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Biomedical subjects

W Shapiro

Publications and source records attributed to W Shapiro.

At least 55 records · Page 3Linked to original sources
PubMed1982

Acebutolol therapy for ventricular arrhythmia. A randomized placebo-controlled double-blind multicenter study.

The safety and efficacy of acebutolol in suppressing ventricular ectopy was evaluated in 60 males (average 59 years) using 24-hour Holter recordings and a double-blind, randomized, crossover protocol. Acebutolol, 200 mg and 400 mg thrice daily, was compared with placebo. Only patients who had a mean of at least 30 ventricular premature complexes (VPCs) per hour on three 24-hour control Holter recordings were included. Analysis of Holter recordings revealed greater than 70% reduction in VPCs/hour from control levels during acebutolol therapy in over 50% of the 60 patients; dose-related reduction in the mean number of single and paired VPCs and ventricular tachycardia episodes (p less than 0.05) by acebutolol; and significant, asymptomatic reduction in resting heart rate and blood pressure. All side effects were transient. Acebutolol was discontinued because of side effects in one patient only.

Acebutolol↗
PubMed1982

The effects of lidoflazine on exercise performance and thallium stress scintigraphy in patients with stable angina pectoris.

Lidoflazine is a synthetic drug with calcium-channel blocking effects. In a 7-month study, 36 patients with stable angina pectoris were tested during a 3-month single-blind placebo phase. Nineteen were then randomized by double-blind methods to lidoflazine and 17 to placebo therapy. The lidoflazine group had a significant (p less than 0.01) reduction in anginal attacks; the placebo group did not. Exercise testing demonstrated that lidoflazine therapy was associated with a 34% increase in total work performance and a 15.6% increase in peak calculated oxygen uptake during double-blind treatment (both p less than 0.004 compared with the placebo group). Heart rate was significantly reduced at submaximal levels of exercise during lidoflazine therapy (p less than 0.04). Nitroglycerin consumption and electrocardiographic changes at the end of exercise did not change during the double-blind phase. In a second study of six similar patients, single-blind administration of lidoflazine was associated with improved myocardial perfusion during exercise as determined by thallium-201 stress scintigraphy. These studies demonstrate that lidoflazine therapy is associated with relief of angina, an increased physical work capacity, and improved regional myocardial perfusion during exercise.

Angina Pectoris↗
PubMed1981

Effect of acetazolamide in blood acid-base and electrolyte values in dogs.

The effects of acetazolamide administration on arterial blood acid-base equilibrium and electrolyte concentrations were evaluated in 13 clinical patients and in a 4-week experiment in 6 conditioned mixed-breed dogs. Findings included persistent acidemia characterized by hyperchloremic metabolic acidosis, elevated partial pressure of oxygen, and mild depletion of potassium. Changes in the partial pressure of carbon dioxide were variable, and there was no change in plasma sodium concentration or osmolality. Measured disturbances were apparent within 12 hours of the commencement of acetazolamide administration, peaked at between 1.5 and 5.0 days, and thereafter stabilized. Abnormalities were restored to normal within 1.5 days following termination of drug administration.

Acetazolamide↗
PubMed1981

Computerized tomography findings in multifocal glioma.

Six patients with multifocal glioma are presented. Computerized tomography revealed multiple, discrete, contrast-enhancing lesions in the cerebral hemispheres, suggestive of multiple intracranial metastases. The most accessible lesion was resected at craniotomy in each patient, confirming the diagnosis of primary malignant glioma. Postoperative radiation therapy and chemotherapy were instituted according to current protocols. Since neuroradiological studies may not allow distinction of multifocal glioma from multiple brain metastases, surgical biopsy is suggested in those patients who have no history of cancer.

Aged↗
PubMed1981

Comparison of nadolol, a new long-acting beta-receptor blocking agent, and placebo in the treatment of stable angina pectoris.

