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Biomedical subjects

F G Yanowitz

Publications and source records attributed to F G Yanowitz.

13 recordsLinked to original sources
PubMed1991

Beta-blockade with bucindolol in heart failure caused by ischemic versus idiopathic dilated cardiomyopathy.

BACKGROUND: We investigated the effects of bucindolol, a nonselective, non-ISA beta-blocker with mild-vasodilatory properties, in patients with congestive heart failure from ischemic dilated cardiomyopathy (ISCDC, n = 27) and compared the results with those in subjects with heart failure from idiopathic dilated cardiomyopathy (IDC, n = 22). METHODS AND RESULTS: Patients were randomized in a double-blind fashion to receive 12 weeks' treatment with either bucindolol or placebo, with randomization stratified for IDC or ISCDC: Invasive (right heart catheterization) and noninvasive (echo, MUGA, central venous norepinephrine, exercise treadmill studies, and symptom scores) tests of heart failure severity were determined at baseline and end of the study. For all subjects (ISCDC plus IDC), relative to placebo treatment, bucindolol-treated patients had significant improvement in ejection fraction, left ventricular size and filling pressure, stroke work index, symptom score, and central venous norepinephrine. However, most of these differences could be attributed to improvement in the IDC subgroup, as the only parameter with a statistically significant degree of improvement in the bucindolol-treated ISCDC subgroup was left ventricular size. CONCLUSIONS: We conclude that beta-blockade may produce quantitatively different degrees of response in different kinds of heart muscle disease.

Adrenergic beta-Antagonists↗
PubMed1990

Long-term beta-blocker vasodilator therapy improves cardiac function in idiopathic dilated cardiomyopathy: a double-blind, randomized study of bucindolol versus placebo.

PURPOSE: Bucindolol is a potent nonselective beta-blocking agent with vasodilatory properties. In this study, we evaluated the effects of long-term bucindolol therapy in the treatment of heart failure from idiopathic dilated cardiomyopathy. PATIENTS AND METHODS: Patients were eligible for enrollment if they had symptomatic heart failure, idiopathic dilated cardiomyopathy, and left ventricular ejection fraction less than 0.40. All patients received an initial test dose of 12.5 mg bucindolol orally every 12 hours for two or three doses. Patients tolerating the test dose were randomly assigned (double-blind) to receive bucindolol or placebo in a 3:2 ratio. Study medication was begun at a dose of 12.5 mg orally every 12 hours and gradually increased over a 1-month period until either a maximum tolerated dose or a target dose of 100 mg every 12 hours was reached. Study medication was then continued for an additional 2 months. RESULTS: A total of 24 patients were enrolled into the study. Twenty-three patients tolerated bucindolol test challenge; 14 were randomized to receive bucindolol, and nine were randomly assigned to receive placebo. The placebo group (age 56 +/- 2 years) was significantly older than the bucindolol group (46 +/- 3 years), but by all other clinical and hemodynamic parameters the two groups were comparable. Twenty-two of 23 patients completed the study. Patients treated with bucindolol had significant improvements in clinical heart failure symptoms and in resting hemodynamic function, including an increase of left ventricular ejection fraction (0.26 +/- 0.02 to 0.35 +/- 0.09, p = 0.003), cardiac index (2.2 +/- 0.1 to 2.5 +/- 0.4 L/minute/m2, p = 0.014), and left ventricular stroke work index (25 +/- 3 to 35 +/- 7 g.m/m2, p = 0.002) and a decrease in pulmonary artery wedge pressure (17 +/- 3 to 10 +/- 5 mm Hg, p = 0.005) and heart rate (86 +/- 3 to 75 +/- 9 beats/minute, p = 0.012). Patients treated with bucindolol also had a significant increase in exercise left ventricular ejection fraction (0.26 +/- 0.03 to 0.32 +/- 0.14, p = 0.015) and reduction in questionnaire-measured symptoms (p = 0.007) and New York Heart Association functional class (p less than 0.001). However, total treadmill exercise duration and maximal oxygen consumption with exercise did not change. No changes in rest or exercise parameters were observed in the placebo-treated group. Central venous plasma norepinephrine concentration decreased significantly in the bucindolol-treated group (423 +/- 79 to 212 +/- 101 pg/mL, p = 0.010), but was unchanged in the placebo-treated group. CONCLUSION: Bucindolol is well tolerated in patients with idiopathic dilated cardiomyopathy and congestive heart failure, and therapy for 3 months is associated with improved resting cardiac function, improved heart failure symptoms, and a reduction in venous norepinephrine concentration.

Adrenergic beta-Antagonists↗
PubMed1990

Small-sample reproducibility estimates: an example using rebreathing measurements.

