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Background Data related to electrophysiologic characteristics of atypical atrial flutter (AFL) following atrial fibrillation (AF) ablation and its prognostic value on repeat ablation success are limited. Methods We studied consecutive patients who underwent a repeat left atrial (LA) ablation procedure for either recurrent AF or atypical AFL, at least 3 months after index AF ablation, between January 2012 and July 2019. The demographics, clinical history, procedural data, complications, and 1-year arrhythmia-free survival rates were recorded for each subject after the first repeat ablation. Results A total of 336 patients were included in our study. Among these 336 patients, 102 underwent a repeat ablation procedure for atypical AFL and 234 underwent a repeat ablation procedure for recurrent AF. The mean age was 63.7 ± 10.7 years, and 72.6% of patients were men. The atypical AFL cohort had significantly higher LA diameters (4.6 vs. 4.4 cm, p = .04) and LA volume indices (LAVi; 85.1 vs. 75.4 ml/m2 , p = .03) compared to AF patients at repeat ablation. Atypical AFL patients were more likely to have had index radiofrequency (RF) ablation (as opposed to cryoballoon) than recurrent AF patients (98% vs. 81%, p = .01). Atypical AFLs were roof-dependent in 35.6% and peri-mitral in 23.8% of cases. Major complications at repeat ablation occurred in 0.9% of the total cohort. Arrhythmia-free survival at one year was significantly higher in the recurrent atypical AFL compared to the recurrent AF cohort (75.5 vs. 65.0%, p = .04). Conclusion In our series, roof-dependent flutter is the most common form of atypical atrial flutter post AF ablation. Patients developing atypical AFL after index AF ablation have greater LA dimensions than patients with recurrent AF. The success rate of first repeat ablation is significantly higher among patients with recurrent atypical AFL as compared to recurrent AF after index AF ablation.

BACKGROUND Left atrial appendage (LAA) closure with the Watchman device is increasingly used in patients with nonvalvular atrial fibrillation for stroke prevention. Though clinical trials have shown a similar combined risk of ischemic and hemorrhagic stroke, there is an increased risk of ischemic stroke in patients with a Watchman device compared with anticoagulation. Some ischemic strokes are related to a device-related thrombus (DRT), which may be attributable to delayed endothelialization of exposed fabric and metal. METHODS AND RESULTS Patients undergoing Watchman LAA occlusion between January 2016 and June 2018 were enrolled in a prospective registry. From this cohort, 46 patients who had both transesophageal echocardiogram (TEE) and computed tomography (CT) at 45 days follow-up were selected for this study. The degree of LAA occlusion and type of leak were assessed by CT and TEE. TEE identified no patients with a significant (>5 mm) peri-device leak, 27 (58.6%) with nonsignificant peri-device leak (

RationalePatients with ischemic cardiomyopathy (ICMP) are at high risk for malignant arrhythmias, largely due to electrophysiological remodeling of the non-infarcted myocardium. The electrophysiological properties of the non-infarcted myocardium of patients with ICMP remain largely unknown.ObjectivesTo assess the pro-arrhythmic behavior of non-infarcted myocardium in ICMP patients and couple computational simulations with machine learning to establish a methodology for the development of disease-specific action potential models based on clinically measured action potential duration restitution (APDR) data.Methods and ResultsWe enrolled 22 patients undergoing left-sided ablation (10 ICMP) and compared APDRs between ICMP and structurally normal left ventricles (SNLVs). APDRs were clinically assessed with a decremental pacing protocol. Using genetic algorithms (GAs), we constructed populations of action potential models that incorporate the cohort-specific APDRs. The variability in the populations of ICMP and SNLV models was captured by clustering models based on their similarity using unsupervised machine learning. The pro-arrhythmic potential of ICMP and SNLV models was assessed in cell- and tissue-level simulations. Clinical measurements established that ICMP patients have a steeper APDR slope compared to SNLV (by 38%, p < 0.01). In cell-level simulations, APD alternans were induced in ICMP models at a longer cycle length compared to SNLV models (385–400 vs 355 ms). In tissue-level simulations, ICMP models were more susceptible for sustained functional re-entry compared to SNLV models.ConclusionMyocardial remodeling in ICMP patients is manifested as a steeper APDR compared to SNLV, which underlies the greater arrhythmogenic propensity in these patients, as demonstrated by cell- and tissue-level simulations using action potential models developed by GAs from clinical measurements. The methodology presented here captures the uncertainty inherent to GAs model development and provides a blueprint for use in future studies aimed at evaluating electrophysiological remodeling resulting from other cardiac diseases.

The purpose of this study was to evaluate the usefulness of intra-atrial dyssynchrony as a marker of underlying left atrial (LA) remodeling to predict recurrence after the first atrial fibrillation (AF) ablation.Catheter ablation for AF remains far from curative with relatively high recurrence rates. One of the causes of recurrence is poor patient selection out of a diverse patient population with different degrees of LA remodeling.We included 208 patients with a history of AF (59.4 ± 10.0 years of age; 26.0% nonparoxysmal AF) referred for catheter ablation of AF who underwent pre-ablation cardiac magnetic resonance in sinus rhythm. Clinical follow-up was 20 ± 6 months. Using tissue tracking cardiac magnetic resonance, we measured the LA longitudinal strain in each of 12 equal-length segments in 2- and 4-chamber views. We defined intra-atrial dyssynchrony as the standard deviation of the time to the peak longitudinal strain corrected by the cycle length (SD-time to peak strain [TPS], %).Patients with AF recurrence after ablation (n = 101) had significantly higher SD-TPS than those without (n = 107; 3.9% vs. 2.2%; p 0.001). Multivariable cox analysis showed that SD-TPS was associated with recurrence after adjusting for clinical risk factors, AF type, LA structure and function, and fibrosis (p 0.001). Furthermore, receiver-operating characteristics analysis showed SD-TPS improved prediction of recurrence better than clinical risk factors, LA structure and function, and fibrosis.Intra-atrial dyssynchrony during sinus rhythm is an independent predictor of recurrence after the first catheter ablation of paroxysmal or persistent AF. Assessment of intra-atrial dyssynchrony may improve ablation outcomes by refining patient selection.

