Effect of mitral valve repair/replacement surgery on atrial arrhythmia behavior.

Atrial fibrillation (AF) is a common accompanimentof chronic mitral regurgitation, and is caused byincreased atrial pressure, progressive left atrial stretchand dilatation. It is present in 40-60% of patientsundergoing mitral valve surgery (1-3), and is associat-ed with significant excess long-term morbidity andmortality during follow up after surgery (4).Chronic AF associated with mitral valve diseaseoften persists despite surgical correction of the under-lying valvular lesion (5,6). The results of several stud-ies have suggested that variables such as the durationof AF, left atrial size, age and the severity of left ven-tricular dysfunction allow persistence of AF aftermitral valve surgery to be predicted. However, pub-lished results are discordant, with little consistency ofpredictive variables being identified (5,7-11).In recent years, many cardiothoracic surgeons con-vinced of the benefits of adding specifically anti-arrhythmic procedures at the time of mitral valvesurgery have begun routinely to perform the com-bined operation. Various studies have reported therestoration of sinus rhythm in 85-98% of cases with thecombined procedure (12-16). However, systematicreview of the literature reveals remarkably few studiesin which the effect of mitral valve surgery alone onatrial rhythm has been reported. Thus, although thesuccess of anti-arrhythmic procedures is established,the need for the combined operation - particularly inpatients with paroxysmal AF - is more speculative.Undoubtedly, cardiac surgery offers a unique oppor-tunity to perform additional procedures to restore andmaintain sinus rhythm in patients with chronic AF.However, some of these patients might return to sinusrhythm with mitral valve surgery alone. It is desirable,therefore, to distinguish this small group who do notrequire additional surgery, from the majority who