We developed a statistical technique to estimate the reproducibility of a parameter from a population in which only two repeated measurements can be made in a single individual. The following data were analyzed: acetylene cardiac output (Qc), lung tissue volume (Vti), and carbon monoxide diffusing capacity (DLCO) measured by rebreathing techniques in a population of 86 healthy subjects (51 men and 35 women). Each subject was measured twice with a computerized rebreathing system using a test gas of 10% He-0.3% C18O-0.7% C2H2-25% O2-balance N2 while sitting at rest. The estimated coefficients of variation for repeated measurements were 6.8, 10.3, and 5.7% for Qc, Vti, and DLCO, respectively. Chebyshev's inequality was used to estimate the imprecision for a single measurement of these parameters and for averages of two or more repeated values. A single measurement of Qc would be within 14.2% of a "true" mean 90% of the time, whereas an average of three consecutive measurements would be within 8.2% of the true mean 90% of the time. Single measurements of Vti and DLCO were found to be within 21.7 and 12.0%, respectively, of the true mean 90% of the time. When three consecutive measurements are averaged, Vti is within 12.6% and DLCO is within 6.9% of the true mean 90% of the time. We conclude that 1) rebreathing Qc is as reproducible as other measurements of cardiac output, 2) rebreathing measurements of DLCO are as reproducible as those made by the single-breath technique, and 3) an average of two to three measurements of Vti should be made to obtain values with a reasonable degree of precision.

Acetylene↗
PubMed1989

Noninvasive evaluation of world class athletes engaged in different modes of training.

This study evaluated by noninvasive methods the cardiac structure and functional characteristics of world class athletes participating in different types of training programs. Fourteen subjects, including 4 strength-trained (discus and shot put), 4 endurance-trained (long distance runners), 4 decathlon-trained (strength and endurance), 2 wheelchair athletes and 31 college-age control subjects were evaluated using electrocardiography, M-mode echocardiography and maximal oxygen consumption. M-mode echocardiography measurements of left ventricular structure and function were compared before and after normalization for lean body weight. As expected, endurance athletes had greater maximal O2 consumption than the other groups (p less than 0.05). Before normalization for lean body weight, there were no significant differences in end-diastolic dimensions. After normalization, the endurance, wheelchair and control subjects had end-diastolic dimensions larger than those of strength athletes. Strength athletes appeared to have a much larger posterior wall and septal thickness than all groups except the decathlon athletes. However, when normalized, there was no difference among any of the groups. Previous investigators have attempted to determine "normalcy" of cardiac hypertrophy by looking at the ratio of left ventricular wall thickness to left ventricular radius. In the present study, the thickness to radius ratio in strength athletes was 33% greater than that in endurance athletes. It appears that the left ventricular wall thickness in the strength athletes occurred without a concomitant increase in left ventricular radius and that the left ventricular hypertrophy of world class athletes is related to the total increase in lean body weight. However, ventricular dimensions may be related more to the type of overload experienced.

Diastole↗
PubMed1987

Occurrence of exercise-induced and spontaneous wide complex tachycardia during therapy with flecainide for complex ventricular arrhythmias: a probable proarrhythmic effect.

Flecainide acetate, a new antiarrhythmic agent, possesses favorable pharmacokinetic and hemodynamic properties and demonstrates highly favorable antiarrhythmic activity in patients with ventricular arrhythmias. However, the proarrhythmic potential of flecainide deserves further evaluation. In 7 (13%) of 55 consecutive patients treated with oral flecainide, 200 to 600 mg/day, for complex ventricular arrhythmias (including sustained ventricular tachycardia in 14), we observed the appearance of new or more sustained exercise-induced (five patients) or spontaneous (two patients) wide complex tachycardia. The mechanism of wide complex tachycardia appeared to be ventricular tachycardia in all seven. In our series, episodes were self-remitting or successfully treated. In four patients, wide complex tachycardia did not recur during exercise testing during alternative antiarrhythmic therapy (three patients) or no antiarrhythmic therapy (one patient). These observations raise the possibility of flecainide-related proarrhythmia, manifested as an increased propensity to exercise (activity)-induced wide complex tachycardia, which was not reliably predicted by results of Holter recordings or programmed electrical stimulation. Patients with complex ventricular arrhythmias beginning long-term treatment with oral flecainide should be considered for treadmill exercise testing together with ambulatory monitoring as part of the initial assessment of drug efficacy.

Adult↗
PubMed1987

Turbine flowmeter vs. Fleisch pneumotachometer: a comparative study for exercise testing.

The purpose of this study was to investigate the characteristics of a newly developed turbine flowmeter (Alpha Technologies, model VMM-2) for use in an exercise testing system by comparing its measurement of expiratory flow (VE), O2 uptake (VO2), and CO2 output (VCO2) with the Fleisch pneumotachometer. An IBM PC/AT-based breath-by-breath system was developed, with turbine flowmeter and dual-Fleisch pneumotachometers connected in series. A normal subject was tested twice at rest, 100-W, and 175-W of exercise. Expired gas of 24-32 breaths was collected in a Douglas bag. VE was within 4% accuracy for both flowmeter systems. The Fleisch pneumotachometer system had 5% accuracy for VO2 and VCO2 at rest and exercise. The turbine flowmeter system had up to 20% error for VO2 and VCO2 at rest. Errors decreased as work load increased. Visual observations of the flow curves revealed the turbine signal always lagged the Fleisch signal at the beginning of inspiration or expiration. At the end of inspiration or expiration, the turbine signal continued after the Fleisch signal had returned to zero. The "lag-before-start" and "spin-after-stop" effects of the turbine flowmeter resulted in larger than acceptable error for the VO2 and VCO2 measurements at low flow rates.

