David N. Kenigsberg

Histopathologic characterization of chronic radiofrequency ablation lesions for pulmonary vein isolation.

OBJECTIVES This study describes the histopathologic and electrophysiological findings in patients with recurrence of atrial fibrillation (AF) after pulmonary vein (PV) isolation who underwent a subsequent surgical maze procedure. BACKGROUND The recovery of PV conduction is commonly responsible for recurrence of AF after catheter-based PV isolation. METHODS Twelve patients with recurrent AF after acutely successful catheter-based antral PV isolation underwent a surgical maze procedure. Full-thickness surgical biopsy specimens were obtained from the PV antrum in areas of visible endocardial scar. Before biopsy, intraoperative epicardial electrophysiological recordings were taken from each PV using a circular mapping catheter. RESULTS Twenty-two PVs were biopsied from the 12 patients 8 ± 11 months after ablation. Eleven of the 22 specimens (50%) revealed transmural scar, and 11 (50%) showed viable myocardium with or without scar. Each biopsy specimen demonstrated evidence of injury, most commonly endocardial thickening (n = 21 [95%]) and fibrous scar (n = 18 [82%]). Seven of the 22 specimens (32%) showed conduction block at surgery. Transmural scar was more likely to be seen in the biopsy specimens from the PVs with conduction block than in specimens from the PVs showing reconnection. However, viable myocardium alone or mixed with scar was seen in 2 specimens from PVs with conduction block. CONCLUSIONS PVs showing electrical reconnection after catheter-based antral ablation frequently reveal anatomic gaps or nontransmural lesions at the sites of catheter ablation. Nontransmural lesions are noted in some PVs with persistent conduction block, suggesting that lesion geometry may influence PV conduction. The histological findings show that nontransmural ablation can produce a dynamic cellular substrate with features of reversible injury. Delayed recovery from injury may explain late recurrences of AF after PV isolation.

Quantification of the cryoablation zone demarcated by pre- and postprocedural electroanatomic mapping in patients with atrial fibrillation using the 28-mm second-generation cryoballoon.

BACKGROUND There are 2 Food and Drug Administration-approved catheters (ThermoCool RF and Arctic Front Advance cryoballoon) for the treatment of drug refractory and symptomatic paroxysmal atrial fibrillation. Each tool is used to ablate the area surrounding the pulmonary veins (PVs). However, no study has described and quantified the ablated surface area after the application of cryoablation lesions with the second-generation cryoballoon. OBJECTIVE The purpose of this study was to determine the area of ablation during cryoballoon PV isolation. METHODS Preprocedural computed tomography angiography of the left atrium (LA) was conducted in 43 patients to accurately determine spatial chamber dimensions. Before and after the ablation procedure, a detailed 3-dimensional electroanatomic map of the LA was created and merged onto the computed tomography angiogram to improve the accuracy of the data recordings. RESULTS The posterior LA wall had a mean surface area of 31.1 (±1.6 SEM) cm(2). Left- and right-sided antral PV surface areas of cryoballoon ablation were not statistically different (P = .935), which were 11.4 (±0.8 SEM) and 11.3 (±0.8 SEM) cm(2), respectively. In total, 27% of the posterior LA wall remained unablated, electrically functional, and homogeneous with regard to voltage conductivity. This ablation strategy resulted in 95.3% freedom from atrial fibrillation at 6 months. CONCLUSION The area of the posterior LA wall ablation with the cryoballoon catheter is wide and antral, and the resulting posterior LA wall debulking could be a part of the cryoballoon efficacy beyond discrete PV isolation.

Sensing Failure Associated with the Medtronic Sprint Fidelis Defibrillator Lead

Introduction: The diameter of implantable cardioverter‐defibrillator (ICD) leads has become progressively smaller over time. However, the long‐term performance characteristics of these smaller ICD leads are unknown.

Physiologic Pacing: More Answers, More Questions

Right ventricular apical (RVA) pacing is deleterious and may result in left ventricular dysfunction, heart failure, and increased mortality.1-5 Pacing from the RVA results in a left bundle branch block morphology, due to depolarization of the right ventricle prior to the left ventricle and from the apex to the base.6,7 It has been suggested that pacing the heart in a manner closer to the normal physiologic pattern of activation may reduce the incidence of these negative clinical outcomes.8,9 The determination of the best site(s) to pace has been a question that remains unanswered. Before we abandon right ventricular pacing altogether, it seems worthwhile to consider if there are other RV sites that should be evaluated. One of the potential sites that can be paced and results in near-normal depolarization of the heart is the septal aspect of the right ventricular outflow tract (RVOT).10-12 Septal RVOT pacing results in a reduced QRS duration when compared with RVA pacing.13-17 This translates into a shorter ventricular activation time and possibly less ventricular dyssynchrony. Furthermore, whereas RVA pacing has been shown to result in myofibrillar disarray and detrimental ultrastructural changes, septal pacing in canine hearts does not.18 All of these findings suggest a potentially less harmful role of RVOT pacing than RVA pacing. However, in order to draw any clinical conclusions, a comparison between different pacing sites is needed. In this issue of the Journal, Muto et al. report the results of the Effect of Pacing the Right Ventricular Mid-Septum tract in Patients with Permanent Atrial Fibrillation and Low Ejection Fraction study.19 This retrospective analysis of singlechamber right ventricular mid-septal (RVMS) pacing compared with RVA pacing in patients with an ejection fraction (EF) of less than or equal to 30% and permanent atrial fibrillation (AF) is the tipping point and aids in our understanding of “physiologic pacing.” In this study, patients with pacing of the RVMS experienced a significant improvement in NYHA class, EF, and quality of life measured at 18 months follow-up when compared with patients with RVA pacing. This study’s patient population, with over 100 subjects in each arm followed for 1.5 years, is an improvement from prior studies that have attempted to address this question

