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Biomedical subjects

L G Ekelund

Publications and source records attributed to L G Ekelund.

At least 19 recordsLinked to original sources
PubMed1991

Effects of 4 percent and 6 percent carboxyhemoglobin on arrhythmia production in patients with coronary artery disease.

In this study, we assessed the effects of exposure to 4 percent and 6 percent carboxyhemoglobin on ventricular arrhythmias in 41 subjects (nonsmokers) with documented coronary artery disease. We used a randomized, double-blind, crossover design. On day 1, a training session with no exposure, the baseline carboxyhemoglobin level was measured, and a supine bicycle exercise test was done. On days 2 through 4, subjects were exposed to room air, 100 parts per million (ppm)2 carbon monoxide (target, 4 percent blood carboxyhemoglobin), or 200 ppm carbon monoxide (target, 6 percent blood carboxyhemoglobin), and they then did a supine bicycle exercise test. Radionuclide ventriculography was performed at rest and during exercise. Ambulatory electrocardiogram recordings were made during the four consecutive days to determine the frequency of premature ventricular contractions at various intervals. The frequency of single premature ventricular contractions per hour during exercise was significantly greater on the 6 percent carboxyhemoglobin day than on the room air day (167.72 +/- 37.99 for 6 percent carboxyhemoglobin compared with 127.32 +/- 28.22 for room air, p = 0.03). The frequency of multiple premature ventricular contractions per hour was also significantly greater during exercise on the 6 percent carboxyhemoglobin day compared with the room air day (9.59 +/- 3.70 for the 6 percent carboxyhemoglobin day compared with 3.18 +/- 1.67 for the room air day, p = 0.02). Patients who developed increased arrhythmias during exercise on the 6 percent carboxyhemoglobin day were significantly older than those who had no increased arrhythmia, and, in addition, exercised longer and had a higher peak workload during exercise. No effect of carbon monoxide exposure was seen on the 4 percent carboxyhemoglobin day.

Aged↗
PubMed1991

Nicardipine as antihypertensive monotherapy: positive effects on quality of life.

The effects of nicardipine and propranolol on patients' quality of life were compared during a double-blind, multicentre, parallel, randomised study of hypertension therapy. After a placebo run-in period, the doses for each patient were successfully titrated to reduce supine diastolic blood pressure to less than 90 mmHg with either nicardipine 60 or 90 mg/day (123 patients) or with propranolol 90-240 mg/day (120 patients). Both drugs demonstrated similar efficacy in reducing systolic and diastolic blood pressure. Total duration of therapy ranged from 6-12 weeks. The Nottingham Health Profile questionnaire was used to assess the effect of each treatment on the patients' quality of life. The overall quality of life score for patients on nicardipine showed a tendency toward improvement, while for those on propranolol, the trend was toward overall worsening. The differences between the two treatment groups were statistically significant for males (P = 0.02). The analysis of the separate components of this evaluation demonstrated that physical mobility was reported to be decreased more for the propranolol-treated patients than for the nicardipine-treated patients (P = 0.02). In contrast to the propranolol-treated patients, the nicardipine-treated patients reported improvements for sleep, social life, work, sex life, and for activities related to hobbies and interests. A second questionnaire was used to assess the effects of the therapies on work productivity. Among those patients who worked for pay, more patients treated with propranolol than those treated with nicardipine rated themselves as less productive at work (P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Sensitivity of exercise electrocardiography for acute cardiac events during moderate and strenuous physical activity. The Lipid Research Clinics Coronary Primary Prevention Trial.

