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Biomedical subjects

R A Bruce

Publications and source records attributed to R A Bruce.

At least 109 records · Page 6Linked to original sources
PubMed1981

Approximate normal standards of maximal cardiac output during upright exercise in women.

The observed normal ranges of age- and weight-adjusted maximal oxygen uptake and age-adjusted maximal heart rate during upright exercise using the Bruce protocol are shown for 104 asymptomatic women. Cardiac output was measured during upright exercise in 11 normal women with the use of the direct Fick method. On the basis of the relation between oxygen uptake and cardiac output in these 11 women, the cardiac output and stroke volume were estimated by regression in the 104 women to provide normal ranges of age-adjusted values for cardiac output and stroke volume. The potential usefulness of these age-adjusted normal ranges is illustrated by analysis of 21 observations of maximal cardiac output in 16 women with heart disease.

Adult↗
PubMed1981

Improved exercise performance in persons with stable angina pectoris receiving diltiazem.

The effects of diltiazem, a calcium antagonist drug, we compared with those of placebo on exercise performance during a series of symptom-limited upright exercise tests. Ten patients with chronic stable angina were studied over a period of 7 weeks. The drug was administered in a random double-blind fashion and was evaluated at increasing dose levels of 120, 180 and 240 mg/day. Diltiazem was effective in increasing the total duration of exercise (p < 0.001) and the time the first onset of angina (p < 0.02) and to the first appearance of 1 mm of S-T depression (p < 0.02). These effects were most marked at the highest dose level of diltiazem. The heart rate was reduced at rest (p < 0.05) and during submaximal exercise (p < 0.001). There was a reduction in diastolic blood pressure during submaximal exercise (p < 0.04) but no change in systolic pressure. Pressure-rate product was significantly reduced at submaximal (p < 0.001) but not maximal exercise. The reduction in pressure-rate product is postulated as the mechanism by which diltiazem enhances duration of exercise. There was no reduction in electrocardiographic evidence of myocardial ischemia at peak exercise by either clinical observation or computer analysis of spatial electrocardiographic variables Five of the six patients who continued to take the drug maintained or improved their exercise performance on follow-up study 8 to 10 months later.

Angina Pectoris↗
PubMed1981

A computer terminal program to evaluate cardiovascular functional limits and estimate coronary event risks.

A system of computer terminals was set up in a group of office practices, industrial medical departments and hospitals and connected to a central computer. This service provides a means of analyzing treadmill exercise results, which are displayed graphically on the computer printout. The system also provides estimates of probabilities of primary or secondary coronary heart disease events developing based on the exercise responses.

Adult↗
PubMed1980

Evaluation of hypertensive males for primary coronary heart disease events using conventional risk factors and maximal exercise testing.

Whereas hypertension is a risk factor for primary coronary heart disease events, the relative contributions of other risk factors and abnormal responses to symptom-limited maximal exercise are not well-established. After 5.2 +/- 1.5 years of follow-up of 633 men with clinically-diagnosed hypertension based upon criteria of examining physicians (whether or not the men were currently treated for hypertension), 54 primary events were revealed. The annual coronary heart disease (CHD) event rate of 16.9/1000 men at risk was significantly higher than the annual rate of 3.6/1000 found for healthy men (p < 0.0001). Variables associated with increased risk were smoking cigarettes, risk factor count or tally, chest pain during exercise, percentage of functional aerobic impairment, and percentage heart rate impairment, the latter two variables suggesting early evidence of left ventricular dysfunction on strenuous exertion. Ischemic ST depression was not an important predictor. The three exercise variables were included in an exercise predictor count, and multivariate analysis revealed that this count and the risk factor count were the most important predictors of primary CHD events. Combining the risk factor count and the exercise predictor count, three groups with increasing risk of primary CHD events were identified. In those persons with both a risk factor count and exercise predictor count of zero, the annual rate was 7.3 events/1000 man-years; when either count was one or more, the rate was 15.5 events/1000 man-years; when both counts were one or more, the rate was 49.5 events/1000 man-years.

Adult↗
PubMed1980

Influence of propranolol on exercise prescription of training heart rates.

Review of a longitudinal study of the effects of 40 mg of propranolol orally in 14 patients with coronary heart disease demonstrated a minor but not statistically significant change in the relationship of percentage of maximal oxygen uptake to percentage of maximal heart rate. In a cross-sectional comparison of several hundred patients who showed no other significant difference in initial findings in relation to propranolol, significant differences were present with respect to resting heart rate and responses to symptom-limited exercise, nevertheless the relationship of percentage of maximal oxygen uptake to the percentage of maximal heart rate was similar. Accordingly, we recommend maximal exercise testing in all patients prior to undertaking an exercise program so that their maximal heart rate can be determined accurately and rational training heart rates advised. The exercise test should be performed with the patients taking medications they anticipate continuing during the period of physical training, and if a change in medications is subsequently made then the exercise test should be repeated.

