Search PubMed⌕ Search

Biomedical subjects

R W Squires

Publications and source records attributed to R W Squires.

At least 19 recordsLinked to original sources
PubMed1992

Exercise and the heart. Good, benign, or evil?

The risks and benefits of regular aerobic exercise have been studied extensively. Because of the potential risks, we believe that sedentary persons over age 40 who have cardiac risk factors, as well as patients with coronary artery disease (CAD), should have a complete physical examination and probably an exercise electrocardiogram before starting a vigorous exercise program. In general, however, regular exercise has proven to be extra-ordinarily safe and the theoretical and proven benefits appear to greatly outweigh the risks in most people, including those with CAD, those with severe left ventricular dysfunction, and the elderly.

Coronary Disease↗
PubMed1992

Low-dose, time-release nicotinic acid: effects in selected patients with low concentrations of high-density lipoprotein cholesterol.

In a retrospective analysis, 63 participants in a cardiac rehabilitation-preventive cardiology program were identified as having low blood concentrations (mean, 34 mg/dl) of high-density lipoprotein cholesterol (HDL-C) and a mean total cholesterol level of 223 mg/dl after 3 months of hygienic measures (aerobic exercise, avoidance of tobacco, diet, and weight loss) designed to increase the HDL-C level. These patients (treatment group) were treated with low-dose, time-release nicotinic acid (mean, 1,297 mg/day) for a mean duration of 7.4 months. All subjects were able to take the drug without intolerable side effects. Fifty-four patients similar to those in the treatment group participated in the same program but were not treated with nicotinic acid (control group). Exercise, diet, body weight, and smoking remained stable throughout the period of observation. For the treatment group, HDL-C levels increased a mean of 18% (+6 mg/dl), total cholesterol concentrations decreased 9% (-20 mg/dl), the ratio of total cholesterol to HDL-C decreased 25% (from 6.8 to 5.1), low-density lipoprotein cholesterol levels decreased 13% (-20 mg/dl), and triglyceride levels decreased 20% (from 165 mg/dl to 132 mg/dl). Aspartate aminotransferase and uric acid concentrations were minimally increased after treatment, and the blood glucose level was unchanged. In the control group, HDL-C levels increased a mean of 8% (+3 mg/dl) and the other blood lipid variables were not improved after a mean of 8.3 additional months of diet and exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol, HDL↗
PubMed1991

Transtelephonic electrocardiographic monitoring of cardiac rehabilitation exercise sessions in coronary artery disease.

Transtelephonic monitoring of a single-lead electrocardiogram and on-demand 2-way voice communication were accomplished at 1,865 exercise sessions for 67 cardiac patients. Exercise sessions occurred either at the patients' homes or at remote hospital sites and began an average of 25 or 14 weeks, respectively, after hospital dismissal. Monitoring centers provided experienced nurses to direct all exercise sessions. The transtelephonic monitoring equipment was reliable with only one instance of system failure observed. A broad spectrum of patients with coronary artery disease, including some classified at higher risk, participated in the program. Patients exercised with a variety of equipment (cycle ergometer, treadmill, arm ergometer, cross-country ski simulator, combination arm-leg cycle ergometer, rowing machine), for 30 to 50 minutes, 1 to 3 times each week. No medical emergencies occurred, although 18 specific problems were discovered that led to further evaluation or change in the medical program of specific patients. Transtelephonic monitoring of cardiac rehabilitation exercise sessions at home and at remote hospitals appears safe and is attractive because not all patients have access to supervised exercise programs; this exercise assessment helps to maximally use highly trained cardiac rehabilitation personnel.

Aged↗
PubMed1991

Niacin-induced hepatitis: a potential side effect with low-dose time-release niacin.

