Killu, Ammar M.

We would like to thank the authors for their letter and interest in our manuscript. We appreciate their valuable comments. The authors have raised the following important points: 1. The heterogenicity of our cohort with mitral valve surgery (MVS) 2. Elucidating the characteristics and causes of ventricular arrhythmias (VA) in patients with primary versus secondary mitral disease as well as in those with ischemic versus non-ischemic heart disease 3. The paucity of cardiac magnetic resonance imaging (MRI) as a limitation of the study 4. The need for careful evaluation of patients prior to ablation since most arrhythmias did not originate from the perimitral area.

AbstractWe report a case of alcohol ablation into a vein of Marshall for recurrent dormant conduction into the pulmonary veins with adenosine testing in a patient where two prior ablation attempts failed to isolate the left vein.

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.

AbstractBackgroundThough infrequent, incomplete left atrial appendage closure (LAAC) may result from residual leaks. Percutaneous closure has been described though data is limited.MethodsWe compiled a registry from four centers of patients undergoing percutaneous closure of residual leaks following LAAC via surgical means or with the Watchman device. Leak severity was classified as none (no leak), mild (1–2 mm), moderate (3–4 mm), or severe (≥5 mm). Procedural and clinical success was defined as the elimination of leak or mild residual leak at the conclusion of the procedure or follow‐up, respectively.ResultsOf 72 (age 72.2 ± 9.2 years; 67% male) patients, 53 had undergone prior LAAC using the Watchman device and 19 patients surgical LAAC. Mean CHADS2‐VA2Sc score was 4.0 ± 1.8. The median leak size was 5 mm, range: 2–13). A total of 13 received Amplatzer Vascular Plug‐II, 18 received Amplatzer Duct Occluder‐II and 40 patients received coils. One underwent closure using a 21 mm‐Watchman. Procedural success was 94%. Zero surgical and nine Watchman patients (13%) had a residual leak at procedural‐end (five mild, three moderate, and one severe)—only one patient had no reduction in leak size. Overall leak size reduction was 94%. Two (3%) had intraoperative pericardial effusion. There were no device embolizations, device‐related thrombi, or procedural deaths. Clinical success was maintained at 94%. Two had cerebrovascular accidents—at 2 days (transient ischemic attack) and 10 months postprocedure. Two had major bleeding outside the 30‐day periprocedural window.ConclusionPercutaneous closure of residual leaks following left atrial appendage closure is feasible and associated with good outcomes. The procedural risk appears to be satisfactory.

Abstract Pulsed electric fields (PEFs) have emerged as an ideal cardiac ablation modality. At present numerous clinical trials in humans are exploring PEF as an ablation strategy for both atrial and ventricular arrhythmias, with early data showing significant promise. As this is a relatively new technology there is limited understanding of its principles and biophysics. Importantly, PEF biophysics and principles are starkly different to current energy modalities (radiofrequency and cryoballoon). Given the relatively novel nature of PEFs, this review aims to provide an understanding of the principles and biophysics of PEF ablation. The goal is to enhance academic research and ultimately enable optimization of ablation parameters to maximize procedure success and minimize risk.

AbstractBackgroundData regarding ventricular tachycardia (VT) or premature ventricular complex (PVC) ablation following mitral valve surgery (MVS) is limited. Catheter ablation (CA) can be challenging given perivalvular substrate in the setting of mitral annuloplasty or prosthetic valves.ObjectiveTo investigate the characteristics, safety, and outcomes of radiofrequency CA in patients with prior MVS and ventricular arrhythmias (VA).MethodsWe identified consecutive patients with prior MVS who underwent CA for VT or PVC between January 2013 and December 2018. We investigated the mechanism of arrhythmia, ablation approach, peri‐operative complications, and outcomes.ResultsIn our cohort, 31 patients (77% men, mean age 62.3 ± 10.8 years, left ventricular ejection fraction 39.2 ± 13.9%) with prior MVS underwent CA (16 VT; 15 PVC). Access to the left ventricle was via transseptal approach in 17 patients, and a retrograde aortic approach was used in 13 patients. A combined transseptal and retrograde aortic approach was used in one patient, and a percutaneous epicardial approach was combined with trans‐septal approach in one patient. Heterogenous scar regions were present in 94% of VT patients and scar‐related reentry was the dominant mechanism of VT. Forty‐seven percent of PVC patients had abnormal substrate at the site targeted for ablation. Clinical VA substrates involved the peri‐mitral area in six patients with VT and five patients with PVC ablation. No procedure‐related complications were reported. The overall recurrence‐free rate at 1‐year was 72.2%; 67% in the VT group and 78% in the PVC group. No arrhythmia‐related death was documented on long‐term follow‐up.ConclusionCA of VAs can be performed safely and effectively in patients with MVS.

