Εlectrocardiographic and electrophysiological characteristics of idiopathic ventricular arrhythmias with acute successful ablation at the anterior portion of the mitral annulus

Background: We sought to clarify the electrocardiographic and electrophysiological characteristics of ventricular arrhythmias (VAs), including idiopathic ventricular tachycardia (VT) and premature ventricular contractions (PVCs), with acute successful radiofrequency catheter ablation (RFCA) at the anterior portion of the mitral annulus (AP-MA). Methods and Results: Among 437 consecutive patients who presented with VAs for RFCA, twenty-six patients with acute successful RFCA at the AP-MA were included in this study. The ratio of the amplitude of the first positive peak (if present) vs. the nadir in the unipolar electrogram (EGM) was 0.00 – 0.03 (0.00) at the acute successful RFCA site. The time interval between the QRS onset to the maximum descending slope (D-Max) in the unipolar EGM (QRS - Uni) were 18.8 ± 13.6 ms. With bipolar mapping, the V-QRS interval was 3.75 – 17.3 (11) ms, 6 (23.1%) patients showed earliest V-QRS interval of 0 ms, and the other 20 patients (76.9%) showed V-QRS interval of 10-54 ms. The RFCA start-to-effect time was 14.1 ± 7.2 seconds in 23 patients (88.5%). In the remaining 3 patients (11.5%), the mean duration of successful RFCA were not well determined due to infrequent nature of clinical VAs during RFCA. Early (within 3 days) and late (one-year) recurrence rates were 23.1% (6 patients) and 26.9% (7 patients), respectively. The VAs disappeared 3 days later due to delayed RFCA efficacy in 2 patients (7.7%). No complications occurred during RFCA or the one-year follow up. Conclusions: AP-MA VAs are a rare but distinct subgroup of VAs. Bipolar and unipolar EGM features can help to detect the optimal RFCA site, and the QRS - Uni interval may work as a marker for guiding RFCA.