Hepatitis developed in five patients who were taking low dosages (3 g/day or less) of time-release niacin. In four of the five patients, clinical symptoms of hepatitis developed after the medication had been taken for a relatively short time (2 days to 7 weeks). This manifestation of hepatotoxicity seems to differ from that previously reported in association with use of crystalline niacin, which occurred with high dosage and prolonged usage of the medication. In view of the recent increased frequency of prescribing niacin for the treatment of hyperlipidemia, physicians should be aware of the potential for hepatotoxicity with even low-dose and short-term use of time-release niacin.

Adult↗
PubMed1991

Exercise training after cardiac transplantation.

During the last decade, cardiac transplantation has become the accepted form of treatment for selected patients with end-stage heart disease, which usually results from dilated cardiomyopathy or coronary artery disease. Although 5-yr survival is currently 85%, patients have complicated courses after surgery, with an ever present risk of infection and graft rejection. Because of physical inactivity and severe limitation of cardiac output preoperatively, these deconditioned patients are excellent candidates for medically supervised rehabilitative exercise training programs. Denervation of the myocardium, which occurs with cardiac transplantation, results in a loss of autonomic nervous system modulation of cardiac output, with reliance on circulating catecholamines and with a delayed heart rate and cardiac output response to the onset of exercise. Oxygen uptake kinetics are prolonged, and maximal oxygen uptake is reduced. Additional abnormalities in cardiac and pulmonary artery pressures and in ventilation during exercise have been described. The literature contains seven studies concerning the effects of exercise training in cardiac transplant recipients. Benefits resulting from training include increases in maximal oxygen uptake, peak exercise power output, anaerobic threshold, and lean body mass, reduced perceived exertion, heart rate, and blood pressure during submaximal exercise, and a lowered resting heart rate and blood pressure. There are no data to suggest that exercise training alters the incidence of infection or rejection or improves longevity or return to pre-illness lifestyle.

Coronary Disease↗
PubMed1990

Cardiovascular rehabilitation: status, 1990.

Cardiovascular rehabilitation is defined as the process of development and maintenance of a desirable level of physical, social, and psychologic functioning after the onset of a cardiovascular illness. Patient education, counseling, nutritional guidance, and exercise training play prominent roles in the process of rehabilitation. Benefits from cardiac rehabilitation include improved exercise capacity and decreased symptoms of angina pectoris, dyspnea, claudication, and fatigue. Recent pooled data regarding exercise training after myocardial infarction demonstrated a 20 to 25% reduction in mortality and major cardiac events. Exercise training may result in an improvement in systemic oxygen transport, a reduction in the myocardial oxygen requirement for a given amount of external work, and a decrease in the extent of myocardial ischemia during physical activity. The efficacy of modification of risk factors in reducing the progression of coronary artery disease and future morbidity and mortality has been established. Herein we review the history, current practice and results, and future challenges of cardiovascular rehabilitation.

Ambulatory Care↗
PubMed1990

Differences between prebreakfast and late afternoon glycemic responses to exercise in IDDM patients.

Little information is available regarding the optimal timing of exercise in insulin-dependent diabetes mellitus (IDDM) patients. In this study, six IDDM patients receiving ultralente-based intensive insulin therapy were studied during 30 min of exercise (approximately 60% VO2max), before breakfast, and at 1600. On two other occasions, they were studied at rest. Plasma glucose increased from 6.7 +/- 0.4 to 9.1 +/- 0.4 mM during morning exercise (P less than 0.01). In contrast, mean plasma glucose did not change during afternoon exercise (delta = 0.3 +/- 0.5 mM, NS); however, there was a 0.3- to 1.0-mM decrease in three subjects. The observed difference in the glycemic response to exercise could not be explained on the basis of changes in plasma glucagon, growth hormone, norepinephrine, or epinephrine. Plasma cortisol was higher (P less than 0.02) in the morning than in the afternoon, and plasma free-insulin concentrations were lower (P less than 0.05). These data indicate that the risk of exercise-induced hypoglycemia is lowest before breakfast. The reason for the divergent glycemic responses to exercise is not entirely clear but may be related to the observed differences in free-insulin concentrations. Because of the lower risk of hypoglycemia, our results suggest prebreakfast exercise may be preferable for some IDDM patients receiving intensive insulin therapy. Whether these findings are relevant to patients receiving other types of insulin therapy will require further investigation.

