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BACKGROUND Radiofrequency (RF) ablation with half-normal saline (HNS) has shown promise as a bail-out strategy following failed ventricular tachycardia ablation using standard approaches. OBJECTIVE To use a novel infrared thermal imaging (ITI) model to evaluate biophysical and lesion characteristics during RF ablation using normal saline (NS) and HNS irrigation. METHODS Left ventricular strips of myocardium were excised from fresh porcine hearts. RF ablation was performed using an open-irrigated ablation catheter (Thermocool ST/SF) with NS (n = 75) and HNS (n = 75) irrigation using different power settings (40/50 W), RF durations (30/60 s), contact force of 10-15 g, and flow rate of 15 ml/min. RF lesions were recorded using an infrared thermal camera and border zone, lethal, 100° isotherms were matched with necrotic borders after 2% triphenyltetrazolium chloride staining. Lesion dimensions and isotherms (mm2 ) were measured. RESULTS In total, 150 lesions were delivered. HNS lesions were deeper (6.4 ± 1.1 vs. 5.7 ±0.8 mm; p = .03), and larger in volume (633 ± 153 vs. 468 ± 107 mm3 ; p = .007) than NS lesions. Steam pops (SPs) occurred during 19/75 lesions (25%) in the NS group and 32/75 lesions (43%) in the HNS group (p = .34). Lethal (57.8 ± 6.5 vs. 36.0 ± 3.9 mm2 ; p = .001) and 100°C isotherm areas (16.9 ± 6.9 vs. 3.8 ± 4.2 mm2 ; p = .003) areas were larger and were reached earlier in the HNS group. CONCLUSIONS RFA using HNS created larger lesions than NS irrigation but led to more frequent SPs. The presence of earlier lethal isotherms and temperature rises above 100°C on ITI suggest a potentially narrower therapeutic-safety window with HNS.

Objectives The aim of this study was to assess the feasibility and outcomes of left bundle branch area pacing (LBBAP) in patients eligible for cardiac resynchronization therapy (CRT) in an international, multicenter, collaborative study. Background CRT using biventricular pacing is effective in patients with heart failure and left bundle branch block (LBBB). LBBAP has been reported as an alternative option for CRT. Methods LBBAP was attempted in patients with left ventricular ejection fraction (LVEF) Results LBBAP was attempted in 325 patients, and CRT was successfully achieved in 277 (85%) (mean age 71 ± 12 years, 35% women, ischemic cardiomyopathy in 44%). QRS configuration at baseline was LBBB in 39% and non-LBBB in 46%. Procedure and fluoroscopy duration were 105 ± 54 and 19 ± 15 min, respectively. LBBAP threshold and R-wave amplitudes were 0.6 ± 0.3 V at 0.5 ms and 10.6 ± 6 mV at implantation and remained stable during mean follow-up of 6 ± 5 months. LBBAP resulted in significant QRS narrowing from 152 ± 32 to 137 ± 22 ms (p Conclusions LBBAP is feasible and safe and provides an alternative option for CRT. LBBAP provides remarkably low and stable pacing thresholds and was associated with improved clinical and echocardiographic outcomes.

Left atrial appendage occlusion is utilized as a second line therapy to long-term oral anticoagulation in appropriately selected patients with atrial fibrillation (AF). We examined the feasibility of cryoballoon (CB) pulmonary vein isolation (PVI) subsequent to Watchman device implantation. The study prospectively identified patients with Watchman devices (>90 days old) who underwent CB-PVI ablation between 2018 and 2019. Twelve consecutive patients (male 50%; mean age 71 ± 9 years; CHA2DS2-VASc score 3.4 ± 1.1) underwent CB-PVI procedures after Watchman device implantation (mean 182 ± 82 days). Acute PVI was achieved in 100% of patients. All patients had evidence of complete (n = 9) or partial (n = 3) endothelialization of the surface of the Watchman device with conductive tissue properties demonstrated during electrophysiologic testing. There were no major procedure-related complications including death, stroke, pericardial effusion, device dislodgment, device thrombus, or new or increasing peri-device leak. Mean peri-device leak size (45-day postimplant: 0.06 ± 0.09 mm vs Post-PVI: 0.04 ± 0.06 mm; p = 0.61) remained unchanged. Two patients had recurrence of AF after the 90-day blanking period (13.2 ± 6.6 months). One patient underwent a redo ablation procedure for recurrent AF. This pilot study suggests the potential feasibility of CB-PVI ablation in patients with chronic Watchman left atrial appendage occlusion devices. Larger prospective studies are needed to confirm the clinical efficacy and safety of this approach.

Objective This study aimed to assess the feasibility and success rates of permanent His-Purkinje conduction system pacing (HPCSP) in patients requiring pacing after transcatheter aortic valve replacement (TAVR). Background TAVR is associated with increased risk for atrioventricular block. HPCSP has the potential to reduce electromechanical dyssynchrony associated with right ventricular pacing. The feasibility and safety of HPCSP in this population are unknown. Methods Consecutive patients requiring pacemakers after TAVR in whom His bundle pacing (HBP) and/or left bundle branch area pacing (LBBAP) was attempted at 5 centers were included in the study. Implant success rates, pacing characteristics, QRS duration, and left ventricular ejection fraction were assessed. Any procedure-related complications, lead revisions, heart failure hospitalizations, and deaths were documented. Results HPCSP was successful in 55 of 65 (85%) patients studied. HBP was successful in 29 of 46 patients (63%), and LBBAP was successful in 26 of 28 (93%) patients in whom it was attempted. HBP was more successful in patients with Sapien valves than in those with CoreValves (69% vs. 44%; p Conclusions HPCSP is feasible in the majority of patients requiring pacemakers post-TAVR. Success rates of HBP were lower in patients with CoreValves compared to Sapien valves. LBBAP was associated with higher success rates and lower pacing thresholds compared with HBP.

