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Biomedical subjects

R A Bruce

Publications and source records attributed to R A Bruce.

At least 73 records · Page 4Linked to original sources
PubMed1985

Long-term monotherapy of angina pectoris with diltiazem.

Eighteen patients with exertional angina were treated with diltiazem (360 mg/day). Serial exercise testing was performed and the results were compared to evaluations when patients were receiving placebo at the initiation and termination of the study. Serial exercise tests indicated significant improvement in duration of exercise (+18%, p less than 0.001), time to 1 mm ST depression (+32%, p less than 0.005), and time to angina (+46%, p less than 0.001) when patients were receiving diltiazem. During diltiazem treatment, there was a significant reduction in myocardial oxygen demand as indicated by the change in submaximal pressure rate product. This may contribute to the beneficial effect of diltiazem in patients with exertional angina. The reduction in pressure rate product was due primarily to a change in heart rate. This study provides evidence that diltiazem is an effective long-term monotherapy for angina; no evidence of drug tachyphylaxis was apparent after a total of 16 months treatment with diltiazem.

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PubMed1984

Estimation of inferobasal myocardial infarct size by late activation abnormalities of the QRS complex.

This report describes the relation of myocardial infarct (MI) size in the left ventricular inferobasal wall, measured at necropsy, to late activation abnormalities of the QRS complex, measured by computerized spatial vectorcardiography. Fifteen patients with single inferobasal MIs and 10 patients with no evidence of heart disease were studied. The percentage of MI in the inferobasal wall was significantly related to the vectorcardiographic abnormalities noted late (i.e., 31 +/- 13 ms before the end of the QRS waveform) (r = 0.96, p less than 0.00001). The integral of the vector magnitudes during late abnormal activation significantly predicted the amount of MI in the basal inferior wall (r = 0.88) and in the basal inferior wall plus the outer, subepicardial half of the transmural middle inferior, lateral and inferoseptal walls (r = 0.91). The additional information obtained from late activation of the QRS complex contributed more significance to the estimation of the left ventricular inferobasal MI size than the abnormalities commonly noted during early activation (i.e., during the Q wave).

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PubMed1984

Evaluation of hematoporphyrin photoradiation therapy to treat choroidal melanomas.

Hematoporphyrin derivative-photoradiation therapy (HPD-PRT) was used to treat choroidal melanomas in 23 human subjects. Tumor sizes were divided into three categories: less than 500 mm3 (11 patients), 500-1,000 mm3 (four patients), and greater than 1,000 mm3 (eight patients). Tumors were exposed to 630 nm laser light at total doses of 300-3,000 J/cm2. Significant tumor reduction was noted in the subjects with initial tumor volume of less than 500 mm3 and 500-1,000 mm3.

Choroid Neoplasms↗
PubMed1984

Long-term study of high-dose diltiazem in chronic stable exertional angina.

The efficacy of a calcium slow channel-blocking drug, diltiazem (360 mg/day), was compared to placebo in 15 men with exertional angina during a 21-week study. Symptom-limited exercise testing was used to evaluate the effects of the drug. Analysis of variance indicated the increase in the values of three time-related variables, time to onset of angina, time to onset of 1 mm ST depression, and total duration of exercise, were highly significant (all p less than 0.001). The increase from the second week of placebo to the last week of diltiazem was 4 X 1 minutes for time to angina, 2 X 4 minutes for time to 1 mm ST depression, and 2 X 3 minutes for total duration. In addition, the differences between mean values of these variables for placebo and corresponding diltiazem period at weeks 3 and 4 were significant (p less than 0.01, p less than 0.01, p less than 0.05) and for diltiazem week 20 and placebo week 21 were significant (p less than 0.005, p less than 0.01, p less than 0.005). Weekly angina frequency was reduced from a mean of 17 episodes/week during placebo to one episode/week during diltiazem (p less than 0.001). Submaximal pressure-rate product was reduced significantly during diltiazem (p less than 0.001), and the ECG evidence of myocardial ischemia was reduced by diltiazem at submaximal (p less than 0.02) and maximal exercise (p less than 0.001). The drug was well tolerated and appears to be effective monotherapy for exertional angina.

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PubMed1984

Mean systolic ejection rate after aortocoronary bypass graft surgery.

In 62 patients with coronary artery disease who underwent aortocoronary bypass graft surgery, we measured the mean systolic ejection rate invasively at rest and during upright exercise before and several months after operation. After bypass surgery, mean systolic ejection rate did not show any change at either supine or sitting rest and at submaximal exercise levels of walking on a treadmill. At maximal exercise, only patients with complete revascularization showed a significant increase in heart rate from 105 to 147 (+40%) and mean systolic ejection rate from 339 ml/sec to 404 ml/sec (+19%, P less than 0.001). Patients with incomplete revascularization did not show a substantial change in these variables. Beta-blocker withdrawal did not affect the result significantly.