Nadolol, a new nonselective beta 1 and beta 2 adrenergic blocking agent, has a plasma half-life of 17 to 23 hours. We studied 37 volunteers with stable angina pectoris who had five or more episodes of pain per week and who also had a 1 mm or greater ST segment depression 80 msec past the J point during a Bruce protocol treadmill test. An eight-week placebo controlled run-in period preceded double-blind randomization to nadolol administered once per day (17 patients) or identical appearing placebo for four weeks (20 patients), after which an exercise test was done. Diaries for pain episodes and nitroglycerin consumption were kept. Exercise tests were performed 24 hours after the last nadolol or placebo dose. Episodes of pain per week were reduced 59.8 percent after nadolol and 28.2 percent after placebo (P less than .01). Nitroglycerin consumption after nadolol was reduced 66.8 percent while after placebo it was reduced 36.2 percent (P less than .05). Resting and peak heart rates and peak rate-pressure products showed typical reductions due to beta-blockade 24 hours after nadolol compared with stability of these during placebo, all P less than .001. Exercise time after nadolol increased 42.2 percent, which was more than the 14.5 percent increase after placebo (P less than .05). Exercise work after nadolol increased 64.7 percent, greater than the 22 percent increase after placebo (P less than .05). Mean ST segment depression at end of exercise was little changed before and after treatment in both groups, reflecting consistency of effort. Improvement in symptoms and work capacity associated with nadolol significantly exceeded the placebo group responses. Unlike other available agents of this class, a single daily dose of nadolol produced therapeutically effective 24-hour beta-blockade in patients with disabling angina pectoris.

Angina Pectoris↗
PubMed1981

Digitalis update.

Explore the source record for details and available documents.

Arrhythmias, Cardiac↗
PubMed1980

Submaximal exercise testing after unstable angina.

Sixty-one consecutive men, mean age 56 years, who fulfilled criteria for unstable angina and who responded to medical therapy, underwent submaximal exercise testing prior to hospital discharge and at least 3 days after their last episode of angina. Forty-two patients were receiving propranolol at the time of exercise. Submaximal exercise was targeted to 120 beats/minute and strict criteria for the premature termination of each study were followed. Follow-up data were available on 55 patients post-discharge over a period of 6 to 36 weeks. No patient suffered recurrence of unstable angina or myocardial infarction due to the exercise test. Exercise was prematurely terminated by an ischemic response (chest pain and/or ST segment changes) in 34 patients (56%) and by leg fatigue in 13 patients (21%). Only five patients had exercise-induced ventricular ectopic activity, four of whom were not receiving propranolol. Nine patients achieved the target heart rate. Exercise-induced abnormal electrocardiographic changes predicted the postdischarge recurrence of episodes of unstable angina (p less than 0.05). Comparison of predischarge submaximal exercise data with postdischarge maximal exercise shows that recovery in cardiovascular function after unstable angina occurs soon after stabilization and prior to the submaximal test.

Adult↗
PubMed1979

Exercise testing in men with significant left main coronary disease.

The exercise tests of 26 male patients with significant left main disease were compared with those of 51 patients with three-vessel disease and 38 patients with two-vessel disease. Exercise-induced ischaemia (chest pain and/or greater than 1 mm ST segment change) occurred in 100 per cent of left main, 69 per cent of three-vessel, and 45 per cent of two-vessel disease patients. Though the mean peak work load was significantly higher in the two-vessel disease group than in those with three-vessel of left main disease, there was a wide overlap between groups. No intergroup differences were found in mean peak heart rates. In patients taking propranolol, no differences in mean peak work loads and heart rates were seen. The study showed that the absence of an exercise-induced abnormal electrocardiographic response virtually excludes left main disease. As judged by exercise performance, the presence of left main disease did not correlate with the severity of the patient's symptomatology. Propranolol did not influence the frequency of an ischaemic response in patients with left main or three-vessel disease.

Coronary Disease↗
PubMed1978

Correlative studies of serum digitalis levels and the arrhythmias of digitalis intoxication.

Correlative studies of serum digoxin levels, cardiac rhythm and related clinical laboratory data were carried out in 114 patients. Seventy-three patients who presented with 79 episodes of arrhythmias typical of digitalis intoxication could be separated into a normokalemic group of 55 patients whose serum digoxin level was 6.68 +/- 0.17 ng/ml (mean +/- standard error of the mean), and a hypokalemic group of 24 with a mean serum digoxin level of 1.13 +/- 0.04 ng/ml (P less than 0.001). Of 45 consectutive normokalemic patients with a high serum digoxin level (more than 2 mg/ml) who underwent serial studies, 17 had arrhythmias. Serial studies in 10 hypokalemic patients revealed an inconsistent relation between presence of arrhythmia and serum digoxin level. During repletion of serum potassium in seven of these patients with an arrhythmia, the arrhythmia disappeared without a significant change in serum digoxin level in four patients. A group of seven patients had 16 episodes of serum digoxin level greater than 2.2 ng/ml, but an arrhythmia occurred during only 3 of these episodes. A sharp border between toxic and therapeutic serum digoxin values was not found in these groups of study patients. The serum digoxin level at which arrhythmias occurred appeared to be variable for both groups and individual patients. However, correlative studies utilizing serum digoxin levels can define existing thresholds for therapeutic and toxic effects and may often be more useful than isolated observations.

