Naksuk, Niyada

Background: Conduction tissue in the ventricles is closely intertwined with myocardium. Owing to high velocity of conduction, there is near simultaneous activation , making it difficult to discern. Restricted sampling rates and limited dynamic range make real time signal processing challenging for these signals in routine recording systems. Objectives: We aimed to use novel signal processing techniques in a new system to isolate the conduction tissue signals from the rest of the myocardial activation. Methods: We used the PURE-EP™ (BioSig Technologies, MN) signal processing system to record endocardial and epicardial signals from 6 anesthetized canines in an acute study setting. A novel filter based on proprietary algorithms to isolate the high frequency signal was applied at sites where the electrogram signals were thought to have a conduction tissue component to them. . In addition, ventricular fibrillation (VF) was induced at the end of the experiment and signals were then recorded from the endocardium and the conduction system. Results: This filter was successfully able to isolate conduction tissue signals in the myocardium from those of the ventricular muscle. It did over sense atrial signals at the basal left ventricular septum owing to the high frequency components of the atrial signal at this location. When applied to epicardial signals, it did not pick up any conduction tissue signals. In VF, we could discern signals originating from the conduction system endocardially. (Figure 1) Conclusions: This filter can isolate conduction tissue signals from those of the myocardium and may prove to be a useful adjunct in mapping arrhythmias originating near the conduction system.

Background: It is known that hypokalemia, hypocalcemia and hypomagnesemia cause a prolonged QTc interval and are associated with an increased risk of ventricular arrhythmias. However, there are limited data on optimal serum electrolytes for patients admitted to the coronary care unit (CCU). Objective: Here, we aimed to evaluate the relationship between serum potassium, ionized calcium and magnesium levels and in-hospital mortality in the CCU setting. Methods: This retrospective cohort study included 8,498 consecutive patients admitted to the CCU at an academic tertiary medical center from 2004 through 2013. The mean of serum electrolytes was categorized as <3.5, 3.5-<4.0, 4.0-<4.5 (reference), 4.5-<5.0, and ≥5.0 mEq/L for potassium; <4.4, 4.4-<4.6, 4.6-<4.8, 4.8-<5.0 (reference), and ≥5.0 mg/dL for ionized calcium; and <1.8, 1.8-<2.0, 2.0-<2.2 (reference), 2.2-<2.4, and ≥2.4 mg/dL for magnesium. Multivariate logistic regression analysis was used to determine the association between the mean of serum electrolytes and in-hospital mortality. Results: Of the 8,498 patients, 599 (7%) died during hospitalization. Relationship between mean serum potassium (U-shaped), ionized calcium (inverted J-shape) and magnesium (J-shaped) and in-hospital mortality was present in Figure. Serum potassium levels <3.5, 4.5-<5.0 and ≥5.0 mEq/L were independently associated with an increased risk of in-hospital mortality (adjusted OR 1.7 95% CI 1.1-2.5, OR 1.7 95% CI 1.3-2.2, and OR 3.4 95% CI 2.4-4.8, respectively), compared to the reference group. As for serum ionized calcium, the levels of <4.4, 4.4-<4.6, and 4.6-<4.8 mg/dL independently increased risk of mortality (adjusted OR 3.0 95% CI 2.3-4.0, OR 2.0 95% CI 1.5-2.6, and OR 1.4 95% CI, 1.1-1.8, respectively). As for serum magnesium, an only level above 2.4 mg/dL was associated with an increased mortality risk (OR 1.6 95% CI, 1.1-2.2). Conclusions: In the CCU setting, serum potassium 3.5-<4.5 mEq/L, ionized calcium ≥5.0 mg/dL and magnesium <2.4 mg/dL are associated with the lowest in-hospital mortality. These findings do not support supratherapeutic repletion of potassium and magnesium.

Background: The use of direct current electroporation has the potential for significant utility because of its non-thermal approach to tissue destruction. However, the fear of inducibility of cardiac arrhythmias (particular ventricular fibrillation) when using electroporation remains of concern due to membrane poration and ion flux during periods of vulnerability occurring in ventricular repolarization. Objectives: Critically examine the incidence of arrhythmias in a series of acute canine studies to retrospectively determine cause and safe electoporative dosing margins. Methods: We performed electroporation ablation in 6 acute canine studies. These were experimental studies performed at sites critical in arrhytmogenesis. Sites included the pulmonary veins, left atrial appendage, superior vena cavae, right atrium and ventricle. Electroporation was delivered using an ECG gating algorithm so that QRS complexes are tagged and direct current energy is not delivered during the vulnerable portion of the T wave. Results: In 6 acute canine experiments, we delivered a total of 62 electroporation applications for ablation purposes. The average electroporation dosage delivered involved an average of 1427 Volts (range 750-3000 V), Pulse length of 100 ms, and number of pulses of 20.2 (range 10-100). AF was induced in 27.4% of electroporiatve applications. Atrial flutter/tachycardia occurred in 8.1%. VF occurred in only one application at a location of the left superior pulmonary vein. Conclusion: These data suggest that induction of VF is relatively uncommon with ECG gating and highlight its importance when using this modality. However, the induction of AF occurs with higher frequency. The actual mechanism as to why this occurs requires further systematic study.

