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BACKGROUND Cardiac resynchronization therapy (CRT) using bi-ventricular pacing (BVP) is effective in patients with heart failure, left bundle branch block (LBBB), and reduced left ventricular function. Left bundle branch area pacing (LBBAP) has been reported as an alternative option for CRT. OBJECTIVE The purpose of this study was to assess the feasibility and outcomes of LBBAP in patients who failed conventional BVP because of coronary venous (CV) lead complications or who were nonresponders to BVP. METHODS At 16 international centers, LBBAP was attempted in patients with conventional CRT indication who failed BVP because of CV lead complications or lack of therapeutic response to BVP. Heart failure hospitalization (HFH) and death, echocardiographic outcomes, procedural data, pacing parameters, and lead complications including CV lead failure are reported. RESULTS LBBAP was successfully performed in 200 patients (CV lead failures 156; nonresponders 44) (age 68 +/- 11 years; female 35%; LBBB 55%; right ventricular pacing 23%; ischemic cardiomyopathy 28%; nonischemic cardiomyopathy 63%; left ventricular ejection fraction [LVEF]

Cardiac resynchronization therapy (CRT) with biventricular pacing (BVP) is well-established therapy in patients with reduced left ventricular ejection fraction (LVEF) and bundle branch block or indication for pacing. Conduction system pacing (CSP) using His-bundle pacing (HBP) or left bundle branch area pacing (LBBAP) has been shown to be a safe and more physiological alternative to BVP.The purpose of this study was to compare the clinical outcomes between CSP and BVP among patients undergoing CRT.This observational study included consecutive patients with LVEF ≤35% and class I or II indications for CRT who underwent successful BVP or CSP at 2 major health care systems. The primary outcome was the composite endpoint of time to death or heart failure hospitalization (HFH). Secondary outcomes included subgroup analysis in left bundle branch block as well as individual endpoints of death and HFH.A total of 477 patients (32% female) met inclusion criteria (BVP 219; CSP 258 [HBP 87, LBBAP 171]). Mean age was 72 ± 12 years, and mean LVEF was 26% ± 6%. Comorbidities included hypertension 70%, diabetes mellitus 45%, and coronary artery disease 52%. Paced QRS duration in CSP was significantly narrower than BVP (133 ± 21 ms vs 153 ± 24 ms; P.001). LVEF improved in both groups during mean follow-up of 27 ± 12 months and was greater after CSP compared to BVP (39.7% ± 13% vs 33.1% ± 12%; P.001). Primary outcome of death or HFH was significantly lower with CSP vs BVP (28.3% vs 38.4%; hazard ratio 1.52; 95% confidence interval 1.082-2.087; P = .013).CSP improved clinical outcomes compared to BVP in this large cohort of patients with indications for CRT.

Cardiac resynchronization therapy (CRT) using biventricular pacing has limited efficacy in patients with heart failure (HF) and right bundle branch block (RBBB). Left bundle branch area pacing (LBBAP) is a novel physiologic pacing option. OBJECTIVE The aim of the study was to assess the feasibility and outcomes of LBBAP in HF patients with RBBB and reduced left ventricular systolic function, and indication for CRT or ventricular pacing. METHODS LBBAP was attempted in patients with left ventricular ejection fraction (LVEF) = 5% increase in ejection fraction) to LBBAP were assessed. RESULTS LBBAP was attempted in 121 patients and successful in 107 (88%). Patient characteristics included age 74 +/- 12 years, female 25%, ischemic cardiomyopathy 49%, and ejection fraction 35% +/- 9%. QRS axis at baseline was normal in 24%, left axis 63%, right axis 13%. LBBAP threshold and R-wave amplitudes were 0.8 +/- 0.3 V@ 0.5 ms and 10 +/- 9 mV at implant and remained stable during mean follow-up of 13 +/- 8 months. LBBAP resulted in narrowing of QRS duration (156 +/- 20 ms to 150 +/- 24 ms (P = .01) with R-wave peak times in V-6 of 85 +/- 16 ms. LVEF improved from 35% +/- 9% to 43% +/- 12% (P,.01). Clinical and echocardiographic response was observed in 60% and 61% of patients, respectively. Female sex and reduction in QRS duration with LBBAP were predictive of echocardiographic response and super-response. CONCLUSION LBBAP is a feasible alternative to deliver CRT or physiologic ventricular pacing in patients with RBBB, HF, and LV dysfunction.

Ventricular tachycardia (VT) is a significant cause of morbidity and mortality in patients with ischaemic and non-ischaemic cardiomyopathies. In most patients, the primary strategy of VT catheter ablation is based on the identification of critical components of reentry circuits and modification of abnormal substrate which can initiate reentry. Despite technological advancements in catheter design and improved ability to localise abnormal substrates, putative circuits and site of origins of ventricular arrhythmias (VAs), current technologies remain inadequate and durable success may be elusive when the critical substrate is deep or near to critical structures that are at risk of collateral damage. In this article, we review the available and potential future non-surgical investigational approaches for treatment of VAs and discuss the viability of these modalities.

