angina pectoris. Clinical, angiographic, and myocardial scintigraphic observations.

The clinical, left ventricular and coronary angiographic data, and the technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigraphic results are presented in 31 patients with unstable angina pectoris. One-third of these patients had positive 99mTc-PYP myocardial scintigrams in a pattern suggesting limited and diffuse subendocardial necrosis. The positive 99mTc-PYP myocardial scintigrams occurred without diagnostic electrocardiographic and cardiac enzyme changes suggestive of myocardial infarction; positive scintigrams seemed to occur more commonly in patients with continuing pain after admission and in those without previous history of myocardial infarction. The positive 99mTc-PYP myocardial scintigrams did not correctly predict coronary anatomical patterns except that positive scintigrams occurred only in patients with coronary artery disease. Neither did the positive scintigrams necessarily occur in that group of patients with the poorest ventricular function though the 2 patients with the lowest ejection fractions both had positive 99mTc-PYP myocardial scintigrams. Finally, when positive 99mTc-PYP scintigrams are the only evidence suggestive of limited subendocardial infarction in patients with unstable angina pectoris, they do not appear to have any prognostic significance in terms of longevity or response to pharmacological or surgical therapy, though the follow-up period so far is short.

Adult↗
PubMed1976

Similarities in coronary flow between external counterpulsation and intra-aortic balloon pumping.

The ability of external counterpulsation (Cardiassist) and intra-aortic balloon pumping (AVCO) to influence collateral coronary blood flow in ischemic myocardium was measured in anesthetized dogs. Cardiac output and heart rate (atrial pacing) were held constant on right-heart bypass. Both external counterpulsation and balloon pumping augmented peak diastolic pressure (30 mmHg and 38 mmHg, respectively), while mean aortic pressure, peak left-ventricular pressure, left-ventricular end-diastolic pressure, maximum left-ventricular dp/dt, hematocrit, and osmolality remained unchanged. Regional coronary blood flow was measured using 9-mum radioactive microspheres. External counterpulsation and balloon pumping begun immediately following ligation of the left-anterior descending coronary artery significantly increased collateral coronary blood flow 29 +/- 7.5% (SE, P is less than .01) and 20 +/- 8% (P is less than .05), respectively, to ischemic myocardium. This redistribution of collateral coronary blood flow produced by both methods of counterpulsation was primarily to the subepicardial region of the ischemic myocardium. The mechanism responsible for the measured increases in collateral coronary blood flow appears most likely to be an increased pressure gradient produced by diastolic augmentation.

Animals↗
PubMed1976

Influence of dobutamine on regional myocardial blood flow and ventricular performance during acute and chronic myocardial ischemia in dogs.

The data from this study document that dobutamine is a powerful inotropic agent in anesthetized dogs with acute myocardial ischemia and in awake, unsedated ones with chronic myocardial infarction. Dobutamine significantly increases heart rate at relatively small doses in anesthetized dogs with acute myocardial ischemia but considerably larger amounts of dobutamine are required to significantly increase heart rate in awake, unsedated dogs with myocardial infarction. Dobutamine also significantly increases regional myocardial blood flow to all areas of the heart at 20mug/kg/min in both anesthetized dogs with acute myocardial ischemia and awake, unsedated ones with myocardial infarction. However, in anesthetized dogs 20mug/kg/min of dobutamine significantly increases epicardial ST-segment elevation during acute myocardial ischemia. Propranolol prevents the inotropic and chronotropic effects of dobutamine in both anesthetized and awake, unsedated dogs. This study suggests that during experimental acute myocardial ischemia dobutamine given at doses that significantly increase heart rate and contractility may increase the extent of myocardial damage. The data also suggest that this agent should be of value in the setting of severe myocardial depression without associated severe coronary artery disease to increase cardiac contractility at doses that do not markedly alter heart rate. The hemodynamic and coronary blood flow effects of dobutamine in patients with and without severe coronary artery disease should be evaluated.

Acute Disease↗
PubMed1976

The influence of combined intra-aortic balloon counterpulsation and hyperosomotic mannitol on regional myocardial blood flow in ischemic myocardium in the dog.

