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Biomedical subjects

K F Hossack

Publications and source records attributed to K F Hossack.

At least 55 records · Page 3Linked to original sources
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↗
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.

Aged↗
PubMed1982

Efficacy of diltiazem in angina on effort: a multicenter trial.

During a multicenter study 57 patients with exercise-induced angina were evaluated with serial exercise testing to assess the efficacy of diltiazem, a calcium slow channel blocking agent, compared with a placebo. The study consisted of a 1 week single-blind placebo stabilization period followed by a double-blind triple crossover between diltiazem and placebo. Three dose levels were tested (120, 180 and 240 mg/day) in each patient. For the three time-related variables there was a significant dose-related response, with 240 mg/day being the most effective. The increases, over the washout placebo stabilization values, of the time-related variables for the 240 mg/day week compared with the corresponding placebo week were total duration of exercise 1.87 versus 1.05 minutes (p less than 0.002), time to onset of angina 1.81 versus 1.17 minutes (p less than 0.01) and time to appearance of 1 mm S-T segment depression 1.81 versus 1.01 minutes (p less than 0.002). Analysis of exercise variables indicated a significant reduction in heart rate, diastolic blood pressure, and pressure-rate product at submaximal exercise after administration of diltiazem. Diastolic blood pressure was significantly reduced at maximal exercise. Heart rate and pressure-rate product were unchanged at rest during submaximal or maximal exercise. Submaximal and maximal exercise S-T depression was not significantly altered by diltiazem. The reduction in pressure-rate product at submaximal exercise was a possible mechanism for the drug's beneficial effect in enhancing the three time-related variables.

Adult↗
PubMed1982

Evaluation of automated blood pressure measurements during exercise testing.

Measurements of systolic (SBP) and diastolic (DBP) blood pressure were made at rest and during symptom-limited exercise with an automated blood pressure measuring device (EBPM). Comparisons were made between the EBPM readings and those made with mercury manometer. Correlations were high (SBP r = 0.92, DBP r = 0.80) when readings were made in the same arm, but were less satisfactory when the cuffs were on different arms (SBP r = 0.80, DBP r = 0.46). The correlation between two mercury manometer readings was SBP r = 0.90, and DBP r = 0.75. Comparison between EBPM and intra-arterial measurements were similar (SBP r = 0.74, DBP r = 0.79) to comparison between mercury manometer and intra-arterial measurements (SBP r = 0.81, DBP r = 0.61). The EBPM detected SBP at consistently higher levels than did physicians, which may be an advantage in the noisy environment of an exercise test. There was a definite tendency for physicians to record blood pressure to the nearest 10 mm Hg, whereas the frequency distribution curve for EBPM measurements was smoother. The EBPM operated satisfactorily at rest and during maximal exercise and gave as reliable measurements as a physician using a mercury manometer and, in the small number of available cases, detected exertional hypotension more often than the physician.

Blood Pressure↗
PubMed1982

Comprehensive evaluation of electrocardiographic methods for detection of myocardial infarction.

In two groups of patients the detection of myocardial infarction (MI) by analysis of four different electrocardiographic methods was evaluated. The various methods included the conventional 12 lead ECG (CV-ECG), the 12 lead ECG derived from Frank XYZ lead system signals (D-ECG), the polarcardiogram (PCG) and the vectorcardiogram (VCG). An invasive group consisted of 137 patients who had undergone cardiac catheterization. An MI was defined as a regional wall motion abnormality in the distribution of a coronary artery with at least 70% diameter reduction. The noninvasive group consisted of 116 patients in whom independent clinical information was limited to noninvasive assessments. In this group, Telemed Computer Systems' interpretation of the conventional (TC-ECG) and derived (TD-ECG) electrocardiogram was also available for comparison. An MI was defined in this group as either a compatible history with documented cardiac enzyme elevations, a resting defect on thallium scan, or a regional wall motion abnormality in a resting, radionuclide isotope ventriculogram. In this study the other methods of ECG evaluation demonstrated no advantage over the electrocardiographer's reading of the conventional ECG.

Adult↗
PubMed1982

Acute and chronic effects of diltiazem on A-V conduction at rest and during exercise.

The acute and chronic electrocardiographic effects of diltiazem, a drug which inhibits calcium passage through slow channels, were examined both at rest and during symptom-limited exercise. In the acute study, 12 patients with coronary artery disease (CAD), three patients with hypertrophic cardiomyopathy (HCM), and one patient with both CAD and HCM performed symptom-limited upright exercise prior to and one hour after receiving 120 mg oral dose of diltiazem. In the chronic study, three dose levels of diltiazem (120 mg/day, 180 mg/day, 240 mg/day) were compared with placebo in ten patients with CAD. Each patient received one week of placebo followed by placebo or diltiazem in a double-blind random cross-over fashion, so that each patient received four weeks of placebo and three weeks of diltiazem, one week at each dose level. Each week, symptom-limited upright exercise testing was performed. In the acute study, diltiazem did not significantly affect the mean PR, QRS, QTC intervals or the heart rate at rest or at maximal exercise. In one patient, diltiazem markedly slowed the ventricular response to atrial fibrillation and in another patient, provoked transient Mobitz I block. In the chronic study, the only significant difference observed was a prolongation of the resting PR interval on the 240 mg/day dose schedule (p less than .005).

Administration, Oral↗
PubMed1982

Maximal cardiac function in sedentary normal men and women: comparison of age-related changes.

The normal range of maximal values for oxygen consumption, heart rate, cardiac index, and stroke index during treadmill exercise testing are presented for 98 men and 104 women for ages 20-75 yr. These variables decrease with age in both sexes, but men show a significantly greater reduction than women with respect to oxygen consumption (P = 0.05), heart rate (P less than 0.02), and cardiac index (P less than 0.02). Comparison of the normal ranges of oxygen consumption, cardiac index, and stroke index indicated that men have significantly higher values than women (P less than 0.001). The normal range of heart rate was higher in younger men than women, but because of a more rapid decline with age in men, the older women had higher heart rates than the older men. Invasive measurements of cardiac index in 12 normal men and 11 normal women were within the defined normal range. These measurements showed that there was a greater increase in stroke index from supine rest to maximal upright exercise in men compared with the increase in women (means +/- SD, 12 +/- 9 m/m2 vs. 2 +/- 7 ml/m2, P less than 0.01).

Adult↗
PubMed1981

Altered exercise ventilatory responses by apparent propranolol-diminished glucose metabolism: implications concerning impaired physical training benefit in coronary patients.

The effect of a single oral 40 mg dose of propranolol on ventilatory responses to symptom-limited maximal exercise were studied in 14 coronary artery disease (CAD) patients and in four normal volunteers. In both groups, there was significant reduction of carbon dioxide production, minute ventilation, and respiratory exchange ratio at matched workloads. Propranolol did not affect oxygen uptake at matched workloads. A possible explanation of these findings was that propranolol, as a result of beta blockade, inhibited stimulation of glucose metabolism during exercise. Such an effect may diminish ability of CAD patients taking propranolol to obtain beneficial results of an exercise training program.

Adult↗
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↗