BACKGROUND Congenitally corrected transposition of the great arteries (CCTGA) is associated with spontaneous atrioventricular block and pacing-induced cardiomyopathy. Conduction system pacing is a potential alternative to conventional cardiac resynchronization therapy (CRT). OBJECTIVE The purpose of this study was to determine the outcomes of conduction system pacing for CCTGA. METHODS Retrospective data were collected from 10 international centers. RESULTS His bundle (HBP) or left bundle branch pacing (LBBP) was attempted in 15 CCTGA patients (median age 23 years; 87% male). Previous surgery had been performed in 8 and chronic ventricular pacing in 7. Conduction system pacing (11 HBP, 2 LBBP 2; nonselective in 10, selective in 3) was acutely successful in 13 (86%) without complication. In 9 cases, electroanatomic mapping was available and identified the distal His bundle and proximal left bundle branches within the morphologic left ventricle below the pulmonary valve separate from the mitral annulus. Median implant HV interval was 42 ms (interquartile range [IQR] 35-48), R wave 6 mV (IQR 5-18), and threshold 0.5 V (IQR 0.5-1.2) at median 0.5 ms. QRSd was unchanged compared to junctional escape rhythm (124 vs 110 ms; P = .17) and decreased significantly compared to baseline ventricular pacing (112 vs 164 ms; P < .01). At a median of 8 months, all patients were alive without significant change in pacing threshold or lead dysfunction. New York Heart Association functional class improved in 5 patients. CONCLUSION Permanent conduction system pacing is feasible in CCTGA by either HBP or proximal LBBP. Narrow paced QRS and stable lead thresholds were observed at intermediate follow-up. Unique anatomic characteristics may favor this approach over conventional CRT.

Fluoroscopy remains a cornerstone imaging modality for catheter placement and positioning in electrophysiology device and ablation procedures. However, efforts are being made to reduce the cumulative exposure to radiation in the patient and physician alike. We present the case of a 59-year-old male patient with hypertension, chronic kidney disease, and paroxysmal atrial fibrillation who underwent successful near-fluoroless laser balloon (LB) pulmonary vein isolation (PVI) ablation. Though this case demonstrates the usage of a novel protocol for near-fluoroless LB ablation that resulted in successful, uncomplicated acute PVI, the feasibility and safety of this technique should be validated in a larger series or prospective comparative study.

INTRODUCTION Radiation exposure during catheter ablation procedures is a significant hazard for both patients and operators. Atrial fibrillation (AF) ablation procedures have been historically associated with higher fluoroscopy usage than other electrophysiology procedures. Recent efforts have been made to reduce dependence on fluoroscopy during pulmonary vein isolation (PVI) ablation procedures using alternative techniques. METHODS We performed a meta-analysis of studies comparing zero or low fluoroscopy (LF) vs conventional fluoroscopy (CF) approaches for AF ablation. Outcomes of interest included acute and 12-month procedural efficacy, safety, procedure duration, fluoroscopy time, and dose area product. Aggregated data were analyzed with random-effects models, using a Bayesian hierarchical approach. RESULTS A total of 2228 participants (LF, n = 1190 vs CF, n = 1038) from 15 studies were included in the meta-analysis. Risk of AF recurrence in 12 months (odds ratio [OR], 95% confidence interval [95% CI] = 1.343 [0.771-2.340]; P = .297), redo-ablation procedures (OR [95% CI] = 0.521 [0.198-1.323]; P = .186), and procedural complications (OR [95% CI] = 0.99 [0.485-2.204]; P = .979) were similar between LF- and CF-ablation groups. In comparison to CF ablation, LF ablation led to shorter procedure duration (weighted mean differences [WMDs] [95% CI] = -14.6 minutes [-22.5 to -6.8]; P

We highlight a diagnostic challenge in a patient with dyspnea on exertion due to radiation therapy–induced severe first-degree atrioventricular block and how permanent His bundle pacing was helpful in overcoming these symptoms. (Level of Difficulty: Intermediate.), Graphical abstract, This case highlights a diagnostic challenge in a patient with dyspnea on exertion due to radiation therapy–induced severe first-degree…

BACKGROUND Cardiac resynchronization therapy (CRT) based on the conventional biventricular pacing (BiV-CRT) technique sometimes results in broad QRS complex and suboptimal response. OBJECTIVE We aimed to assess the feasibility and outcomes of CRT based on left bundle branch area pacing (LBBAP, in lieu of the right ventricular lead) combined with coronary venous left ventricular pacing in an international multicenter study. METHODS LBBAP-optimized CRT (LOT-CRT) was attempted in nonconsecutive patients with CRT indications. Addition of the LBBA (or coronary venous) lead was at the discretion of the implanting physician, who was guided by suboptimal paced QRS complex, and/or on clinical grounds. RESULTS LOT-CRT was successful in 91 of 112 patients (81%). The baseline characteristics were as follows: mean age 70 +/- 11 years, female 22 (20%), left ventricular ejection fraction 28.7% +/- 9.8%, left ventricular end-diastolic diameter 62 +/- 9 mm, N-terminal pro-B-type natriuretic peptide level 5821 +/- 8193 pg/mL, left bundle branch block 47 (42%), nonspecific intraventricular conduction delay 25 (22%), right ventricular pacing 26 (23%), and right bundle branch block 14 (12%). The procedure characteristics were as follows: mean fluoroscopy time 27.3 +/- 22 minutes, LBBAP capture threshold 0.8 +/- 0.5 V @ 0.5 ms, and R-wave amplitude 10 mV. LOT-CRT resulted in significantly greater narrowing of QRS complex from 182 +/- 25 ms at baseline to 144 +/- 22 ms (P < .0001) than did BiV-CRT (170 +/- 30 ms; P < .0001) and LBBAP (162 +/- 23 ms; P < .0001). At follow-up of >= 3 months, the ejection fraction improved to 37% +/- 12%, left ventricular end-diastolic diameter decreased to 59 +/- 9 mm, N-terminal pro-B-type natriuretic peptide level decreased to 2514 +/- 3537 pg/mL, pacing parameters were stable, and clinical improvement was noted in 76% of patients (New York Heart Association class 2.9 vs 1.9). CONCLUSION LOT-CRT is feasible and safe and provides greater electrical resynchronization as compared with BiV-CRT and could be an alternative, especially when only suboptimal electrical re synchronization is obtained with BiV-CRT. Randomized controlled trials comparing LOT-CRT and BiV-CRT are needed.