BACKGROUND Pacemaker patients experience battery depletion that activates pacemaker's alert for replacement notification. Automatic reprogramming at replacement notification can result in loss of rate response and atrioventricular (AV) synchrony. OBJECTIVE To determine if relevant symptoms or clinical events may be associated with automatic reprogramming at replacement notification. METHODS Electronic medical record review was undertaken for 298 patients referred for pacemaker generator replacement. Primary endpoints were symptoms or clinical events during replacement notification period. RESULTS Following elimination of duplicate pacemaker replacements (n = 12), "near-replacement notification" or "recalled" (n = 15) and pacemakers at "end of life" (n = 5), 266 subjects were included. Three distinct reprogramming cohorts were identified; those with no change (control) in pacing mode (n = 46), those with loss of rate response (n = 154), and those with loss of AV synchrony ± rate response (n = 66). In total, 83 subjects (31.2%) had symptoms with significant differences seen between groups (control = 4.3%, loss of rate response = 26.0%, loss of AV synchrony ± rate response = 62.1%, P

Aims Historically, cardiac resynchronization therapy (CRT) response in non-left bundle branch block (non-LBBB) patients has been suboptimal in comparison with that observed in left bundle branch block patients. The electrical activation pattern of the left ventricle (LV) is different between these two QRS morphologies. Small non-randomized studies have suggested that targeting the LV wall with greatest electrical delay may be superior to conventional anatomical pacing from the lateral wall in non-LBBB patients. This article outlines the design and rationale of a prospective, randomized, pilot study, which assesses the effect of a non-traditional LV lead implant strategy on the clinical composite score after 12 months of follow-up in a non-LBBB patient population. Methods All patients will receive an Abbott quadripolar CRT-D system (Quartet 1458Q LV lead with Unify Quadra™, Quadra Assura™ CRT-D or any market-approved CRT-D device with quadripolar pacing capabilities). Patients will be randomized in a 2:1 ratio between a QLV-based implant strategy vs. standard of care. Up to 250 patients will be enrolled in the study. Conclusions If the primary endpoint is achieved, this study will provide important information about reducing the non-responder rate in non-LBBB patients and provide further evidence for the QLV-based implant strategy.

Background Patients go without pacemaker, defibrillator, and cardiac resynchronization therapies (devices) each year due to the prohibitive costs of devices. Objective We sought to examine data available from studies regarding contemporary risks of reused devices in comparison with new devices. Methods We searched online indexing sites to identify recent studies. Peer-reviewed manuscripts reporting infection, malfunction, premature battery depletion, and device-related death with reused devices were included. The primary study outcome was the composite risk of infection, malfunction, premature battery depletion, and death. Secondary outcomes were the individual risks. Results Nine observational studies (published 2009-2017) were identified totaling 2,302 devices (2,017 pacemakers, 285 defibrillators). Five controlled trials were included in meta-analysis (2,114 devices; 1,258 new vs 856 reused). All device reuse protocols employed interrogation to confirm longevity and functionality, disinfectant therapy, and, usually, additional biocidal agents, packaging, and ethylene oxide gas sterilization. Demographic characteristics, indications for pacing, and median follow-up were similar. There were no device-related deaths reported and no statistically significant difference in risk between new versus reused devices for the primary outcome (2.23% vs 3.86% respectively, P = 0.807, odds ratio = 0.76). There were no significant differences seen in the secondary outcomes for the individual risks of infection, malfunction, and premature battery depletion. Conclusions Device reuse utilizing modern protocols did not significantly increase risk of infection, malfunction, premature battery depletion, or device-related death in observational studies. These data provide rationale for proceeding with a prospective multicenter noninferiority randomized control trial.

AIMS Prior studies identified a relationship between epicardial bipolar and endocardial unipolar voltage. Whether the relationship is valid with smaller multielectrode mapping catheters has not been reported. We explored the association of right ventricular (RV) endocardial unipolar voltage mapping with epicardial bipolar voltage mapping using a multielectrode mapping catheter. METHODS Electrograms from patients who underwent multielectrode endocardial and epicardial RV electroanatomical mapping during ablation procedures were analyzed. Each endocardial mapping point was matched to the corresponding nearest epicardial point. The correlation between unipolar endocardial voltage and epicardial bipolar voltage was determined. The optimal unipolar threshold to detect epicardial low voltage (

Atrial fibrillation (AF) is a commonly sustained atrial arrhythmia with associated morbidity and mortality. AF is associated with increased risk of thromboembolism and stroke, requiring use of anticoagulation. Anticoagulation decreases the risk of stroke but is associated with a higher risk of bleeding, necessitating discontinuation in some patients. The left atrial appendage is the likely source of thrombus in the majority of patients with AF. This has led to the development of left atrial appendage occlusion as a means to reduce stroke risk in patients who have a contraindication to long‐term anticoagulation. Multiple implantable devices have surfaced in the last few years, with some promising prospects. The main purpose of this review is to highlight the indications and use of these devices for left atrial appendage occlusion.

All contemporary pacemakers undergo automatic reprogramming upon reaching elective replacement indication due to battery depletion. The majority of such reprogramming will result in changes to both pacing mode and pacing rate. The exact software reprogramming varies considerably among pacemaker manufacturers and may even vary among models of the same manufacturer. Accordingly, it is essential for healthcare providers managing pacemaker patients to have a detailed understanding of the automatic reprogramming seen at elective replacement indication as well as their potential physiological and clinical consequences.