We investigated the combined effectiveness of intra-aortic balloon counterpulsation and hyperosmotic mannitol (25%) on regional myocardial blood flow during acute coronary insufficiency. Cardiac output and paced heart rate were held constant in chloralose-anesthetized dogs during right heart bypass. Acute coronary insufficiency was produced by ligation of the proximal left anterior descending coronary artery (LAD). Regional myocardial blood flow was measured using radioactive microspheres. Left ventricular end-diastolic pressure, mean aortic pressure, maximum left ventricular dp/dt, and hematocrit were unchanged by combined mannitol infusion and balloon pumping. Studies of combined treatment with balloon pumping and mannitol immediately after the second of two 13-minute consecutive reversible ligations of the LAD demonstrated that (1) collateral coronary blood flow increased 46% (P less than 0.02) in ischemic myocardium compared with mannitol infusion along during the first LAD ligation, and (2) collateral coronary blood flow increased 27% (P less than 0.05) in ischemic myocardium compared with balloon pumping along during the first LAD ligation. Studies in which combined treatment was delayed until 20 minutes after LAD ligation demonstrated that collateral coronary blood flow was elevated by 33% (P les than 0.05) in ischemic myocardium compared to control studies in which balloon pumping alone had no effect. The results suggest that the increase in collateral coronary blood flow was in part a result of an increased transmural pressure gradient produced by balloon diastolic augmentation and the ability of mannitol to reduce coronary vascular resistance in ischemic myocardium.

Animals↗
PubMed1976

Perioperative myocardial infarction diagnosed by technetium 99m stannous pyrophosphate myocardial scintigrams.

Two groups of patients have been studied using 99mTc stannous pyrophosphate myocardial imaging prior to and 3-5 days after myocardial revascularization. The first group consisted of 48 patients undergoing revascularization, including 26 with unstable angina and seven with concomitant valve replacement. There were 3 deaths (6%), and the incidence of perioperative infarction by electrocardiogram (ECG) and enzyme analysis was 6/48 (12%), while 15 of 48 (31%) had positive myocardial scintigrams. The second group of 29 patients included one nonischemic death (3%) that was excluded. The operative technique was changed (optical magnification used, silastic tapes avoided, venting avoided, while aortic cross clamping was used frequently). In this latter group two of 29 (7%) had ECG evidence of infarction while four of 28 (14%) had positive scintigrams, compared to the pervious incidence of 31%. The imaging technique is simple, reliable, and probably more sensitive in the postoperative setting than ECG and enzyme analysis. It appears useful in evaluating the influence of changes in operative technique on myocardial preservation.

Female↗
PubMed1975

Intraaortic balloon counterpulsation in patients in cardiogenic shock, medically refractory left ventricular failure and/or recurrent ventricular tachycardia.

Of the 27 patients described, 23 were in cardiogenic shock, 2 had severe left ventricular failure, and 2 had medically refractory ventricular tachycardia. Utilizing intraaortic counterpulsation, adequate systemic blood pressure was initially restored in 19 patients. Nine of these were subsequently weaned from circulatory assistance, but only three were discharged from the hospital and are currently alive. The remaining 10 patients who derived initial benefit from circulatory assistance were balloon-dependent in that they could not be weaned from circulatory assistance. Eight of these patients subsequently underwent cardiac catheterization; four had inoperable disease. The remaining four patients underwent surgery for either resection of the area of infarction and/or for myocardial revascularization; only one survived to subsequently leave the hospital. Ventricular volumes were abnormal and ejection fractions were below 30 per cent in all the patients in cardiogenic shock except one who underwent cardiac catheterization and ultimately died. Ejection fractions were greater than 30 per cent in the two patients with cardiogenic shock who were weaned from balloon support and survived to leave the hospital without surgery. Both of these patients had inferior myocardial infarction. The data obtained from this experience suggest that intraaortic counterpulsation is a very useful adjunct to currently existing medical measures to treat both cardiogenic shock and medically refractory left ventricular failure but that most patients have such extensive disease that they can neither be weaned from balloon support nor undergo successful infarctectomy or myocardial revascularization.

Adult↗
PubMed1975

Five-day partial bypass using a membrane oxygenator without systemic heparinzation.

These studies indicate that a heparin bound membrane oxygenator can be used in venovenous bypass circuit in dogs for a period of 5 days without systemic heparinization. The plasma SGOT, plasma hemoglobin, and MLW of the animals increased after initiation of bypass but returned to control levels. Oxygen transfer did not deteriorate in the membrane oxygenator, eliminating the necessity of membrane exchange during the 5-day bypass.

Animals↗