Diaphragm movement sensor for phrenic nerve monitoring during cryoballoon procedures: the first clinical evaluation.

Background and aims: Right phrenic nerve palsy is the most frequent complication of cryoballoon procedures. The SMARTFREEZE™ console (Boston Scientific, St. Paul, MN, USA) has integrated a new tool for diaphragm monitoring-the Diaphragm Movement Sensor; however, it has not been evaluated in clinical practice. We aimed to assess the diagnostic performance of the Diaphragm Movement Sensor based on compound motor action potential data recorded simultaneously. Methods: Thirty consecutive patients (mean age 63.2 ± 10.2 years) were included. We simultaneously recorded the compound motor action potential and the Diaphragm Movement Sensor during cryoapplications in the right pulmonary veins. The right phrenic nerve was paced at 60 per minute, 12 V and 2.9 ms. Compound motor action potential monitoring with a 30% decrease cutoff for the diagnosis of phrenic nerve threatening was considered the gold standard. The Diaphragm Movement Sensor decrease threshold was also set at 30%. Results: Considering compound motor action potential monitoring, phrenic nerve threatening occurred 11 times (in seven patients) among 84 cryoapplications (13.1%) at the right pulmonary veins. The sensitivity and specificity of the Diaphragm Movement Sensor were, respectively, 33% (95% CI: 7%-70%) and 49% (95% CI: 38%-61%; P < 0.001). The predictive positive and negative values for the Diaphragm Movement Sensor were, respectively, 7% (95% CI: 2%-20%) and 86% (95% CI: 72%-95%). The Diaphragm Movement Sensor gave an erroneous diagnosis in 44/84 cryoapplications (52.4%). Conclusions: The diagnostic performance of the Diaphragm Movement Sensor is low, and the relevance of its use in clinical practice may be debated.

Patient experience of very high power short duration radiofrequency ablation for atrial fibrillation under mild conscious sedation.

BACKGROUND: Very high power short duration (vHPSD) radiofrequency ablation (RFA) may reduce ablation times and improve patient tolerability, permitting pulmonary vein isolation (PVI) under mild conscious sedation (mCS) and promoting same day discharge (SDD). METHODS: First, a retrospective feasibility study was performed at 2 tertiary cardiac centres in the UK. Consecutive cases of first-time PVI using vHPSD ablation with 90 W lesions for up to 4 s were compared against cases performed using standard RF (sRF) and cryoballoon (Cryo) therapy. Subsequently, a prospective study of patients who had vHPSD or Cryo exclusively under mCS was undertaken. Questionnaires based on Likert and visual analogue scales (VAS) were used to measure anxiety, discomfort and pain. RESULTS: In total, 182 patients (59 vHPSD, 62 sRF and 61 Cryo) were included in the retrospective study, with 53 (90%) of vHPSD cases successfully performed under mCS. PVI ablation time in the vHPSD group (5.8 ± 1.7 min) was shorter than for sRF (16.5 ± 6.3 min, p < 0.001) and Cryo (17.5 ± 5.9 min, p < 0.001). Fifty-one vHPSD and 52 Cryo patients were included in the prospective study. PVI ablation time in the vHPSD group was shorter than for the Cryo group (6.4 ± 2.9 min vs 17.9 ± 5.7 min, p < 0.001), but overall procedure duration was longer (121 ± 39 min vs 95 ± 20 min, p < 0.001). There were no differences in the patient experience of anxiety, discomfort or pain. SDD rates were the same in both groups (61% vs 67%, p = 0.49). CONCLUSIONS: vHPSD RFA for PVI can be performed under mCS to achieve SDD rates comparable to cryoablation, without compromising patient experience.

Ablation index-guided 50W radiofrequency ablation for left atrial posterior wall isolation in atrial fibrillation.

BACKGROUND: Ablation index (AI)-guided ablation for posterior wall isolation (PWI) using high-power, short-duration remains untested. We sought to evaluate the acute outcomes of AI-guided 50 W ablation vs. conventional ablation, and investigate the differences in relationship between contact force (CF), time and AI in both groups. METHODS: Consecutive patients undergoing first-time AI-guided ablation with PWI using either 50 W or 35-40 W ablation were enrolled. Acute procedural metrics and individual lesion level ablation data were compared between groups. RESULTS: 40 patients (50 W: n = 20, 35-40 W: n = 20) with atrial fibrillation were included. Total procedure time was significantly reduced with 50 W (120 vs. 143 mins, p = 0.004) and there was a trend toward decreased ablation time (22 vs. 28 mins, p = 0.052). First pass and acute success of PWI were comparable between the 50 W and 35-40 W groups (10 vs. 8 patients, p = 0.525 and 20 vs. 19 patients, p = 1.000, respectively). Individual lesion analysis of all 959 RF applications (50 W: n = 458, 35-40 W: n = 501) demonstrated that 50 W ablation led to lower ablation time per lesion (10.4 vs. 13.0s, p < 0.001), and increased AI (471 vs. 461, p < 0.001) and impedance drop (7.4 vs. 6.9ohms, p = 0.007). Excessive ablations (AI>600 for roof line; AI>500 elsewhere) were more frequently observed in the 50 W group (9.0% vs. 4.6%, p = 0.007). CF had very good discriminative capability for excessive ablation in both groups. At 50 W, limiting the CF to <10 g reduced the number of excessive ablations on the floor line and within the posterior box to 12% and 4%,respectively. Recurrence of atrial arrhythmias at 12 months were comparable between the groups. CONCLUSION: AI-guided 50 W RF ablation reduces the ablation time of individual lesions and total procedure time without compromising first pass and acute success rates of PWI or 12-month outcomes compared to conventional powers.

Procedural efficiencies, lesion metrics, and 12-month clinical outcomes for Ablation Index-guided 50 W ablation for atrial fibrillation.

AIMS: The safety of Ablation Index (AI)-guided 50 W ablation for atrial fibrillation (AF) remains uncertain, and mid-term clinical outcomes have not been described. The interplay between AI and its components at 50 W has not been reported. METHODS AND RESULTS: Eighty-eight consecutive AF patients (44% paroxysmal) underwent AI-guided 50 W ablation. Procedural and 12-month clinical outcomes were compared with 93 consecutive controls (65% paroxysmal) who underwent AI-guided ablation using 35-40 W. Posterior wall isolation (PWI) was performed in 44 (50%) and 23 (25%) patients in the 50 and 35-40 W groups, respectively, P < 0.001. The last 10 patients from each group underwent analysis of individual lesions (n = 1230) to explore relationships between different powers and the AI components. Pulmonary vein isolation was successful in all patients. Posterior wall isolation was successful in 41/44 (93.2%) and 22/23 (95.7%) in the 50 and 35-40 W groups, respectively (P = 0.685). Radiofrequency times (20 vs. 26 min, P < 0.001) and total procedure times (130 vs. 156 min, P = 0.002) were significantly lower in the 50 W group. No complication or steam pop was seen in either group. Twelve-month freedom from arrhythmia was similar (80.2% vs. 82.8%, P = 0.918). A higher proportion of lesions in the 50 W group were associated with impedance drop >7 Ω (54.6% vs. 45.5%, P < 0.001). Excessive ablation (AI >600 anteriorly, >500 posteriorly) was more frequent in the 50 W group (9.7% vs. 4.3%, P < 0.001). CONCLUSION: Ablation Index-guided 50 W AF ablation is as safe and effective as lower powers and results in reduced ablation and procedure times. Radiofrequency lesions are more likely to be therapeutic, but there is a higher risk of delivering excessive ablation.