Bipolar ablation of therapy-refractory ventricular arrhythmias: application of a dedicated approach.

AIMS: Bipolar radiofrequency ablation (B-RFA) has been reported as a bail-out strategy for the treatment of therapy refractory ventricular arrhythmias (VA). Currently, existing setups have not been standardized for B-RFA, while the impact of conventional B-RFA approaches on lesion formation remains unclear. METHODS AND RESULTS: (i) In a multicentre observational study, patients undergoing B-RFA for previously therapy-refractory VA using a dedicated B-RFA setup were retrospectively analysed. (ii) Additionally, in an ex vivo model lesion formation during B-RFA was evaluated using porcine hearts. In a total of 26 procedures (24 patients), acute success was achieved in all 14 ventricular tachycardia (VT) procedures and 7/12 procedures with premature ventricular contractions (PVC), with major complications occurring in 1 procedure (atrioventricular block). During a median follow-up of 211 days in 21 patients, 6/11 patients (VT) and 5/10 patients (PVC) remained arrhythmia-free. Lesion formation in the ex vivo model during energy titration from 30 to 50 W led to similar lesion volumes compared with initial high-power 50 W B-RFA. Lesion size significantly increased when combining sequential unipolar and B-RFA (1429 mm3 vs. titration 501 mm3 vs. B-RFA 50 W 423 mm3, P < 0.001), an approach used in overall 58% of procedures and more frequently applied in procedures without VA recurrence (92% vs. 36%, P = 0.009). Adipose tissue severely limited lesion formation during B-RFA. CONCLUSION: Using a dedicated device for B-RFA for therapy-refractory VA appears feasible and safe. While some patients need repeat ablation, success rates were encouraging. Sequential unipolar and B-RFA may be favourable for lesion formation.

Comparison of procedural efficacy and biophysical parameters between two competing cryoballoon technologies for pulmonary vein isolation: Insights from an initial multicenter experience.

INTRODUCTION: Recently a novel cryoballoon system (POLARx, Boston Scientific) became available for the treatment of atrial fibrillation. This cryoballoon is comparable with Arctic Front Advance Pro (AFA-Pro, Medtronic), however, it maintains a constant balloon pressure. We compared the procedural efficacy and biophysical characteristics of both systems. METHODS: One hundred and ten consecutive patients who underwent first-time cryoballoon ablation (POLARx: n = 57; AFA-Pro: n = 53) were included in this prospective cohort study. RESULTS: Acute isolation was achieved in 99.8% of all pulmonary veins (POLARx: 99.5% vs. AFA-Pro: 100%, p = 1.00). Total procedure time (81 vs. 67 min, p < .001) and balloon in body time (51 vs. 35 min, p < .001) were longer with POLARx. After a learning curve, these times were similar. Cryoablation with POLARx was associated with shorter time to balloon temperature -30°C (27 vs. 31 s, p < .001) and -40°C (32 vs. 54 s, p < .001), lower balloon nadir temperature (-55°C vs. -47°C, p < .001), and longer thawing time till 0°C (16 vs. 9 s, p < .001). There were no differences in time-to-isolation (TTI; POLARx: 45 s vs. AFA-Pro 43 s, p = .441), however, POLARx was associated with a lower balloon temperature at TTI (-46°C vs. -37°C, p < .001). Factors associated with acute isolation differed between groups. The incidence of phrenic nerve palsy was comparable (POLARx: 3.5% vs. AFA-Pro: 3.7%). CONCLUSION: The novel cryoballoon is comparable to AFA-Pro and requires only a short learning curve to get used to the slightly different handling. It was associated with faster cooling rates and lower balloon temperatures but TTI was similar to AFA-Pro.

In Silico Study of Local Electrical Impedance Measurements in the Atria - Towards Understanding and Quantifying Dependencies in Human.

BACKGROUND: Electrical impedance measurements have become an accepted tool for monitoring intracardiac radio frequency ablation. Recently, the long-established generator impedance was joined by novel local impedance measurement capabilities with all electrical circuit terminals being accommodated within the catheter. OBJECTIVE: This work aims at in silico quantification of distinct influencing factors that have remained challenges due to the lack of ground truth knowledge and the superposition of effects in clinical settings. METHODS: We introduced a highly detailed in silico model of two local impedance enabled catheters, namely IntellaNav MiFi OI and IntellaNav Stablepoint, embedded in a series of clinically relevant environments. Assigning material and frequency specific conductivities and subsequently calculating the spread of the electrical field with the finite element method yielded in silico local impedances. The in silico model was validated by comparison to in vitro measurements of standardized sodium chloride solutions. We then investigated the effect of the withdrawal of the catheter into the transseptal sheath, catheter-tissue interaction, insertion of the catheter into pulmonary veins, and catheter irrigation. RESULTS: All simulated setups were in line with in vitro experiments and in human measurements and gave detailed insight into determinants of local impedance changes as well as the relation between values measured with two different devices. CONCLUSION: The in silico environment proved to be capable of resembling clinical scenarios and quantifying local impedance changes. SIGNIFICANCE: The tool can assists the interpretation of measurements in humans and has the potential to support future catheter development.

