Citations

Background: Reentrant ventricular arrhythmias are a major cause of sudden death in patients with structural heart disease. Current treatments focus on electrically homogenizing regions of scar contributing to ventricular arrhythmia with ablation or altering conductive properties using antiarrhythmic drugs. The high conductivity of carbon nanotubes may allow restoration of conduction in regions where impaired electrical conduction results in functional abnormalities. We propose a new concept for arrhythmia treatment using a stretchable, flexible biopatch with conductive properties to attempt to restore conduction across regions in which activation is disrupted. Methods: Carbon nanotube patches composed of nanofibrillated cellulose/single-walled carbon nanotube ink 3-dimensionally printed in conductive patterns onto bacterial nanocellulose were developed and evaluated for conductivity, flexibility, and mechanical properties. The patches were applied on 6 canines to epicardium before and after surgical disruption. Electroanatomic mapping was performed on normal epicardium, then repeated over surgically disrupted epicardium, and then finally with the patch applied passively. Results: We developed a 3-dimensional printable carbon nanotube ink complexed on bacterial nanocellulose that was (1) expressable through 3-dimensional printer nozzles, (2) electrically conductive, (3) flexible, and (4) stretchable. Six canines underwent thoracotomy, and, during epicardial ventricular pacing, mapping was performed. We demonstrated disruption of conduction after surgical incision in all 6 canines based on activation mapping. The patch resulted in restored conduction based on mapping and assessment of conduction direction and velocities in all canines. Conclusions: We have demonstrated 3-dimensional custom-printed electrically conductive carbon nanotube patches can be surgically manipulated to improve cardiac conduction when passively applied to surgically disrupted epicardial myocardium in canines.

AbstractBackgroundLeadless cardiac pacing (LCP) has emerged as a new modality for permanent pacing. We sought to describe comparative outcomes between LCP and transvenous pacemakers.MethodsPatients receiving LCP (Micra [Medtronic, Minneapolis, MN, USA] and Nanostim [St. Jude Medical/Abbott Laboratories, Chicago, IL, USA]) between 2014 and 2017 at the Mayo Clinic Heart Rhythm Enterprise practice (Rochester, MN, USA; Jacksonville, FL, USA; and Scottsdale, AZ, USA) were identified. We identified 1:1 age‐ and sex‐matched controls receiving single‐chamber transvenous ventricular pacemakers (TVP). Statistical analyses were performed with JMP 13.0.0 (SAS, Institute Cary, NC, USA).ResultsNinety patients underwent LCP implantation (73 Micra and 17 Nanostim) with a median follow‐up duration of 62 (interquartile range 28‐169) days. Both groups had 100% successful device implant rates. There were no differences in procedure‐related major (0% vs 1%) or minor complications (8% vs 3%) in the LCP versus TVP groups (P > 0.05). Excluding Nanostim patients, there was a lower rate of device‐related revision or extraction in the Micra versus TVP groups (0% vs 5%, P = 0.028). Device endocarditis was more common in the TVP group (0% vs 3%, P = 0.04). Estimated longevity was greater for the LCP group (median 12.0 vs 10.0 years, P < 0.0001). An increase in severity of tricuspid valve regurgitation (TR) by ≥2 grades occurred in none of the LCP patients, and in 19% of the TVP patients (P = 0.017).ConclusionThere are no significant differences in procedural complications among patients receiving LCP versus TVP. The Micra group had lower rates of device‐related revision/extraction compared to the TVP group. Patients with leadless pacemaker were less likely to develop endocarditis or worsening TR.

Background Current thermal ablation methods for atrial fibrillation, including radiofrequency and cryoablation, have a suboptimal success rate. To avoid pulmonary vein (PV) stenosis, ablation is performed outside of the PV, despite the importance of triggers inside the vein. We previously reported on the acute effects of a novel direct current electroporation approach with a balloon catheter to create lesions inside the PVs in addition to the antrum. In this study, we aimed to determine whether the effects created by this nonthermal ablation method were associated with irreversible lesions and whether PV stenosis or other adverse effects occurred after a survival period. Methods and Results Initial and survival studies were performed in 5 canines. At the initial study, the balloon catheter was inflated to contact the antrum and interior of the PV. Direct current energy was delivered between 2 electrodes on the catheter in ECG‐gated 100 μs pulses. A total of 10 PVs were treated demonstrating significant acute local electrogram diminution (mean amplitude decrease of 61.2±19.8%). After the survival period (mean 27 days), computed tomography imaging showed no PV stenosis. On histologic evaluation, transmural, although not circumferential, lesions were seen in each treated vein. No PV stenosis or esophageal injury was present. Conclusions Irreversible, transmural lesions can be created inside the PV without evidence of stenosis after a 27‐day survival period using this balloon‐based direct current ablation approach. These early data show promise for an ablation approach that could directly treat PV triggers in addition to traditional PV antrum ablation.

