Wilber Su

Background and Aims: MODULAR ATP is an ongoing trial assessing the efficacy of a subcutaneous implantable cardioverter defibrillator (S-ICD) in communication with a leadless pacemaker (LP) that can deliver bradycardia pacing and antitachycardia pacing. The objective of this study was to assess safety and pacing performance of the investigational LP. Methods: The study enrolled patients with an ICD indication and at high risk for monomorphic ventricular tachycardia. Pacemaker dependent patients were excluded. Primary safety endpoint 2 was the percentage of patients free from major LP-related complications at 12 months. The secondary effectiveness endpoint assessed the rate response performance of the LP under workload. Parameters related to the pacing performance were also measured. Results: In 297 patients, the mean age was 59±12 years, the mean left ventricular ejection fraction was 35.3±13.1%, and 17.5% were female. LP implant was attempted in 286 patients and was successful in 100%. The major LP-related complication free rate at 12 months was 97.2% (one-sided 97.5% LCL 94.5%), surpassing the performance goal of 81%. There were no LP-related complications following Implant. For the secondary effectiveness endpoint, the slope of the normalized sensor rate versus the normalized workload was 0.96 (95% LCL 0.91, 95% UCL 1.02), within the performance goal range of 0.65-1.35. At 12 months, 96.8% of patients had a pacing capture threshold ≤ 2V @ 0.4ms pulse width. Conclusions: The performance of the modular pacing-defibrillator system at one year demonstrated a low complication rate and reliable pacing functionality.

Background: Electrographic flow (EGF) mapping is an FDA 510(k)‐cleared method for visualizing atrial activation wavefronts in atrial fibrillation (AF). Its clinical efficacy in detecting AF sources was demonstrated in the FLOW‐AF randomized controlled trial, and the underlying machine learning strategy used to develop and refine EGF source detection has been recently detailed. However, EGF mapping metrics can also characterize other properties of atrial wavefront propagation—most notably Electrographic Flow Consistency (EGFC) as a measure of the health of the atrial substrate. Patients with low EGFC have been found to have recurrent AF more frequently than those with high EGFC. EGFC may therefore be additive to source presence to phenotype AF patients based on mechanism of disease and recurrence likelihood. Objectives: Present the EGFC‐based Kaplan–Meier curves for each study arm of FLOW‐AF and explore the clinical relevance of EGFC using prospective studies. Methods: Unipolar electrograms were recorded using 64‐electrode basket catheters in AF patients across three clinical trials. The EGF algorithm then processed these recordings to reconstruct wavefront propagation patterns. EGFC was quantified from the vector length at each point in space and averaged across spatial coordinates and mapping positions to determine the mean EGFC for each patient. As applicable, EGFC and related EGF map characteristics were compared with 12‐month freedom from AF, patient demographic factors, and bipolar voltage mapping data. Results: Primarily, mean biatrial EGFC < 0.62 was found to be the best metric at predicting recurrent AF in No Source and Treatment patients in FLOW‐AF: it had 86% ± 11% accuracy after fivefold cross‐validation. Among these patients, those with EGFC ≥ 0.62 had 6% recurrence vs. 51% recurrence in those with EGFC < 0.62; p < 0.001. Control patients with sources post‐procedure had 77% vs. 100% recurrence in respective EGFC groups; p = 0.032. Follow‐up analyses showed that EGFC dropped from 0.58 ± 0.15 to 0.51 ± 0.14 (paired p = 0.041) in a subgroup of patients who underwent repeat mapping 103 ± 22 days later, but it was not affected by pulmonary vein isolation (PVI) or source ablation (paired p > 0.30). It was also higher among de novo and paroxysmal AF patients than redo ( p = 0.043) and non‐paroxysmal AF patients ( p = 0.022), respectively. Among the group of patients with low EGFC and no sources post‐procedure, recurrent patients had increased EGFC spatial variability ( p = 0.026) and more near‐threshold sources with source activity ≥ 25% but < 26.5% ( p = 0.038). Lastly, EGFC was globally and locally correlated to bipolar voltage across multiple rhythms, atria, mapping software and analysis techniques ( p = 0.009). Conclusions: EGFC may provide insights on the substrate health of the patient and is predictive of recurrence likelihood. An understanding of EGFC may therefore increase mechanistic understanding of the progression and therapeutic strategies for AF ablation that can be tailored to the individual patient. Clinical Trial Registration: FLOW‐AF: NCT04473963; FLOW EVAL‐AF: NCT06260670; AF‐FLOW Global Registry: NCT05481359.

