The Impact Of Ablation Technology On Surgical Outcomes Following The Cox Maze Procedure: A Propensity Analysis
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Objective
Since its introduction in 1987, the Cox maze (CM) procedure has been established as the gold standard for treatment of atrial fibrillation (AF). At our institution, this procedure has evolved from the cut-and-sew technique (CM III) to one using bipolar radiofrequency energy as an ablative source to replace most incisions (CM IV). This study compares surgical outcomes of patients undergoing the CM III versus the CM IV.
Methods
From April 1992 to July 2005, 242 patients underwent the CM procedure for atrial fibrillation. Of these, 154 patients had the CM III and 88 had the CM IV. Logistic regression analysis was used to identify covariates among 7 baseline patient variables, including age, gender, ejection fraction, type and duration of AF, operative procedure (lone CM versus CM with a concomitant procedure), and New York Heart Association (NYHA) class. Using the significant regression coefficients, each patient's propensity score was calculated allowing selectively matched subgroups. Post-operative outcomes including length of intensive care unit (ICU) and hospital stay, 30-day mortality, permanent pacemaker placement, and early atrial tachyarrhythmias were analyzed for differences between the two groups. Late follow-up was available for 229 patients (95%). Mean follow-up was 4.3±2.7 years and 1.2±0.8 years for the CM III and CM IV respectively. Freedom from AF recurrence was calculated at one year by Kaplan-Meier analysis.
Results
A logistic regression analysis identified only older age and higher NYHA class as significant predictors of group assignment. Propensity scoring closely matched 58 patients who underwent the CM III with 58 who had the CM IV. There were no significant differences between the two groups in age, gender, NYHA class, operative procedure, duration, or type of AF. The CM III had significantly longer cross-clamp times than the CM IV. There was no significant difference in ICU and hospital stay, 30-day mortality, permanent pacemaker placement, and early atrial tachyarrhythmias. Freedom from AF recurrence was greater than 90% in both groups at one year (see Table).
Post-operative outcomes of the propensity matched cut-and-sew (CM III) vs. ablation-assisted (CM IV) | Cut-and-sew group | Ablation-assisted group | p-value |
| Mean cross clamp time (min) | 120.6 ± 34.1 | 75.6 ± 36.5 | <0.001 |
| Median ICU stay (days) | 2 (IQR: 1-4) | 2 (IQR:1-5) | 0.966 |
| Median hospital stay (days) | 10 (IQR: 8-16) | 9 (IQR: 7-16) | 0.765 |
| Pacemaker placement | 9 (15.8%) | 6 (10.2%) | 0.417 |
| Early atrial tachyarrhythmias | 27 (47.4%) | 36 (61.0%) | 0.192 |
| 30-day mortality | 1 (1.8%) | 3 (5.1%) | 0.619 |
| Freedom from AF at one year | 96.0% | 92.6% | 0.022 |
Conclusions
The CM IV, using bipolar radiofrequency ablation, has greatly simplified the procedure from a technical standpoint making it applicable to virtually all patients with AF having concomitant cardiac surgery. Comparing matched populations, the operation can be done with a shorter cross-clamp time and produces similar surgical outcomes to the cut-and-sew technique of the original CM procedure.
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