Catheter ablation procedure
Antiarrhythmic medications were discontinued at least three days prior to the procedure, which was carried out by seasoned electrophysiologists. Fluoroscopy, set at 7-15 frames per second, facilitated visualization. In cases where PVCs were scarce or absent at baseline, the procedure proceeded only if PVCs emerged frequently following intravenous administration of isoproterenol. For non-sustained VT, either programmed ventricular stimulation or isoproterenol infusion would be used to induce VT. The decision to employ ICE with a frequency range of 5–10 MHz (Johnson and Johnson, Inc.) was made during pre-procedure consultations between patients and their doctors.
Ablation targeted the site of earliest ectopic activation, utilizing an open-irrigation catheter with a tip size of either 3.5 mm or 4.0 mm (Celsius, Johnson and Johnson, Inc.; Coolffex, St. Jude Medical Inc.) at settings typically ranging from 30–45 W and a maximum temperature of 45 °C. In conjunction with a 3D electroanatomic mapping system (CARTO 3, Johnson and Johnson, Inc.), ideal ablation sites were identified based on local activation time, a unipolar QS-pattern, and the presence of reversed polarity13. PVC origin was classified as originating from a variety of anatomical locations such as the right ventricular outflow tract (RVOT), left ventricular outflow tract (LVOT), papillary muscles, tricuspid or mitral annulus, epicardium or LV summit, and areas adjacent to the His bundle and left bundle branch.
ICE was conducted as per established guidelines7. Through bilateral femoral vein access, images of the annulus, right ventricle, aortic long axis, RVOT, and LVOT long axis were obtained in the right atrium view; whereas images of the right ventricle, LV, moderator band, interventricular septum, and papillary muscles were captured in the right ventricular view (refer to Supplementary Figure 1). Radiofrequency energy levels (with a 3.5 mm-tip open-irrigation deflectable catheter manufactured by Johnson and Johnson Inc. or Coolflex by St. Jude Medical Inc.;)—ranging from 30 to 45W, depending on the ablation site (with a maximum temperature of 45°C, a flow rate of 20–30 mL/min, and a duration of 90 to 180 seconds)—were used for ablation. A site was designated as the origin if PVCs ceased within 5 seconds of energy application.
Acute procedural success was defined as the abolition of the targeted PVCs for a minimum of 30 minutes post-procedure, inclusive of isoproterenol infusion and programmed electrical stimulation4,13. The success of the treatment was evaluated based upon 80% reduction in PVC burden, a commonly adopted criterion in literature4. Complications were categorized as either major or minor, the former requiring procedural intervention, blood transfusion, prolonged hospitalization, or resulting in enduring clinical detriment.