Adult↗
PubMed1989

Dopa in plasma increases during acute exercise and after exercise training.

Plasma dihydroxyphenylalanine (dopa) has been shown to originate in sympathetic neurons, and it has been suggested that plasma level reflects activity of tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of catecholamines. In this study, we measured the effects of acute exercise and exercise training on the levels of dopa and catecholamines in the plasma of healthy, older individuals. Venous blood was drawn from 19 men, from 52 to 75 years of age, at rest, at a standard submaximal work load, at peak exercise, and 3 minutes after exercise on a cycle ergometer. Ten of 12 men then completed 12 to 16 weeks of supervised training, and seven continued normal activity. All 17 men were then retested. The seven control subjects subsequently underwent exercise training as above and were retested again. Levels of dopa and catecholamines in plasma samples were measured by high-performance liquid chromatography with electrochemical detection. Dopa levels at rest were considerably higher than free dopamine, epinephrine, and norepinephrine. During short-term exercise, levels of dopa and catecholamines increased. The absolute increase in dopa was greater than the increase in epinephrine or dopamine but was not greater than that in norepinephrine. After the training period, basal dopa levels increased significantly and correlated with the increase in peak oxygen uptake. There was no change in basal conjugated norepinephrine or dopamine levels with exercise or training, but the level of conjugated epinephrine decreased slightly. No changes occurred in levels of dopa or catecholamines in the untrained group. Free dopamine, norepinephrine, and epinephrine levels at peak exercise were increased after exercise training.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Specimen Collection↗
PubMed1989

Does exercise training alter myocardial creatine kinase MB isoenzyme content?

Skeletal muscle biopsies from highly trained endurance athletes have been shown to contain an increased percentage of the creatine kinase MB (CK-MB) isoenzyme, which has been attributed to continuous regeneration of the skeletal muscle fibers in response to exercise-induced injury. The purpose of this study was to determine whether myocardium undergoes a similar degenerative-regenerative process as a result of exercise training. Fifteen mongrel dogs underwent a 12-wk period of training (N = 8) or cage confinement (N = 7). The animals were then sacrificed, and samples of left and right ventricular myocardium were analyzed for total CK activity and CK-MB isoenzyme content. Percentages of CK-MB were slightly but insignificantly higher from both ventricles of exercise-trained as compared with cage-confined dogs: left ventricle, 4.6 +/- 0.6% vs 3.3 +/- 0.6%, respectively (P = 0.15); right ventricle, 4.0 +/- 0.4% vs 3.0 +/- 0.8%, respectively (P = 0.29). We conclude that chronic exercise training does not induce physiologically important degenerative changes in myocardium.

Animals↗
PubMed1988

Management of lipids in primary and secondary prevention of cardiovascular diseases.

Although the frequency of cardiovascular disease is declining, it remains a major present and future threat to health in the United States. The deleterious effects of abnormal blood lipid concentrations have long been recognized, but the benefit of corrective intervention in this process has only recently been demonstrated. We review the major lipid abnormalities and the available clinical therapeutic interventions. In addition, we discuss data that address the premise that reducing low-density lipoprotein cholesterol or raising high-density lipoprotein cholesterol should decrease the progression of coronary atherosclerosis, and we summarize drug trials in which clofibrate, niacin, cholestyramine, and gemfibrozil decreased coronary heart disease events. Studies that used cholestyramine and the combination of colestipol and niacin resulted in decreased progression of coronary artery disease. On the basis of early experience with lovastatin, inhibitors of hydroxymethylglutaryl-coenzyme A reductase are likely to be effective in the treatment of hypercholesterolemia. The available information on the association of low cholesterol levels and cancer suggests that low total cholesterol is a consequence rather than a cause of carcinoma. Current data strongly support the concept of vigorous intervention directed at management of lipids, both with non-pharmacologic treatment and with drug therapy, for the primary and secondary prevention of coronary atherosclerosis.

