Background-Cryoablation has emerged as an alternative to radiofrequency catheter ablation (RFCA) for the treatment of atrioventricular (AV) nodal reentrant tachycardia (AVNRT). The purpose of this prospective randomized study was to test whether cryoablation is as effective as RFCA during both short-term and long-term follow-up with a lower risk of permanent AV block. Methods and Results-A total of 509 patients underwent slow pathway cryoablation (nϭ251) or RFCA (nϭ258). The primary end point was immediate ablation failure, permanent AV block, and AVNRT recurrence during a 6-month follow-up. Secondary end points included procedural parameters, device functionality, and pain perception. Significantly more patients in the cryoablation group than the RFCA group reached the primary end point (12.6% versus 6.3%; Pϭ0.018). Whereas immediate ablation success (96.8% versus 98.4%) and occurrence of permanent AV block (0% versus 0.4%) did not differ, AVNRT recurrence was significantly more frequent in the cryoablation group (9.4% versus 4.4%; Pϭ0.029). In the cryoablation group, procedure duration was longer (138Ϯ54 versus 123Ϯ48 minutes; Pϭ0.0012) and more device problems occurred (13 versus 2 patients; Pϭ0.033). Pain perception was lower in the cryoablation group (PϽ0.001). Conclusions-Cryoablation for AVNRT is as effective as RFCA over the short term but is associated with a higher recurrence rate at the 6-month follow-up. The risk of permanent AV block does not differ significantly between cryoablation and RFCA. The potential benefits of cryoenergy relative to ablation safety and pain perception are counterbalanced by longer procedure times, more device problems, and a high recurrence rate. Clinical Trial Registration-URL: http://www.clinicaltrials.gov.

Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an uncommon, potentially lethal, ion channelopathy. Standard therapies have high failure rates and little is known about treatment in children. Newer options such as flecainide and left cardiac sympathetic denervation (LCSD) are not well validated. We sought to define treatment outcomes in children with CPVT. Methods and Results This is a Pediatric and Congenital Electrophysiology Society (PACES) multicenter, retrospective cohort study of CPVT patients diagnosed before 19 years of age. The cohort included 226 patients, including 170 probands and 56 relatives. Symptomatic presentation was reported in 176 (78%). Symptom onset occurred at 10.8 (IQR 6.8–13.2) years with a delay to diagnosis of 0.5 (0–2.6) years. Syncope (p<0.001), cardiac arrest (p<0.001) and treatment failure (p=0.008) occurred more often in probands. Beta-blockers were prescribed in 205 of 211 patients (97%) on medication, and 25% experienced at least one treatment failure event. Implantable cardioverter defibrillators (ICDs) were placed in 121 (54%) and was associated with electrical storm in 22 (18%). Flecainide was used in 24% and LCSD in 8%. Six deaths (3%) occurred during a cumulative follow-up of 788 patient-years. Conclusions This study demonstrates a malignant phenotype and lengthy delay to diagnosis in CPVT. Probands were typically severely affected. Beta-blockers were almost universally initiated; however, treatment failure, non-compliance and sub-therapeutic dosing were often reported. ICDs were common despite numerous device-related complications. Treatment failure was rare in the quarter of patients on flecainide. LCSD was not uncommon although the indication was variable.

This large, multicentre study identifies contemporary challenges related to the diagnosis and prognostication of CPVT patients. Structural modelling of RyR2 can improve our understanding severe CPVT phenotypes. Wakeful rest, rather than exertion, often precipitated life-threatening cardiac events.