Introduction The interplay between electrical activation and mechanical contraction patterns is hypothesized to be central to reduced effectiveness of cardiac resynchronization therapy (CRT). Furthermore, complex scar substrates render CRT less effective. We used novel cardiac computed tomography (CT) and non-invasive electrocardiographic imaging (ECGI) techniques in an ischemic dyssynchronous heart failure (DHF) animal model to evaluate electrical and mechanical coupling of cardiac function, tissue viability and venous accessibility of target pacing regions. Methods and Results Ischemic DHF was induced in 6 dogs using coronary occlusion, left bundle ablation and tachy RV pacing. Full body ECG was recorded during native rhythm followed by volumetric first-pass and delayed enhancement CT. Regional electrical activation were computed and overlaid with segmented venous anatomy and scar regions. Reconstructed electrical activation maps show consistency with LBBB starting on the RV and spreading in a “U-shaped” pattern to the LV. Previously reported lines of slow conduction are seen parallel to anterior or inferior inter-ventricular grooves. Mechanical contraction showed large septal to lateral wall delay (80±38 vs 123 ± 31 ms, p = 0.0001). All animals showed electromechanical correlation except dog 5 with largest scar burden. Electromechanical decoupling was largest in basal lateral LV segments. Conclusion We demonstrated a promising application of CT in combination with ECGI to gain insight into electromechanical function in ischemic dyssynchronous heart failure that can provide useful information to study regional substrate of CRT candidates. This article is protected by copyright. All rights reserved

The aims of this study were to: 1) use a novel method of late gadolinium enhancement (LGE) quantification that uses normalized intensity measures to confirm the association between LGE extent and atrial fibrillation (AF) recurrence following ablation; and 2) examine the presence of interaction and effect modification between LGE and AF persistence.Recurrent AF after catheter ablation has been reported to associate with the baseline extent of left atrial LGE on cardiac magnetic resonance. Traditional methods for measurement of intensity lack an objective threshold for quantification and interpatient comparisons of LGE.The cohort included 165 participants (mean age 60.0 ± 10.2 years, 77% men, 57% with persistent AF) who underwent initial AF ablation. The association of baseline LGE extent with AF recurrence was examined using multivariable Cox proportional hazards models. Multiplicative and additive interactions between AF type and LGE extent were examined.During 10.2 ± 5.7 months of follow-up, 63 patients (38.2%) experienced AF recurrence. Baseline LGE extent was independently associated with AF recurrence after adjusting for confounders (hazard ratio: 1.5 per 10% increased LGE; p 0.001). The hazard ratio for AF recurrence progressively increased as a function of LGE. The magnitude of association between LGE35% and AF recurrence was greater among patients with persistent AF (hazard ratio: 6.5 [p = 0.001] vs. 3.6 [p = 0.001]); however, there was no evidence for statistical interaction.Regardless of AF persistence at baseline, participants with LGE ≤35% have favorable outcomes, whereas those with LGE35% have a higher rate of AF recurrence in the first year after ablation. These findings suggest a role for: 1) patient selection for AF ablation using LGE extent; and 2) substrate modification in addition to pulmonary vein isolation in patients with LGE extent exceeding 35% of left atrial myocardium.

Background Catheter ablation utilizing radiofrequency (RF), Cryothermal (Cryo), or Laser energy is effective for treatment of atrial fibrillation (AF). Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) has been used to estimate the burden of left atrial (LA) fibrosis, but no data exist regarding structural changes following each modality. We sought to compare the baseline to postprocedure change in LA scar burden following RF, Cryo, or Laser ablation for treatment of AF. Methods Seventeen patients with AF underwent initial pulmonary vein (PV) isolation (PVI) using RF (n = 7), Cryo (n = 5), and Laser (n = 5). LGE-MRI was performed prior to and at 24 hours and 3 months after PVI. Results In a linear mixed-effects model, accounting for intrapatient clustering of data and interpatient differences in baseline scar, LGE extent was significantly increased at 24 hours postablation (+14.6 ± 1.9% of LA myocardium, P < 0.001), and remained stable from 24 hours to 3 months (+0.12 ± 1.9%, P = 0.951). There was no statistically significant difference between the postablation scar extent among ablation modalities when compared to RF (Cryo +4.5 ± 3.0%, P = 0.123; Laser −3.2 ± 3.0%, P = 0.291). The PV antral LGE intensity was increased by 25.1 ± 3.8% (P

Mercury affects the nervous system and has been implicated in altering heart rhythm and function. We sought to better define its role in modulating heart rate variability, a well-known marker of cardiac autonomic function.This is a systematic review study.We searched PubMed, Embase, TOXLINE, and DART databases without language restriction. We report findings as a qualitative systematic review because heterogeneity in study design and assessment of exposures and outcomes across studies, as well as other methodological limitations of the literature, precluded a quantitative meta-analysis.We identified 12 studies of mercury exposure and heart rate variability in human populations (ten studies involving primarily environmental methylmercury exposure and two studies involving occupational exposure to inorganic mercury) conducted in Japan, the Faroe Islands, Canada, Korea, French Polynesia, Finland, and Egypt. The association of prenatal mercury exposure with lower high-frequency band scores (thought to reflect parasympathetic activity) in several studies, in particular the inverse association of cord blood mercury levels with the coefficient of variation of the R-R intervals and with low-frequency and high-frequency bands at 14 years of age in the Faroe Islands birth cohort study, suggests that early mercury exposure could have a long-lasting effect on cardiac parasympathetic activity. Studies with later environmental exposures to mercury in children or in adults were heterogeneous and did not show consistent associations.The evidence was too limited to draw firm causal inferences. Additional research is needed to elucidate the effects of mercury on cardiac autonomic function, particularly as early-life exposures might have lasting impacts on cardiac parasympathetic function.

Despite the revolutionary advancements in the past 3 decades in the treatment of ventricular tachyarrhythmias with device-based therapy, sudden cardiac death (SCD) remains an enormous public health burden. Survivors of SCD are generally at high risk for recurrent events. The clinical management of such patients requires a multidisciplinary approach from postresuscitative care to a thorough cardiovascular investigation in an attempt to identify the underlying substrate, with potential to eliminate or modify the triggers through catheter ablation and ultimately an implantable cardioverter-defibrillator (ICD) for prompt treatment of recurrences in those at risk. Early recognition of low left ventricular ejection fraction as a strong predictor of death and association of ventricular arrhythmias with sudden death led to significant investigation with antiarrhythmic drugs. The lack of efficacy and the proarrhythmic effects of drugs catalyzed the development and investigation of the ICD through several major clinical trials that proved the efficacy of ICD as a bedrock tool to detect and promptly treat life-threatening arrhythmias. The ICD therapy is routinely used for primary prevention of SCD in patients with cardiomyopathy and high risk inherited arrhythmic conditions and secondary prevention in survivors of sudden cardiac arrest. This compendium will review the clinical management of those surviving SCD and discuss landmark studies of antiarrhythmic drugs, ICD, and cardiac resynchronization therapy in the primary and secondary prevention of SCD.