INTRODUCTION Left bundle branch pacing (LBBP), a form of conduction system pacing in addition to His bundle pacing (HBP), can potentially maintain left ventricular electrical synchrony with better sensing and a low and stable capture threshold. METHODS We performed both HBP and LBBP using a canine model (n = 3; male; weight 30-40 kg). The electrocardiogram (ECG), intracardiac electrogram characteristics, and pacing parameters were compared between HBP and LBBP. The hearts were isolated and stained by Lugol's iodine (5%) to assess the relative locations of the leads in relation to the conduction system. RESULTS The average potential to ventricle interval was longer with HBP compared to LBBP (26.67 ± 3.06 ms vs 12.67 ± 1.15 ms; P = .002). There were also notable differences in the pacing parameters between HBP and LBBP: R-wave amplitude (2.67 ± 0.42 mV vs 11.33 ± 3.06 mV; P = .008), pacing impedance (423.3 ± 40.4 vs 660.0 ± 45.8; P = .003), and threshold (2.30 ± 0.66 V/0.4ms vs 0.67 ± 0.15 V/0.4 ms; P = .014). The paced morphology of ECG was similar to the intrinsic with HBP while a right bundle branch block pattern was noted with LBBP. The anatomical evaluation revealed the location of the leads and the average lead depth was significantly more with LBBP as compared to HBP (12.33 ± 1.53 mm vs1.83 ± 0.29 mm; P

The His-SYNC pilot trial was the first randomized comparison between His bundle pacing in lieu of a left ventricular lead for cardiac resynchronization therapy (His-CRT) and biventricular pacing (BiV-CRT), but was limited by high rates of crossover.To evaluate the results of the His-SYNC pilot trial utilizing treatment-received (TR) and per-protocol (PP) analyses.The His-SYNC pilot was a multicenter, prospective, single-blinded, randomized, controlled trial comparing His-CRT vs BiV-CRT in patients meeting standard indications for CRT (eg, NYHA II-IV patients with QRS120 ms). Crossovers were required based on prespecified criteria. The primary endpoints analyzed included improvement in QRS duration, left ventricular ejection fraction (LVEF), and freedom from cardiovascular (CV) hospitalization and mortality.Among 41 patients enrolled (aged 64 ± 13 years, 38% female, LVEF 28%, QRS 168 ± 18 ms), 21 were randomized to His-CRT and 20 to BiV-CRT. Crossover occurred in 48% of His-CRT and 26% of BiV-CRT. The most common reason for crossover from His-CRT was inability to correct QRS owing to nonspecific intraventricular conduction delay (n = 5). Patients treated with His-CRT demonstrated greater QRS narrowing compared to BiV (125 ± 22 ms vs 164 ± 25 ms [TR], P.001;124 ± 19 ms vs 162 ± 24 ms [PP], P.001). A trend toward higher echocardiographic response was also observed (80 vs 57% [TR], P = .14; 91% vs 54% [PP], P = .078). No significant differences in CV hospitalization or mortality were observed.Patients receiving His-CRT on-treatment demonstrated superior electrical resynchronization and a trend toward higher echocardiographic response than BiV-CRT. Larger prospective studies may be justifiable with refinements in patient selection and implantation techniques to minimize crossovers.

The aim of the study was to evaluate the clinical outcomes of nonselective (NS) His bundle pacing (HBP) compared with selective (S) HBP.HBP is the most physiologic form of ventricular pacing. NS-HBP results in right ventricular septal pre-excitation due to fusion with myocardial capture in addition to His bundle capture resulting in widened QRS duration compared with S-HBP wherein there is exclusive His bundle capture and conduction.The Geisinger and Rush University HBP registries comprise 640 patients who underwent successful HBP. Our study population included 350 consecutive patients treated with HBP for bradyarrhythmic indications who demonstrated ≥20% ventricular pacing burden 3 months post-implantation. Patients were categorized into S-HBP or NS-HBP based on QRS morphology (NS-HBP n = 232; S-HBP n = 118) at the programmed output at the 3-month follow-up. The primary analysis outcome was a combined endpoint of all-cause mortality or heart failure hospitalization.The NS-HBP group had a higher number of men (64% vs. 50%; p = 0.01), higher incidence of infranodal atrioventricular block (40% vs. 9%; p 0.01), ischemic cardiomyopathy (24% vs. 14%; p = 0.03), and permanent atrial fibrillation (18% vs. 8%; p = 0.01). The primary endpoint occurred in 81 of 232 patients (35%) in the NS-HBP group compared with 23 of 118 patients (19%) in the S-HBP group (hazard ratio: 1.38; 95% confidence interval: 0.87 to 2.20; p = 0.17). Subgroup analyses of patients at greatest risk (higher pacing burden or lower left ventricular ejection fraction) revealed no incremental risk with NS-HBP.NS-HBP was associated with similar outcomes of death or heart failure hospitalization when compared with S-HBP. Multicenter risk-matched clinical studies are needed to confirm these findings.

Conventional right ventricular (RV) pacing, particularly RV apical pacing, can have deleterious effects on cardiac function. Long-term RV apical pacing has been associated with increased risk of atrial fibrillation, hospitalization for heart failure, pacing-induced cardiomyopathy and associated death. His bundle pacing (HBP) results in physiological ventricular activation and has generated tremendous research interest and enthusiasm. By stimulating the His-Purkinje network directly, HBP results in synchronized ventricular activation, which might translate into improved clinical outcomes compared with dyssynchronous ventricular activation with RV apical pacing. HBP can also overcome bundle branch block patterns, and data are accumulating on the benefit of HBP for cardiac resynchronization therapy. In this Review, we summarize the anatomy of the His bundle and early clinical observations, implantation techniques and available outcome data associated with permanent HBP. We also highlight the challenges with HBP and the need for additional tools and more randomized data before widespread application of permanent HBP.

