Surgery for Atrial Fibrillation

Abstract

Atrial fibrillation (AF) is a common and serious arrhythmia that traditionally has been treated with antiarrhythmic drugs and warfarin for anticoagulation. Patients often are symptomatic. Normal cardiac function may be impaired due to loss of atrioventricular synchrony and the abnormal irregular ventricular activation. Despite the widespread use of medical therapy in these patients, a recent 21-year follow-up study of patients with AF treated medically showed no improvement in mortality risk over time and in fact showed a substantial excess risk of death.1 Thus, the goal of intervention has shifted over the last 30 years from efforts to improve ventricular rate control while leaving the atria in atrial fibrillation to attempting to permanently atrial fibrillation and restore the atria to sinus rhythm. The late 1970’s and early B0’s ushered in a variety of new invasive surgical procedures. Cox initially developed the atrial isolation designed to confine the atrial fibrillation to the left atrium and allow the heart to beat in sinus rhythm from the right atrium.2•4 Guiraudon created the corridor procedure that joined the sinus node to the atrioventricular node with an isolated strip of right atrial wall.5 In both procedures, the left atrium continued to fibrillate and posed a continued risk of thromboembolism. Open surgical ablation of the atrioventricular node with cryothermia and pacemaker implantation was performed by us in the late 1970’s in selected patients who had difficulty controlling their heart rate through medical therapy. This latter was soon superseded by catheter ablation of the His bundle that was reported by Scheinman in 1982.6 Warfarin continued to be required for rate-controlled atrial fibrillation. The development of a surgical cure for atrial fibrillation was delayed due to the erroneous belief that it was a microreentrant arrhythmia. The initial breakthrough in understanding the mechanism of atrial fibrillation was first achieved by Dr. James Cox and his electrophysiologist colleagues at Duke and then at Washington University. In a series of elegant experiments on dogs and humans, the precise patterns of atrial activation in atrial flutter and fibrillation were elucidated. A mapping computer with 256 electrodes on right and left atrial arrays clearly demonstrated that atrial fibrillation was a macroreentry arrhythmia and that microreentry and automaticity were not present in established atrial fibrillation.3•4 This was consistent with the earlier work published by Allessie on the mapping of atrial flutter in the isolated heart model, which demonstrated that multiple macroreentrant wave fronts were present during atrial flutter.7 Thus, surgical efforts were directed toward creating a series of atrial incisions that would allow normal activation of the entire left and right atria but would prevent propagation of macroreentrant circuits. The specific areas considered at high risk of supporting macroreentry were the vena caval orifices, the base of the left atrial appendage, the four pulmonary veins, the interatrial septum, and the tricuspid orifice. These studies and subsequent clinical experience led to the development of the Cox-Maze Ill procedure, which was introduced into clinical practice in 1991 and continues to be the gold standard for cure of atrial fibrillation. Even with the high cure rate reported by Dr. Cox and confirmed by other centers, the Cox-Maze was never widely adopted. This was due in part to a perception that it was difficult to learn. It also was a significant surgical procedure: Dr. Cox initially performed the operation by making multiple and extensive full-thickness atrial incisions that then had to be sutured.3•4 The introduction of new technologies such as high frequency ultrasound (HIFU) and bipolar radiofrequency devices has greatly simplified this process and made it easier to apply as a combined in patients with atrial fibrillation and structural heart disease such as coronary or valvular lesions. Despite the surgery’s safety record and long-term cure rate of over 95%, however, the need for an open surgical incision and the now-outdated perception of it being a major undertaking continues to limit its application as a freestanding procedure.