We determined whether the exercise electrocardiogram predicted acute cardiac events during moderate or strenuous physical activity among 3617 asymptomatic, hypercholesterolemic men (age range, 35 to 59 years) who were followed up in the Coronary Primary Prevention Trial. Submaximal exercise test results were obtained at entry and at annual follow-up visits in years 2 through 7. ST-segment depression or elevation (greater than or equal to 1 mm or 10 microV-sec) was considered to be a positive test result. The circumstances that surrounded each nonfatal myocardial infarction and coronary heart disease death were determined through a record review. The cumulative incidence of activity-related acute cardiac events was 2% during a mean follow-up period of 7.4 years. The risk was increased 2.6-fold in the presence of clinically silent, exercise-induced, ST-segment changes at entry (95% confidence interval [Cl], 1.3 to 5.2) after adjustment for 11 other potential risk factors. Of 62 men who experienced an activity-related event, 11 had a positive test result at entry (sensitivity, 18%; 95% Cl, 8 to 27). The specificity of the entry exercise test was 92% (95% Cl, 91 to 93). The sensitivity and specificity were similar when the length of follow-up was restricted to 1 year after testing. For a newly positive test result on a follow-up visit, the sensitivity was 24% (95% Cl, 12 to 36), and the specificity was 85% (95% Cl, 84 to 86); for any positive test result during the study (mean number of tests per subject, 6.2), the sensitivity was 37% (95% Cl, 25 to 49), and the specificity was 79% (95% Cl, 77 to 80). Our findings suggested that the presence of clinically silent, exercise-induced, ischemic ST-segment changes on a submaximal test was associated with an increased risk of activity-related acute cardiac events. However, this test was not sensitive when used to predict the occurrence of activity-related events among asymptomatic, hypercholesterolemic men. For this reason, the utility of the submaximal exercise test to assess the safety of physical activity among asymptomatic men at risk of coronary heart disease is likely to be limited.

Adult↗
PubMed1990

Production of arrhythmias by elevated carboxyhemoglobin in patients with coronary artery disease.

OBJECTIVE: To assess the effects of exposure to 4% and 6% carboxyhemoglobin on ventricular arrhythmias in patients with coronary artery disease. DESIGN: Randomized, double-blind, crossover design. SETTING: Exercise laboratory with an environmentally controlled exposure. PATIENTS: Forty-one nonsmokers with documented coronary artery disease. INTERVENTION: On day 1, a training session with no exposure, the baseline carboxyhemoglobin level was measured, and a supine bicycle exercise test was done. On days 2 to 4, patients were exposed to room air, 100 ppm carbon monoxide (target, 4% carboxyhemoglobin) or 200 ppm carbon monoxide (target, 6% carboxyhemoglobin), and they then did supine bicycle exercise with radionuclide ventriculography. Ambulatory electrocardiogram recordings were made during the 4 consecutive days to determine the frequency of ventricular premature depolarization (VPD) at various intervals. MEASUREMENTS AND MAIN RESULTS: The frequency of single VPD/h was significantly greater on the 6% carboxyhemoglobin day than on the room air day during the exercise period (167.72 +/- 37.99 for 6% carboxyhemoglobin compared with 127.32 +/- 28.22 for room air, P = 0.03). During exercise, the frequency of multiple VPD/h was greater on the 6% carboxyhemoglobin day compared with room air (9.59 +/- 3.70 on the 6% carboxyhemoglobin compared with 3.18 +/- 1.67 on room air, P = 0.02). Patients who developed increased single VPD during exercise on the 6% carboxyhemoglobin day were significantly older than those who had no increased arrhythmia, whereas patients who developed complex arrhythmias were also older and, in addition, exercised longer and had a higher peak workload during exercise. CONCLUSION: The number and complexity of ventricular arrhythmias increases significantly during exercise after carbon monoxide exposure producing 6% carboxyhemoglobin compared with room air but not after exposure producing 4% carboxyhemoglobin.

Age Factors↗
PubMed1990

Aging and pain perception in ischemic heart disease.

Age is a recognized risk factor for coronary artery disease, but the relationship between age and silent ischemia is not well understood. We analyzed the data from 35 rest/stress radionuclide ventriculography examinations in patients with documented ischemic coronary artery disease who had experienced 1 mm ST segment depression accompanied by angina during exercise testing. An index of ischemic cardiac pain perception (PPI) was calculated by subtracting the time of onset of 1 mm ST segment depression from the time of onset of angina. The mean value of PPI was -97 +/- 311 seconds. PPI was significantly correlated with age (r = 0.37, p = 0.03). This suggests that as age increases, perception of pain during myocardial ischemic episodes becomes muted. This relationship remained significant when we controlled for the presence of medication and severity of disease (change in ejection fraction from rest to peak exercise). These findings suggest that age is an independent risk factor for a decreased perception of ischemic cardiac pain, and thus for silent myocardial ischemia.

Adult↗
PubMed1990

Quality of life among hypertensive patients with a diuretic background who are taking atenolol and enalapril.