Permanent His bundle pacing (PHBP) has shown significant clinical benefits in patients requiring ventricular pacing compared with conventional right ventricular pacing. There is an emerging role for PHBP in patients with interventricular dyssynchrony. This article reviews the mechanisms and the available data on the use of PHBP in overcoming dyssynchrony.

Left bundle branch area pacing (LBBAP) has been shown to be a feasible option for patients requiring ventricular pacing.The purpose of this study was to compare clinical outcomes between LBBAP and RVP among patients undergoing pacemaker implantation METHODS: This observational registry included patients who underwent pacemaker implantations with LBBAP or RVP for bradycardia indications between April 2018 and October 2020. The primary composite outcome included all-cause mortality, heart failure hospitalization (HFH), or upgrade to biventricular pacing. Secondary outcomes included the composite endpoint among patients with a prespecified burden of ventricular pacing and individual outcomes.A total of 703 patients met inclusion criteria (321 LBBAP and 382 RVP). QRS duration during LBBAP was similar to baseline (121 ± 23 ms vs 117 ± 30 ms; P = .302) and was narrower compared to RVP (121 ± 23 ms vs 156 ± 27 ms; P.001). The primary composite outcome was significantly lower with LBBAP (10.0%) compared to RVP (23.3%) (hazard ratio [HR] 0.46; 95%T confidence interval [CI] 0.306-0.695; P.001). Among patients with ventricular pacing burden20%, LBBAP was associated with significant reduction in the primary outcome compared to RVP (8.4% vs 26.1%; HR 0.32; 95% CI 0.187-0.540; P.001). LBBAP was also associated with significant reduction in mortality (7.8% vs 15%; HR 0.59; P = .03) and HFH (3.7% vs 10.5%; HR 0.38; P = .004).LBBAP resulted in improved clinical outcomes compared to RVP. Higher burden of ventricular pacing (20%) was the primary driver of these outcome differences.

His bundle pacing (HBP) can reverse left ventricular (LV) remodeling in patients with right ventricular (RV) pacing-induced cardimyopathy (PICM) but may be unable to correct infranodal atrioventricular block (AVB). Left bundle branch pacing (LBBP) results in rapid LV activation and may be able to reliably pace beyond the site of AVB. Our study was conducted to assess the feasibility, safety, and outcomes of permanent LBBP in infranodal AVB and PICM patients. Patients with infranodal AVB and PICM who underwent LBBP for cardiac resynchronization therapy (CRT) were included. Clinical evaluation and echocardiographic and electrocardiographic assessments were recorded at baseline and follow-up. Permanent LBBP upgrade was successful in 19 of 20 patients with a median follow-up duration of 12 months. QRS duration (QRSd) increased from 139.3 ± 28.0 ms at baseline to 176.2 ± 21.4 ms (P < 0.001) with right ventricular pacing (RVP) and was shortened to 120.9 ± 15.2 ms after LBBP (P < 0.001). The mean LBBP threshold was 0.7 ± 0.3 V at 0.4 ms at implant and remained stable during follow-up. The left ventricular ejection fraction (LVEF) increased from 36.3% ± 6.5% to 51.9% ± 13.0% (P < 0.001) with left ventricular end-systolic volume (LVESV) reduced from 180.1 ± 43.5 to 136.8 ± 36.7 ml (P < 0.001) during last follow-up. LBBP paced beyond the site of block, which results in a low pacing threshold with a high success rate in infranodal AVB patients. LBBP improved LV function with stable parameters over the 12 months, making it a reasonable alternative to cardiac resynchronization pacing via a coronary sinus lead in infranodal AVB and PICM patients.

Conduction system pacing (CSP) is a technique of pacing that involves implantation of permanent pacing leads along different sites of the cardiac conduction system and includes His bundle pacing and left bundle branch pacing. There is an emerging role for CSP to achieve cardiac resynchronisation in patients with heart failure with reduced ejection fraction and inter-ventricular dyssynchrony. In this article, the authors review these strategies for resynchronisation and the available data on the use of CSP in overcoming dyssynchrony.

Long-term RV apical pacing has been associated with increased risk of atrial fibrillation, heart failure hospitalizations, pacing-induced cardiomyopathy, and associated mortality. The search for an alternative site of pacing for ventricular activation has led us to His–Purkinje conduction system pacing (HP-CSP) which presently includes His bundle pacing (HBP) and left bundle branch pacing (LBBP). HP-CSP results in synchronized ventricular activation by direct stimulation of the His–Purkinje network and may result in prevention of some of the adverse clinical outcomes. HP-CSP can also overcome bundle branch block patterns and might be an option for cardiac resynchronization therapy. In this chapter, we review the anatomy of the conduction system and mechanisms of QRS narrowing with HP-CSP and review some of the best practices during implantation to allow for better long-term performance and outcomes.

Background: Left bundle branch pacing (LBBP) has recently emerged as a promising alternative modality for conduction system pacing. However, limited real-world data exists on the advantages and complications associated with LBBP. We analyzed the Rush conduction system pacing registry on LBBP to assess the success rates and complications associated with LBBP. Methods: All patients with an indication for permanent pacemaker or cardiac resynchronization therapy that underwent LBBP for various reasons from June 2018 to April 2020 were included in the analysis. Results: A total of 57 of 59 patients underwent successful LBBP (success rate 97%). The average follow-up duration was 6.2±5 months. The implanted devices included 38 dual-chamber pacemakers, 17 cardiac resynchronization therapy defibrillators, and 2 cardiac resynchronization therapy pacing systems. The most common reason for performing LBBP was a high His-Bundle pacing threshold (n=23) at implant. The mean LBBP capture threshold at implant was 0.62±0.21 V at 0.4 ms which remained stable during follow-up at 0.65±0.68 V at 0.4ms. In 21 patients with cardiomyopathy, there was a significant improvement in left ventricle ejection fraction from 30±11% to 42±15%. A total of 7 lead-related complications (12.3%) were noted in the follow-up period. Three patients (5.3%) required lead revision during the follow-up period. Interventricular septal perforation occurred (as late sequela) after 2 weeks in one patient. Conclusions: LBBP can be achieved with a high success rate and low capture thresholds. Left ventricular dysfunction improved significantly during follow-up. Lead-related complications were relatively common occurring in 12.3% of initially successful implants. Lead revision was required in 3 (5%) of patients.

