The mechanisms of transition from regular rhythms to ventricular fibrillation (VF) are poorly understood. The concordant to discordant repolarization alternans pathway is extensively studied; however, despite its theoretical centrality, cannot guide ablation. We hypothesize that complex repolarization dynamics, i.e. oscillations in the repolarization phase of action potentials with periods over two of classic alternans, is a marker of electrically unstable substrate, and ablation of these areas has a stabilizing effect and may reduce the risk of VF. To prove the existence of higher-order periodicities in human hearts. We performed optical mapping of explanted human hearts obtained from recipients of heart transplantation at the time of surgery. Signals recorded from the right ventricle endocardial surface were processed to detect global and local repolarization dynamics during rapid pacing. A statistically significant global 1:4 peak was seen in three of six hearts. Local (pixel-wise) analysis revealed the spatially heterogeneous distribution of Periods 4, 6, and 8, with the regional presence of periods greater than two in all the hearts. There was no significant correlation between the underlying restitution properties and the period of each pixel. We present evidence of complex higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex vivo human hearts. We infer that the oscillation of the calcium cycling machinery is the primary mechanism of higher-order dynamics. These higher-order regions may act as niduses of instability and may provide targets for substrate-based ablation of VF.

A previous randomized study demonstrated that the subcutaneous implantable cardioverter defibrillator (S-ICD) was noninferior to transvenous ICD with respect to device-related complications and inappropriate shocks. However, that was performed prior to the widespread adoption of pulse generator implantation in the intermuscular (IM) space instead of the traditional subcutaneous (SC) pocket. The aim of this analysis was to compare survival from device-related complications and inappropriate shocks between patients who underwent S-ICD implantation with the generator positioned in an IM position in comparison with an SC pocket. We analysed 1577 consecutive patients who had undergone S-ICD implantation from 2013 to 2021 and were followed up until December 2021. Subcutaneous patients (n = 290) were propensity matched with patients of the IM group (n = 290), and their outcomes were compared. : During a median follow-up of 28 months, device-related complications were reported in 28 (4.8%) patients and inappropriate shocks were reported in 37 (6.4%) patients. The risk of complication was lower in the matched IM group than in the SC group [hazard ratio 0.41, 95% confidence interval (CI) 0.17-0.99, P = 0.041], as well as the composite of complications and inappropriate shocks (hazard ratio 0.50, 95% CI 0.30-0.86, P = 0.013). The risk of appropriate shocks was similar between groups (hazard ratio 0.90, 95% CI 0.50-1.61, P = 0.721). There was no significant interaction between generator positioning and variables such as gender, age, body mass index, and ejection fraction. Our data showed the superiority of the IM S-ICD generator positioning in reducing device-related complications and inappropriate shocks. Clinical Trial Registration: ClinicalTrials.gov; NCT02275637.

This study sought to assess the effect of ethanol infusion into the vein of Marshall (EIVOM) on the acute success of left pulmonary vein (LPV) isolation in persistent atrial fibrillation (PeAF). A total of 313 patients with drug-resistant PeAF were enrolled (135 in Group 1 and 178 in Group 2). In Group 1, EIVOM was firstly performed, followed by radiofrequency ablation (RFA) including bilateral pulmonary vein isolation (PVI) and linear ablation at roofline, cavotricuspid isthmus, and mitral isthmus (MI). In Group 2, PVI and linear ablations were completed with RFA. First-pass isolation of the LPV was achieved in 119 (88.1%) and 132 (74.2%) patients in Groups 1 and 2, respectively (P = 0.002). The rate of acute pulmonary vein reconnection (PVR) was significantly lower in Group 1 (9.6% vs. 22.5%, P = 0.003). About half of acute PVR occurred in the carina with or without EIVOM. EIVOM is effective in achieving a higher first-pass isolation and a lower acute PVR of LPV in PeAF.

In the light of an increasing prevalence of atrial fibrillation (AF) and growing evidence for the superiority of early invasive rhythm control, the demand for ablation therapy is rising. Accordingly, ablation centres will have to maximize their capacity by either adding electrophysiology laboratory resources or optimizing process management. In order to optimize process management, we applied "Lean Six Sigma" method to a single ablation center. We compared procedural parameters, acute efficacy and safety of cryoballoon pulmonary vein isolation (cryoPVI) before and after modifications. Patients (n = 713) undergoing cryoPVI (108 before and 605 after process optimization) were analysed. Within 3 years of process optimization, electrophysiology laboratory occupancy time (150.7 ± 44.4 vs. 94 ± 22.1 min, P < 0.001), procedure time (84.5 ± 21-47.4 ± 12 min, P < 0.001), left-atrial dwell time (53.9 ± 18.4-31.9 ± 9.9 min, P < 0.001), and fluoroscopy time (15.8 ± 5.1 vs. 6.2 ± 2.8 min, P < 0.001) decreased. Contrast dye use (116 ± 35 vs. 27 ± 15 mL, P < 0.001) and radiation dose (893 ± 1078 vs. 253 ± 249 cGy cm2, P < 0.001) were reduced by ∼77 and ∼72%, respectively. There was no difference in safety endpoint occurrence (3.7 vs. 1.5%, P = 0.11). The process optimization of cryoPVI for AF therapy using the 'Lean Six Sigma' method significantly increases efficiency without compromising patient safety.