"2 for 1 phenomenon" is simultaneous anterograde conduction over the fast and slow pathways of the atrioventricular (AV) nodal pathway, leading to a double ventricular response from each atrial beat. This phenomenon can initiate AV nodal reentrant tachycardia (AVNRT). The unique induction of AVNRT was observed in a patient with an implantable cardioverter defibrillator in our case. Minimal to no retrograde invasion of the slow pathway from the anterogradely conducted fast pathway depolarization is the most accepted explanation.

It is known that expanded epicardial fat is associated with atrial fibrillation (AF). However, infiltrated intraatrial fat has not been previously quantified in individuals at risk as determined by the ARIC AF risk score.Patients in sinus rhythm (N=90, age 57 ± 10 years; 55 men [63.2%]), in 3 groups at risk of AF as determined by the ARIC AF risk score [low (≤ 11 points; n=15), moderate (12-18 points; n=40), high (≥ 19 points; n=23) risk of AF], and paroxysmal AF (n=12) underwent cardiac magnetic resonance study. Intraatrial and epicardial fat was analyzed with a Dark-blood DIR-prepared Fat-Water-separated sequence in the horizontal longitudinal axis. OsiriX DICOM viewer (Geneva, Switzerland) was used to quantify the intraatrial fat area. Width of the cephalad portion of the interatrial septum was measured at the level of the fossa ovalis.Intraatrial fat monotonically increased with growing AF risk in study groups (low AF risk 16 ± 4 vs. moderate AF risk 32 ± 18 vs. high AF risk 81 ± 83 mm(2); ANOVA P=0.012). Log-transformed intraatrial fat predicted ARIC AF risk score in multivariate ordered probit regression after adjustment for sex, race, left and right atrial area indices, and body mass index (β-coefficient 0.50 [95% CI 0.03-0.97]; P=0.037), whereas epicardial fat did not. Interatrial septum width showed similar association (3.0 ± 1.4 vs. 5.0 ± 1.8 vs. 7.1 ± 2.7 mm; ANOVA P0.001; adjusted β-coefficient 2.80 [95% CI 1.19-4.41]; P=0.001).Infiltrated intraatrial fat characterizes evolving substrate in individuals at risk of AF.

Previous studies showed that the quantity of the left atrial (LA) periatrial fat tissue predicts recurrence after catheter ablation of atrial fibrillation (AF). We hypothesized that the quality of the LA periatrial fat tissue, measured by the mean computed tomography (CT) attenuation, predicts

Dofetilide is a class III antiarrhythmic requiring hospitalization for initiation due to the risk for torsades de pointes (TdP) ventricular tachycardia early in therapy. Dofetilide is subject to many drug interactions, which may increase the risk for intolerance. This is a single-center

Background The measurement of late gadolinium–enhanced magnetic resonance imaging (LGE-MRI) intensity in arbitrary units limits the objectivity of thresholds for focal scar detection and interpatient comparisons of scar burden. Objective To develop and validate a normalized measure, the image intensity ratio (IIR), for the assessment of left atrial (LA) scar on LGE-MRI. Methods Electrocardiogram- and respiratory-gated 1.5 Tesla LGE-MRI was performed in 75 patients (75% men; 62 ± 8 years) before atrial fibrillation ablation. The local IIR was defined as LA myocardial signal intensity for each of the 20 sectors on contiguous axial image planes divided by the mean LA blood pool image intensity. Intracardiac point-by-point sampled electroanatomic map points were coregistered with the corresponding image sectors. Results The average bipolar voltage for all 8153 electroanatomic map points was 0.9 ± 1.1 mV. In a mixed effects model accounting for within patient clustering, and adjusting for age, LA volume, mass, body mass index, sex, CHA 2 DS 2 -VASc score, atrial fibrillation type, history of previous ablations, and contrast delay time, each unit increase in local IIR was associated with 91.3% decrease in bipolar LA voltage ( P 0.97 and >1.61 corresponded to bipolar voltage Conclusions Normalization of LGE-MRI intensity by the mean blood pool intensity results in a metric that is closely associated with intracardiac voltage as a surrogate of atrial fibrosis.

Background Previous studies suggest that magnetic resonance imaging with late gadolinium enhancement (LGE) may identify slowly conducting tissues in scar-related ventricular tachycardia (VT). Objective To test the feasibility of image-based simulation based on LGE to estimate ablation targets in VT. Methods We conducted a retrospective study in 13 patients who had preablation magnetic resonance imaging for scar-related VT ablation. We used image-based simulation to induce VT and estimate target regions according to the simulated VT circuit. The estimated target regions were coregistered with the LGE scar map and the ablation sites from the electroanatomical map in the standard ablation approach. Results In image-based simulation, VT was inducible in 12 (92.3%) patients. All VTs showed macroreentrant propagation patterns, and the narrowest width of estimated target region that an ablation line should span to prevent VT recurrence was 5.0 ± 3.4 mm. Of 11 patients who underwent ablation, the results of image-based simulation and the standard approach were consistent in 9 (82%) patients, where ablation within the estimated target region was associated with acute success (n = 8) and ablation outside the estimated target region was associated with failure (n = 1). In 1 (9%) case, the results of image-based simulation and the standard approach were inconsistent, where ablation outside the estimated target region was associated with acute success. Conclusions The image-based simulation can be used to estimate potential ablation targets of scar-related VT. The image-based simulation may be a powerful noninvasive tool for preprocedural planning of ablation procedures to potentially reduce the procedure time and complication rates.