Coronary Disease↗
PubMed1980

Failure of mannitol to reduce electrocardiographic evidence of myocardial ischemia during upright exercise despite augmentation of cardiac output.

9 patients with clinically manifest ischemic heart disease underwent hemodynamic and electrocardiographic monitoring at rest, during several levels of submaximal and near maximal exercise on a treadmill and in recovery. The observations were repeated following infusion of mannitol. Despite augmentation of cardiac output at near maximal exercise, the electrocardiographic evidence of ischemia worsened.

Cardiac Output↗
PubMed1980

Pilot study examining the motivational effects of maximal exercise testing to modify risk factors and health habits.

A mailed questionnaire was sent to 2,892 men aged 35-65 years who had undergone symptom-limited treadmill exercise testing. The study was designed to assess the possible role of exercise testing as a means of motivating patients to modify appropriate risk factors and health habits. There was a 69% response to the questionnaire and 63% of patients replying indicated they modified one or more risk factors and health habits and this change they attributed to the exercise test. It was found that persons with an abnormal functional aerobic impairment, demonstrated by the exercise test, were more likely to be motivatged to change. This pilot study raises the possibility that exercise testing may play an important role in modification of coronary risk factors and health habits and the design of a better controlled study is suggested.

Adult↗
PubMed1980

Age of patients and morbidity associated with mandibular third molar surgery.

The purpose of this study was to define the incidence of operative and postoperative morbidity associated with the removal of impacted mandibular third molars in patients of various ages. Results of this investigation show that there is a significant increase in surgical morbidity as patients become older. When it has been determined that the mandibular third molars must be removed, the operation should be performed on the young adult.

Adolescent↗
PubMed1980

Longitudinal variations in maximal oxygen consumption in healthy men.

Maximal oxygen consumption [(VO2)max] was measured on three separate occasions over 8 years in 12 healthy men. The decline in (VO2)max with age was less than noted in previous studies and was smallest in men taking regular physical exercise. The presence of ST depression during or after exercise did not influence the decline in (VO2)max.

Aged↗
PubMed1979

Comprehensive analysis of exertional ECG changes before and after oral propranolol.

In 12 patients with symptomatic coronary heart disease and three normal persons, comprehensive analyses of the electrocardiographic changes associated with symptom-limited upright exercise are made by computer analysis of the electrocardiogram recorded using a Frank XYZ lead system. This analysis provided a display of the 12 lead ECG, vectorcardiogram, polarcardiogram, and spatial cardiogram and measurements of spatial magnitudes of heart vectors. The effect of 40 mg of oral propranolol was assessed by repeating the exercise protocol 60--90 min later. There is evidence that propranolol reduces the electrocardiographic features of myocardial ischemia. This reduction in myocardial ischemia correlates with reductions in pressure rate product and heart rate. The presence of infarct criteria with exercise is variable and not apparently influenced by propranolol.

Adult↗
PubMed1979

Acute effects of oral propranolol on hemodynamic responses to upright exercise.

Noninvasive measurements of maximal oxygen intake and invasive measurement of systemic and pulmonary arterial pressures, arterial and mixed venous oxygen contents and direct Fick cardiac output are reported for 3 healthy men and 14 men with coronary heart disease. Observations were obtained at supine and sitting rest, during graded levels of upright exercise on a treadmill up to symptom-limited maximal effort and in two periods of recovery. The effects of 40 mg of propranolol orally were ascertained by repeating the measurements 1 to 1 1/2 hours later. The most consistent effect of propranolol was reduction of pressure-rate products at all phases; slowing of heart rate was significant only during exercise and recovery, and the greater slowing was accompanied by a significant increase in stroke volume. These changes were similar in patients with and without evidence of left ventricular impairment greater than 15 percent on exercise testing. Maximal oxygen intake decreased in healthy subjects and decreased slightly in patients with coronary heart disease with less than 15 percent left ventricular impairment or percent deviation of pressure-rate product from age-predicted normal values during the control study. Maximal oxygen intake increased in patients with more than 15 percent left ventricular impairment. Arterial-mixed venous oxygen difference increased after propranolol because of a reduction of mixed-venous oxygen content attributed to greater peripheral extraction of oxygen.

Blood Pressure↗
PubMed1979

Clinical importance of directional statistics for electrocardiographic differentiation of smoking habits.

Statistical methods for the analysis of directional data are of relatively recent origin and have not been generally applied in clinical investigations where they are appropriate. This study compares spherical means and standard deviations for directional polarcardiographic variables with the linear means and standard deviations of the same variables for a typical industrial cohort of male white collar workers. Normal subjects were classified by smoking status and by independent clinical evidence of the presence of CHD, and both directional and linear statistics are applied to compare the PCG variables in these groups. Directional statistics more accurately define the spherical means and variances of heart vectors and thereby permit more reliable differentiation of directions, or angles to aid diagnosis.

Adult↗