Surgical procedures for atrial fibrillation are called Cox maze procedure in recognition of the pioneering work done by Cox and his colleagues [Cox JL et al. The development of the Maze procedure for the treatment of atrial fibrillation. Semin Thorac Cardiovasc Surg. 2000; 12: 2–14]. Initial work on atrial fibrillation from this group was left atrial isolation. Though this produced sinus rhythm in right atrium left atrium continued to fibrillate and was a source for thromboembolism.
Maze I procedure
In the initial maze procedure, position of the sinus node was identified and atriotomies were made surrounding it on three sides to allow impulse propagation in only one direction. Additional incisions were made to direct impulses to all areas of the atrium while interrupting all possible macro reentrant circuits in the atrium. This prevent atrial fibrillation and restored atrioventricular synchrony. The first maze procedure was done on 25th September, 1987.
Maze II procedure
Two important problems with Maze I procedure were chronotropic incompetence of the sinus node and occasional left atrial dysfunction. In Maze II, the incision through the sinus node area in the high lateral right atrium was skipped and the transverse incision at the roof of the left atrium was moved posteriorly to permit better intra atrial conduction. But Maze II had a problem in that it was necessary to transect the superior vena cava to expose the left atrium.
Maze III procedure
In Maze III, placing the septal incision posterior to the opening of the superior vena cava improved the exposure of the left atrium. Higher rates of sinus rhythm was achieved by Maze III procedure and they had improved long term sinus node function. Atrial transport function was better and the need for pacemaker was lesser and so was arrhythmia recurrence. Later it has been performed as a minimally invasive procedure with right sub mammary incision and even without cardiopulmonary bypass.
Maze IV procedure
Even with Maze III, multiple atrial incisions were required contributing to morbidity and complexity of the procedure. In 1990s the first cryomaze procedures were performed, with cryoablation replacing the surgical incisions with transmural ablation lines. The first non-cut-and-sew maze procedure with cryo was performed in 1999. In Maze IV, pulmonary veins are isolated bilaterally and a connecting lesion was also made. Since then various energy sources like radiofrequency, high frequency ultrasound, microwave and laser have been used for creating the ablation lines in Maze procedure [Edgerton ZJ et al. Heart Rhythm. 2009; 6:S1-S4].