Introduction Phrenic nerve injury (PNI) is a well-known, although uncommon, complication of pulmonary vein isolation (PVI) using radiofrequency energy. Currently, there is no consensus about how to avoid or minimize this injury. The purpose of this study was to determine how often the phrenic nerve, as identified using a high-output pacing, lies along the ablation trajectory of a wide-area circumferential lesion set. We also sought to determine if PVI can be achieved without phrenic nerve injury by modifying the ablation lesion set so as to avoid those areas where phrenic nerve capture (PNC) is observed. Methods and results We prospectively enrolled 100 consecutive patients (age 61.7 ± 9.2 years old, 75 men) who underwent RF PVI using a wide-area circumferential ablation approach. A high-output (20 mA at 2 milliseconds) endocardial pacing protocol was performed around the right pulmonary veins and the carina where a usual ablation lesion set would be made. A total of 30% of patients had PNC and required modification of ablation lines. In the group of patients with PNC, the carina was the most common site of capture (85%) followed by anterior right superior pulmonary vein (RSPV) (70%) and anterior right inferior pulmonary vein (RIPV) (30%). A total of 25% of PNC group had capture in all 3 (RSPV, RIPV, and carina) regions. There was no difference in the clinical characteristics between the groups with and without PNC. RF PVI caused no PNI in either group. Conclusion High output pacing around the right pulmonary veins and the carina reveals that the phrenic nerve lies along a wide-area circumferential ablation trajectory in 30% of patients. Modification of ablation lines to avoid these sites may prevent phrenic nerve injury during RF PVI.

Background We recently demonstrated that high frequency alternating current (HFAC) electric fields can reversibly block propagation in the heart by inducing an oscillating, elevated transmembrane potential (V m ) that maintains myocytes in a refractory state for the field duration and can terminate arrhythmias, including ventricular fibrillation (VF). Objectives To quantify and characterize conduction block (CB) induced by HFAC fields and to determine whether the degree of CB can be used to predict defibrillation success. Methods Optical mapping was performed in adult guinea pig hearts (n = 14), and simulations were performed in an anatomically accurate rabbit ventricular model. HFAC fields (50–500 Hz) were applied to the ventricles. A novel power spectrum metric of CB—the loss of spectral power in the 1–30 Hz range, termed loss of conduction power (LCP)—was assessed during the HFAC field and compared with defibrillation success and VF vulnerability. Results LCP increased with field strength and decreased with frequency. Optical mapping experiments conducted on the epicardial surface showed that LCP and the size of CB regions were significantly correlated with VF initiation and termination. In simulations, subsurface myocardial LCP and CB sizes were more closely correlated with VF termination than surface values. Multilinear regression analysis of simulation results revealed that while CB on both the surface and the subsurface myocardium was predictive, subsurface myocardial CB was the better predictor of defibrillation success. Conclusions HFAC fields induce a field-dependent state of CB, and defibrillation success is related to the degree and location of the CB.

The Effect of Antiarrhythmic Drugs Ablation Outcomes Background Patients commonly present for atrial fibrillation (AF) ablation while taking antiarrhythmic (AA) medications. It is unknown if AA use at the time of ablation affects procedural outcome. This study compares the AF ablation outcomes of patients who underwent ablation while on AA medications to those who were not on AA medications. Methods and Results A total of 180 consecutive patients who underwent their first catheter ablation of AF were identified from the Johns Hopkins Hospital AF registry and divided into 2 cohorts: those On AA at the time of ablation (127 patients, mean follow-up 24.6 months) and those Off AA at the time of ablation (53 patients, mean follow-up 20.3 months). Follow-up was performed to identify recurrent AF. There was no statistically significant difference in the percentage of patients without a recurrence of symptomatic AF (single procedure success rate) in the On and Off AA groups at 6 months postablation (53.5% vs 50.1%, P = 0.75), or by the end of follow-up (37.8% vs 41.5%, P = 0.64). For those patients who had symptomatic AF recurrence, the average time to recurrence was 6.2 ± 9.0 months in the On AA group and 4.2 ± 7.2 months in the Off AA group (P = 0.27). Conclusions There was no statistically significant difference in the rate of symptomatic AF recurrence between the On AA and Off AA groups in this study. The use of AA medications at the time of ablation does not appear to affect procedural outcomes in this population.

Objectives The aim of this study was to assess the feasibility of real-time computed tomographic (CT) imaging to guide the percutaneous placement of left ventricular (LV) leads in an animal model. Background Cardiac resynchronization therapy has been shown to improve morbidity and mortality in patients with chronic heart failure. However, placement of the coronary sinus lead can be challenging and may require a more aggressive surgical approach. Methods Nine swine were placed in a real-time CT scanner to define the safest percutaneous access strategy. Under real-time CT guidance, a 3.5-F pacing lead was placed percutaneously in the anterolateral LV epicardium (n = 6 swine) or to the posterolateral wall after the creation of intentional left pneumothorax (n = 3 swine) in a tangential (n = 12) or perpendicular (n = 1) approach. Pacing parameters and CT images were assessed during 30-min follow-up. Necropsy findings were compared with real-time CT images. Results CT imaging successfully defined the safest percutaneous access route in all 13 lead placements and guided the therapeutic creation of pneumothoraces. Needle trajectory remained within 5 mm of the access route defined on CT imaging. LV lead placement under CT guidance was successful in all attempts within 19 ± 7 min. The mean pacing thresholds was 2.5 ± 1.5 V, the mean R wave amplitude was 11.2 ± 5.6 mV, and the mean impedance was 686 ± 103 Ω and remained unchanged after tangential placement during 30-min follow-up. Although no cardiac complications were observed with tangential lead placement (12 of 12), the perpendicular approach resulted in a pericardial effusion requiring pericardiocentesis. At necropsy, CT images correlated well with the in situ pathological results. Conclusions Percutaneous placement of LV pacing leads under CT guidance is feasible and might offer an alternative to more invasive surgical approaches in patients with complicated coronary sinus lead placement.

"2 for 1 phenomenon" is simultaneous anterograde conduction over the fast and slow pathways of the atrioventricular (AV) nodal pathway, leading to a double ventricular response from each atrial beat. This phenomenon can initiate AV nodal reentrant tachycardia (AVNRT). The unique induction of AVNRT was observed in a patient with an implantable cardioverter defibrillator in our case. Minimal to no retrograde invasion of the slow pathway from the anterogradely conducted fast pathway depolarization is the most accepted explanation.

