Clinical evaluation in therapy of patients with atrial fibrillation or flutter.

The weight of evidence clearly indicates that both atrial fibrillation and atrial flutter are due to a reentrant mechanism. Atrial fibrillation seems almost certainly due to multiple circulating reentrant wavelets of the leading circle type, whereas atrial flutter appears to be caused by single reentrant circuit located in the right atrium. The diagnosis of both atrial fibrillation and atrial flutter should always be possible using either old or new techniques. The interruption of atrial flutter should be possible using pacing or direct current cardioversion techniques, and the conversion of atrial fibrillation to sinus rhythm also is most often possible by direct current cardioversion or antiarrhythmic drug therapy. Long-term antiarrhythmic drug therapy to suppress recurrent atrial fibrillation and atrial flutter may be a problem, but availability of newer antiarrhythmic agents holds promise for finding an effective regimen. Catheter ablation techniques may be used to cause complete heart block in the treatment of either atrial fibrillation or atrial flutter when these rhythms cannot be satisfactorily suppressed and are associated with unacceptably rapid ventricular response rates. Finally, recent data suggest that atrial flutter may be successfully treated on a chronic basis with an antitachycardia pacing device, may be cured with catheter ablation techniques applied to a critical portion of the atrial flutter reentry circuit, and may be treated successfully with innovative surgical techniques. The latter is also true for atrial fibrillation.