The cardioselective beta-blocker atenolol and the angiotensin-converting enzyme inhibitor enalapril were compared for efficacy, safety, and quality-of-life factors in 30 patients with hypertension whose hypertension was inadequately controlled with diuretic alone. Atenolol (50 to 100 mg once a day) and enalapril (2.5 to 40 mg once a day), combined with hydrochlorothiazide (25 mg once a day), had similar levels of efficacy and safety. A comprehensive battery of psychologic assessments for quality of life was administered, including measures of anxiety, depression, psychiatric symptoms, memory, and psychomotor function. These five conceptually based clusters were first analyzed by multivariate analysis of variance procedures, followed by univariate analyses of the individual variables composing each domain. In general, neither atenolol nor enalapril was associated with major changes in psychologic functioning. The only data cluster with a statistically significant change was memory function, primarily as a result of lower scores of the digit span (backward) test, for atenolol relative to enalapril. These preliminary findings suggest that atenolol and enalapril have comparable degrees of efficacy and safety, with no major disparities in quality-of-life effects, for hypertensive patients with a history of taking diuretics and this sort of quality-of-life assessment can be performed during trials of antihypertensive drugs.

Analysis of Variance↗
PubMed1990

Black-white differences in exercise blood pressure. The Lipid Research Clinics Program Prevalence Study.

After exclusion of persons on blood pressure medication or with prevalent cardiovascular disease, we studied 83 black and 2,548 white men and 113 black and 1,519 white women 20-69 years old from the Lipid Research Clinics population sample who had performed a standardized treadmill exercise test. Resting systolic and diastolic blood pressures were similar in black and white men, but the diastolic pressure was significantly higher in black than in white women (81.4 vs 77.4 mm Hg). Body weight was higher in black than in white women, and reported physical activity was higher in black than in white men. The proportion of smokers was somewhat higher in blacks than in whites. During the treadmill exercise test with a modified Bruce protocol, mean systolic blood pressure at stage 2 was 174 mm Hg in black men and 166 mm Hg in white men (p less than 0.02), but stage 2 blood pressures did not differ between black and white women (153 and 152 mm Hg, respectively). Even after adjustments were made for levels of baseline characteristics (age, weight, resting systolic blood pressure, smoking, low density lipoprotein cholesterol, physical activity, and alcohol intake), black men responded with a 7-mm Hg higher systolic blood pressure during exercise than white men (p less than 0.01). Another new finding was a highly significant positive association between stage 2 systolic blood pressure and low density lipoprotein cholesterol in men. The findings suggest a higher systemic vascular resistance during exercise in the selected sample of black men, which is consistent with the higher incidence of hypertension in black men.

Adult↗
PubMed1989

A comparison of amplitude-modulated and frequency-modulated ambulatory monitoring systems.

To compare the results of monitoring for ischemia with amplitude-modulated (AM) and frequency-modulated (FM) ambulatory recorders, 22 patients with coronary artery disease were monitored during exercise and during 24 to 48 hours of daily activities. Simultaneous recordings were obtained with Oxford Medilog 4000-II and Medilog MR-35 systems from the same 2 bipolar leads. Each potential ischemic episode was interpreted blindly by 2 investigators. Significant ST depression was strictly defined as greater than or equal to 1 mm of horizontal or down-sloping ST depression persisting for 0.06 second beyond the J point and lasting greater than or equal to 1 minute. Of 82 episodes reviewed, 63 (77%) were either positive (37) or negative (26) for ischemia by both systems. However, 17 episodes were interpreted as positive on AM tracings but negative on FM tracings; the converse was true for only 2 episodes (p less than 0.01). For episodes read as positive with both systems, there were close correlations between recorders for duration (r = 0.80) and magnitude (r = 0.90) of ST depression. Because of the greater number of positive AM events, however, the mean total duration of ST depression for patients with ischemia during daily activities was greater on AM than on FM recordings (74 +/- 77 vs 39 +/- 42 minutes, p less than 0.10). Discrepancies between AM and FM tracings were invariably due to small differences in ST-segment morphology or in the magnitude of ST-segment depression. In summary, AM monitors generate complexes similar in appearance to those produced by FM devices in most instances.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1989

Coronary heart disease morbidity and mortality in hypercholesterolemic men predicted from an exercise test: the Lipid Research Clinics Coronary Primary Prevention Trial.

