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Post Acute Transmurality Of Bipolar Radiofrequency In The Clinical Settings: An Electrophysiological Study
Stefano Benussi1, Andrea Galanti1, Valerio Zerbi1, Massimo Mariani2, Ottavio Alfieri1
1Hospital San Raffaele, division of cardiac surgery, Milano, Italy2Thorax Centrum Twente, Enschede, Netherlands
BACKGROUND:
Clinical success of surgical ablation for atrial fibrillation (AF) depends upon persistent transmurality of the lesions. Although bipolar radiofrequency achieves acute transmurality and therefore isolation of the pulmonary vein, the post acute fate of this isolation is presently unknown. The aim of this study is to assess short-term pulmonary vein isolation after open chest surgical ablation with bipolar radiofrequency.
METHODS:
Thirteen patients with mitral valve disease (mean age: 60±10 years) and AF (persistent/permanent: 7/6) who underwent concomitant mitral valve surgery and ablation with the BP2 bipolar device (®Medtronic Inc., Minneapolis, MN) were prospectively enrolled for electrophysiological assessment. During surgery pairs of temporary wires were positioned on the right superior pulmonary vein (RSPV), left atrium, right atrium and right ventricle. Entrance block (abatement or disconnection of atriogram potentials) and exit block (no entrainment at pacing threshold = 10mA) were assessed before and after ablating, 1 week and 3 weeks after surgery, respectively. Isolation of the RSPV was defined by the presence of bidirectional block between the isolated segment and the remaining atrial regions. After isolation of the RSPV was obtained, one additional ablation line was added in each patient.
RESULTS:
Before ablation, RSPV pacing threshold was 2.9±1.6 mA. After an average of 3±1 ablations, isolation was obtained in all RSPVs. At 1 week after surgery, the electrophysiological study confirmed the complete isolation in all cases. At 3 weeks 11/13 were still isolated (85%). All patients were discharged in sinus rhythm. At follow-up (19±7 months) 12/13 patients were in sinus rhythm (92%).
CONCLUSIONS:
Surgical ablation with bipolar radiofrequency grants a complete transmurality 1 week after surgery. However, complete transmurality tends to decline 3 weeks after surgery. In fact, according to our findings, total isolation of the pulmonary veins with the BP2 ablation device declines from 100% to 85% of cases after 3 weeks. Therefore, we conclude that a complete transmurality with bidirectional block at the time of surgery does not guarantee effective pulmonary vein isolation at follow-up.
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