Methods

In this retrospective propensity score–matched cohort study, patients with implantable cardioverter-defibrillators (ICDs) who underwent catheter ablation only (n = 56) and RSDN in adjunct to catheter ablation (n = 16) for refractory VAs from April 2014 to June 2015 were included. All patients provided written informed consent before the procedure. The study was approved by the Institutional Ethics Committee on Human Research at our institution.

Because of the statistically significant differences in the baseline characteristics among patient groups, we performed propensity score–matching analysis. Baseline characteristics of the patients before and after propensity score matching are listed in Table 1 . Matching criteria included age, gender, ischemic etiology of the cardiomyopathy, arterial hypertension, diabetes mellitus, estimated glomerular filtration ratio (eGFR), left ventricular (LV) ejection fraction, LV end-diastolic diameter, and medications at baseline. After propensity matching, for simplifying comparisons between the 2 groups, we named “catheter ablation–only group” as “group I” and “RSDN in adjunct to catheter ablation group” as “group II.”

Patients who had recurrent or incessant VAs despite optimal antiarrhythmic drug therapy underwent electroanatomical mapping to identify the underlying substrate of the arrhythmia. Patients were ablated under conscious sedation maintained with boluses of midazolam and fentanyl. Invasive monitoring of arterial blood pressure and oxygen saturation were carried out throughout the procedure. LV was approached by retrograde and/or transseptal access. Electroanatomic maps were obtained using CARTO electroanatomic mapping system (CARTO3; Biosense Webster Inc., Diamond Bar, California). Ablation was performed using 3.5-mm saline-irrigated catheters (ThermoCool; Biosense Webster, 40–50 W, and 30 ml/min) and a multichannel recording system (PruckaCardio-Lab; GE, Milwaukee, Wisconsin). In case the underlying rhythm was VT, either activation or entrainment mapping was performed to locate exit sites and critical isthmuses. After ablation of these sites and terminating the VT (a), iso-voltage maps were constructed to discriminate healthy myocardial tissue (>1.5 mV) or dense scar (<0.5 mV) and fragmented late potentials (b). Subsequently, radiofrequency (RF) ablation of these sites was additionally performed. In case the patient was in sinus rhythm, (b) was performed first and then VT induction was forced using programmed stimulation which was followed by (a). For hemodynamically unstable VTs, substrate modification was performed based on local potentials. The epicardial approach was applied in case of failed endocardial ablation attempts. Ablation end point was accepted as the elimination of the clinical (partial acute success) or any induced VT (complete acute success). All the procedures were performed by the same operators.

RSDN was performed after catheter ablation for VT. To avoid severe visceral pain generated by ablation, fentanyl and midazolam boluses were administered. In addition, heparin was given intravenously to achieve an activated clotting time >250 seconds. First, bilateral renal arteriography was performed through an 8F sheath (Agilis; St Jude Medical, St. Paul, Minnesota), which was also used during catheter ablation for VT. An open-irrigated ablation catheter (Thermocool; Biosense Webster) was advanced into each renal artery, and RF energy was delivered starting from the distal segments to the ostium spirally up to 12 W for 30 seconds at a flow rate of 17 cm ³ /min. At least 6 RF lesions were generated in both renal arteries. Catheter tip impedance and temperature were continuously monitored throughout the procedure. At the end of the procedure, a control renal arteriography was performed to assess the vascular integrity. Renal functions were checked by blood tests during hospitalization.

ICD interrogations were routinely performed before the procedure, at the third month following the procedure, and then at 6-month intervals in the follow-up. In case of delivery of shock therapies or patient’s experience of any related symptoms, the interrogation was performed at any time in the outpatient clinics. Rhythm was analyzed by 2 experienced cardiologists through the recorded electrograms. True VT/VFs and appropriate therapies were counted and analyzed. ICD therapy was defined as either antitachycardia pacing (ATP) or ICD shock. The VF zone was typically set to >200 bpm for at least 1 train of ATP to be delivered before the shock therapy, where the VT zone was programmed to 170 to 200 bpm with at least 3 trains of ATP to be delivered before the shock therapy. The monitor and atrial arrhythmia detection zones were set to 150 to 170 and >180 bpm, respectively, and tachycardia discriminators were enabled.

Continuous variables were presented as mean ± SD or median (range) if skewed and were compared using student t test and Mann Whitney U test, respectively. Categorical data were presented as percentage and compared with the chi-square test. Two-way repeated measures of ANOVA was used for comparing repeated events between the 2 groups.

To estimate the propensity score, we used logistic regression including the following covariates: age, gender, percent of ICM, eGFR, diabetes mellitus, hypertension, LV ejection fraction, LV end-diastolic diameter, and NYHA functional class. Matching was performed by the nearest neighbor method, one-to-one (1:1) ratio, (R extension pack, version 2.15.0; IBM SPSS Statistics, Armonk, New York). Analyses were conducted in the unmatched and matched cohorts. The level of significance was set to 0.05. Analyses were performed with SPSS software (version 22.0; IBM, Armonk, New York).