Between March 1997 and March 2002, 81 patients with permanent AF and mitral valve disease underwent the maze IV procedure utilizing RF energy and cryoablation while undergoing concomitant valvular operations. All patients had mitral valve disease and permanent AF, which was defined as AF lasting for > 4 weeks. Of these patients, 11 patients were in New York Heart Association (NYHA) functional class IV, 57 patients were in NYHA functional class III, 12 patients were in NYHA functional class II, and 1 patient with a huge left atrial thrombus was in NYHA functional class I. The RF maze procedure was simultaneously performed with mitral valve replacement (mechanical valve, 37 patients; tissue valve, 6 patients), mitral valve repair (36 patients), Ross II operation (2 patients),12 aortic valve replacement (mechanical valve, 12 patients; tissue valve, 2 patients), aortic valve repair (2 patients), tricuspid tissue valve replacement (1 patient), tricuspid annuloplasty (56 patients), and coronary artery bypass graft surgery (4 patients). Therefore, 46.9% of these patients underwent mechanical valve replacement. There was one surgical death (1.2%) due to Pseudomonas pneumonia and sepsis 5 days after the patient underwent the operation. Another patient, who regained sinus rhythm after undergoing the maze procedure, died of acute necrotizing pancreatitis 13 months later. Two patients (2.5%) developed sick sinus syndrome and received transvenous permanent pacemaker implantation. Electrophysiologic studies of these two patients showed extensive absence of atrial electric potential and high stimulation threshold of both atria, suggesting irreversible myocardial damage that was present before the RF maze procedure. The remaining 77 patients constituted the population of this study. There were 38 men and 39 women, with a mean (± SD) age of 51 ± 11 years (age range, 21 to 71 years). The success of the RF maze procedure was defined as persistence in sinus rhythm without the use of antiarrhythmic drugs or electrical cardioversion after the 2-month follow-up. At a mean follow-up of 38 months, 65 patients (84.4%) had persistent sinus conversion after undergoing the RF maze procedure (group 1), and 12 patients did not regain sinus rhythm (group 2) [persistent AF, 9 patients; paroxysmal AF, 2 patients; persistent atrial flutter, 1 patient). Informed consent was obtained from each patient. The study protocol was approved by the Institutional Review Committee on Human Research in our institution.