Carbon Dioxide↗
PubMed1985

A randomized trial of low-dose beta-blockade therapy for idiopathic dilated cardiomyopathy.

Beta-blockade therapy to improve survival in idiopathic dilated cardiomyopathy (IDC) has been both advocated and criticized. However, randomized studies have not been performed. Thus, 50 patients with IDC were randomized in pairs to standard therapy (C) alone or with beta blockade (BB). Beta-blockade therapy with metoprolol was titrated from 12.5 to 50 mg twice daily as tolerated (final average dose, 61 mg/day). Groups were comparable in age (C, 50 +/- 15 years; BB, 51 +/- 13 years), gender (C, 76% male; BB, 56% male), entry functional class (C, 2.8 +/- 0.8; BB, 2.7 +/- 0.7), and left ventricular ejection fraction (C, 27 +/- 12%; BB, 29 +/- 10%). Follow-up averaged 19 months (range 1 to 38). One subject in each group was lost to follow-up. There were 3 early BB dropouts (within 2 days) due to low-output syndrome (2 patients) or fatigue (1 patient). Eleven patients died. By intention to treat, 5 BB and 6 C patients died (difference not significant). By actual treatment, 3 BB patients died, including 2 late dropouts (at 0.2, 10 and 17 months), and 8 C patients died (at 2, 9, 9, 15, 18, 24, 29 and 32 months, p = 0.12). In additional, functional evaluation on follow-up (functional class, San Diego questionnaire and exercise time) all tended to favor those receiving BB. Low-dose BB is tolerated in 80% of IDC patients on a long-term basis. Those continuing to take BB have a good prognosis. Mortality in C patients, however, is less than in some retrospective studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1985

Effect of intravenous aminophylline upon the incremental exercise performance of healthy men.

Aminophylline increases the contractile force of fatiguing muscles. The effects of aminophylline upon maximal exercise performance are not defined. 6 healthy men performed incremental bicycle ergometry before and after receiving intravenous aminophylline (6 mg/kg). Maximal oxygen uptake, maximum work rate, and maximum minute ventilation were unchanged following aminophylline. Heart rate measured at rest and at 50-watt increments of work rate was significantly increased following aminophylline (p less than 0.03). The heart rate response to incremental exercise (delta HR/delta VO2) was unchanged by aminophylline. We conclude that aminophylline does not increase maximal exercise performance of healthy men.

Adult↗
PubMed1985

Heritability of cardiac size: an echocardiographic and electrocardiographic study of monozygotic and dizygotic twins.

Because of the uncertainty as to the extent to which cardiac size is determined by exercise training vs genetic endowment, this study investigated familial (genetic plus common family environment) vs nonfamilial influences on cardiac size. College-age monozygotic twins (group 1, 31 sets), dizygotic twins (group 2, 10 sets), siblings of like sex (group 3, six sets), and nonrelated subjects (group 4, 15 sets) underwent echocardiographic and electrocardiographic tests, measurement of maximum oxygen uptake (VO2max), and evaluation of pulmonary and body composition; mean intrapair differences of the four groups were compared. Mean intrapair differences in cardiac size varied as much for subjects in group 1 as for those in groups 2 and 3. However, subjects in groups 1, 2, and 3 had less variation (p less than .05) than those in group 4. After the initial testing, 14 pairs of monozygotic twins, five sets of dizygotic twins, and six sets of siblings underwent 14 weeks of exercise training (both members participated) and all tests were repeated. After exercise training, subjects in group 1 still had as much intrapair variability in cardiac size as those in groups 2 and 3. The data suggest cultural familial influences are more important in determining cardiac size than nonfamilial influences or even genetic influences alone.

Adult↗
PubMed1977

Evaluation of a computerized arrhythmia alarm system.

A prospective study of a computerized arrhythmia alarm system was carried out in the coronary care unit during 200 patient hours of monitoring. The computer system was designed to activate an alarm on the development of rhythm and conduction disorders including asystole, ventricular tachycardia, atrial tachycardia, sinus tachtcardia, bradycardia, frequent premature ventricular beats, atrial fibrillation and bundle branch block. Study patients were simultaneously monitored by the computer system and a conventional analog heart rate alarm system. All alarms generated by the two systems were evaluated. Of 79 computer alarms, 42 (53 percent) were true positive alarms; during the same period there were 167 analog alarms of which only 13 (8 percent) were true positive alarms. In both systems, false positive alarms were primarily due to patient movement, but they occurred only 25 percent as often with the computer system as with the analog system. These results indicate that computerized arrhythmia monitoring systems offer significant advantages over conventional monitoring techniques.

Arrhythmias, Cardiac↗