Venkatachalam, K

Radiofrequency (RF) ablation for cardiac arrythmias is an established curative therapy. However, catheter-tip coagulum formation leading to thromboembolic stroke is a persistent problem despite heparinization. Recent studies demonstrated an up to 70% incidence of thrombus formation on the catheter tip during ablation and a 10 % incidence of thromboembolic events. Catheter tip thrombus can impede the delivery of RF energy to the tissue, resulting in reduced efficacy and longer procedure times. Here we report on a novel method to prevent coagulum formation on ablation catheters by delivering a negative charge to the catheter tip to repel negatively charged fibrinogen molecules during RF ablation. A novel circuit was built with a charge delivery unit using a 9 voltage battery to deliver a fixed offset direct current charge, placed in parallel to the RF delivery unit for negative charge placement during RF delivery. In in-vivo canine experiments (n=50) standard 6/4, 8/5 ablation catheters and catheters with abraded tips were advanced from right femoral veins into atria and ventricles under intra-cardiac echo (ICE) and biplane fluoroscopic guidance. The dogs received 1 of 2 therapies: no RF energy delivered with and without negative charge delivery, RF energy delivery with and without negative charge delivery. The presence of thrombus was identified with ICE. The catheter tips were examined also macroscopically with visual inspection and also with field emission scanning electron microscopy (FESEM). FESEM of the catheter tips showed surface coverage of fibrin clot of the catheter tip to be 90 % for non-charged catheters compared to 0 % (p< 0.01) in negatively-charged catheters. There was no significant difference in surface coverage of fibrin clot between negatively-charged catheters with the abraded tips (98.8%) and non-charged catheters with smooth tips (90.7 %, p=ns). Clot volume formed on the catheter tip decreased with increased amount of charge. Application of a negative charge did not affect the quality of the intracardiac electrograms or induce malignant ventricular arrhythmias. Negative charge delivery during RF ablation is feasible and safe and can eliminate coagulum formation, potentially reducing thromboembolic complications.

Introduction: Percutaneous left atrial appendage closure is well established as an alternative to anticoagulation therapy for stroke prophylaxis among patients with non-valvular atrial fibrillation (NVAF) with relative or absolute contraindications to anticoagulation. Only the Watchman® (BSC) device has FDA approval for this indication. There are no current guidelines on the choice of short term antithrombotic therapy following placement of the Watchman® device. The landmark Watchman® clinical trials utilized warfarin and aspirin in the first 45 days to facilitate endothelialization; however these studies were started prior to direct oral anticoagulants (DOAC) becoming widely available. Our main objective was to compare bleeding outcomes with warfarin vs. DOACs following Watchman® device placement. Methods: We conducted a retrospective chart review of all patients who received a Watchman® device at all three Mayo Clinic sites (MN, FL, AZ) between January 2010 and December 2018 with follow up for outcomes at 45 days or 6 weeks following procedure. We conducted bivariate analysis using t-tests and chi-square tests as appropriate. A logistic regression model was constructed to evaluate the effect of anticoagulant choice on bleeding and thromboembolic outcomes. Clinically significant bleeding was defined as bleeding leading to interruption of anticoagulation regimen or requiring transfusion. Results: 232 patients were identified (33% female), mean age in years, CHADS2VASC score and HASBLED scores were 77, 5 and 4 respectively. Overall, 39% were initiated on non-warfarin therapies and 11% had a significant bleeding episode during follow up. There was no difference in clinically significant bleeding events (11% vs. 12%; OR 0.92, 95% CI: 0.32 – 2.65) with short term DOAC use compared to warfarin. Patients who received a Watchman® due to GI bleeding were more likely to have a bleeding event in the first 6 weeks following Watchman® (OR: 4.08, 95% CI: 1.30 – 12.75). Conclusion: This observational study demonstrates no significant difference in bleeding episodes with DOACs compared to warfarin during the first 6 weeks following Watchman® device placement in patients at high risk for bleeding. Larger prospective studies are needed.

Abstract Aims Current electrophysiology signal recording and mapping systems have limited dynamic range (DR) and bandwidth, which causes loss of valuable information during acquisition of cardiac signals. We evaluated a novel advanced signal processing platform with the objective to obtain and assess additional information of clinical importance. Methods and results Over 10 canines, we compared intracardiac recordings within all cardiac chambers, in various rhythms, in pacing and during radiofrequency (RF) ablation across two platforms; a conventional system and the PURE EP™ [(PEP); Bio Sig Technologies, Inc., Los Angeles, CA, USA]. Recording cardiac signals with varying amplitudes were consistently and reproducibly observed, without loss of detail or introduction of artefact. Further the amplitude of current of injury (COI) on the unipolar signals correlated with the instantaneous contact force (CF) recorded on the sensing catheter in all the animals (r2 = 0.94 in ventricle). The maximum change in the unipolar COI correlated with the change in local electrogram amplitude during non-irrigated RF ablation (r2 = 0.61 in atrium). Reduction in artefact attributable to pacing (20 sites) and noise during ablation (48 sites) was present on the PEP system. Within the PEP system, simultaneous display of identical signals, filtered differently, aided the visualization of discrete conduction tissue signals. Conclusion Compared to current system, the PEP system provided incremental information including identifying conduction tissue signals, estimates of CF and a surrogate for lesion formation. This novel signal processing platform with increased DR and minimal front-end filtering may be useful in clinical practice.

BackgroundEndocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters.MethodsPhase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters.ResultsPhase 1: Direct current (DC) in varying doses (blocking [7–12 μA], electroporation [300–500 μA], ablation [3,000–7,500 μA]), radiofrequency ablation (25–50 W), ultrasound (1.5 MHz), and alcohol (2–5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500–5,000 μA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 μA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium.ConclusionPercutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

ECG Lead I and Outflow Tract ArrhythmiaIntroductionOutflow tract ventricular arrhythmia (OTVA) can be complicated to target for ablation when originating from either the periaortic or pulmonary valve (PV) region. Both sites may present with a small R wave in lead V1. However, the utility of lead I in distinguishing these arrhythmia locations is unknown.Methods and ResultsThirty‐six consecutive patients (mean age 41 ± 14 years, 13 male) underwent catheter ablation for OTVA. OTVA origin was determined from intracardiac electrogram tracings and electroanatomic maps. Observers blinded to results measured QRS waveform amplitude and duration from standard 12‐lead ECG tracings. Measurements with highest diagnostic performance were modeled into an algorithm. Sites of successful ablation were anterior right ventricular outflow tract (RVOT; n = 6), posterior RVOT (n = 4), PV (n = 18), and right coronary cusp (RCC; n = 8). Highest performing surface ECG discriminators were from lead I to V1 vectors: RCC, lead I R wave ≥ 1.5 mV, and V1 R wave ≥2.0 mV (sensitivity 87%, specificity 93%); PV, V1 R wave > 0 mV, and lead I R/(R+S) ≤ 0.75 (sensitivity 78%, specificity 72%); anterior RVOT, V1 R wave = 0 mV, and lead I R/(R+S) <0.4 (sensitivity 67%, specificity 97%); posterior RVOT, V1 R wave > 0 mV, and lead I R/(R+S) > 0.75 (sensitivity 75%, specificity 84%). Sequential algorithmic application of these criteria resulted in an overall accuracy of 72% in predicting site of OTVA origin.ConclusionsA relatively large R wave in lead I is seen with RCC origin but not PV origin. A sequential algorithm has limited but potentially significant value beyond assessment of lead I in approaching OTVA.