Background Conventional right ventricular pacing (RVP) has been associated with an increased incidence of atrial fibrillation (AF). We sought to compare the occurrence of new‐onset AF and assessed AF disease progression during long‐term follow‐up between His bundle pacing (HBP) and RVP. Methods and Results We included patients undergoing initial dual‐chamber pacemaker implants at Rush University Medical Center between January 1, 2016, and June 30, 2019. A total of 360 patients were evaluated, and 225 patients (HBP, n=105; RVP, n=120) were included in the study. Among the 148 patients (HBP, n=72; RVP, n=76) with no history of AF, HBP demonstrated a lower risk of new‐onset AF (adjusted hazard ratio [HR], 0.53; 95% CI, 0.28–0.99; P =0.046) compared with traditional RVP. This benefit was observed with His or RVP burden exceeding 20% (HR, 0.29; 95% CI, 0.13–0.64; P =0.002), ≥40% (HR, 0.31; P =0.007), ≥60% (HR, 0.35; P =0.015), and ≥80% (HR, 0.40; P =0.038). There was no difference with His or RV pacing burden P =0.404). In patients with a prior history of AF, there was no difference in AF progression ( P =0.715); however, in a subgroup of patients with a pacing burden ≥40%, HBP demonstrated a trend toward a lower risk of AF progression (HR, 0.19; 95% CI, 0.03–1.16; P =0.072). Conclusions HBP demonstrated a lower risk of new‐onset AF compared with RVP, which was primarily observed at a higher pacing burden.

Introduction We sought to determine the effectiveness and safety of hydroxychloroquine–azithromycin (HCQ-AZM) therapy in hospitalized patients with COVID-19. Methods This was a retrospective cohort study of 613 patients hospitalized (integrated health system involving three hospitals) for RT-PCR-confirmed COVID-19 infection between March 1, 2020 and April 25, 2020. Intervention was treatment with HCQ-AZM in hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Outcomes of interest were in-hospital all-cause mortality, cardiovascular mortality, pulseless electrical activity (PEA) arrest, non-lethal arrhythmias, and length of hospital stay. Secondary measures included in-hospital corrected QT (QTc) interval parameters and serum biomarkers levels. Results Propensity-matched groups were composed of 173 patients given HCQ-AZM and 173 matched patients who did not receive treatment. There was no significant difference in in-hospital mortality (odds ratio [OR] 1.52; 95% confidence interval [CI] 0.80–2.89; p = 0.2), PEA arrest (OR 1.68, CI 0.68–4.15; p = 0.27), or incidence of non-lethal arrhythmias (10.4% vs. 6.8%; p = 0.28). Length of hospital stay (10.5 ± 7.4 vs. 5.8 ± 6.1; p

Lithium-induced type 1 Brugada pattern in asymptomatic patients is an uncommon occurrence that is challenging to manage and to estimate the risk of sudden cardiac death (SCD). We describe a case of a 74-year-old woman who presented with type 1 Brugada pattern while on lithium therapy. Her lithium level was within the therapeutic range at the time of presentation. There was no evidence of ventricular ectopy or malignant arrhythmias. Review of electrocardiogram (ECG) prior to initiation of lithium therapy demonstrated type 3 Brugada pattern. Lithium was promptly discontinued, and the patient was closely monitored in the hospital for 48 hours with serial ECGs and telemetry, as her lithium levels decreased. The Brugada pattern resolved on day 10 of discontinuation of lithium therapy and no further intervention was performed. Early diagnosis and prompt discontinuation of lithium leads to the resolution of type 1 Brugada pattern and may reduce the risk of SCD. The case highlights the importance of obtaining baseline ECG when initiating lithium especially in patients with type 2 or 3 Brugada pattern and provides an overview of the serial changes in ECG pattern until resolution following discontinuation of lithium. Electrophysiology study for risk stratification in asymptomatic patients does not appear to provide any additional benefit.

Aims We sought to compare the effectiveness and safety of high-power short-duration (HPSD) radiofrequency ablation (RFA) with conventional RFA in patients with atrial fibrillation (AF). Methods and results MEDLINE, Cochrane, and ClinicalTrials.gov databases were searched until 15 May 2020 for relevant studies comparing HPSD vs. conventional RFA in patients undergoing initial catheter ablation for AF. A total of 15 studies involving 3718 adult patients were included in our meta-analysis (2357 in HPSD RFA and 1361 in conventional RFA). Freedom from atrial arrhythmia was higher in HPSD RFA when compared with conventional RFA [odds ratio (OR) 1.44, 95% confidence interval (CI) 1.10–1.90; P = 0.009]. Acute PV reconnection was lower (OR 0.56, P = 0.005) and first-pass isolation was higher (OR 3.58, P Conclusion High-power short-duration RFA was associated with better procedural effectiveness when compared with conventional RFA with comparable safety and shorter procedural duration.

Background Cryoballoon ( CB ) ablation is widely performed for pulmonary vein isolation ( PVI ) in patients with atrial fibrillation ( AF ). Anatomic variations in patient pulmonary vein ( PV) anatomy are believed to impact short‐ and long‐term procedural success of CB PVI . Methods and Results We hypothesized that failure of initial PV isolation with a standard technique (ie, requiring >2 freeze cycles per PV and/or radiofrequency ablation [RFA] to achieve PV isolation) during index CB PVI procedures would be associated with decreased freedom from AF . We examined a cohort of 177 consecutive patients with drug‐refractory AF who underwent CB PVI with a 28‐mm balloon second‐generation CB device. Mean follow‐up time was 19±9 months. Forty‐three patients had AF recurrence after the 90‐day blanking period after ablation. In 40 patients, acute isolation of one or more PV s could not be achieved by CB ablation with the standard technique (single freeze with or without bonus freeze). To obtain complete acute PVI , 15 patients received extra freeze applications, 20 required supplemental RFA , and 5 received both extra freeze applications and supplemental RFA . Multivariate regression analysis revealed supplemental RFA use during index CB PVI procedures was independently associated with a threefold increased risk of AF recurrence (adjusted hazard ratio, 3.01; 1.45–10.87; P =0.003). Conclusions Use of supplemental RFA during CB PVI procedures to assist with isolation of one or more PV s was independently associated with increased risk of AF recurrence. Use of additional freezes to achieve PVI did not increase the risk for recurrent AF .