AbstractBackgroundLittle is known about the ablation outcomes of premature ventricular contractions (PVCs) that originate from the periprosthetic aortic valve (PPAV) regions of patients with aortic valve replacement (AVR).Methods and ResultsOur study had 11 patients who underwent catheter ablation for PVCs arising from the PPAV regions (bioprosthetic aortic valve, n = 5; mechanical aortic valve, n = 6). The PVC characteristics, procedure characteristics, and efficacy of ablation were compared with the control group (n = 33). At baseline, the PPAV group had a lower left ventricular ejection fraction (mean [SD], 41% [12%] vs. 51% [8%]; p = .002). The rate of acute ablation success was 90.9% in the PPAV group. Ablation sites were identified above the left coronary cusp (LCC) and right coronary cusp commissure (LRCC) in one PVC, below the prosthetic valve in eight PVCs (four below LCC and four below LRCC), and within the distal coronary sinus in two PVCs. The mean procedure time, fluoroscopy time, and radiation in the PPAV group were all significantly greater than those in the control group (all p < .05). However, the number of radiofrequency ablation energy deliveries was not different. The PPAV group had a long‐term success rate compared with the control group (72.7% vs. 87.9%, p = .48) and an increase of left ventricular ejection fraction from 43% to 49% after successful PVC ablation at follow‐up (p < .001). Echocardiography showed no significant change in valve regurgitation after ablation. No new atrioventricular block occurred.ConclusionPVCs arising from PPAV regions can be successfully ablated in patients with prior AVR, without damaging the prosthetic aortic valve and atrioventricular conduction.

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.

Background and Aims Hepatologists often determine whether transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR) is preferred for patients with cirrhosis and severe aortic stenosis. The goal of this cohort study is to compare outcomes following TAVR and SAVR in patients with cirrhosis to inform the preferred intervention. Approach and Results Prospectively collected data on 105 consecutive patients with cirrhosis and aortic stenosis who underwent TAVR (n = 55) or SAVR (n = 50) between 2008 and 2016 were reviewed retrospectively. Two control groups were included: 2,680 patients without cirrhosis undergoing TAVR and SAVR and 17 patients with cirrhosis who received medical therapy alone. Among the 105 patients with cirrhosis, the median Society of Thoracic Surgeons score was 3.8% (1.5, 6.9), and the median Model for End‐Stage Liver Disease (MELD) score was 11.6 (9.4, 14.0). The TAVR group had similar in‐hospital (1.8% vs. 2.0%) and 30‐day mortality (3.6% vs. 4.2%) as the SAVR group. During the median follow‐up of 3.8 years (95% confidence interval, 3.0‐6.9), there were 63 (60%) deaths. MELD score (adjusted hazard ratio, 1.13; 95% confidence interval, 1.05‐1.21; P = 0.002) was an independent predictor of long‐term survival. In the subgroup of patients with MELD score <12, the TAVR group had reduced survival compared with the SAVR group (median survival of 2.8 vs. 4.4 years; P = 0.047). However, in those with MELD score ≥12, survival after TAVR, SAVR, and medical therapy was similar (1.3 vs. 2.1 vs. 1.6 years, respectively; P = 0.53). Conclusion In select patients with cirrhosis, both TAVR and SAVR have acceptable and comparable short‐term outcomes. MELD score, but not Society of Thoracic Surgeons score, independently predicts long‐term survival after TAVR and SAVR. For patients with MELD score <12, SAVR is a preferred procedure; however, neither procedure appears superior to medical therapy in patients with MELD score ≥12.

Abstract Background Choosing the appropriate animal model for development of novel technologies requires an understanding of anatomy and physiology of these different models. There are little data about the characteristics of different animal models for the study of technologies used for epicardial ablation. We aimed to compare the incidence of ventricular arrhythmias during epicardial radiofrequency ablation between swine and canine models using novel epicardial ablation catheters. Methods We conducted a retrospective study using data obtained from epicardial ablation experiments performed on swine ( Sus Scrofa ) and canine ( Canis familiaris ) models. We compared the incidence of ventricular arrhythmias during ablation between swine and canine using multivariate regression analysis. Six swine and six canine animals underwent successful epicardial radiofrequency ablation. A total of 103 ablation applications were recorded. Results Ventricular arrhythmias requiring cardioversion occurred in 13.11% of radiofrequency ablation applications in swine and 9.75% in canine (relative risk: 117.6%, 95% confidence interval [CI]: 83.97‐164.69, animal‐based odds ratio [OR]: .55, 95% CI: .23‐61.33; P = .184). When adjusting for application position, duration of ablation and power, the odds of developing potentially lethal ventricular arrhythmia in swine increased significantly compared to canine (OR: 3.60, 95% CI: 1.35‐9.55; P = .010). Conclusions The swine myocardium is more susceptible to developing ventricular arrhythmias compared to canine model during epicardial ablation. This issue should be carefully considered in future studies.