Intracardiac Correlate of the Epsilon Wave in a Patient With Arrhythmogenic Right Ventricular Dysplasia

A 29-year-old man with no significant past medical history presented to the emergency department of a local hospital with complaints of dyspnea and palpitations. A 12-lead ECG was obtained, revealing a wide complex tachycardia (QRS duration 160 ms) at a rate of 196 beats per minute with a right bundle-branch block morphology and left axis deviation. In the emergency department, the ECG was thought to represent supraventricular tachycardia, and the patient was given adenosine and diltiazem intravenously. This did not terminate or change the rate of the tachycardia. He was then given metoprolol 5 mg intravenously, and the tachycardia slowed and terminated. A 12-lead ECG in normal sinus rhythm is shown (Figure 1). Figure 1. Twelve-lead ECG in normal sinus rhythm. The findings include right atrial abnormality, normal QRS axis, anteroseptal Q waves, and precordial T-wave inversions. The most striking finding is the presence of an epsilon wave (black arrow) in V1 and V2. A …

ICD arrhythmia detection and discrimination: are we there yet?

Implantable cardioverter defibrillator (ICD) therapy is beneficial to patients who have experienced life-threatening ventricular arrhythmias (secondary prevention) and those at risk for ventricular arrhythmias due to the presence of structural heart disease (primary prevention).1-5 The DAVID trial suggested that dual-chamber ICDs programmed to “force” ventricular pacing result in an increase in morbidity and mortality.6 The increased costs and added complexity of dualchamber ICDs, along with results from DAVID and other trials, have lead to the recommendation that, in the absence of a pacing indication, single-chamber ICDs should be implanted and programmed to permit intrinsic ventricular activation and avoid right ventricular pacing.7 ICD technology has evolved to allow more accurate rhythm detection to avoid inappropriate shocks. There are, however, differences in the sensitivity and specificity of ventricular tachycardia (VT) detection dependent on the specific device programming, the type of device (single vs dual chamber), and the clinical arrhythmia. Furthermore, expectations related to the ability of the device to detect and provide therapy are different, dependent on the clinical arrhythmia. For example, ICD detection of ventricular fibrillation (VF) must have high sensitivity, as the consequences of underdetection are potentially fatal.8 In contrast, detection algorithms for ventricular tachycardia (VT) must balance the risks of underdetection with the painful, psychologically troubling, and potentially proarrhythmic consequences of inappropriate therapy.9-17 A highly sensitive detection algorithm is appropriate for faster tachycardias because the risks of underdetection are high and the probability of rate-zone overlap with supraventricular tachycardia (SVT) is low. On the other hand, a highly specific algorithm is appropriate for hemodynamically stable, slower VT because the risks of underdetection are low and the probability of rate-zone overlap with SVT is high. Historically, when tiered-therapy ICDs detected VT by rate criteria only, inappropriate therapy for SVT occurred in 45% of patients.8 The problem of inappropriate therapy was greater for tiered-therapy ICDs because the probability of rate overlap between the target VT and SVT was greater. Pacing therapies delivered during SVT could potentially induce VT; or could induce atrial fibrillation, which in turn could be sensed as VT and treated with pacing, reinitiating VT.

Mechanisms of Undersensing by a Noise Detection Algorithm That Utilizes Far‐Field Electrograms With Near‐Field Bandpass Filtering

Implantable cardioverter defibrillators (ICDs) must establish a balance between delivering appropriate shocks for ventricular tachyarrhythmias and withholding inappropriate shocks for lead‐related oversensing (“noise”). To improve the specificity of ICD therapy, manufacturers have developed proprietary algorithms that detect lead noise. The SecureSenseTM RV Lead Noise discrimination (St. Jude Medical, St. Paul, MN, USA) algorithm is designed to differentiate oversensing due to lead failure from ventricular tachyarrhythmias and withhold therapies in the presence of sustained lead‐related oversensing.

Anti-arrhythmic medications increase non-cardiac mortality - A meta-analysis of randomized control trials.

Anti‐arrhythmic medications (AAMs) are known to increase cardiac mortality significantly due to their pro‐arrhythmic effects. However, the effect of AAMs on non‐cardiac mortality has not been evaluated.

Reply to the Editor—The merit of real-world ‘clinical’ research vs the promise of ‘pre-clinical’ future developments

1 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 Given the recent data/publications illustrating that prolonged cryoapplications are associated with increased adverse events (atrio-esophageal fistula, bronchial injury), cryoablation dosing can impact both procedural efficacy and safety. Hence, there is an immense need for a “dosing algorithm” to help standardize the procedure. We previously examined procedural/biophysical markers of durable pulmonary vein isolation (PVI) and discovered that time to PVI represented the most powerful indicator of this endpoint. Consequently, this was chosen in our study to guide cryoablation dosing, whereas cryoapplication durations were derived from preceding preclinical work. But arguably, no single marker to date has emerged as the gold standard, and the same applies to radiofrequency. Whereas traditionally, parameters such as power and impedance have been used, recent data suggest that multiparametric indices (ie, lesion size index) that incorporate multiple biophysical markers are more precise than each of their individual components alone. Accordingly, we recently proposed a more comprehensive model incorporating the most powerful procedural/biophysical cryoablation predictors of PVI (ie, time to PVI 60 seconds and interval thaw time at 0 C [iTT0] 10 seconds) and showed that this model highly predicted PVI durability (.99%). Although there may be a future role for measures such as “impedance of ice formation,” which represent “preclinical” research based on manufacturer-designed concept catheters, contemporary practice must be based on “clinical”/currently avail-