Background In the USA, ∼300 000 people are affected by Chagas heart disease, a growing, but commonly overlooked, public health issue. Chagas as a potential aetiology of dilated cardiomyopathy remains under-recognized. We present a case where multimodality imaging was essential in the diagnosis and management of Chagas heart disease. Case summary A 54-year-old man, originally from Mexico, presented to the emergency department with chest pain and recurrent syncopal episodes, found to be in haemodynamically unstable ventricular tachycardia (VT) requiring urgent cardioversion. Urgent coronary angiography revealed no obstructive disease. A transthoracic echocardiogram revealed moderately reduced left ventricular systolic function (left ventricular ejection fraction 35–40%) with apical akinesis and an aneurysm of the apical septum. Cardiac magnetic resonance (CMR) confirmed a prominent apical aneurysm with dyskinesis of the apical septum, with the evidence of transmural myocardial late gadolinium enhancement of the entire left ventricular apex and a small apical thrombus. Serologic testing was positive for Trypanosoma cruzi IgG antibody, which was confirmed on repeat testing at the Centers for Disease Control and Prevention. Patient underwent VT ablation and was discharged on guideline-directed medical therapy including a regimen of anticoagulation, beta-blocker, and angiotensin-converting enzyme inhibitor therapies. He has had no subsequent syncope or VT. Discussion Chagas heart disease remains under-recognized and under-diagnosed despite the growing burden of T. cruzi infection in the USA. Suspicion for Chagas heart disease should be considered in patients presenting with heart failure symptoms and ventricular arrhythmias with the right corresponding history and imaging findings on echocardiogram and CMR.

Despite the global COVID-19 pandemic, during the past 2 years, there have been numerous advances in our understanding of arrhythmia mechanisms and diagnosis and in new therapies. We increased our understanding of risk factors and mechanisms of atrial arrhythmias, the prediction of atrial arrhythmias, response to treatment, and outcomes using machine learning and artificial intelligence. There have been new technologies and techniques for atrial fibrillation ablation, including pulsed field ablation. There have been new randomized trials in atrial fibrillation ablation, giving insight about rhythm control, and long-term outcomes. There have been advances in our understanding of treatment of inherited disorders such as catecholaminergic polymorphic ventricular tachycardia. We have gained new insights into the recurrence of ventricular arrhythmias in the setting of various conditions such as myocarditis and inherited cardiomyopathic disorders. Novel computational approaches may help predict occurrence of ventricular arrhythmias and localize arrhythmias to guide ablation. There are further advances in our understanding of noninvasive radiotherapy. We have increased our understanding of the role of His bundle pacing and left bundle branch area pacing to maintain synchronous ventricular activation. There have also been significant advances in the defibrillators, cardiac resynchronization therapy, remote monitoring, and infection prevention. There have been advances in our understanding of the pathways and mechanisms involved in atrial and ventricular arrhythmogenesis.

INTRODUCTION His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) have emerged as attractive alternatives to traditional biventricular pacing to achieve cardiac resynchronization therapy. Early reported results have been inconsistent, particularly amongst patients in whom initial placement with traditional approaches has been unsuccessful or those with complex anatomy or congenital abnormalities. In this report, we describe the use of three-dimensional electroanatomic mapping (EAM) in five selected cases. METHODS Five patients from multiple clinical sites underwent EAM-guided HBP or LBBAP by highly trained electrophysiologists with significant experience with conduction system pacing. Each patient in this series underwent EAM-guided conduction system pacing due to complex anatomy and/or prior failed lead implantation. RESULTS EAM-guided lead implantation was successful in all five cases. Capture thresholds were relatively low and patients continued to have evidence of successful lead implantation with minimum 1-month follow-up. The fluoroscopy time varied, likely owing to the variable complexity of the cases. CONCLUSIONS The use of EAM, in combination with traditional intracardiac electrograms with or without fluoroscopy, allows more targeted and precise placement of leads for HBP and LBBAP pacing. Further investigation is needed to determine this strategy's long-term performance and to optimize patient selection.

With the increasing adoption of left atrial appendage occlusion (LAAO) procedures and the eligibility of patients for pulmonary vein isolation (PVI) post device placement, we examined the feasibility and safety of laser balloon (LB) for PVI in patients with prior LAAO.We retrospectively examined consecutive patients with paroxysmal or persistent, drug-resistant atrial fibrillation (AF) who underwent LB PVI, after Watchman FLX device implantation at Rush University Medical Center between January 2020 and December 2021.Seven patients (four persistent and three paroxysmal) with a mean age of 64 ± 11 years, predominantly male sex (86%), were included in the study. Two (29%) patients had prior cryoablation PVI with recurrence of AF. The mean CHALB PVI was safe and effective with 100% acute isolation of left-sided veins in patients with prior LAAO device.

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.

