Catheter ablation of repetitive monomorphic ventricular tachycardia from left ventricular outflow tract guided by unipolar mapping

Role of the notched unipolar electrogram in guiding catheter ablation of frequent premature ventricular contractions originating from the ventricular outflow tract

Objective

To investigate the value of a notched unipolar electrogram (N-uniEGM) in confirming the origin of premature ventricular contractions originating from the ventricular outflow tract (VOT-PVC) during mapping and ablation procedures.

Methods

This retrospective study enrolled consecutive patients with symptomatic idiopathic frequent VOT-PVCs that underwent radiofrequency ablation. The characteristics of the uniEGM of the successful ablation targets were analysed. N-uniEGM was defined as the uniEGM presenting a QS morphology with ≥1 steep notches on the downstroke deflection. All patients were followed-up for 3 months post-ablation.

Results

The study enrolled 190 patients with a mean ± SD age of 49.0 ± 15.3 years. N-uniEGMs were recorded in 124 of 190 (65.3%) patients. The N-uniEGM distribution area was limited to a mean ± SD of 0.8 ± 0.4 cm². N-uniEGM showed consistency with the outcomes of activation mapping and pace mapping. Patients with an N-uniEGM had an ablation success rate of 98.4% (122 of 124) and their ablation times were significantly shorter than those without an N-uniEGM (7.6 ± 3.8 s versus 15.8 ± 8.8 s, respectively). The sensitivity and specificity of N-uniEGM in predicting successful ablation of VOT-PVCs were 72.6% and 91.7%, respectively.

Conclusion

N-uniEGM was a highly specific and moderately sensitive predictor of successful radiofrequency ablation in patients with VOT-PVCs.