Author + information
- Francesco Onorati, MD, PhD⁎ (, )
- Francesco Santini, MD,
- Giuseppe Faggian, MD and
- Alessandro Mazzucco, MD
- ↵⁎Primary Work Division of Cardiac Surgery, University of Verona, Piazzale Stefani, 37126 Verona, Italy
We are grateful to Drs. Lee and McCarthy for their interest in our report (1). They raise several important issues and wonder whether the enrollment of patients undergoing either monopolar or bipolar radiofrequency (RF) ablation in the “limited” group might have worsened the results (1).
In August 2004, we substituted monopolar with bipolar RF ablation because of the suggested easier and more reproducible achievement of transmural lesions due to the “real-time” measurement of tissue impedance (1). However, it has not yet been demonstrated that tissue impedance directly parallels the depth of the lesion or that it results in definitive conduction blocks (2). Indeed, some percentage of recurrence is continuously reported even after bipolar RF ablation, underscoring the risk for an incomplete conduction block with the latter technique (3). However, the ability of monopolar RF ablation to induce definitive conduction block is suggested by some percentage of success, even on long-term follow-up (3). Furthermore, monopolar RF ablation is not proven to predict recurrences (3). In view of this controversial issue, we reach the conclusion that the problem is related to the electrophysiological substrates rather than the effectiveness of transmurality, which should be achievable with both energy sources and considered a pre-requisite for any ablative procedure. Furthermore, if a grossly normal right atrium is capable to support only 1 macro–re-entrant circuit (corresponding to the right atrial flutter wave), an enlarged or stretched right atrium (as in patients with mitral and/or tricuspid disease, pulmonary hypertension, and so on) may harbor 2 or more simultaneous macro–re-entrant circuits (4). In these cases, atrial fibrillation of right origin may recur, even after a right atrial flutter lesion, and certainly after isolated left-sided ablations (4). Accordingly, most experiences support a biatrial approach instead of the isolated left-sided approaches (4).
We are aware that our study had the well-recognized limitations related to its nonrandomized design and to the “growing” or “ongoing” experience perspective, whereby different surgical techniques were applied in different time periods. However, we overcame these limitations with statistical analysis using propensity score matching and by subgroup analysis investigating the 5 different techniques, which confirmed that isolated bipolar left ablation achieved worse results than biatrial approaches. Moreover, to further avoid the risk for a “learning curve” effect, the last 10 patients of the “limited” approach were compared with the first 10 patients of the “extensive” approach, leading again to the conclusion that superior results were achieved after biatrial approaches.
We agree with Drs. Lee and McCarthy that the role of ablation in curing atrial fibrillation remains a “hot topic” warranting further research in view of the complexity of the issue and the persistent scarcity of data.
- American College of Cardiology Foundation
- Onorati F.,
- Mariscalco G.,
- Rubino A.S.,
- et al.
- Calkins H.,
- Brugada J.,
- Packer D.L.,
- et al.