In patients with cardiomyopathy, radiofrequency catheter ablation (CA) for ventricular tachycardia (VT) is an adjunctive and alternative treatment option to long-term anti-arrhythmic drug therapy. We sought to compare CA with medical therapy for the management of VT in patients with ischemic and non-ischemic cardiomyopathies.MEDLINE, Cochrane, and ClinicalTrials.gov databases were evaluated for relevant studies.Eleven studies with 2126 adult patients were included (711 in CA, 1415 in medical therapy). In the randomized controlled trial (RCT) analysis, CA reduced risk of recurrent VT (risk ratio (RR) 0.79 [95% CI 0.67 to 0.93], p = 0.005), ICD shocks (RR 0.64 [95% CI 0.45 to 0.89] p = 0.008), and cardiac hospitalizations (RR 0.76 [95% CI 0.63 to 0.92] p = 0.005). There was no difference in all-cause mortality (RR 0.94, p = 0.71). In combined RCT and observational study analysis, there was a trend for reduction in all-cause mortality (RR 0.75 [95% CI 0.55 to 1.02] p = 0.07). In subgroup analysis of studies with mean left ventricular ejection fraction (LVEF) 35%, CA demonstrated reduction in mortality (RR 0.71, p = 0.004), ICD shocks (RR 0.63, p = 0.03), VT recurrence (RR 0.76, p = 0.004), and cardiac hospitalizations (RR 0.75, p = 0.02). The subgroup of early CA prior to ICD shocks demonstrated reduction in ICD shocks (RR 0.57, p 0.001) and VT recurrence (RR 0.74, p = 0.01).CA for VT demonstrated a lower risk of VT recurrence, ICD shocks, and hospitalization in comparison to medical therapy. The subgroups of early CA and LVEF 35% demonstrated better 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.

Permanent His Bundle Pacing (HBP) has recently gained popularity. However, implanting physicians and those who perform the device checks must invest in additional education in order to accurately program these devices, identify changes in morphology and perform troubleshooting to help achieve the best outcomes for the patients. This paper reviews key aspects of HBP and provides the educational tools for successful HBP follow-up and troubleshooting.

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.

Ablation Index (AI) is a multiparametric quality marker to assess the durability of radiofrequency (RF) lesions. The comparative effectiveness and safety of AI versus time-based energy dosing for ablation of ventricular arrhythmias are unknown.We compared AI and time-based RF dosing strategies in the left ventricles (LVs) of freshly harvested porcine hearts.Ablation was performed in vitro with an open-irrigated ablation catheter (Thermocool ST/SF), 40 W, contact force 10-15 g. Tissue samples were stained in triphenyltetrazolium chloride for the measurement of lesion dimensions.A total of 560 lesions were performed (AI-group: [n = 360]; time-group: [n = 200]). Using normal saline (NS) (n = 280), growth in lesion depth slowed after 30 s and AI 550 in comparison to width, volume, and magnitude of impedance drops which continued to increase with longer RF duration. Risk of steam pop (SP) was higher for RF 30 s (RF 30 s:1 SP [2.5%] vs. RF 30 s: 15 SP [25%]; p = .002) or AI targets550 (AI: 350-550: 2 SP [2%] vs. AI 600-750: 15 SP [19%]; p = .001). Using half-normal saline (HNS) (n = 280), lesion dimension and impedance drops were larger and growth in lesion depth slowed earlier (AI: 500). Risk of SPs was higher above AI 550 (AI: 350-550: 7 [7%] SPs vs. AI 600-750: 28 [35%] SPs; p .00001). While codependent variables, correlation between AI and time was modest-to-strong but decreased with longer RF duration.In this ex vivo study, AI was a better predictor of lesion dimensions than ablation time and magnitude of impedance drop in the LV using NS and HNS irrigation. AI targets above 550 led to a higher risk of SPs. Future trials are required to verify these findings.

The coronary cusps (CCs) are utilized as an alternative vantage point for radiofrequency catheter ablation (RFCA) of left ventricular summit ventricular arrhythmias but are sometimes a challenge despite favorable activation timing and pace mapping.Ex vivo experiments were performed in 12 intact porcine hearts submerged in a 37°C saline bath. Radiofrequency (RF) applications were delivered with an irrigated contact force sensing catheter oriented 45° to the endocardial left ventricular outflow tract (LVOT) surface and nadir of the CCs using different dosing parameters. Sections were stained in 2% triphenyltetrazolium chloride and lesion dimensions were measured. Thermal infrared imaging analysis was used to compare time-to-lethal tissue temperature and depth/area of lethal isotherms.A total of 60 RF applications were performed under different dosing parameters for (1) 30, 40, and 50 Watts (W) × 30 s and (2) 40 W × 30, 45, and 60 s. Lesion depth was greater with RFCA from LVOT than from the CCs (maximum depth 6.11 vs. 2.68 mm). Longer RF duration led to larger lesion volume in the CC group (40 W × 30 s: 8.1 ± 0.4 vs. 40 W × 60 s: 10.1 ± 0.96 mm; p = .002). One steam pop occurred in both the LVOT (50 W × 30 s) and CC groups (40 W × 60 s). Time-to-reach lethal temperature of 58°C was longer in the CC group than in the LVOT group (4.7 vs. 11.3 s; p = .02) CONCLUSIONS: RFCA from the CC led comparatively to shallower lesion depth than from the LVOT. Longer RF duration led to an increase in lesion volume during ablation from CCs.