Anticholesteremic Agents↗
PubMed1987

Graded exercise testing and training after renal transplantation: a preliminary study.

Aerobic exercise training has been used as part of the treatment for a variety of chronic disorders, most notably cardiovascular disease. In order to determine the feasibility and utility of regular exercise after renal transplantation, the responses of 10 patients to graded exercise testing were compared before training (T1), immediately after a program of supervised exercise training (T2), and a mean of 2.2 years after completion of the supervised program (T3). Supervised exercise sessions began a mean of 17 days postoperatively and continued for a mean of 5.5 weeks. Patients were encouraged to continue regular unsupervised exercise thereafter. All patients easily tolerated the supervised exercise sessions, which consisted of treadmill walking and cycle ergometry. Exercise capacity improved 90% between T1 and T2 and an additional 12% between T2 and T3. On the average, patients achieved a normal exercise capacity by 8 weeks after transplantation. Of the 10 patients, 7 had continued regular exercise training at T3. The observed increase in aerobic exercise capacity was probably related to improved renal function, an increased hemoglobin concentration, and the surgical healing process as well as the exercise training. We conclude that supervised exercise training for selected patients after renal transplantation is feasible and worthwhile.

Adolescent↗
PubMed1987

Cardiac rehabilitation in patients with severe ischemic left ventricular dysfunction.

Twenty patients who had had a myocardial infarction and who had a resting left ventricular ejection fraction of 25% or less participated in an 8-week outpatient supervised exercise and education program. No morbidity or mortality occurred during the program, and most patients achieved a substantial improvement in exercise capacity. During a follow-up interval of a mean of 29.7 +/- 13.0 months, four patients died, an annualized mortality of 8 +/- 4%. The outcome of cardiac rehabilitation was assessed 19.1 +/- 4.4 months after completion of the supervised program. Of the 16 survivors, all of whom had been fully employed before their most recent myocardial infarction, 9 (56%) had returned to full-time work, 6 (38%) were medically disabled, and 1 was retired (age 73 years) but fully active. Of the 16 survivors, 13 (81%) completed a questionnaire about their perceptions of their current quality of life. Of the 13 patients, 12 (92%) had continued to exercise regularly. Four patients (31%) reported the ability to perform all desired activities without symptoms, whereas nine patients (69%) noted some impairment in their functional capacity. Thus, in this group of patients with profound left ventricular dysfunction, the rehabilitation potential, as evidenced by return to productive employment and the ability to perform desired activities-including exercise training-was generally favorable.

Electrocardiography↗
PubMed1984

Work capacity and left ventricular function during rehabilitation after myocardial revascularization surgery.

A prospective randomized trial was conducted to evaluate the effects of exercise-based cardiac rehabilitation after myocardial revascularization surgery (MRS) on work capacity (measured in mets) and left ventricular function as determined from ejection fraction (LVEF). Twenty-eight patients undergoing MRS were randomly assigned to experimental (aerobic exercise, n = 19) or control (muscle relaxation and low-level exercise, n = 9) groups. Patients were studied before surgery (T1) and 2 (T2), 8 (T3), and 24 (T4) weeks after surgery with first-pass radionuclide angiography both while they were at rest and during maximal upright cycle ergometric exercise. Subsets of patients were also studied at T2, T3, and T4 at a standard workload of 75 W, and during maximal exercise 1 year after surgery (T5). Work capacity improved in both groups although significantly more so in the experimental group (3.9, 3.8, 6.0, and 7.3 mets and 3.7, 3.7, 4.9, and 5.7 mets at T1, T2, T3, and T4 in the experimental and control groups, respectively). The differences between groups were significant by T3. Peak exercise LVEF increased significantly in both groups from T1 to T2 then decreased at T3 and remained unchanged through T5. Peak exercise LVEF at T3 to T5 remained significantly above that observed at T1. LVEF responses were not related to the exercise program. During a standard workload, heart rate decreased, blood pressure increased, and LVEF did not change in either group. After conclusion of the formal protocol (T4), work capacity and LVEF did not change for either group throughout an additional 6 months (T5).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1984

Cardiovascular profiling.

