Related Experiment Videos
Functional capacity of patients with atrial fibrillation and controlled heart rate before and after cardioversion
1Internal Medicine Department, Royal Alexandra Hospitals, Edmonton, Alberta.
Insights
Restoring normal sinus rhythm through cardioversion significantly improves exercise duration in atrial fibrillation patients, offering greater gains than heart rate control alone. This enhanced exercise tolerance is linked to restored atrial function.
Area of Science:
- Cardiology
- Electrophysiology
- Exercise Physiology
Background:
- Atrial fibrillation (AF) commonly diminishes exercise duration.
- Effective management strategies are needed to improve exercise capacity in AF patients.
Purpose of the Study:
- To quantify exercise duration improvements from heart rate control versus cardioversion in AF patients.
- To compare the efficacy of these two strategies in enhancing exercise tolerance.
Main Methods:
- Eighteen AF patients underwent treadmill stress tests.
- Heart rate control was achieved using verapamil, followed by repeat stress tests.
- Patients then underwent chemical or electrical cardioversion, with subsequent stress tests.
- Left atrial size was measured via echocardiography before and after cardioversion.
Main Results:
- Heart rate control increased exercise duration by an average of 164 seconds.
- Cardioversion further increased exercise duration by an additional 90 seconds (total 254 seconds gain).
- Exercise performance improved in most patients post-cardioversion, except those with fixed cardiac output.
Conclusions:
- Conversion to normal sinus rhythm via cardioversion significantly improves exercise tolerance in AF patients.
- Restoration of mechanical atrial function is the likely mechanism for improved exercise performance.
- Cardioversion offers superior exercise capacity gains compared to heart rate control alone.
Objective:
To measure exercise duration (which frequently is diminished by atrial fibrillation) and to compare the gain in exercise duration achieved by heart rate control with the gain after cardioversion.
Methods And Results:
Eighteen patients (10 with structural heart condition and eight with lone atrial fibrillation) did the treadmill exercise stress test using the Bruce protocol. Resting supine heart rate was lowered below 100 beats/min by verapamil (initial exercise stress test). An exercise stress test was then repeated as often as needed to achieve 'heart rate control' (less than 130 beats/min at the end of a 3 min walk at 10 degrees elevation and 2.74 km/h speed). This heart rate control was obtained by gradual increases in verapamil dose. Subsequently, the patients were converted to normal sinus rhythm chemically (seven patients) or electrically (11 patients) and an exercise stress test was repeated. At cardioversion, patients were on antiarrhythmic therapy and verapamil was discontinued in most. All patients had left atrial size measured by echocardiogram before and after cardioversion, and all were followed for four months. Upon achieving controlled heart rate, exercise duration increased in 16 patients (average gain was 164 s). After cardioversion to normal sinus rhythm, exercise duration further increased in 13 cases with an average additional gain of 90 s. The total increase in exercise duration after cardioversion was 254 s. Post cardioversion, all patients with lone atrial fibrillation improved. A decline in exercise performance occurred in four patients with fixed cardiac output. Average gain in exercise duration was independent of drugs used. Left atrial size remained increased post cardioversion (50.4 mm before and 52 mm after). During four months of follow-up, only eight patients could continue on the same medication given for cardioversion. Three patients did not maintain normal sinus rhythm.
Conclusions:
Conversion to normal sinus rhythm in patients with atrial fibrillation is associated with improved exercise tolerance except in cases with fixed cardiac output. Restoration of mechanical atrial function appears to be responsible for improved exercise performance following cardioversion.