Increased repolarization lability is known to be associated with the risk of ventricular tachycardia (VT)/ventricular fibrillation (VF). Premature ventricular contractions (PVCs) are excluded from the analysis of QT variability. However, QT dynamics after PVCs is poorly understood.We analyzed data of 33 patients with structural heart disease (mean age 60.5 ± 12.1; 24 (73%) men; 26 (79%) whites; 22 (67%) ischemic cardiomyopathy) and single-chamber ICD implanted for primary (28 patients, 85%) or secondary prevention of SCD. Arrhythmia group comprised 16 patients with VT/VF/death outcomes. Alive patients (n = 17) without VT/VF served as controls. The baseline far-field (FF) ICD electrogram (EGM) was recorded at rest. RR and QT intervals of 15 sinus beats before and after PVC in 33 patients were analyzed. The prematurity index, C(i)Mean(RR), where C(i) is coupling interval, was used to select the most premature PVC. QT variability index (QTVI) was calculated. Difference in QTVI was calculated as QTVI(diff) = QTVI(after)-QTVI(before.)In paired analysis QTVI significantly increased after PVC in controls (0.64 ± 1.02 vs. 0.26 ± 1.15; P = 0.046), but decreased in patients in the arrhythmia group (0.16 ± 0.85 vs. 0.43 ± 0.84; P = 0.190). QTVI(diff) was significantly lower in patients with VT/VF, as compared to controls (-0.197 ± 0.650 vs. 0.207 ± 0.723; P=0.030). In multivariate logistic regression after adjustment for the type of cardiomyopathy and NYHA class the decrease in QTVI after PVC was associated with increased risk of VT/VF (OR 9.24; 95% CI 1.11-76.82; P=0.040).Elevated at baseline QTVI is decreased during first 15 beats after PVC in patients at risk for VT/VF.

The clinical importance of the J-point elevation on electrocardiogram is controversial.To study intracardiac J-point amplitude before ventricular arrhythmia.Baseline 12-lead electrocardiogram and far-field right ventricular intracardiac implantable cardioverter-defibrillator electrograms were recorded at rest in 494 patients (mean age 60.4 ± 13.1 years; 360 [72.9%] men) with structural heart disease (278 [56.3%] ischemic cardiomyopathy) who received primary (463 [93.9%] patients) or secondary prevention implantable cardioverter-defibrillator. Ten-second intracardiac far-field electrograms before the onset of arrhythmia were compared with the baseline. The J-point amplitude was measured on the baseline 12-lead surface electrocardiogram and the intracardiac far-field electrogram. The relative J-point amplitude was calculated as the ratio of J-point amplitude to peak-to-peak R-wave.The paired t test showed that the relative intracardiac J-point amplitude was significantly higher before polymorphic ventricular tachycardia/ventricular fibrillation (VF) onset (0.28 ± 0.08 vs -0.19 ± 0.39; P = .012) than at baseline. In a mixed-effects logistic regression model, adjusted for multiple episodes per patient, each 10% increase in relative J-point amplitude increased the odds of having ventricular tachycardia/VF by 13% (odds ratio 1.13 [95% confidence interval 1.07-1.19]; P.0001) and increased the odds of having polymorphic ventricular tachycardia/VF by 27% (odds ratio 1.27 [95% confidence interval 1.11-1.46]; P = .001).The relative intracardiac J-point amplitude is augmented immediately before the onset of polymorphic ventricular tachycardia/VF in patients with structural heart disease.

Background— The goal of the present study was to determine the predictive value of beat-to-beat QT variability in heart failure patients across the continuum of left ventricular dysfunction. Methods and Results— Beat-to-beat QT variability index (QTVI), log-transformed heart rate variance, normalized QT variance, and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca heart failure study (mean age, 63.1±11.7; men, 70.6%; left ventricular ejection fraction >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death (subhazard ratio, 1.67 [95% CI, 1.14–2.47]; P =0.009) and, in particular, with non-SCD (subhazard ratio, 2.91 [1.69–5.01]; P P =0.031) and non-SCD in multivariate competing risk model (subhazard ratio, 2.58 [1.13–3.78]; P =0.001). No interaction between QTVI and left ventricular ejection fraction was found. QTVI predicted neither noncardiac death ( P =0.546) nor SCD ( P =0.945). Decreased heart rate variability rather than increased QT variability was the reason for increased QTVI in the present study. Conclusions— Increased QTVI because of depressed heart rate variability predicts cardiovascular mortality and non-SCD but neither SCD nor extracardiac mortality in heart failure across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from heart failure patients at risk.

Background: Electrophysiology studies (EPS) have historically played a role in sudden death risk stratification. More recent studies point to the left ventricular ejection fraction (EF) as a guide to implantable cardioverter defibrillators (ICD) implantation. The extent of EPS use in patients undergoing ICD implantation in the current era remains unknown. Methods: Patients undergoing de novo ICD implantation in the ICD Registry between September 2006 and March 2009 who also underwent EPS within 30 days before implant were compared to the remaining cohort to identify clinical characteristics that correlated with EPS performance. Multivariate models were generated using hierarchical logistic regression analysis. Results: EPS were performed in 33,786 of 275,273 patients. Those undergoing EPS were more likely to have had a history of syncope, family history of sudden death, lack of congestive heart failure, narrower QRS intervals, and higher EF. Overall, 63.9% of EPS were performed in patients receiving primary prevention ICDs. Ventricular tachyarrhythmias were induced in 46.1% of primary prevention and 54.2% of secondary prevention ICD recipients. Monomorphic ventricular tachycardia was the most common type of arrhythmia induced in both groups. Complication rates were not higher in those undergoing EPS. Conclusions: EPS were performed predominantly in patients with borderline or less well-defined risk factors for sudden death. Ventricular arrhythmias induced from EPS were not uncommon and may help identify individuals at higher risk for future ICD therapies. Efforts to better define the role of EPS in patients undergoing ICD implantation should be considered. (PACE 2012; 35:912–918)

Increased longevity of patients with systolic heart failure caused by the use of implantable cardioverter-defibrillators (ICDs) is one of the most successful achievements in contemporary medicine. During the last 2 decades, the scientific community has striven to increase the benefits of ICD usage by specifying indications for primary prevention ICD implantation. Left ventricular ejection fraction is neither highly specific nor is it a highly sensitive risk marker of sudden cardiac death. The authors discuss risk-stratification approaches in different patient populations with structural heart disease and systolic heart failure.