A positive exercise electrocardiogram (ECG) has been proved to predict cardiovascular events in asymptomatic normolipidemic men. To study whether it is also predictive for hypercholesterolemic men, data from 3,806 asymptomatic hypercholesterolemic men in the Lipid Research Clinics Coronary Primary Prevention Trial were analyzed. All the men had performed a submaximal treadmill exercise test at baseline, before they were assigned to the cholestyramine or placebo treatment group. Because of missing or inconclusive data, 31 men were excluded from the analyses. A test was positive if the ST segment was displaced by greater than or equal to 1 mm (visual code) or there was greater than or equal to 10 microV-s change in the ST integral (computer code), or both. The prevalence of a positive test was 8.3%. During the 7 to 10 year (mean 7.4) follow-up period, the mortality rate from coronary heart disease was 6.7% (21 of 315) in men with a positive test and 1.3% (46 of 3,460) in men with a negative test (placebo and cholestyramine groups combined). The age-adjusted rate ratio for a positive test, compared with a negative test, was 6.7 in the placebo group and 4.8 in the cholestyramine group. With use of Cox's proportional hazards models, it was found that the risk of death from coronary heart disease associated with a positive test was 5.7 times higher in the placebo group and 4.9 times higher in the cholestyramine group after adjustment for age, smoking history, systolic blood pressure, high density lipoprotein cholesterol and low density lipoprotein cholesterol. A positive test was not significantly associated with nonfatal myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1988

Physical fitness as a predictor of cardiovascular mortality in asymptomatic North American men. The Lipid Research Clinics Mortality Follow-up Study.

Limited data are available on the relation between physical fitness and mortality from cardiovascular disease. We examined this question in a study of 4276 men, 30 to 69 years of age, whom we followed for an average of 8.5 years. Examinations at base line included assessment of conventional coronary risk factors and treadmill exercise testing. The heart rate during submaximal exercise (stage 2 of the exercise test) and the duration of exercise were used as measures of physical fitness. Men with incomplete data (n = 308) or who were using cardiovascular drugs (n = 213) were excluded from the analysis. Men who had clinical evidence of cardiovascular disease at base line (n = 649) were analyzed separately. Forty-five deaths from cardiovascular causes occurred among the remaining 3106 men. A lower level of physical fitness was associated with a higher risk of death from cardiovascular and coronary heart disease, after adjustment for age and cardiovascular risk factors. The relative risk of death from cardiovascular causes was 2.7 (95 percent confidence interval, 1.4 to 5.1; P = 0.003) for healthy men with an increment of 35 beats per minute in the heart rate during stage 2, and 3.0 (95 percent confidence interval, 1.6 to 5.5; P = 0.0004) for those with a decrement of 4.4 minutes in the exercise time spent on the treadmill. The corresponding values for death from coronary heart disease were 3.2 (95 percent confidence interval, 1.5 to 6.7; P = 0.003) and 2.8 (95 percent confidence interval, 1.3 to 6.1; P = 0.007), respectively. We conclude that a lower level of physical fitness is associated with a higher risk of death from coronary heart disease and cardiovascular disease in clinically healthy men, independent of conventional coronary risk factors.

Adult↗
PubMed1988

Correlates of systolic and diastolic blood pressure in men 40 to 59 years of age sampled from United States of America and Union of Soviet Socialist Republics Lipid Research Clinics populations.

The correlates of blood pressure (BP) were investigated in 2 samples using common protocols, one from a Union of Soviet Socialist Republics study in 2 locations and one from a United States of America study in 9 locations. Age, heart rate, Quetelet index, high density lipoprotein cholesterol, natural logarithm of triglycerides and fasting glucose were positively related to systolic BP in both samples. In diastolic BP, alcohol consumption, heart rate, Quetelet index and natural logarithm of triglycerides were positively associated, and number of cigarettes smoked was negatively related in both samples.

Adult↗
PubMed1988

Cyclic seasonal variation in plasma lipid and lipoprotein levels: the Lipid Research Clinics Coronary Primary Prevention Trial Placebo Group.

Seasonal plasma lipid and lipoprotein cycles were studied in 1446 hypercholesterolemic 35-59 year-old men followed for 7 years as the placebo group of the Lipid Research Clinics (LRC) Coronary Primary Prevention Trial (CPPT). Separate periodic time series were calculated for each study participant; mean parameter estimates were obtained by vector algebra. Highly significant (p less than 0.001) synchronous sinusoidal seasonal cycles, peaking in the first month of winter, were demonstrated for plasma levels of total (TOT-C), low-density lipoprotein (LDL-C), and high-density lipoprotein (HDL-C) cholesterol. Their mean seasonal changes (nadir to zenith) were 7.4, 6.4, and 0.8 mg/dl, respectively. An irregular but statistically significant seasonal pattern was also observed for plasma triglyceride (TG) levels, with peak levels in the autumn. The variation of these seasonal effects among subgroups and geographic locales and their correlation with seasonal weight and dietary patterns yielded few clues as to their underlying etiologic mechanisms.

