High-density biatrial pacing protects against atrial fibrillation by synchronizing left atrial tissue.

PURPOSE: The induction and sustainability of atrial fibrillation (AF) are most commonly due to pulmonary vein (PV) triggers and left atrial (LA) substrate. We hypothesized that simultaneous pacing of the PV ostia, LA, and right atrium (RA) reduces AF susceptibility by synchronizing atrial activity. METHODS: Mongrel dogs were rapidly paced and maintained in AF for 3 months before cardioversion. Pacing leads were then placed at PV ostia, LA, and RA sites. For single-site pacing (SSP), a drive train (S1) and premature stimulus (S2) were delivered from the same electrode. Multisite pacing (MSP) consisted of S1 at all leads simultaneously and S2 at one site. Pacing trials were performed with decremental S2 coupling intervals (CI) to endpoints of AF induction or refractoriness. RESULTS: AF induction was reduced by 40.0% with MSP vs. SSP (7.2% vs. 12.0%, p < 0.001). LA S2 sites were more likely to induce AF than RA sites (11.5% vs. 2.6%, p < 0.0001), with benefit of MSP over SSP at LA sites (8.6% vs. 14.6%, p < 0.0001). The CI for AF induction was longer with SSP vs. MSP (119.4 +/- 13.3 vs. 104.4 +/- 11.2 ms, p < 0.05). Atrial activation times were shortened with MSP vs. SSP (87.4 +/- 4.9 vs. 97.1 +/- 10 ms, p < 0.005). CONCLUSIONS: Atrial synchronization was shown by the decreased activation times with MSP. AF induction was reduced by 40.0% with MSP, supporting the hypothesis of decreased AF susceptibility with synchronization. This is the first study demonstrating AF protection with high-density pacing at LA sites associated with triggers and substrate for the induction and maintenance of AF.

An Update on the Energy Sources and Catheter Technology for the Ablation of Atrial Fibrillation.

The ablation of atrial fibrillation (AF) is an area of intense research in cardiac electrophysiology. In this review, we discuss the development of catheter-based interventions for AF ablation. We outline the pathophysiologic and anatomic bases for ablative lesion sets and the evolution of various catheter designs for the delivery of radiofrequency (RF), cryothermal, and other ablative energy sources. The strengths and weaknesses of various specialized RF catheters and alternative energy systems are delineated, with respect to efficacy and patient safety.

Scenes from a CFAE: Complex Fractionated Atrial Electrogram Map in a Woman with Longstanding Persistent Atrial Fibrillation Following Mechanical Mitral Valve Replacement.

Case: A 62-year-old woman was referred for atrial fibrillation (AF) ablation. She had longstanding persistent AF for 8 years since mechanical mitral valve replacement for rheumatic heart disease. EPS: A strategy of substrate-based ablation targeting areas of complex fractionated atrial electrograms (CFAE) was pursued. These sites were identified by inspection of electrograms and verified with software-based electrogram analysis, with the left atrial roof demonstrating the highest density of CFAE sites. Successful catheter ablation was performed. The patient has remained free of recurrence over 4 months of follow-up. Discussion: This case presents a successful ablation procedure using the emerging strategy of CFAE-targeted ablative lesions. Given the patient's longstanding persistent AF and mechanical mitral valve, the high density of CFAE sites on the left atrial roof was an unexpected finding. Analysis for CFAE sites guided the procedure in a direction that might otherwise not have been undertaken, leading to a successful ablation.

The A That Did Not Fib:Two Roads Both Traveled By.

Case: A 64-year-old woman presented with palpitations. Her 24-hour Holter monitor revealed runs of presumed atrial fibrillation (AF). The patient was referred for EP study and AF ablation. EPS: At EPS, an anterograde A-H jump was noted. Spontaneous bursts of tachycardia were seen, consisting of sinus atrial beats with dual ventricular responses, each preceded by a His deflection. There was no atrial fibrillation during the study. Radiofrequency ablation of the slow AV node pathway was performed. There were no inducible tachycardias and no A-H jump following the ablation. The patient had no recurrence post-procedure. Discussion: This case presents a rare example of simultaneous dual anterograde AV-nodal conduction. The conditions leading to this phenomenon include dual AVN pathways, markedly slowed conduction in the slow pathway, and lack of retrograde conduction up either pathway such that reentry was impossible. An irregular, narrow-complex tachycardia resulted, initially interpreted as AF. Slow-pathway ablation was curative.