Success rates for the Cox maze IV procedure

SAINT LOUIS, MISSOURI. The Cox maze procedure for the purpose of curing atrial fibrillation (AF) has been performed since 1987. It has gone through several iterations from the use of a cut-and-sew protocol to create the lesion set to the now prevalent use of ablation catheters or clamps powered by radiofrequency or cryo energy. The last cut-and-sew version, the Cox maze III, had a complete success rate (no AF, no antiarrhythmics) of 70% and a partial success rate of 27% (no AF, but still on antiarrhythmics) after a mean follow-up of 5 years.

Cardiothoracic surgeons at the University of Washington Medical School (Dr. Damiano’s group) now report on the success of the Cox maze IV procedure. This procedure still involves open heart surgery and the use of a heart/lung machine, but now uses bipolar radiofrequency-powered clamps (Atricure or Medtronic) to create the main lesions (on both the left and right atrium). At the tricuspid and mitral valve openings cryoablation is generally used. A study was recently completed to establish the one-year success rate of the Cox maze IV procedure.

The study involved 282 patients (63% men) of which 42% had paroxysmal AF, 10% had the persistent variety, and 48% were in long-standing persistent (permanent) AF. The median duration was 3.7 years. The majority (66%) of patients had other reasons than the presence of AF for undergoing the maze procedure, 28% underwent mitral valve replacement, 20% had coronary bypass surgery with or without valve replacement, and another 18% had various other indications for the surgery. The remaining 34% had AF as the only indication for the procedure.

The study participants underwent the Cox maze IV between January 2002 and December 2009 and were followed up to 3, 6, 9 and 12 months post-procedure with 24-hour Holter monitoring. In procedures done since 2005, a second superior connecting lesion was added (the box lesion set) to anatomically isolate the entire posterior left atrium. All participants were on antiarrhythmics at discharge but these were discontinued if the patients were afib-free at two months. Anticoagulation was usually stopped after three months.

Complete success was defined as being free of atrial tachyarrhythmias (AF, atrial flutter and atrial tachycardia) lasting longer than 30 seconds without the use of antiarrhythmics. Complete success rates were 63%, 79%, and 78% at 3, 6 and 12 months respectively. Partial success rates (arrhythmia-free, but still on antiarrhythmics) were 26%, 14%, and 20% respectively, giving overall afib-free rates (with or without antiarrhythmics) of 89%, 93%, and 89% respectively. There was no difference in success rates for paroxysmal versus persistent and permanent AF.

Early post-operative atrial arrhythmias were quite common (53% of patients), but usually resolved over the first month following the procedure. Postoperative mortality was 1% among patients with AF only and 3% among those with concomitant valve or other problems. Eleven percent of patients had major procedure-related complications including serious bleeding, renal failure, and stroke. The median length of hospital stay was 9 days with a range of 4 to 73 days. The major factors associated with failure were early atrial arrhythmias (OR=3.0), and larger left atrial diameter (OR=1.4). Having completed the box set lesions around the pulmonary veins were significantly associated with improved outcome (OR=0.38).

The authors conclude that the Cox maze IV procedure has a high success rate at one year even with improved follow-up and stricter definition of failure.

Damiano, RJ, et al. The Cox maze IV procedure: predictors of late recurrence. Journal of Thoracic and Cardiovascular Surgery, Vol. 141, No. 1, January 2011, pp. 113-21

Editor’s comment: The Washington School of Medicine is one of the world’s most successful centers for the performance of the Cox maze. Thus, it is reasonable to compare their results with such catheter ablation centers as the Cleveland Clinic (during Dr. Natale’s tenure), the California Pacific Medical Center, and the Bordeaux group at Hopital Cardiologique du Haut-Leveque. The 2008 Ablation/Maze Survey included 165 lone afibbers treated at these three institutions. Complete success rate (no AF, no antiarrhythmics) for the three institutions combined was 71% and the partial success rate was 5%, giving an overall success rate of 76% after an average of 1.3 procedures. No procedure-related deaths were reported from any of the institutions.

Thus, the Cox maze IV is clearly more successful than even the best catheter ablation. However, it is a substantially more complicated procedure, has a substantially higher mortality and rate of serious complications, and a longer recovery period. It also involves the use of a heart/lung machine, which in itself can cause problems, especially of a cognitive nature. Finally, it would appear that only arrhythmia incidences happening at the 3, 6, 9 and 12 months follow-ups were counted. It would seem very unlikely that episodes would not have occurred outside of these four 24-hour monitoring periods. My opinion has not changed – a full Cox maze procedure is “overkill” for a paroxysmal lone afibber.