The healthcare sector accounts for nearly 5% of global greenhouse gas emissions (GHG) and is a significant contributor to complex waste. Reducing the environmental impact of technology-heavy medical fields such as cardiac electrophysiology (EP) is a priority. The aim of this survey was to investigate the practice and expectations in European centres on EP catheters environmental sustainability. A 24-item online questionnaire on EP catheters sustainability was disseminated by the EHRA Scientific Initiatives Committee in collaboration with the Lyric Institute. A total of 278 physicians from 42 centres were polled; 62% were motivated to reduce the environmental impact of EP procedures. It was reported that 50% of mapping catheters and 53% of ablation catheters are usually discarded to medical waste, and only 20% and 14% of mapping and ablation catheters re-used. Yet, re-use of catheters was the most commonly cited potential sustainability solution (60% and 57% of physicians for mapping and ablation catheters, respectively). The majority of 69% currently discarded packaging. Reduced (42%) and reusable (39%) packaging also featured prominently as potential sustainable solutions. Lack of engagement from host institutions was the most commonly cited barrier to sustainable practices (59%). Complexity of the process and challenges to behavioral change were other commonly cited barriers (48% and 47%, respectively). The most commonly cited solutions towards more sustainable practices were regulatory changes (31%), education (19%), and product after-use recommendations (19%). In conclusion, EP physicians demonstrate high motivation towards sustainable practices. However, significant engagement and behavioural change, at local institution, regulatory and industry level is required before sustainable practices can be embedded into routine care.

Inappropriate sinus tachycardia (IST) is a syndrome characterized by an elevated sinus rate unassociated with known physiological, pathological, or pharmacological causes. Despite published consensus documents, IST definitions appear to vary in the literature. In this study, we reviewed IST publications to evaluate IST definition variability and ascertain the degree to which consensus definitions are being adopted. English-language articles in PubMed, Ovid MEDLINE, Ovid Embase, and Google Scholar published from 1 January 1970 to 1 June 2021 with the title terms 'inappropriate sinus tachycardia,' 'non-paroxysmal sinus tachycardia,' or 'permanent sinus tachycardia' were searched. In each, the IST definition used, qualifying characteristics, and publications cited to support each definition were recorded. We identified 138 publications meeting the search criteria. Inappropriate sinus tachycardia definitions were provided in 114 of 138 articles (83%). A majority of definitions (92/114, 81%) used distinct heart rate (HR) thresholds. Among these, the most common threshold was ≥100 beats per minute (BPM) (75/92, 82%), mainly measured at rest (54/92, 59%). Most definitions (47/92, 51%) included a second criterion to qualify for IST; these were most often an HR threshold of 90 BPM measured over 24 h by ambulatory electrocardiogram (37/47, 79%). Diagnosis of exclusion was a common criterion (75/92, 82%) but symptom status was not (41/92, 45%). The 2015 Heart Rhythm Society IST consensus was commonly cited but adopted in only 37% of definitions published after 2015. Inappropriate sinus tachycardia definitions in current literature are inconsistent, and professional society consensus IST definitions have, to date, had limited impact.

Left atrial ablation using radiofrequency (RF) is associated with endoscopically detected thermal oesophageal lesions (EDELs). The aim of this study was to compare EDEL occurrence after conventional contact force-guided (CFG) RF ablation vs. an ablation index-guided (AIG) approach in clinical routine of voltage-guided ablation (VGA). Predictors of EDEL were also assessed. This study compared CFG (n = 100) with AIG (n = 100) in consecutive atrial fibrillation ablation procedures, in which both pulmonary vein isolation and VGA were performed. In the AIG group, AI targets were ≥500 anteriorly and ≥350-400 posteriorly. Upper endoscopy was performed after ablation.The CFG and AIG groups had comparable baseline characteristics. The EDEL occurred in 6 and 5% (P = 0.86) in the CFG and AIG groups, respectively. Category 2 lesions occurred in 4 and 2% (P = 0.68), respectively. All EDEL healed under proton pump inhibitor therapy. The AI > 520 was the only predictor of EDEL [odds ratio (OR) 3.84; P = 0.039]. The more extensive Category 2 lesions were predicted by: AI max > 520 during posterior ablation (OR 7.05; P = 0.042), application of posterior or roof lines (OR 5.19; P = 0.039), existence of cardiomyopathy (OR 4.93; P = 0.047), and CHA2DS2-VASc score (OR 1.71; P = 0.044). The only Category 2 lesion with AI max < 520 (467) occurred in a patient with low body mass index. Both methods were comparable with respect to clinical complications and EDEL. In consideration of previous reconnection data and our study results regarding oesophageal safety, optimal AI target range might be between 400 and 450.

