Presence Of Exercise-induced Ischemia Research Articles

Symptom-limited exercise capacity is associated with long-term survival.

The prognostic value of exercise capacity has been demonstrated in subjects with established cardiovascular diseases. We aim to evaluate the independence of exercise capacity measured by treadmill exercise test (TET) in predicting long-term outcomes among various comorbidities. This study was conducted from January 2003 to December 2012 in a tertiary medical center in Taiwan. Subjects referred for symptom-limited TET were recruited. Peak achieved metabolic equivalents (METs) were determined by treadmill grade and speed at peak exercise. The main outcomes were cardiovascular and all-cause mortality by linking to the National Death Registry. A total of 18,954 participants (57.8 ± 12.8 years, 62% men) achieved a mean peak METs of 9.2. Subjects in the lowest tertile of peak METs were older, had poorer renal function, lower hemoglobin, and more comorbidities. During a median follow-up of 4.3 years, there were 642 mortalities and 132 cardiovascular deaths. Peak METs significantly predicted cardiovascular death and all-cause mortality in the multivariable Cox regression models [hazard ratio (95% confidence intervals): 0.788 (0.660-0.940) and 0.835 (0.772-0.903), respectively]. The prognostic influence of peak METs consistently appeared in the subgroups, regardless of age, gender, body weight, comorbidities, use of beta-blockers, or the presence of exercise-induced ischemia. The fitness was more predictive of long-term outcomes in young or those with ischemic changes during TET (P for interaction: 0.035 and 0.018, respectively). The benefit of fitness was nonlinearly associated with long-term survival. The prognostic impacts of exercise capacity were universally observed in subjects with or without various comorbidities.

Exercise above the ischemic threshold and serum markers of myocardial injury

Current guidelines for exercise training in coronary patients state that in the presence of exercise-induced ischemia, the heart rate during exercise should be at least 10 beats/min below the heart rate associated with an ST segment depression of 1 mm or greater. For patients with a relatively low ischemic threshold, this recommendation does not allow for a sufficient training stimulus. To document the effects of a single session of exercise above the ischemic threshold on biochemical markers of myocardial injury in stable coronary patients with exercise-induced ischemia. Because creatine kinase (CK) and its MB isoenzyme (CK-MB) can both increase after exercise because of skeletal muscle injury, troponin T was also measured. Twenty-one patients with documented coronary artery disease underwent two 20 min exercise sessions. The intensity of the first exercise training session was fixed at a heart rate below the ischemic threshold (ie, approximately 10 beats/min lower than the heart rate associated with the appearance of an ST segment depression of 1 mm or greater). The intensity of the second exercise session was fixed at a heart rate above the ischemic threshold. Blood test measurements at baseline, 6 h after and 24 h after the exercise sessions did not show any increase in total CK, CK-MB or troponin. The value of all measurements remained well below the lower limits associated with myocardial damage. A 20 min period of exercise above the ischemic threshold did not result in myocardial necrosis.

Effects of carbon monoxide exposure in patients with documented cardiac arrhythmias

Objective. This study was designed to determine whether carbon monoxide has proarrhythmic effects at rest and during upright exercise in patients with myocardial ischemia and moderate baseline ectopic activity.Background. Exposure of patients with documented myocardial ischemia to low levels of carboxyhemoglobin (COHb) alters the myocardial response to exercise. Anecdotal reports from patients with myocardial ischemia have noted the development of arrhythmias related to carbon monoxide exposure. Increased frequency of arrhythmias related to carbon monoxide exposure in patients performing supine bicycle exercise has been recently reported.Methods. Twenty-eight nonsmoking men and five nonsmoking women with documented coronary artery disease and a minlmum of 30 ventricular ectopic beats/h over a 20-h period were studied. Subjects were exposed in a randomized double-blind fashion to either room air or sufficient carbon monoxide to elevate their COHb concentration to 3% or 5% in 1 h, followed by a maintenance exposure to carbon monoxide, The subjects then left the laboratory and resumed their normal daily activity to determine changes in ventricular ectopic beats after carbon monoxide exposure.Results. There was no significant change in the frequency of single ventricular ectopic beats at rest from 115 ± 28 (in room air) to 121 ± 31 at 3% COHb to 94 ± 23 at 5% COHb. Exercise itself Increased the frequency of ventricular ectopic beats, but there was no additional effect of carbon monoxide exposure on the exerciseinduced increase in isolated ectopic beats or complex ectopic waveforms. Analysis of the data based on grouping of the subjects by the severity of disease (ventricular ectopic beat frequency, ejection fraction, presence of exercise-induced ischemia) indicated no proarrhythmic effect of carbon monoxide.Conclusions. In patients with frequent ventricular ectopic activity (≥30 ectopic beats/h), exposure to carbon monoxide producing either 3% or 5% COHb does not increase arrhythmia frequency of single or multiple beats during rest or exercise.

A simplified approach for evaluating multiple test outcomes and multiple disease states in relation to the exercise thallium-201 stress test in suspected coronary artery disease

This study describes a simplified approach for the interpretation of etectrocardiographic and thallium-201 imaging data derived from the same patient during exercise. The 383 patients in this study had also undergone selective coronary adenography within 3 months of the exercise test. This matrix approach allows for multiple test outcomes (both tests positive, both negative, 1 test positive and 1 negative) and multiple disease states (no coronary artery disease vs 1-vessel vs multivessel coronary artery disease). Because this approach analyzes the results of 2 test outcomes simultaneously rather than serially, it also negates the lack of test independence, if such an effect is present. It is also demonstrated that ST-segment depression on the electrocardiogram and defects on initial thallium-201 images provide conditionally independent information regarding the presence of coronary artery disease in patients without prior myocardial infarction. In contrast, ST-segment depression on the electrocardiogram and redistribution on the delayed thallium-201 images may not provide totally independent information regarding the presence of exercise-induced ischemia in patients with or without myocardial infarction.