Bipolar Radio-frequency Ablation After Standard Unipolar Approach - Prospective Registry.

Treatment of ventricular arrhythmias (VA) originating at the base of the heart may be challenging. Unipolar radio-frequency (RF) ablation is a standard approach to treat VA, however, it fails in 10 to 75% of patients, depending on the localization of VA. The main reason for unipolar ablation failure is the intramural location of the source of VA. In such patients, bipolar ablation may occur effective. However, there are no prospective studies or registries on consecutive patients wilt failed unipolar ablation, therefore, the proportion of candidates for bipolar ablation after failed unipolar approach is not known. Also, invasive electrophysiological parameters associated with successful unipolar and bipolar ablation have not been well established. It has been hypothesised that (1) bipolar ablation fails in 12-75% (mean 30%) of consecutive patients and these patients are candidates for bipolar ablation, (2) local ventricular signal precocity > 20 ms, unipolar signal without R wave and pace mapping 12/12 predict effective unipolar ablation but not bipolar ablation, (3) morphology of VA from surface ECG can identify patients with possible intramural localization, and (4) successful ablation results in improvement of quality of life (QoL).Aims:To assess how many patients after failed unipolar ablation need redo procedure with bipolar ablation (primary end-point)To assess which intraprocedural electrophysiological parameters predict success during standard unipolar ablation (secondary endpoint)To assess short term efficacy of bipolar ablation (secondary endpoint)To assess one-month efficacy of bipolar ablation (secondary endpoint)To assess which intraprocedural electrophysiological parameters predict success during redo bipolar ablation (secondary endpoint)To evaluate the performance of ECG-based algorithms in predicting the localization / origin of VA, especially of transmural origin (secondary endpoint)To assess the effects of ablation on QoL (secondary endpoint)Methods. The study group consists of all consecutive patients who underwent unipolar ablation of VA originating from the base of the heart in the Grochowski Hospital and collaborating centres. All these patients are referred to Grochowski Hospital for further follow-up and treatment if needed, including bipolar ablation if initial unipolar approach failed. In all patients acute and one-month efficacy of unipolar and bipolar ablation is assessed.

Inclusion Criteria:Baseline Holter ECG before initial unipolar ablation within 6 months prior to the procedure, performed without antiarrhythmic drugs (beta-blockers allowed).Initial unipolar ablation of VA originating from the base of the heart (R in II, III and aVF) performed according to the standard scheme which includes detailed measurements of EP parameters at each examined and/or ablated site and inspection of all three regions (RVOT with PA, GCV and LVOT/AoCusps/AMC/MA) in cases with unsatisfactory EP parameters or failed ablation at first or second site.Typical indications for ablation: a. > 10 000 PVC in 24-hour Holter ECG or b. > 10% PVC in 24-hour Holter ECG or c. less frequent but symptomatic PVC or d. at least 3 episodes symptomatic non-sustained ventricular tachycardia (nsVT) (>3 QRS evolutions) in Holter ECG, regardless of the amount of PVC or e. sustained ventricular tachycardia (sVT), regardless of nsVT or PVCWritten informed consentExclusion Criteria:History of > 1 unipolar ablation for VA originating at the base of the heartLack of properly acquired EP parameters during baseline unipolar ablationLack of baseline Holter ECG performed < 6 months prior to initial unipolar ablationAbsence of typical indication for ablationLack of written informed consent for participation in the study