Variants in SCN5A encoding Nav1.5 are associated with cardiac arrhythmias. We aimed to determine the mechanism by which c.638G>A in SCNA5 resulting in p.Gly213Asp (G213D) in Nav1.5 altered Na+ channel function and how flecainide corrected the defect in a family with multifocal ectopic Purkinje-related premature contractions (MEPPC)-like syndrome. Five patients carrying the G213D variant were treated with flecainide. Gating pore currents were evaluated in Xenopus laevis oocytes. The 638G>A SCN5A variant was introduced to human-induced pluripotent stem cell (hiPSC) by CRISPR-Cas9 gene editing and subsequently differentiated to cardiomyocytes (hiPSC-CM). Action potentials and sodium currents were measured in the absence and presence of flecainide. Ca2+ transients were measured by confocal microscopy. The five patients exhibited premature atrial and ventricular contractions which were suppressed by flecainide treatment. G213D induced gating pore current at potentials negative to -50 mV. Voltage-clamp analysis in hiPSC-CM revealed the activation threshold of INa was shifted in the hyperpolarizing direction resulting in a larger INa window current. The G213D hiPSC-CMs had faster beating rates compared with wild-type and frequently showed Ca2+ waves and alternans. Flecainide applied to G213D hiPSC-CMs decreased window current by shifting the steady-state inactivation curve and slowed the beating rate. The G213D variant in Nav1.5 induced gating pore currents and increased window current. The changes in INa resulted in a faster beating rate and Ca2+ transient dysfunction. Flecainide decreased window current and inhibited INa, which is likely responsible for the therapeutic effectiveness of flecainide in MEPPC patients carrying the G213D variant.

The optimal strategy of monitoring for conduction disturbances in patients undergoing transcatheter aortic valve implantation (TAVI) is uncertain. We evaluated a pre- and post-TAVI remote ambulatory cardiac monitoring (rACM) strategy for identification of conduction disturbances and to reduce unplanned pre-discharge post-TAVI permanent pacemaker implantation (PPMI). REdireCT TAVI (NCT0381820) was a prospective cohort study of patients referred for outpatient TAVI. Patients with prior PPMI were excluded. Remote ambulatory cardiac monitoring consisted of 2 weeks of continuous electrocardiogram (ECG) monitoring (Pocket-ECGTM) both before and after TAVI. Compliance to monitoring, frequency of notifications, unplanned PPMI post-TAVI, and length of hospitalization were measured. Between June 2018 and March 2020, in 192 undergoing TAVI (mean age: 81.8 years; female sex 46%; balloon-expandable valve 95.3%), compliance to rACM was 91.7% pre-TAVI (mean duration: 12.8 days), and 87.5% post-TAVI (mean duration: 12.9 days). There were 24 (12.5%) rACM notifications (13 pre-TAVI; 11 post-TAVI) resulting in 14 (7.3%) planned PPMI: seven pre-TAVI [due to sinus pauses n = 2 or atrio-ventricular block (AVB) n = 5] and seven post-TAVI [due to sinus pauses n = 1 or AVB n = 5 or ventricular tachycardia (VT) n = 1]. In addition, nine (4.7%) patients received pre-TAVI PPMI due to high-risk baseline ECG (right bundle branch block with hemi-block or prolonged PR interval). Unplanned PPMI post-TAVI during index hospitalization occurred in six (3.1%) patients due to AVB and in one patient readmitted with AVB. The median length of stay post-TAVI was 1 day. A strategy of routine rACM was feasible and frequently led to PPMI. Our approach of 2-week rACM both pre- and post-TAVI achieves both high patient compliance and sufficient surveillance. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT03810820.

Ablation of atrial fibrillation (AF) is an established treatment option for symptomatic patients. The cornerstone of all ablation strategies is electrical isolation of the pulmonary veins (PVs). Ablation strategies going beyond PV isolation (PVI) might be considered in the setting of recurrent AF despite durably isolated PVs. The lack of persistent PVI, however, limits the opportunities to perceive the real impact of this endpoint on AF suppression and to fully understand the benefit of extended ablation strategies going beyond. To overcome this limitation, novel and innovative ablation systems have been developed to facilitate acute PVI and to increase its durability. These systems include balloon-based ablation devices incorporating different energy sources such as cryo energy, laser, or radiofrequency current, but also new energy sources such as pulsed field ablation as a non-thermal energy source. These technologies could advance catheter ablation of AF to an early stage of the disease and to the primary treatment tool. The current manuscript focuses on the past, the present, and the future value of PVI as the cornerstone for interventional treatment of AF and on how to achieve durable PVI during the first procedure and to further improve the clinical success rates of AF ablation. It also analyses extended ablation strategies going beyond PVI and their impact.