Adrenergic beta-Antagonists↗
PubMed1984

Changes in cardiac functional capacity after coronary bypass surgery in relation to adequacy of revascularization.

Seventy patients having aortocoronary vein bypass grafting surgery for angina pectoris underwent preoperative invasive exercise testing to symptom limits and again 6 to 14 months postoperatively. Cardiac output was measured using the direct Fick principle. Postoperatively at maximal exercise, there was a 3.11 liters/min (p less than 0.0001) increase in cardiac output in men (n = 61) and a 2.04 liters/min (p less than 0.01) increase in women (n = 9). Patients with complete revascularization showed a significantly greater improvement in cardiac output postoperatively than did those with incomplete revascularization (26 versus 6%, p less than 0.0001). The major reason for the increased maximal cardiac output was a marked increase in heart rate while stroke volume was maintained at the same preoperative level. These findings were true irrespective of preoperative use of beta-adrenergic blocking drugs.

Adrenergic beta-Antagonists↗
PubMed1984

Long-term effect of vasectomy on coronary heart disease.

We investigated the association between coronary heart disease (CHD) and vasectomy in a population of 10,632 men who were under surveillance for multiple CHD risk factors during participation in a university-based exercise testing program. We conducted a mail survey with telephone follow-up to determine the vasectomy status of individuals in the population. Responses were obtained from 6,159 individuals. The 4.944 males on whom information was complete enough to be included in the multivariate analysis comprised the study population. Among the 1,383 (28 per cent) vasectomized males in the study populations, the interval from vasectomy to the time of the survey ranged from less than one year to 37 years with a mean duration of 15 years. Although increased relative risks for CHD were found to be associated with family history of CHD, high blood pressure and smoking in this population, the relative risk of CHD associated with vasectomy was not increased in general, nor was it increased when the vasectomized males were classified by time since vasectomy. Likewise, serum antisperm-antibody titers were not predictive of CHD among vasectomized men. These studies support the findings from previous investigations of populations with shorter average post-vasectomy experience in which vasectomy has been shown to be unassociated with altered risk of CHD in humans.

Adolescent↗
PubMed1984

Improvement in aerobic and hemodynamic responses to exercise following aorta-coronary bypass grafting.

Preoperative and postoperative hemodynamic studies were performed during exercise in 70 patients having aorta-coronary bypass grafting for the treatment of angina. There was significant symptomatic improvement with 88% of patients free of angina postoperatively. In patients with complete revascularization there was a marked improvement during exercise in maximal oxygen consumption, cardiac index, and maximal pressure-rate product. In addition, there was a fall in pulmonary arterial pressure postoperatively. In contrast, patients with incomplete revascularization showed a small but insignificant rise in maximal oxygen consumption and cardiac index. The major reason for the increase in cardiac index was a marked increase in heart rate rather than a change in stroke index. In patients with complete revascularization there was a significant increase in stroke work index at maximal exercise.

Adrenergic beta-Antagonists↗
PubMed1984

Exercise, functional aerobic capacity, and aging--another viewpoint.

Currently, there is strong public interest in exercise conditioning, especially endurance types of dynamic exercise. In addition to the short-term benefits of enhanced fitness and health, there is a growing expectation of long-term benefits in relation to possible reduction of morbidity, disability, and mortality from chronic disease, especially cardiovascular disease. Physical exercise increases aerobic metabolism and the associated pulmonary and cardiovascular responses needed to deliver the required oxygen. Functional aerobic capacity or maximal oxygen consumption (VO2max) defines the functional limits of the cardiovascular system. Aerobic capacity can be measured or be reasonably estimated by appropriate methods of exercise testing, and is probably the best integrated measure of the functional limits of the whole body which can define the effects of the aging process. The rate of decline in VO2max observed in longitudinal studies of the same subjects substantially exceeds that observed in cross-sectional studies sampling male subjects of different ages. This rate is twice as great in sedentary as in physically active male subjects. When these provocative findings are considered in relation to trends observed in survival of populations vs the nearly constant limit of the average life span, the need for appropriately designed long-term prospective, definitive studies becomes apparent.

Adult↗
PubMed1983

Prediction of maximal cardiac output in preoperative patients with coronary artery disease.

