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Effects of carbon monoxide exposure in patients with documented cardiac arrhythmias
T E Dahms1, L T Younis, R D Wiens
1Department of Internal Medicine, Saint Louis University School of Medicine, Missouri 63110-0250.
Insights
Carbon monoxide exposure, even at levels causing 5% carboxyhemoglobin (COHb), does not increase arrhythmias in patients with myocardial ischemia. This study found no proarrhythmic effects during rest or exercise in individuals with moderate baseline ectopic activity.
Area of Science:
- Cardiology
- Environmental Health
- Toxicology
Background:
- Low-level carbon monoxide (CO) exposure alters myocardial response to exercise in patients with myocardial ischemia.
- Anecdotal reports link CO exposure to arrhythmias in individuals with myocardial ischemia.
- Previous studies suggested increased arrhythmias during exercise with CO exposure.
Purpose of the Study:
- To investigate the proarrhythmic effects of carbon monoxide (CO) at rest and during exercise.
- To assess CO's impact on patients with myocardial ischemia and moderate baseline ventricular ectopic activity.
- To determine if elevated carboxyhemoglobin (COHb) levels influence arrhythmia frequency.
Main Methods:
- Twenty-eight men and five women with coronary artery disease and at least 30 ventricular ectopic beats/h were studied.
- Subjects were randomized to room air or CO exposure to achieve 3% or 5% COHb levels.
- Ventricular ectopic beats were monitored at rest and during exercise after CO exposure.
Main Results:
- No significant change in single ventricular ectopic beats at rest was observed across COHb levels (3% or 5%).
- Exercise increased ventricular ectopic beats, but CO exposure did not add to this effect.
- No proarrhythmic effect of CO was found when grouping subjects by disease severity.
Conclusions:
- Carbon monoxide exposure to 3% or 5% COHb does not increase arrhythmia frequency in patients with frequent ventricular ectopic activity.
- The study found no significant proarrhythmic effect of CO during rest or exercise in this patient group.
- Findings suggest CO is not a significant arrhythmogenic factor in patients with myocardial ischemia and moderate ectopic activity.
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 minimum 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 exercise-induced 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 (> or = 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.
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