Pulsed field ablation (PFA) is a cutting‐edge treatment for arrhythmias that targets cardiac tissue with rapid, high‐voltage electric current pulses, resulting in irreversible electroporation. Freed from the constraints of traditional radiofrequency (RF) ablation, the non‐thermal mechanism and myocardial selectivity of PFA has improved procedural safety aspects and efficiency over RF ablation. However, catheter development thus far has focused on waveforms and voltage, such that critical aspects related to the physics of energy delivery at the tissue–blood interface were often overlooked. When delivering high‐voltage pulsed electric fields, differences in electrical impedance, catheter geometry, and field strength impact the resulting precision and durability of lesions; principles that warrant a deeper understanding to inform and optimize future catheter designs. This article examines the engineering considerations behind the success of the first industrial iterations of PFA, with a comparison of catheter form factors for current systems that impact energy delivery, workflow, safety, and performance. We also address the initial assumptions and misconceptions related to PFA design and the development of current generation catheters as considerations for the future of ablation and mapping.

Background Cryoablation to achieve pulmonary vein (PV) isolation has become one of the standard approaches for atrial fibrillation (AF) ablation. The Arctic Front series cryoballoon and Achieve circular mapping catheter (Medtronic) inherently possess design defects that have been associated with unfavorite clinical outcomes. Lately, a new cryoablation system (Nordica Cryoablation System, Synaptic Medical) was developed with improved design of the cryoballoon and circular mapping catheter to address the inadequacies of current cryoablation technology. An animal study was conducted to test the efficacy and safety in performing PVI with the Nordica Cryoablation System. Methods Pulmonary vein isolation with the Nordica Cryoablation System was performed on 12 PVs of six healthy canines. Acute PVI and peri-procedural complications were recorded. All animals underwent a repeat EP study at least 4 weeks after index procedures followed by pathological and histological assessments of the heart and collateral/downstream organs after planned euthanasia. Results Acute PV isolation was achieved in all targeted PVs with 50% of PVs being isolated with a single cryoablation application. There were no major peri-procedural complications or device malfunction events. All PVs remained isolated after 29–30 days follow-up. Histological examination showed transmural cryo-lesions at treated sites with minimal inflammation, neovascularization, and neointima formation but no significant injury to adjacent tissue or embolization in downstream organs. Conclusion Acute and durable PVI can be achieved by using the novel Nordica Cryoablation System. Ablation with this new cryoablation system is associated with transmural lesions at targeted myocardium but creates no injury to the collateral tissues or downstream organs.

Purpose To examine the clinical effect of lead length and lead orientation in patients with cardiac implantable electronic devices (CIEDs) and lead fragments or abandoned leads undergoing 1.5-T MRI. Materials and Methods This Health Insurance Portability and Accountability Act-compliant retrospective study included patients with CIEDs and abandoned leads or lead fragments undergoing 1.5-T MRI from March 2014 through July 2020. CIED settings before and after MRI were reviewed, with clinically significant variations defined as a composite of the change in capture threshold of at least 50%, in sensing of at least 40%, or in lead impedance of at least 30% between before MRI and after MRI interrogation. Adverse clinical events were assessed at MRI and up to 30 days after. Univariable and multivariable analysis was performed. Results Eighty patients with 126 abandoned CIED leads or lead fragments underwent 107 1.5-T MRI examinations. Sixty-seven patients (median age, 74 years; IQR, 66-78 years; 44 male patients, 23 female patients) had abandoned leads, and 13 (median age, 66 years; IQR, 52-74 years; nine male patients, four female patients) had lead fragments. There were no reported deaths, clinically significant arrhythmias, or adverse clinical events within 30 days of MRI. Three patients with abandoned leads had a significant change in the composite of capture threshold, sensing, or lead impedance. In a multivariable generalized estimating equation analysis, lead orientation, lead length, MRI type, and MRI duration were not associated with a significant change in the composite outcome. Conclusion Use of 1.5-T MRI in patients with abandoned CIED leads or lead fragments of varying length and orientation was not associated with adverse clinical events. Keywords: Cardiac Assist Devices, MRI, Cardiac Implantable Electronic Device Supplemental material is available for this article. © RSNA, 2024.