Radiofrequency ablation guided by mechanical termination of idiopathic ventricular arrhythmias originating in the right ventricular outflow tract.

BACKGROUND Termination of ventricular tachycardia (VT) by mechanical pressure has been described for fascicular and postinfarction VT. Mechanical interruption of idiopathic ventricular arrhythmias (VT/premature ventricular complexes [PVCs]) arising in the right ventricular outflow tract (RVOT) has not been described in systematic fashion. METHODS Eighteen consecutive patients (13 females, age 49 +/- 13 years, ejection fraction 0.55 +/- 0.12) underwent mapping and ablation of RVOT VT or PVCs. In 7 patients, 9 distinct VTs (mean cycle length 440 +/- 127 ms), and in 11 patients, 11 distinct PVCs originating in the RVOT were targeted. Mechanical termination was considered present if a reproducibly inducible VT was no longer inducible or if frequent PVCs suddenly ceased with the mapping catheter at a particular location. Endocardial activation time, electrogram characteristics, and pace-mapping morphology were assessed at this location. Radiofrequency energy was delivered if mechanical termination was observed. RESULTS All targeted arrhythmias were successfully ablated. In 7 of 18 patients (39%), catheter manipulation terminated the arrhythmia with the mapping catheter located at a particular site. Local endocardial activation time was earlier at sites of mechanical termination (-31 +/- 7 ms) compared with effective sites without termination (-25 +/- 3 ms, P = 0.04). The 10-ms isochronal area was smaller in patients with mechanical interruption (0.35 +/- 0.2 cm(2)) than in patients without mechanical termination (1.33 +/- 0.9 cm(2), P = 0.01). At all sites susceptible to mechanical trauma, the pace map displayed a match with the targeted VT/PVC. All sites where mechanical termination of VT or PVCs occurred were effective ablation sites. CONCLUSIONS Mechanical suppression at the site of origin of idiopathic RVOT arrhythmias frequently occurs during the mapping procedure and is a reliable indicator of effective ablation sites. Mechanical termination of RVOT arrhythmias may be indicative of a more localized arrhythmogenic substrate.