As in all other medical evaluations, the evaluation of the cardiovascular system in the competitive athlete or the nonathlete wishing to exercise must begin with a carefully performed history and physical examination. Subsequent studies, including chest radiograph and electrocardiogram, may be waived in certain populations of young athletes, but in older individuals wishing to exercise, these should be included and an exercise stress test should also be done to assess the ability of the heart to withstand moderate levels of exercise without ischemia. The mainstay of evaluation of exercise performance is the graded exercise test on either a bicycle ergometer or a treadmill. These protocols are designed to provide increments in workload until the subject reaches maximal oxygen consumption or is symptom limited. Heart rate monitoring and blood pressure monitoring often are adequate to determine individual response to exercise and to provide appropriate exercise advice. When an absolute measure of physical fitness is required, maximal oxygen consumption should be measured. Following the guidelines of thorough medical evaluation plus stress testing, it is unlikely that an athlete or the exercising nonathlete will develop serious cardiovascular problems with exercise.

Cardiac Output↗
PubMed1983

Dysrhythmia detection in myocardial revascularization surgery patients.

Dysrhythmia detection in myocardial revascularization surgery patients. Med. Sci. Sports Exerc., Vol. 15, No. 4, pp. 281-286, 1983. In order to document the type and prevalence of significant dysrhythmias in myocardial revascularization surgery patients, cardiac electrical activity was recorded during graded exercise testing, 24-h ambulatory electrocardiography, and electrocardiographic-monitored exercise training. Patients participated in a cardiac rehabilitation program that began approximately 2 wk post-surgery, and attended three monitored exercise sessions per week for 12 consecutive weeks. Graded exercise testing and 24-h ambulatory electrocardiography were administered in the second and eighth weeks of the study (weeks 1 and 6 of the exercise program) post-surgery. Eighty-eight percent of the patients exhibited significant dysrhythmias. A greater number of significant dysrhythmias were found during the second 6 wk of the study in comparison with the first 6 wk. Graded exercise testing was not as effective as ambulatory electrocardiography and monitored exercise training in dysrhythmia detection. Not all dysrhythmias were detected by any one technique, thus a combination of methods may be best for optimal surveillance and detection.

Anti-Arrhythmia Agents↗
PubMed1982

Aerobic capacity during acute exposure to simulated altitude, 914 to 2286 meters.

In order to systematically assess the effects of acute exposure to moderate hypoxia on aerobic capacity (VO2max), 12 men (regular participants in recreational distance running) performed six treadmill-graded exercise tests (GXTs) in a hypobaric chamber. GXTs 1 and 6 were performed at ambient (control) altitude (362 m, barometric pressure = 730 mmHg). GXTs 2-5 were administered during 1-2 h of exposure to barometric pressures of 681, 656, 632, and 574 mmHg simulating altitudes of 914, 1219, 1524, and 2286 m, respectively, with the order of presentation randomized and blinded for each subject. The mean VO2max for GXTs 1 and 6 (control altitude) were essentially identical with a test-retest correlation of r = 0.92. During peak exercise, HR max was unchanged by hypoxia, while VO2max was significantly lower than the control by 4,8, 6.9, and 11.9% at 1219, 1524, and 2286 m, respectively. SaO2@max percent during maximal exercise was significantly reduced from the control by 3.5, 3.6, 7.0, and 11.6% at 914, 1219, 1524, and 2286 m, respectively. It was concluded that VO2max, in physically well-conditioned persons living at 362 m, is reduced during acute exposure to 1219 m and above.

Acclimatization↗