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The effect of cardioversion on maximal exercise capacity in patients with chronic atrial fibrillation
J E Atwood1, J Myers, M Sullivan
1Cardiology Department, Long Beach Veterans Administration Medical Center, CA 90822.
Insights
Cardioversion significantly improves exercise capacity in patients with chronic atrial fibrillation. Following the procedure, individuals experienced a lower heart rate and increased maximal oxygen uptake, enhancing overall physical performance.
Area of Science:
- Cardiology
- Exercise Physiology
- Internal Medicine
Background:
- Chronic atrial fibrillation (AF) impairs exercise capacity.
- Restoration of normal sinus rhythm is a primary goal in AF management.
Purpose of the Study:
- To assess the impact of successful cardioversion on exercise capacity in patients with chronic AF.
- To evaluate changes in physiological responses during exercise post-cardioversion.
Main Methods:
- Maximal exercise testing using gas exchange was performed on 11 male patients before and after cardioversion.
- Measurements included heart rate, blood pressure, and respiratory gas exchange at rest and during exercise.
- Testing occurred shortly before and approximately 39 days after achieving normal sinus rhythm.
Main Results:
- Cardioversion led to a significant decrease in resting and submaximal exercise heart rates.
- Maximal exercise heart rate was substantially reduced post-cardioversion.
- Maximal oxygen uptake (a measure of exercise capacity) significantly increased after cardioversion.
- Improved ventilation efficiency was noted at higher exercise intensities.
Conclusions:
- Successful cardioversion enhances exercise capacity in patients with chronic atrial fibrillation.
- The improvement is characterized by reduced heart rate and increased oxygen uptake during maximal exertion.
- Restoring normal sinus rhythm positively impacts physiological responses to exercise.
Abstract:
To evaluate the effect of cardioversion on exercise capacity, 11 male patients (59 +/- 8 years) with chronic atrial fibrillation underwent maximal exercise testing using gas exchange techniques before and after successful cardioversion to normal sinus rhythm. Testing was conducted 1 day prior to and a mean of 39 (range 10 to 95) days following cardioversion. Heart rate, blood pressure, and respiratory gas exchange responses were evaluated at rest, at a standard submaximal workload (3.0 mph/0% grade), at the gas exchange anaerobic threshold, and at maximal exertion. Cardioversion resulted in a mean decrease in resting heart rate of 37 beats/min (113 +/- 16 versus 76 +/- 10 beats/min, p less than 0.001). While mean heart rate was approximately 50 beats/min lower following cardioversion at both submaximal stages of exercise p less than 0.001), oxygen uptake was not different. At maximal exercise, heart rate was markedly reduced (192 +/- 24 to 144 +/- 21 beats/min, p less than 0.001) and maximal oxygen uptake was higher (1.86 +/- 0.5 to 2.06 +/- 0.5 L/min, p less than 0.05) after cardioversion. In addition, an improved efficiency of ventilation was observed at exercise levels exceeding 60% of maximal oxygen uptake.