Chronotropic incompetence is the inability of the sinus node to increase heart rate commensurate with increased metabolic demand. Cardiac pacing alone may be insufficient to address exercise intolerance, fatigue, dyspnea on exertion, and other symptoms of chronotropic incompetence. Rate-responsive (adaptive) pacing employs sensors to detect physical or physiological indices and mimic the response of the normal sinus node. This review describes the development, strengths, and limitations of a variety of sensors that have been employed to address chronotropic incompetence. A mini-tutorial on programming rate-adaptive parameters is included along with emphasis that patients' lifestyles and underlying medical conditions require careful consideration. In addition, special sensor applications used to respond prophylactically to physiologic signals are detailed and an in-depth discussion of sensors as a potential aid in heart failure management is provided.

INTRODUCTION Although balloon-based techniques, such as the laser balloon (LB) ablation have simplified pulmonary vein isolation (PVI), procedural fluoroscopy usage remains higher in comparison to radiofrequency PVI approaches due to limited 3-dimensional mapping system integration. METHODS In this prospective study, 50 consecutive patients were randomly assigned in alternating fashion to a low fluoroscopy group (LFG; n = 25) or conventional fluoroscopy group (CFG; n = 25) and underwent de novo PVI procedures using visually guided LB technique. RESULTS There was no statistical difference in baseline characteristics or cross-overs between treatment groups. Acute PVI was accomplished in all patients. Mean follow up was 318 ± 69 days. Clinical recurrence of atrial fibrillation after PVI was similar between groups (CFG: 19% vs LFG: 15%; P = .72). Total fluoroscopy time was significantly lower in the LFG than the CFG (1.7 ± 1.4 vs 16.9 ± 5.9 minutes; P

Cardiac resynchronization therapy (CRT) is an established option for select patients with systolic heart failure. Nonresponse to CRT remains a significant problem. We present five patients who were CRT nonresponders and discuss the conventional and nonconventional approaches employed to achieve CRT benefit.

The right ventricular (RV) apex has been considered to be the primary site for ventricular lead implantation since the original descriptions of permanent pacing. However, long-term RV apical pacing has been shown to have negative effects on ventricular function and hemodynamics as a result of ventricular dyssynchrony. Alternative sites of ventricular pacing, particularly the RV septum and His bundle, have been evaluated for patients with a need for long-term ventricular pacing. In this article, we review the available data on the use of these alternative sites for RV pacing.

His bundle pacing (HBP) prevents ventricular dyssynchrony and its long-term consequences by preserving normal electrical activation of the ventricles. Since the original description of permanent HBP in 2000, the adoption of HBP has increased over the past several years. However, the reporting of procedural and clinical outcomes to date is not uniform. This article is a collaboration between several implanters with significant experience in HBP to establish a uniform set of definitions encompassing the different forms of HBP as well as define a standardized approach to gathering data end points to ensure consistency in reported outcomes.

Background Cardiac resynchronization therapy (CRT) using biventricular pacing (BVP) is effective in patients with heart failure, bundle branch block (BBB), or right ventricular pacing. Permanent His-bundle pacing (HBP) has been reported as an alternative option for CRT. Objective The purpose of this study was to assess the feasibility and outcomes of HBP in CRT eligible or failed patients. Methods HBP was attempted as a rescue strategy in patients with failed left ventricular lead or nonresponse to BVP (group I), or as a primary strategy in patients with AV block, BBB, or high ventricular pacing burden as an alternative to BVP (group II) in patients with indications for CRT. Implant characteristics, New York Heart Association functional class, and echocardiographic data were assessed in follow-up. Results HBP was successful in 95 of 106 patients (90%): 30 in group I and 65 in group II. Mean age was 71 ± 12 years and 30% were female, with BBB in 45%, paced rhythm in 39%, and AV block in 16%. His capture and BBB correction thresholds were 1.4 ± 0.9 V and 2.0 ± 1.2 V at 1 ms, respectively. During mean follow-up of 14 months, both groups demonstrated significant narrowing of QRS from 157 ± 33 ms to 117 ± 18 ms (P = .0001), increase in left ventricular ejection fraction from 30% ± 10% to 43% ± 13% (P = .0001), and improvement in New York Heart Association functional class from 2.8 ± 0.5 to 1.8 ± 0.6 (P = .0001) with HBP. Lead-related complications occurred in 7 patients. Conclusion Permanent HBP is a promising alternative for CRT. HBP may be considered as a rescue strategy for failed BVP and may be a reasonable primary alternative to BVP for CRT.

Biventricular pacing (BiV) is established as the primary modality to achieve cardiac resynchronization therapy (CRT), although nonresponse rates approach 30% to 40% [(1)][1]. His bundle pacing has emerged as a viable option for CRT with physiological restoration of electrical synchrony by

Left atrial appendage occlusion (LAAO) with the Watchman device (Boston Scientific, Natick, MA) is frequently performed as a nonpharmacologic, second-line therapy for stroke prevention in patients with atrial fibrillation (AF)1, 2 and contraindications to long-term anticoagulation. Although combined catheter pulmonary vein isolation (PVI) and Watchman procedures may be performed successfully for patients with symptomatic AF, a simultaneous approach is not always feasible or in some cases PVI may not be clinically indicated at the time of Watchman implantation. Staged radiofrequency PVI and left atrial (LA) catheter ablation following Watchman device placement has been shown to be feasible3, 4, 5; however, other modalities for PVI have not been reported in the postimplant population.