AbstractBackgroundWhile ventricular tachycardia (VT) in the setting of postmyocardial infarction left ventricular aneurysms (LVA) is not uncommonly encountered, there is a scarcity of data regarding the safety, efficacy, and outcomes of ablation of VT in this subset of patients.MethodsOur study included consecutive patients aged 18 years or older with postmyocardial infarction LVA who presented to Mayo Clinic for catheter ablation of VT between 2002 and 2018.ResultsOf 34 patients, the mean age was 70.4 ± 9.1 years; 91% were male. Mean LVEF was 29 ± 9.7% and left ventricular end‐diastolic dimension was 64.9 ± 6.6 mm. The site of the LVA was apical in 21 patients (62%). Fifteen patients (44%) presented with electrical storm or incessant VT. Nine patients (26%) had a history of intracardiac thrombus. All except for one patient had at least one VT originating from the aneurysm. The mean number of VTs was 2.9 ± 1.7. All patients underwent ablation at the site of the aneurysm. Ablation outside the aneurysm was performed in 13 patients (38%). Low‐voltage fractionated potentials and/or late potentials at the aneurysmal site were present in all cases. Complete elimination of all VTs was achieved in 18 (53%), while the elimination of the clinical VT with continued inducibility of nonclinical VTs was achieved in a further 11 patients (32%). Two patients developed cardiac tamponade requiring pericardiocentesis. During a mean follow‐up period of 2.3 ± 2.4 years, 11 patients (32%) experienced VT recurrence. Freedom from all‐cause mortality at 1‐year follow‐up was 94%.ConclusionRadiofrequency catheter ablation targeting the aneurysmal site is a feasible and reasonably effective management strategy for clinical VTs in patients with postinfarction LVA.

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.

Introduction: Prior cardiac surgery, especially the presence of coronary bypass grafts, is thought to preclude percutaneous epicardial access (EpiAcc) and, due to limited catheter maneuverability, mapping and ablation. The objective of our study was to evaluate the feasibility and safety of EpiAcc in patients with prior cardiac surgery. Methods: We retrospectively analyzed all patients who underwent EpiAcc as part of an ablation procedure between 01/01/2004-06/30/2013 at Mayo Clinic, Rochester, MN. All had documented VT or recurring, symptomatic PVCs. Baseline clinical characteristics and procedural characteristics were collected. Results: Of 162 patients that underwent EpiAcc, 18 had prior cardiac surgery (mean age 61 years, all male). This included 10 CABG, 2 epicardial ICD placement, 5 valve surgery (3 aortic valve, 2 mitral valve), 2 septal myectomy, 1 aortic arch replacement, 1 myocardial bridge unroofing and 1 myocardial perforation repair (3 patients had multiple procedures). Access was successful in 12 patients (66.7%); the inferior approach was utilized in 78%. Of patients with prior CABG, successful access was attained in 6 (60%). The average procedural time was 441.6 ± 141.3 minutes. Adhesiolysis was required in 10 patients with the sheath, access wire, pigtail catheter or ablation catheter. Intra-procedural coronary angiography was performed in 8 patients. There were a total of 45 VTs/PVCs ablated in 18 patients (average 2.5 ± 1.7), mean cycle length 463.6 ± 95.9ms. Ultimately, 12 patients (66.7%) underwent endocardial only ablation, 1 (5.5%) had epicardial only ablation while 5 (27.8%) had endocardial/epicardial ablation. The procedure was deemed successful in 13 patients (72.2%). Four patients had bleeding complications (pericardial effusion, pericardial hematoma, hemoperitoneum and pericardial tamponade [the latter required repair of the RV wall]). In patients with coronary grafts, there was no evidence of acute graft disruption. Conclusions: Percutaneous epicardial access is feasible in patients with previous cardiac surgery, including CABG. However, adhesiolysis is frequently required. Although the risk of coronary graft injury is low, life-threatening complications may occur.