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Introduction: Pulmonary vein isolation (PVI) is well established as a primary treatment for atrial fibrillation (AF). The POLAR ICE study was designed to collect prospective real world data on the safety and effectiveness of the POLARxTM cryoballoon for PVI to treat paroxysmal AF. Methods: POLAR ICE, a prospective, non-randomized, multicenter (international) registry (NCT04250714), enrolled 399 patients across 19 European centers. Procedural characteristics, such as time to isolation, cryoablations per pulmonary vein (PV), balloon nadir temperature, and occlusion grade were recorded. PVI was confirmed with entrance block testing. Results: Data on 372 de novo PVI procedures (n = 2190 ablations) were collected. Complete PVI was achieved in 96.8% of PVs. Procedure and fluoroscopy times were 68.2 ± 24.6 and 15.6 ± 9.6 min, respectively. Left atrial dwell time was 46.6 ± 18.3 min. Grade 3 or 4 occlusion was achieved in 98.2% of PVs reported and 71.2% of PVs isolation required only a single cryoablation. Of 2190 cryoapplications, 83% had a duration of at least 120 s; nadir temperature of these ablations averaged −56.3 ± 6.5°C. There were 6 phrenic nerve palsy events, 2 of which resolved within 3 months of the procedure. Conclusion: This real-world usage data on a novel cryoballoon suggests this device is effective, safe, and relatively fast in centers with cryoballoon experience. These data are comparable to prior POLARx reports and in keeping with reported data on other cryoballoons. Future studies should examine the long-term outcomes and the relationship between biophysical parameters and outcomes for this novel cryoballoon.

Background: Recently, a novel cryoballoon ablation catheter has demonstrated acute safety and efficacy in de novo pulmonary vein isolation (PVI) procedures in patients with paroxysmal atrial fibrillation (PAF). However, there are limited studies demonstrating the long-term efficacy. The aim of this study was to evaluate the long-term safety and efficacy of this novel cryoballoon in treating PAF. Methods: This was a non-randomized, prospective, multicentre study enrolling 58 consecutive patients. Cryoablation was delivered for 180 s if time to isolation was ≤ 60 s. Otherwise a 240-s cryoablation was performed. One centre performed pre- and post-ablation high-density mapping (n = 9) to characterize lesion formation. After a 3-month blanking period, recurrence was defined as having any documented, symptomatic episode(s) of AF or atrial tachycardia. All patients were followed for 1 year. Results: Acute PVI was achieved in 230 of 231 pulmonary veins (99.6%) with 5.3 ± 1.6 cryoablations per patient (1.3 ± 0.7 cryoablations per vein). Forty-three (77%) patients remained arrhythmia-free at 1-year follow-up. Four patients (6.9%) experienced phrenic nerve injury (3 resolved during the index procedure; 1 resolved at 6 months). One serious adverse device event was reported: femoral arterial embolism event occurring 2 weeks post-index procedure. For patients who underwent high-density mapping, cryoablation was antral with 50% of the posterior wall ablated. Conclusions: Initial multicentre clinical experience with a novel cryoballoon has demonstrated safety and efficacy of PVI in patients with PAF. Ablation with this cryoballoon provides a wide, antral lesion set with significant debulking of the posterior wall of the left atrium.

Androgens have well-established anabolic actions on skeletal muscle, although the direct effects of the androgen receptor (AR) in muscle remain unclear. We generated satellite cell-specific AR-knockout (satARKO) mice in which the AR is selectively ablated in satellite cells, the muscle precursor cells. Total-limb maximal grip strength is decreased by 7% in satARKO mice, with soleus muscles containing ∼10% more type I fibers and 10% less type IIa fibers than the corresponding control littermates. The weight of the perineal levator ani muscle is markedly reduced (-52%). Thus, muscle AR is involved in fiber-type distribution and force production of the limb muscles, while it is a major determinant of the perineal muscle mass. Surprisingly, myostatin (Mstn), a strong inhibitor of skeletal muscle growth, is one of the most androgen-responsive genes (6-fold reduction in satARKO) through direct transcription activation by the AR. Consequently, muscle hypertrophy in response to androgens is augmented in Mstn-knockout mice. Our finding that androgens induce Mstn signaling to restrain their own anabolic actions has implications for the treatment of muscle wasting disorders.-Dubois, V., Laurent, M. R., Sinnesael, M., Cielen, N., Helsen, C., Clinckemalie, L., Spans, L., Gayan-Ramirez, G., Deldicque, L., Hespel, P., Carmeliet, G., Vanderschueren, D., and Claessens, F. A satellite cell-specific knockout of the androgen receptor reveals myostatin as a direct androgen target in skeletal muscle.