Inappropriate therapy for supraventricular arrhythmias remains a significant source of morbidity in implantable cardioverter-defibrillator (ICD) recipients.The Rhythm ID Goes Head to Head Trial (RIGHT) was designed to compare rhythm discrimination and inappropriate therapies among patients with ICDs from 2 manufacturers.Patients with standard ICD indications were randomized to receive a Guidant VITALITY 2 with Rhythm ID or selective Medtronic pulse generators using the Enhanced PR Logic or Wavelet discrimination algorithms. A single- or dual-chamber device was implanted based on clinical indications and programmed in 2 detection zones with detection enhancements enabled for rates between 150 and 200 bpm. Algorithm performance was compared between randomization groups, stratified by single or dual chamber, for the primary end point of first inappropriate therapy (shock or antitachycardia pacing) for supraventricular arrhythmias.There were 1962 patients enrolled and followed for 18.3 ± 9.2 months, with no difference in all-cause mortality between groups. There were 3973 treated episodes where electrograms were available and adjudicated. The primary end point of inappropriate therapy occurred in 246 of 985 VITALITY 2 patients vs 187 of 977 specific Medtronic ICD patients (hazard ratio = 1.34; confidence interval = 1.11-1.62; P = .003). Differences in inappropriate therapy were confined to single-chamber ICDs. Inappropriate shocks were more frequent in VITALITY 2 ICDs (hazard ratio = 1.63; confidence interval = 1.29-2.06; P.001), with most therapies and performance differences occurring at slower rhythms (rates175 bpm).Rhythm discrimination performed better in the specific Medtronic than in VITALITY 2 ICDs evaluated, particularly for single-chamber devices. Inappropriate therapies, and differences in performance, may be reduced with the use of rate cutoff above 175 bpm.

Switchable Faraday shielding is desirable in situations where electric field shielding is required at certain times and undesirable at other times. In this study, electrostatic finite element modeling was used to assess the effect of different shield geometries on the leakage of an internally applied field and penetration of an externally applied field. "Switching OFF" the shield by electrically disconnecting shield faces from each other was shown to significantly increase external field penetration. Applying this model to defibrillation, we looked at the effect of spacing and size of shield panels to maximize the ability to deliver an external defibrillation shock to the heart when shield panels are disconnected while providing acceptably low leakage of internal defibrillation shocks to avoid painful skeletal muscle capture when shield panels are connected. This analysis may be useful for designing internal defibrillator electrodes that preserve the efficacy of internal and external defibrillation while avoiding the significant morbidity associated with painful defibrillator shocks. Similar analysis could also guide optimizing the switchable Faraday shielding concept for other applications.

Background A need exists to devolop alternative approaches to VT ablation that provide an improved delineation of the arrhythmogenic substrate. Objective The aim of this study was to evaluate the hypotheses that: (1) the heterogeneous zone (HZ, a mixture of normal-appearing tissue and scar) in magnetic resonance imaging (MRI) contains the critical isthmus(es) for ventricular tachycardia (VT), (2) successful ablation of VT would include ablation in the HZ, and (3) inadequate ablation of HZ allows for VT recurrence. Methods MRI and an electrophysiology study (EP) were performed in a model of chronic myocardial infarction in 17 pigs. In animals that were inducible for VT, ablations were done guided by standard EP criteria and blinded to the MRI. After ablation, electroanatomic mapping results were co-registered with MRI. Results In 8 animals, 22 sustained monomorphic VTs were generated. The HZ was substantially larger in inducible (n = 8) compared with noninducible animals (n = 9) [25% ± 10% vs 13% ± 5% of total scar, respectively, P = .007]. Acutely, all targeted VTs were successfully ablated, and postprocedure analysis showed that at least 1 ablation was in the HZ in each animal. In 5 animals, a second EP and MRI were performed 1 week after ablation. Three animals had inducible VTs, and MRI showed that the HZ had not been completely ablated. In contrast, the 2 animals without inducible VT revealed no remaining HZ. Conclusion These findings show that MRI can define an HZ and determine the location of ablated lesions. The HZ may be a promising ablation target to cure ischemic VTs. Remnants of HZ after ablation may be the substrate for clinical relapses.

The reported complication rate of catheter ablation of atrial fibrillation (AF) varies.Our goal was to assess temporal trends and the effect of both institutional and individual operators' experience on the incidence of complications.All patients undergoing AF ablation at Johns Hopkins Hospital between February 2001 and December 2010 were prospectively enrolled in a database. Major complications were defined as those that were life-threatening, resulted in permanent harm, required intervention, or significantly prolonged hospitalization.Fifty-six major complications occurred in 1190 procedures (4.7%). The majority of complications were vascular (18; 1.5%), followed by pericardial tamponade (13; 1.1%) and cerebrovascular accident (12; 1.1%). No cases of death or atrioesophageal fistula occurred. The overall complication rate decreased from 11.1% in 2002 to 1.6% in 2010 (P.05). On univariate analysis, demographic and clinical factors associated with the increased risk of complications were CHADS(2) score of ≥2 (hazard ratio [HR] = 2.5; 95% confidence interval [CI] = 1.4-4.4; P = .002), female gender (HR = 2.0; 95% CI = 1.2-3.5; P = .014), and age (HR = 1.03; 95% CI = 1.0-1.1; P = .042). Gender and CHADS(2) score of ≥2 remained independent predictors of complication on multivariable analysis.The complication rate of catheter ablation of AF decreased with increased institutional experience. Female gender and CHADS(2) score of ≥2 are significant independent risk factors for complications and should be considered when referring patients for AF ablation.

