Effects of intravenous theophylline on exercise-induced myocardial ischemia: II. A concentration-dependent phenomenon

AbstractObjectives. The effects of varying concentrations of theophylline on exercise-induced myocardial ischemia were evaluated in patients with stable coronary artery disease.Background. Theophylline is a competitive antagonist of adenosine and may have potential as an anti-ischemic medication. It is not known whether these effects on myocardial ischemia are concentration dependent.Methods. In a double-blind, randomized, crossover manner, 11 patients received, at 1-week intervals, placebo and each of three theophylline doses by intravenous infusion for 45 min. Graded exercise testing was performed before randomization and immediately after each infusion. Concurrent anti-ischemic medications were withheld for 24 h before each exercise test. Serum theophylline concentrations achieved were 3.9 ± 1.0 mg/liter (low), 8.2 ± 1.8 mg/liter (medium) and 13.2 ± 2.3 mg/liter (high).Results. Compared with placebo, none of the three theophylline infusions produced a significant alteration in rest heart rate, blood pressure, mean frequency or severity of ventricular ectopic activity or noncardiac symptoms. The time to onset of ischemia was progressively increased, with medium and high concentrations achieving statistical significance. Similar patterns were observed for oxygen uptake and the heart rate-systolic blood pressure product at the onset of ischemia. Total exercise duration was significantly prolonged with the medium and high concentrations.Conclusions. It is concluded that administration of varying doses of theophylline before exercise produces a clinically significant and concentration-dependent improvement in the indicators of myocardial ischemia in patients with chronic stable coronary artery disease

Correlates of postmenopausal estrogen use and trends through the 1980s in two Southeastern New England communities

Correlates and prevalence of current postmenopausal estrogen use were examined in two southeastern New England communities for the period 1981 through 1990. Data were obtained from five biennial cross-sectional household health surveys, with current use of postmenopausal estrogen determined by inspection of medication bottles. Analysis included 3,279 women aged 40-64 years, of whom 2,215 (67.6%) were postmenopausal. The prevalence of estrogen use among all postmenopausal women increased from 5.3% (95% confidence interval (CI) 3.2-7.4) in 1981-1982 to 10.9% (95% CI 7.5-14.4) in 1989-1990. Among women with surgical menopause, prevalence increased from 11.4% (95% CI 6.6-16.2) to 20.3% (95% CI 13.6-27.0), while use among women with natural menopause increased from 1.5% (95% CI 0.04-2.9) to 3.5% (95% CI 0.74-6.2). Logistic regression was used to compute age-adjusted prevalence of estrogen use according to demographic characteristics and cardiovascular risk factors. Postmenopausal estrogen use was positively associated with income, and a positive trend with education was suggested. Estrogen use was positively associated with high density lipoprotein cholesterol and was inversely associated with body mass index. Nonsmokers, women who exercised at least once per week, and women who reported having their cholesterol checked in the past year were more likely to use estrogen. These findings suggest that estrogen users have a more healthy profile than do nonusers. In addition, the prevalence of postmenopausal estrogen use appears to be substantially lower in women with natural versus surgical menopause throughout the period studied. © 1993 by The Johns Hopkins University School of Hygiene and Public Health