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28-03-2011 | Cardiology | Article

AF inducible after SVT ablation


Free abstract

MedWire News: Study findings show that atrial fibrillation (AF) can be induced in more than a quarter of successfully ablated supraventricular tachycardia (SVT) patients who have no prior history of the atrial arrhythmia.

However, AF does not appear to be inducible in such patients if their shortest cycle length (CL) that results in atrial capture in a one-to-one (1:1) ratio with a normal cycle is longer than 180 ms.

"These findings suggest that significant further investigation is needed to optimize the specificity of using AF induction as an endpoint for AF ablation," say Xunzhang Wang (Cedars-Sinai Medical Center, Los Angeles, California) and team.

They explain that "while inducibility is often used as an endpoint for radiofrequency ablation of AF, little is known regarding inducibility among normals."

To investigate, Wang and colleagues recruited 86 AF-free patients who underwent catheter ablation for SVT. After successful ablation, two different rapid atrial pacing protocols were used on these patients to determine AF inducibility.

The first protocol involved three episodes of atrial pacing from the coronary sinus ostium (CSO) lasting 5 seconds in duration, at CLs of 300, 250, and 200 ms.

The second protocol was composed of decremental pacing from the CSO, starting at a CL of 250 ms and repeated 3 times until atrial capture was achieved in a 1:1 ratio with a normal cycle.

AF was defined as inducible if it lasted for at least 1 minute.

As reported in the journal Heart Rhythm, use of the second protocol resulted in inducible AF more often than the first protocol, at respective rates of 25.6% versus 3.5%.

When Wang and colleagues divided all patients according to shortest CL required to produce atrial capture in a 1:1 ratio with a normal cycle, they found that AF was more frequently induced in patients whose shortest CL was less than 180 ms (AF induced at a rate of 33.3%) than in those whose shortest CL was 180 ms or more (AF induced at a rate of 4.3%).

"Therefore, it is reasonable to recommend a CL of 180 ms as a cutoff value for the lower limit of pacing during an atrial burst pacing stimulation protocol for AF induction," remark Wang and team.

They conclude that their findings may provide clinical electrophysiologists with much needed direction in their search for a reliable endpoint during catheter ablation of AF.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Lauretta Ihonor

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