Adult↗
PubMed1988

Short-term behavioral effects of beta-adrenergic medications in men with mild hypertension.

beta-Adrenergic-inhibiting drugs are widely prescribed for the treatment of hypertension. These drugs have previously been found to influence a variety of psychologic and behavioral functions and have, in some cases, been associated with serious psychiatric side effects. The present study examined psychologic changes associated with beta-blockade therapy. Twenty-six men with mild hypertension (diastolic blood pressure 90 to 110 mm Hg) were randomly assigned to receive either a selective beta 1-antagonist (atenolol), a nonselective beta 1- and beta 2-antagonist (propranolol), or a placebo. Both before and after a 2-week period of drug administration, subjects completed a comprehensive assessment of quality of life including measures of mood, memory performance, and side effects. In general, beta-blocker therapy was associated with relatively few adverse symptoms, particularly when compared with control subjects taking placebo. Reductions in negative emotional states (tension and anger) were observed for subjects receiving atenolol, and the largest improvements in memory performance were observed for subjects receiving propranolol. These results suggest that beta-blocker therapy is not invariably associated with negative side effects and that some behavioral functions may actually be improved.

Adult↗
PubMed1988

Prevalence of ischemic resting and stress electrocardiographic abnormalities and angina among 40- to 59-year-old men in selected U.S. and U.S.S.R. populations.

The prevalence of electrocardiographic (ECG) abnormalities and angina was investigated in 40- to 59-year-old men from two samples, one from a U.S.S.R. study in two locations and one from a U.S. study in nine locations. ECG abnormalities were defined by the Minnesota code and angina was defined by the Rose questionnaire. No differences were found in the prevalence of major Q waves and major or minor ischemia between the two samples, but differences were found in specific indicators of major ischemia. Major ischemic changes were more prevalent in older subjects in both samples. Estimated prevalence of angina was 50% less in the U.S. sample than in the U.S.S.R. sample, and this was consistent with the proportion of subjects excluded from the exercise test because of angina. In both samples, subjects with ECG abnormalities had higher systolic blood pressures. No difference in exercise test abnormalities was found between samples; however, more subjects with a history compatible with coronary artery disease were excluded from the U.S.S.R. sample.

Adult↗
PubMed1988

Effects of beta-blockade and exercise on cardiovascular and cognitive functioning.

Twenty-four men with mild essential hypertension were assigned randomly to receive propranolol (n = 9), atenolol (n = 7), or a placebo (n = 8). All subjects participated in a 12-week study and provided physiological and behavioral data four times during the study: after a medication-free baseline period (Session 1); after 2 weeks of medication, without exercise (Session 2); after 8 weeks of continued medication while participating in a program of aerobic exercise (Session 3); and after 2 weeks of maintenance exercise without medication (Session 4). Subjects' maximal oxygen uptake increased significantly between Sessions 2 and 3, and the magnitude of this increase did not vary across the drug groups. Subjects' resting heart rates varied as a function of the presence of beta-blocking medication, but there was in addition a reduction attributable to exercise training that did not vary across the drug groups. The decrease in blood pressure associated with beta-blockade (Session 2) was not decreased any further by exercise training (Session 3). Despite an increase in blood pressure following the withdrawal of active medication (Session 4), blood pressure remained significantly lower compared with the Session 1 baseline level. Performance in a reaction-time test of short-term memory functioning improved slightly for all three groups between Sessions 1 and 2 and remained constant thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1988

Physical activity and coronary heart disease among asymptomatic hypercholesterolemic men (the Lipid Research Clinics Coronary Primary Prevention Trial).

We examined the relation between reported regular strenuous exercise or hard physical labor and the incidence of coronary heart disease (CHD) death and nonfatal myocardial infarction among 1,533 hypercholesterolemic men aged 35-59 years who were in the placebo group of the Lipid Research Clinics Coronary Primary Prevention Trial. The mean follow-up of the cohort was 7.4 years. The men were free of clinical heart disease at entry; men with an abnormal resting electrocardiogram or graded exercise test also were excluded. Regular physical activity was not associated with the incidence of CHD (RR = .94, 95% CI = .68, 1.38) in this study population. Adjustment by the proportional hazards model for age, low-density lipoprotein cholesterol, smoking, family history of CHD, and occupation did not alter this finding. This observation suggests that reported regular physical activity may not be related to the risk of coronary heart disease among asymptomatic, hypercholesterolemic, middle-aged men.

Adult↗