Of 100 patients (89 men, 11 women) studied preoperatively to determine their aerobic and hemodynamic profiles at rest and during upright treadmill exercise. The mean maximal cardiac output (CO), measured using the direct Fick principle, was 57 +/- 14% of average normal values. The reduction in maximal heart rate (63 +/- 13% of normal) was a greater factor in the reduction in CO than stroke volume (88 +/- 16% of normal). Maximal oxygen consumption (VO2max) was 48 +/- 15% of normal and the greater reduction in VO2max compared with CO was due to lower peripheral extraction in the coronary patients. Variables that correlated with maximal CO in a univariate analysis included angina severity (r = -0.45), VO2max (r = 0.67), maximal heart rate (r = -0.31), left ventricular dysfunction (r = -0.45), maximal systolic blood pressure (r = -0.31) and number of vessels with greater than or equal to 50% diameter reduction (r = -0.3). Resting ejection fraction did not correlate with maximal CO. In a multivariate analysis, 4 variables correlated significantly (r = 0.77) with maximal CO: in order, VO2max, number of vessels with greater than or equal to 50% stenosis, magnitude of ST depression and sex.

Cardiac Output↗
PubMed1983

Prognostic value of risk factors and exercise testing in men with atypical chest pain.

Of 551 men with atypical chest pain enrolled in the Seattle Heart Watch Study, annual follow-up over a 5- to 10-year period identified 36 persons who experienced a primary coronary heart disease event. Only three events were fatal, and they were in men over the age of 50. Cox's regression model confirmed a significant association of the conventional risk factors of smoking (P = 0.03), elevated resting systolic blood pressure (P = 0.02) and hypercholesterolemia (P = 0.03) with primary coronary heart disease events. A count of these three variables was highly predictive (P = 0.002). A positive family history was not predictive. Functional aerobic impairment (P = 0.002) and ST depression (P = 0.0003) were the most useful exercise predictors. In men who had neither risk factors nor abnormal exercise predictors, the percentage free of coronary events at 9 years was 96% compared to 76% in men with one or more of the abnormal exercise findings (P less than 0.0001). Of men with only risk factors, 86% remained free of events at 9 years. This study demonstrates that the evaluation of both risk factors and exercise responses enhances the prognostic evaluation of men with atypical chest pain. The classification of men into low-, medium- and high-risk groups can be easily accomplished in office practice.

Actuarial Analysis↗
PubMed1983

Enhanced risk assessment for primary coronary heart disease events by maximal exercise testing: 10 years' experience of Seattle Heart Watch.

A 10 year prospective community practice study in Seattle of risk of primary morbidity (defined by hospital admission) and mortality due to coronary heart disease in 3,611 men and 547 women initially free of clinical manifestations of this disease revealed a crude incidence of 202 coronary heart disease events, or 4.9% in 6.1 +/- 2.6 years of follow-up. The case fatality rate was 16.8%. Stratification by clinical classification of asymptomatic healthy persons versus patients with atypical chest pain syndrome (not angina pectoris) and hypertension (as classified by physicians) showed an incidence rate of primary events due to coronary heart disease of 2.9, 5.5 (not significant) and 10.0% (p less than 0.001), respectively. Identification of conventional risk factors is known to be important for risk assessment. However, the presence of any conventional risk factor, in conjunction with two or more selected maximal exercise predictors (which vary with the clinical classification) at enrollment, substantially increased the cumulative 6 year incidence rate to 24.3, 15.5 and 33.3% in asymptomatic healthy men, patients with atypical chest pain syndrome and hypertensive patients, respectively. Observation of the exercise predictors in the absence of conventional risk factors increased the risk much less, suggesting that the use of maximal exercise testing for risk assessment in those with no clinical manifestations of disease might be limited to persons with one or more conventional risk factors.

Adult↗
PubMed1983

Augmented mean systolic ejection rate in coronary patients treated with diltiazem.

The effect of a single 120-mg oral dose of diltiazem on the mean systolic ejection rate (MSER) was studied in 18 patients with exercise-induced angina pectoris, at rest, during, and after symptom-limited, multi-stage, treadmill testing. The patients were subdivided into two groups according to the mean pulmonary capillary pressure at maximal exercise. In group I (9 patients), the mean pulmonary capillary pressure was 16 mm Hg or lower, and in group II (9 patients), this variable was higher than 16 mm Hg at maximal exercise. Before diltiazem, MSER increased in response to exercise in both groups. MSER was correlated with stroke volume (r = 0.90), heart rate (r = 0.34), and systemic vascular resistance (r = 0.82), but not correlated with mean pulmonary capillary pressure (r = 0.18) or mean arterial pressure (r = 0.06) for all patients. 1 h after the administration of diltiazem, patients in group I showed no significant change in MSER. Group II patients showed significant increases in MSER at two submaximal workloads (267 vs. 295, p less than 0.05, 292 vs. 325, p less than 0.02), maximal exercise (289 vs. 333, p less than 0.05), and the 3rd min of recovery (216 vs. 278, p less than 0.05). In patients with exertional left ventricular dysfunction, diltiazem improved cardiac performance, and the changes in MSER suggest that contractility was influenced favorably. Increased coronary blood flow is postulated as a mechanism for this improvement.

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