Aged↗
PubMed1978

Efficacy of propranolol in the control of exercise-induced or augmented ventricular ectopic activity.

The effect of propranolol on exercise-induced or augmented ventricular ectopy was studied in sixteen male patients, six of whom had documented coronary artery disease. Fifteen patients were exercised after two weeks of oral therapy, fourteen after single oral therapy and eight patients after intravenous therapy. Propranolol dosage was titrated to produce maximal beta-adrenergic blockade. Effective reduction of exercise-induced ventricular ectopy occurred in ten of fifteen patients (P less than 0.001), and in five of six patients with coronary disease (P less than 0.02). Propranolol therapy abolished ventricular couplets in eight of twelve patients and ventricular tachycardia in four of the patients. Single oral and intravenous therapy had similar or greater effects. Plasma propranolol levels following different routes of administration did not correlate with exercise-induced maximal heart rates or percent reduction in ventricular ectopy. When compared to exercise in eleven patients, ambulatory monitoring underestimated the severity, particularly the highest grades, of ventricular ectopy.

Adult↗
PubMed1978

Current considerations in digoxin usage.

Basic considerations in biotransformation and pharmacodynamics are presented as a basis for understanding clinical usage. The role of polarity in determining a given glycoside's duration of action and extent of biotransformation is emphasized. The pharmacokinetics are summarized emphasizing the fact that digoxin is not completely absorbed by oral administration. The important relationship of serum digoxin levels to myocardial content and apparently to myocardial response is reviewed. This relationship and the development of precise methods for measurement of digoxin in serum provide the clinician with accurate means to assess myocardial tolerance for digoxin under diverse clinical circumstances. This review includes discussion of methods of digitalization, appropriate use of serum levels, apparent and real resistance to digoxin, and apparent and real sensitivity to digoxin. The limitations of serum levels as a precise guide to toxicity are analyzed. Finally, new developments in use of immunologic therapy for digoxin intoxication are presented.

Arrhythmias, Cardiac↗
PubMed1977

A comparison of the response to arm and leg work in patients with ischemic heart disease.

An exercise test based on arm work was evaluated in a series of 33 male patients, mean age 52 years, with ischemic heart disease. The responses to arm exercise on a modified table-mounted bicycle ergometer and to standard bicycle exercise were compared. Twenty six of 33 patients (79 per cent) had identical end-points with both tests. Three patients had an ischemic response, i.e., significant ST abnormality and/or angina pectoris during leg work only, and four patients during arm work only. 41 per cent of the peakload during leg exercise. Mean values were 181 and 439 kpm./min. (p less than 0.001). Comparison of individual data on peak load demonstrated only a weak correlation between arm and leg work capacity (r = 0.37, p less than 0.05). Peak heart rate was slightly higher during leg work, 129 compared to 122 beats/min. (p less than 0.05) but the mean heart rate-systolic blood pressure products were not significantly different. A subgroup of seven patients had a history of angina pectoris preferentially precipitated by arm work but their physiological responses did not differ significantly from those of patients without a history of arm work sensitivity. The data indicate that arm work is a satisfactory alternate diagnostic test method with respect to myocardial ischemia, but measurements of physical work capacity defined as aerobic capacity, cannot be based on arm work.

Adult↗
PubMed1977

Contraction and resting stiffness of isolated cardiac muscle: effects of inotropic agents.

The purpose of this study was to test the hypothesis that either hypoxia and its combined effects with extracellular calcium (Ca), digoxin, and ouabain, or these positive inotropic agents acting alone or in combination, influence contraction and resting stiffness of isolated papillary muscle. Stiffness was measured utilizing the sinusoidal forcing function technique. Neither an increase in extracellular calcium concentration (from 2.5 to 4.0 mM) nor digoxin or ouabain in either Ca concentration altered contraction or resting stiffness in the well-oxygenated environment. Resting stiffness for any given resting tension was increased at the end of hypoxia only in the presence of digoxin, and this occurred in both 2.5 mM Ca (P less than 0.02) and in 4.0 mM Ca (P = 0.05). Contraction stiffness for any given tension was increased in 2.5 mM Ca by hypoxia alone (P less than 0.05) and by hypoxia in the presence of digoxin (P less than 0.005) and ouabain (P less than 0.02), but was not increased in any experiments conducted in 4.0 mM Ca. The conclusions from these data are that certain experimental conditions of the study evoked different directional changes in stiffness and contractility. Further, changes in contraction stiffness are not always paralleled by changes in resting stiffness.

Animals↗