[Extracorporeal membrane oxygenation and hemodynamics : Therapy is not only a friend of the heart]. / Extrakorporale Membranoxygenierung und Hämodynamik : Die Therapie ist nicht nur des Herzens Freund.

Extracorporeal support systems for the heart and lungs are employed for cardiac, pulmonary and also cardiopulmonary failure; however, neither the pure lung support by venovenous extracorporeal membrane oxygenation (vvECMO) nor the venoarterial (va) ECMO behave in a hemodynamically inert manner with respect to the patient's own cardiovascular system. The success of ECMO treatment is decisively dependent on monitoring before and during the execution and the pathophysiological understanding of the hemodynamic changes that occur during treatment. This article explicitly elucidates these "concomitant phenomena" and discusses fundamental aspects of cardiovascular physiology and the specific interplay with ECMO treatment.

Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates.

The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates.

Local Electrical Impedance Mapping of the Atria: Conclusions on Substrate Properties and Confounding Factors.

The treatment of atrial fibrillation and other cardiac arrhythmias as a major cause of cardiovascular hospitalization has remained a challenge predominantly for patients with severely remodeled substrate. Individualized ablation strategies are extremely important both for pulmonary vein isolation and subsequent ablations. Current approaches to identifying arrhythmogenic regions rely on electrogram-based features such as activation time and voltage. Novel technologies now enable clinical assessment of the local impedance as tissue property. Previous studies demonstrated its use for ablation monitoring and indicated its potential to differentiate healthy substrate, scar, and pathological tissue. This study investigates the potential of local electrical impedance-based substrate mapping of the atria for human in-vivo data. The presented pipeline for impedance mapping particularly contains options for dealing with undesirable effects originating from cardiac motion, catheter motion, or proximity to other intracardiac devices. Bloodpool impedance was automatically determined as a patient-specific reference. Full-chamber, left atrial impedance maps were drawn up from interpolating the measured impedances to the atrial endocardium. Finally, the origin and magnitude of oscillations of the raw impedance recording were probed into. The most dominant reason for exclusion of impedance samples was the loss of endocardial contact. With median elevations above the bloodpool impedance between 29 and 46 Ω, the impedance within the pulmonary veins significantly exceeded the remaining atrial walls presenting median elevations above the bloodpool impedance between 16 and 20 Ω. Previous ablation lesions were distinguished from their surroundings by a significant drop in local impedance while the corresponding regions did not differ for the control group. The raw impedance was found to oscillate with median amplitudes between 6 and 17 Ω depending on the patient. Oscillations were traced back to an interplay of atrial, ventricular, and respiratory motion. In summary, local impedance measurements demonstrated their capability to distinguish pathological atrial tissue from physiological substrate. Methods to limit the influence of confounding factors that still hinder impedance mapping were presented. Measurements at different frequencies or the combination of multiple electrodes could lead to further improvement. The presented examples indicate that electrogram- and impedance-based substrate mapping have the potential to complement each other toward better patient outcomes in future.

Institutional infrastructural preconditions and current perioperative anaesthesia practice in patients undergoing transfemoral transcatheter aortic valve implantation: a cross-sectional study in German heart centres.

OBJECTIVES: Transfemoral transcatheter aortic valve implantation (TF-TAVI) is an established therapy for patients with symptomatic aortic stenosis, which requires periprocedural anaesthesia care. In 2015, the German Federal Joint Committee released a directive on minimally invasive heart valve interventions which defines institutional infrastructural requirements in German heart centres. But still generally accepted expert consensus recommendations or national or international guidelines regarding periprocedural anaesthesia management for TF-TAVI are lacking. This nationwide cross-sectional study had two major objectives: first to assess the concordance with existing national regulations regarding infrastructural requirements and second to evaluate the status quo of periprocedural anaesthesia management for patients undergoing TF-TAVI in German heart centres. DESIGN: Multicentre cross-sectional online study to evaluate the periprocedural anaesthesia management. SETTING: In this nationwide cross-sectional study, electronic questionnaires were sent out to anaesthesia departments at TF-TAVI-performing centres in Germany in March 2019. PARTICIPANTS: 78 anaesthesia departments of German heart centres. RESULTS: 54 (69.2%) centres returned the questionnaire of which 94.4% stated to hold regular Heart Team meetings, 75.9% to have ready-to-use heart-lung machines available on-site, 77.8% to have cardiac surgeons and 66.7% to have perfusionists routinely attending throughout TF-TAVI procedures. Regarding periprocedural anaesthesia management, 41 (75.9%) of the participating centres reported to predominantly use 'monitored anaesthesia care' and 13 (24.1%) to favour general anaesthesia. 49 (90.7%) centres stated to use institutional standard operating procedures for anaesthesia. Five-lead ECG, central venous lines, capnometry and intraprocedural echocardiography were reported to be routine measures in 85.2%, 83.3%, 77.8% and 51.9% of the surveyed heart centres. CONCLUSIONS: The concordance with national regulations, anaesthesia management and in-house standards for TF-TAVI vary broadly among German heart centres. According to the opinion of the authors, international expert consensus recommendations and/or guidelines would be helpful to standardise peri interventional anaesthesia care.