Objectives This study reports on the time course of reimplantation and benefits of the wearable cardioverter-defibrillator (WCD) in patients post implantable cardioverter-defibrillator (ICD) explantation. Background The WCD is used to treat patients at high risk for ventricular tachycardia (VT) and ventricular fibrillation (VF), including patients with ICD–related infections who undergo device removal and cannot be immediately reimplanted. Methods This retrospective study included consecutive patients from 2002 to 2014 who underwent ICD removal because of device-related infection and were prescribed a WCD. WCD-stored electrocardiograms were reviewed. Event outcome was assessed through either the manufacturer WCD registry or the Social Security death index search. Results A total of 8,058 patients (mean age 62 ± 14 years, 75% male) were included in the analysis. Median time to reimplantation of an ICD was 50 days (interquartile range: 24 to 83 days). While wearing the WCD, 334 patients (4%) experienced 406 VT/VF events, of which 348 events were treated. Shocks were averted in 54 events by conscious patients. The overall 24-h survival, both treated and nontreated, was 93% (312 of 334). VT/VF occurrence was the highest in the initial weeks after ICD removal (0.9%, 0.7%, and 0.7% per week for weeks 1, 2, and 3, respectively). The 12-month cumulative event rate was 10%. For all patients, the 30-day post-event survival was 81%. An ICD was reimplanted in 80% of patients. Conclusions The risk of VT/VF reaches 4% during the first 2 months and 10% at 1 year after ICD removal. WCD demonstrated a high efficacy for protecting patients from VT/VF. Clinicians may use the WCD as an ICD alternative when reimplantation is medically delayed.

Atrial fibrillation (AF) is the most commonly encountered sustained tachyarrhythmia. Flecainide is a class IC antiarrhythmic drug used frequently for treatment of supraventricular tachyarrhythmias.1 Common cardiac and noncardiac side effects of flecainide are well described and recognized in clinical practice. Subacute flecainide lung toxicity has been described in a small number of case reports2, 3, 4 but is not commonly recognized or well understood. Here we report a case of acute drug-induced pneumonitis after flecainide administration and discuss key points in the recognition and management of this rare but potentially serious clinical scenario.

Background: The 12-lead ECG is considered the gold standard to differentiate between selective (S), nonselective (NS) His bundle pacing (HBP), and right ventricular septal capture in routine clinical practice. We sought to assess the utility of device EGM recordings as a tool to identify the type of HBP morphology. Methods: One hundred forty-eight consecutive patients underwent HBP with a 3830 Select Secure lead (Medtronic, Inc) at 3 centers between October 2016 and October 2017. The near field V-EGM morphology (NF EGM), near field V-EGM time to peak (NF Time to peak ), and far-field EGM QRS duration (QRSd) were recorded while pacing the His lead with simultaneous 12-lead ECG rhythm strips. Results: Indications for HBP were sinus node dysfunction, atrioventricular conduction disease, and cardiac resynchronization therapy in 68 (46%), 56 (38%), and 24 (16%) patients, respectively. Baseline QRSd was 108±38 ms with QRSd >120 ms in 57 (39%) patients (27 right bundle branch block, 18 left bundle branch block, and 12 intraventricular conduction delay). S-HBP was noted in 54 (36%) patients. A positive NF EGM and NF Time to peak >40 ms were highly sensitive (94% and 93%, respectively) and specific (90% and 94%) for S-HBP irrespective of baseline QRSd. All 3 parameters (+NF EGM , NF Time to peak >40 ms, and far-field EGM QRSd Conclusions: We propose a novel and simple criteria for accurate differentiation between S-HBP, NS-HBP, and right ventricular septal capture morphologies by careful analysis of device EGMs alone. This study paves the way for future studies to assess autocapture algorithms for devices with HBP.

Catheter-based ablation techniques have a well-established role in atrial fibrillation (AF) management. The prevalence and impact of AF is increasing globally, thus mandating an emphasis on improving ablation techniques through innovation. One key area of ongoing evolution in this field is the use of laser energy to perform pulmonary vein isolation during AF catheter ablation. While laser use is not as widespread as other ablation techniques, such as radiofrequency ablation and cryoballoon ablation, advancements in product design and procedural protocols have demonstrated laser balloon ablation to be equally safe and effective compared to these other modalities. Additionally, strategies to improve procedural efficiency and decrease radiation exposure through low fluoroscopy protocols make this technology an increasingly promising and exciting option.

Long-term right ventricular (RV) apical pacing has been associated with an increased risk of death, heart failure, and atrial fibrillation (AF). Alternative sites for RV pacing have not proven to be superior to RV apical pacing. Cardiac resynchronization therapy (CRT) using a biventricular (BiV) lead system is indicated for patients with a low left ventricular ejection fraction and QRS prolongation, but there remains about a 25-30% nonresponse rate. CRT has been less effective for nonleft bundle branch block conduction delay and with normal/low normal left ventricular function. Over the past decade, there have been more data on the feasibility and advantages of pacing at the His Bundle (HB) region. We review the anatomy and physiology of the HB, the available data on permanent HB pacing, its current and potential future applications.

Introduction The diaphragmatic compound motor action potentials (CMAPs) have been used to predict and prevent phrenic nerve injury (PNI) during cryoballoon ablation of right pulmonary veins. We sought to assess factors that influence the amplitude of the surface CMAP recordings. Methods and Results We analyzed CMAPs from consecutive patients undergoing cryoballoon ablation for paroxysmal atrial fibrillation. CMAP recordings were obtained using ECG electrodes positioned in the “modified lead I” method while stimulating the right PN, until loss of capture (ascertained by palpation and fluoroscopy of the right hemi-diaphragm). A total of 55 patients (age 63±11 yrs; 60% men; BMI 31±6) had adequate CMAP recordings and were included for evaluation of CMAP signals. CMAPs demonstrated two distinct components, an early higher amplitude signal (pacing artifact) and a later lower amplitude signal (true diaphragmatic CMAP). There was no significant change in the true CMAP recording amplitude with decrease in stimulus strength (p = 0.1). There was no impact of BMI on CMAP amplitude (p = 0.93). There was a significant phasic respiratory variation in CMAP amplitude with a mean decrease in CMAP amplitude of 10.8% (range: 8–12%) with inspiration lasting an average of 2 beats (p 30% was noted in 6 cases (11%) and termination of cryoablation prevented PNI. Conclusion Diaphragmatic CMAP amplitude is not affected by stimulus strength or BMI. There is a significant respirophasic decrease in CMAP signal amplitude with inspiration. It is important to be aware of this variation to avoid premature termination of cryoablation. This article is protected by copyright. All rights reserved