Background Reverse electrical remodeling (RER) of the native conduction with cardiac resynchronization therapy (CRT) is associated with decreased mortality and antiarrhythmic effect of CRT. Still, mechanisms of RER are largely unknown. In this study, we explored repolarization lability during biventricular pacing. Methods and Results The width of native QRS was measured in lead II electrocardiogram before and at least 6 months after implantation of Cardiac Resynchronization Therapy Defibrillator (CRT-D) devices (Medtronic, Inc [Minneapolis, MN, USA] and Boston Scientific Corporate [Natick, MA, USA]) in 69 patients (mean age, 66.3 ± 13.9 years; 39 men [83%]) with either bundle-branch block (44 patients [64%]) or nonspecific intraventricular conduction delay (25 patients [36%]) and New York Heart Association class III and IV heart failure. Narrowing of the native QRS duration for at least 10 milliseconds was considered a marker of RER. Beat-to-beat QT variability and coherence was measured on surface electrocardiogram and intracardiac near-field electrogram during biventricular pacing. Reverse electrical remodeling was observed in 22 patients (32%) in whom coherence between heart rate variability and intracardiac repolarization lability was stronger (0.483 ± 0.243 vs 0.237 ± 0.146, P = .018) and normalized intracardiac QT variance was smaller (0.28 ± 0.0031 vs 0.46 ± 0.0048, P = .049), as compared with that in patients without RER. During a further 24 ± 13 months of follow-up, 21 patients (33%) died or experienced sustained ventricular tachycardia (VT)/ventricular fibrillation. Low intracardiac coherence (≤0.116) was associated with increased risk of death or sustained VT/VT (hazard ratio, 4.33; 95% confidence interval, 1.51-12.40; P = .006). Conclusion Strong coherence between heart rate variability and intracardiac repolarization lability during biventricular pacing is associated with RER of the native conduction with CRT. Low coherence is associated with increased risk of VT/ventricular fibrillation or death.

End-Stage Renal Disease Predicts Complications in Pacemaker and ICD Implants. Introduction: Patients with chronic kidney disease (CKD) have increased morbidity following invasive procedures. We hypothesized that patients with CKD have higher complication rates following device implantation than patients with normal renal function. Methods: We reviewed the medical records of patients undergoing ICD or pacemaker implantation from August 2004 to August 2007. The estimated glomerular filtration rate (GFR) was calculated using the Cockroft–Gault equation. Those with GFR ≥ 90 cc/min served as controls. The remainder was grouped according to American Kidney Foundation stages of CKD. Bleeding complications were defined as need for pocket exploration or blood transfusion; cardiac tamponade; or hematoma requiring pressure dressing, change in medications or prolonged hospitalization. Infection was defined as infection of the pocket or lead system, or development of bacteremia/sepsis within 60 days. Results: There were 82 bleeding complications (5.7%) and 7 infections (0.5%) temporally related to device implantation in 1,440 patients. End-stage renal disease (ESRD), defined as GFR < 15 mL/min or need for dialysis, was identified in 32 patients. Infection rates were significantly higher in patients with ESRD versus controls (12.5% vs 0.2%; P < 0.0001). A significant increase in bleeding complications was observed in ESRD versus controls (21.9% vs 3.2%, respectively; P

Most studies of catheter ablation for the treatment of ventricular tachycardia (VT) are relatively small observational trials.The purpose of this study was to define the relative risk of VT recurrence in patients undergoing catheter ablation as an adjunct to medical therapy versus medical therapy alone in a pooled analysis of controlled studies.Randomized and nonrandomized controlled trials of patients who underwent adjunctive catheter ablation of VT versus medical therapy alone were sought. MEDLINE, EMBASE, the Cochrane central register of controlled trials (CENTRAL), and Web of Science were searched from 1965 to July 2010. Supplemental searches included Internet resources, reference lists, and reports of arrhythmia experts. Three authors independently reviewed and extracted the data regarding baseline characteristics, ablation methodology, medical therapy, complications, VT recurrences, mortality, and study quality.Five studies were included totaling 457 participants with structural heart disease. Adjunctive catheter ablation was performed in 58% of participants, whereas 42% received medical therapy alone for VT. Complications of catheter ablation included death (1%), stroke (1%), cardiac perforation (1%), and complete heart block (1.6%). Using a random-effects model, a statistically significant 35% reduction in the number of patients with VT recurrence was noted with adjunctive catheter ablation (P.001). There was no statistically significant difference in mortality.Catheter ablation as an adjunct to medical therapy reduces VT recurrences in patients with structural heart disease and has no impact on mortality.

Background Management of oral anticoagulation in patients undergoing pacemaker (PPM) or implantable cardioverter-defibrillator (ICD) implantation remains controversial. Prior studies demonstrate that continuation of warfarin may be safer when compared with strategies requiring interruption and/or heparin bridging. Limited data from randomized trials exist. Objective We conducted a randomized trial to determine whether warfarin continuation is superior to warfarin interruption during PPM or ICD implantation. Methods Patients on oral anticoagulation referred for PPM or ICD implantation were randomized to warfarin continuation versus interruption. Patients randomized to warfarin interruption were further stratified into two groups based on their risk for thromboembolic events in the absence of warfarin. Moderate-risk patients were randomized to warfarin continuation versus warfarin interruption. High-risk patients were randomized to warfarin continuation versus warfarin interruption with heparin bridging. The primary combined outcome included thromboembolic events, anticoagulant-related complications, or any significant bleeding necessitating additional intervention or discontinuation of anticoagulation. Results We studied 100 patients (average age 70.8 years, 21% female, mean body mass index 28.4) who underwent 64 ICD and 36 PPM implantations. Fifty patients were assigned to continue warfarin. The randomized groups were well matched. Among patients randomized to warfarin interruption, there were two pocket hematomas, one pericardial effusion, one transient ischemic attack, and one patient who developed heparin-induced thrombocytopenia. No events were noted among patients continuing warfarin (P = .056). Conclusions While the results were not statistically significant, there was a trend toward reduced complications in patients randomized to warfarin continuation. This strategy should be considered in patients undergoing PPM or ICD implantation.