AbstractBackgroundTransvenous lead implantation has multiple drawbacks and complications that can be overcome by epicardial lead placement. We aimed to design percutaneously implanted epicardial leads that are anchored through the transverse sinus (TS).Methods and resultsWe designed a novel multielectrode pacing device with four bipole electrode pairs. The device is advanced through the TS, with both ends externalized out of the pericardium. We tested the prototype in one proof‐of‐concept and 5 additional acute canine experiments.The TS device recorded ventricular and atrial electrograms. The median amplitude of near‐field ventricular electrograms was 3.3 mA (IQR 2.0–4.3) and of near‐field atrial electrograms was 2.1 mA (IQR 1.3–2.2). The median ventricular threshold (N = 30) was 1.1 mA (IQR 0.7–3.1) at a median pulse width of 0.5 ms (IQR 0.5–0.5). The median atrial threshold (N = 10) was 2.4 mA (IQR 1.1–7.8) at a median pulse width of 0.5 ms (IQR 0.5–0.9). Right and left ventricular and atrial pacing morphologies were noted while pacing electrodes adjacent to these chambers. Simultaneous left (LV) and right ventricular (RV) pacing showed reduction in QRS duration from 116 ms (RV) and 105 ms (LV) to 91 ms. On necropsy, the device was located in the TS in all animals. There were TS abrasions in one animal, and no other acute complications.ConclusionsThis study highlights a novel approach to epicardial pacing harnessing the unique anatomy of the transverse sinus as an anchoring point. Placement of this novel transverse sinus device was safe and feasible, with acceptable atrial and ventricular thresholds.

Among patients undergoing cardioversion for atrial fibrillation, the presence of left ventricular thrombus is a relatively uncommon and challenging clinical dilemma. While left atrial appendage thrombus is a contraindication to cardioversion, there is paucity of data regarding the safety of cardioversion in with the presence of left ventricular apical thrombus. Also, thrombus characteristics such as protrusion and mobility on echocardiography are known risk factors for systemic embolism. In this article, we present a case highlighting the management of atrial fibrillation in the setting of left ventricular dysfunction, acute heart failure, and echocardiographic evidence of acute left ventricular apical thrombus.

BackgroundEchocardiographically detected patent foramen ovale (PFO) has been associated with stroke/transient ischemic attack (TIA) in patients with cardiac implantable electronic devices (CIEDs). We sought to evaluate the relationship between echocardiographic characteristics and risk of stroke/TIA and mortality in CIED patients with PFO.MethodsIn 6,086 device patients, PFO was detected in 319 patients. A baseline echocardiogram was present in 250 patients, with 186 having a follow‐up echocardiogram.ResultsOf 250 patients with a baseline echocardiogram, 9.6% (n = 24) had a stroke/TIA during mean follow‐up of 5.3 ± 3.1 years; and 42% (n = 105) died over 7.1 ± 3.7 years. Atrial septal aneurysm, prominent Eustachian valve, visible shunting across PFO, baseline or change in estimated right ventricular systolic pressure (RVSP)/tricuspid regurgitation (TR), or maximum RVSP were not associated with postimplant stroke/TIA (P > 0.05). An exploratory multivariate analysis using time‐dependent Cox models showed increased hazard of death in patients with increase in TR ≥2 grades (hazard ratio [HR] 1.780, 95% confidence interval [CI] 1.447–2.189, P < 0.0001), or increase in RVSP by >10 mm Hg (HR 2.018, 95% CI 1.593–2.556, P < 0.0001), or maximum RVSP in follow‐up (HR 1.432, 95% CI 1.351–1.516, P < 0.0001). A significant increase (P < 0.001) in TR was also noted during follow‐up.ConclusionsIn patients with CIED and PFO, structural and hemodynamic echocardiographic markers did not predict future stroke/TIA. However, a significantly higher TR or RVSP was associated with higher mortality.

Arrhythmogenic Substrate of Ventricular Arrhythmias at the AMCIntroductionCatheter ablation of ventricular arrhythmia (VA) at the fibrous aortic mitral continuity (AMC) has been described, yet the nature of the arrhythmogenic substrate remains unknown.MethodsProcedural records of 528 consecutive patients undergoing ablation of VA at Mayo Clinic, Rochester, MN, were reviewed. The electrocardiographic and electrophysiologic characteristics of patients with successful ablation at the AMC were analyzed to characterize the underlying arrhythmogenic substrate.ResultsOf the 21 patients (mean age 53.2 ± 13.4 years, 47.6% male) who underwent ablation of VA at the AMC with acute success, prepotentials (PPs) were found at the ablation sites preceding the ventricular electrogram (VEGM) during arrhythmias in 13 (61.9%) patients and during sinus rhythm in 7 (53.8%) patients. VAs with PPs were associated with a significantly higher burden of premature ventricular complexes (PVCs; 26.1 ± 10.9% vs. 14.9 ± 10.1%, P = 0.03), shorter VEGM to QRS intervals (9.0 ± 28.5 milliseconds vs. 33.1 ± 8.8 milliseconds, P = 0.03), lower pace map scores (8.7 ± 1.6 vs. 11.4 ± 0.8, P = 0.001), and a trend toward shorter V‐H intervals during VA (32.1 ± 38.6 milliseconds vs. 76.3 ± 11.1 milliseconds, P = 0.06) as compared to those without PP. A strong and positive correlation was found between V‐H interval and QRS duration during arrhythmia in those with PPs (B = 2.11, R2 = 0.97, t = 13.7, P < 0.001) but not in those without PPs.ConclusionLocal EGM characteristics and relative activation time of the His bundle suggest the possibility of conduction tissue as the origin for VA arising from the fibrous AMC. Specific identification and targeting of PPs when ablating VAs at this location may improve procedural success.