Similar to endless loop tachycardia (ELT), repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) is a ventriculoatrial (VA) synchrony pacemaker-mediated arrhythmia. RNRVAS was first described in 1990 and can only occur in the presence of retrograde VA conduction and dual-chamber or cardiac resynchronization devices with tracking (P-synchronous ventricular pacing such as DDD, DDDR) or nontracking pacing modes that allow AV-sequential pacing (DDI, DDIR). RNRVAS is promoted by (1) high lower rate limit or any feature that allows rapid pacing, (2) long AV intervals, or (3) long postventricular atrial refractory period (PVARP). In contrast to ELT, RNRVAS is a less well-recognized form of pacemaker-mediated arrhythmia; thus, unlike ELT, there are no specific device algorithms to prevent, recognize, and terminate RNRVAS. However, RNRVAS has been recently shown to occur frequently. We present a series of cases, some of which were found fortuitously. Owing to its clinical implications, we propose that algorithms should be developed to prevent, identify, and terminate RNRVAS.

BACKGROUND Ganglionic plexi (GPs) have been implicated as triggers of atrial fibrillation (AF) and are known to have functional interconnections. Understanding these connections could result in a more effective ablation. The objective of this study is to assess relationships between right- and left-sided GPs in patients undergoing mini-maze (MM) surgery. We also analyzed the impact of these findings on AF recurrence. METHODS The GPs were accessed thoracoscopically right side first (group 1) or left side first (group 2). GPs were identified by high-frequency stimulation at 20 predetermined sites and ablation of GPs was performed using a selective or an empiric anatomic approach. Ganglionic plexus (GP) activity was then assessed on the contralateral side and ablated. RESULTS Sixty-seven patients underwent MM (45 patients in group 1 and 22 in group 2). Fewer patients with active left GPs (LGP) were noted in group 1 (13, 29%) as compared to group 2 (18, 82%). The number of active LGP was also lower (0.6 ± 1.2) in group 1 compared to group 2 (4.7 ± 2.7); P 0.05). There were no differences in atrial tachyarrhythmia (AT)/AF recurrence rates between groups 1 and 2 (P = 0.21). However, group 1 patients who underwent selective GP ablation alone had higher recurrence rates (P = 0.016). CONCLUSION Mapping and ablation of RGPs first decreased identifiable LGP activity. With selective GP ablation, patients who underwent RGP ablation first had higher AT/AF recurrence.

His-bundle pacing (HBP) is a physiological alternative to right ventricular pacing (RVP). The outcomes of HBP in patients with longstanding atrioventricular block (AVB) and RVP are unknown OBJECTIVE: The purpose of this study was to retrospectively assess the feasibility of HBP in patients with chronic RVP and longstanding AVB and to evaluate its efficacy in reversing the adverse remodeling induced by RVP.HBP was attempted in patients with longstanding AVB and chronic RVP and/or pacing-induced cardiomyopathy (PICM) in need for resynchronization therapy. The site of conduction block and feasibility of HBP was documented. Electrocardiographic and echocardiographic assessments at baseline and follow-up were recorded.HBP was successful in 79 of 85 patients (93%) with RVP for 77.6 ± 74.8 months (range 2-540 months). AV nodal block was present in 59 and infranodal block in 26. QRS duration increased from 123 ± 31 ms at baseline to 177 ± 17 ms (P.001) during RVP and decreased to 115 ± 20 ms with HBP (P.001). T-wave memory was observed in 53 of 79 patients with HBP and normalized in 2-12 weeks. HBP threshold was 1.47 ± 0.9 V @ 1 ms at implant and 1.9 ± 1.3 V @ 1 ms at last follow-up (25 ± 24 months). In 60 patients with PICM in whom left ventricular ejection fraction decreased from 54% ± 7.7% at baseline to 34.3% ± 9.6% (P .001), ejection fraction improved to 48.2% ± 9.8% (P .001) after HBP CONCLUSION: Despite a long duration of AVB and chronic RVP, HBP normalized QRS complexes and T waves with stable thresholds, suggesting that progression of distal conduction disease is uncommon in this population. Electrical and structural changes induced by chronic RVP were consistently reversed with HBP.

Interest in permanent His bundle pacing as a means of both preventing pacing-induced cardiomyopathy and providing physiological resynchronization by normalization of His-Purkinje activation is steadily growing. However, there are differences in atrioventricular timing cycles, sensing, and tissue capture that distinguish His bundle pacing from right ventricular pacing, and hence it is of utmost importance to bear these differences in mind when implanting a His pacing lead and programming the His pacing system. This article focuses on critical considerations and troubleshooting options available to the implanter and follow-up clinic personnel.

Although amiodarone is considered the most effective antiarrhythmic agent, its use is limited by a wide variety of potential toxicities. The purpose of this review is to provide a comprehensive "bench to bedside" overview of the ways amiodarone influences thyroid function. We performed a systematic search of MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other clinically relevant studies. The search was limited to English-language reports published between 1950 and 2017. Amiodarone was searched using the terms adverse effects, hypothyroidism, myxedema, hyperthyroidism, thyroid storm, atrial fibrillation, ventricular arrhythmia, and electrical storm. Google and Google scholar as well as bibliographies of identified articles were reviewed for additional references. We included 163 germane references in this review. Because amiodarone is one of the most frequently prescribed antiarrhythmic drugs in the United States, the mechanistic, diagnostic and therapeutic information provided is relevant for practicing clinicians in a wide range of medical specialties.