G. Stuart Mendenhall

Fluoroscopic Screening of Asymptomatic Patients Implanted With the Recalled Riata Lead Family

Background— The Food and Drug Administration recently issued a class I recall of the St. Jude Medical Riata implantable cardioverter-defibrillator lead presumably because of increased risk of electric failure and mechanical separation via inside-out abrasion. We sought to examine the incidence and time dependence of inside-out abrasion in asymptomatic patients implanted with the Riata lead. Methods and Results— Asymptomatic patients implanted with the Riata lead at our institution were offered voluntary fluoroscopic screening in 3 views. Electric testing of the Riata lead with provocative isometric muscle contraction was performed at the time of fluoroscopic screening. Of the 245 patients undergoing fluoroscopic screening, 53 (21.6%) patients showed clear evidence of lead separation. Of these externalized leads, 0%, 13%, and 26% had a dwell time of <3 years, 3 to 5 years, and >5 years, respectively (P=0.037). Externalized leads had a significantly pronounced decrease in R-wave amplitude (−1.7±2.9 mV versus +0.35±2.5 mV; P<0.001), and more patients with externalized leads had ≥25% decrease in R-wave amplitude from baseline (28.0% versus 8.1%; P=0.018). One patient with externalization exhibited new noise on near-field electrogram. Conclusions— The Riata lead exhibits time-dependent high rates of cable externalization exceeding 20% at >5 years of dwell time. Externalized leads are associated with a more pronounced decrease in R-wave amplitude, which may be an early marker of future electric failure. The use of fluoroscopic and electric screening of asymptomatic patients with the Riata lead remains controversial in the management of patients affected by the recent Food and Drug Administration recall.

Frequency of Toxicity With Chemical Conversion of Atrial Fibrillation With Dofetilide

Dofetilide is a class III antiarrhythmic agent approved for the maintenance of sinus rhythm in patients with persistent atrial fibrillation (AF). The goal of this study was to determine if chemical cardioversion (CCV) suggests a greater sensitivity to dofetilide and, therefore, portends a higher risk of proarrhythmia. We analyzed 99 consecutive patients with persistent AF who were loaded on dofetilide before cardioversion. CCV occurred after 2 ± 1.5 doses of dofetilide in 46 patients whereas electrical cardioversion (ECV) was required in the remaining 53 patients after 4.7 ± 1.3 doses. During index hospitalization, there were higher rates of dofetilide discontinuation because of QT prolongation or torsades de pointes (TdP) in the CCV group compared with the ECV group (24% vs 2%, p = 0.001). All patients with CCV requiring drug discontinuation converted after a single dose of dofetilide. Additionally, all 3 patients with TdP were in the CCV group. Furthermore, 15 of the 21 patients with CCV (71%) who converted after the first dose of dofetilide developed significant QT prolongation, requiring dose adjustment or discontinuation of drug. Among patients discharged on drug, AF recurrence and drug discontinuation rates were similar between groups at 2-year follow-up. In patients hospitalized for initiation of dofetilide, CCV occurs in almost 50% and is associated with higher rates of pathologic QT prolongation and TdP compared with those who require ECV. Once discharged on dofetilide, safety and efficacy is similar in both groups. In conclusion, patients with CCV may require closer monitoring for proarrhythmia.

Effect of Ischemia on Implantable Defibrillator Intracardiac Shock Electrograms

Introduction: Few attempts have been made to extract information from the ventricular electrogram (EGM) recorded by implantable cardioverter defibrillators (ICD) aside from the discrimination of supraventricular tachycardia and ventricular tachycardia. The current study aims to examine the effect of ischemia in the major coronary artery distributions on the shock EGM from ICDs.

New-onset left bundle branch block–associated idiopathic nonischemic cardiomyopathy and left ventricular ejection fraction response to guideline-directed therapies: The NEOLITH study

BACKGROUND Left ventricular ejection fraction (LVEF) response to guideline-directed medical therapy (GDMT) and to early cardiac resynchronization therapy (CRT) in new-onset idiopathic nonischemic cardiomyopathy (NICM) and left bundle branch block (LBBB) is not well described. CRT is recommended if LVEF remains ≤35% after at least 3 months of GDMT. OBJECTIVE The purpose of this study was to describe LVEF response to GDMT at 3 months and to early CRT in new-onset LBBB-associated idiopathic NICM. METHODS A retrospective cohort study was performed in subjects with new-onset idiopathic NICM, LVEF ≤35%, and LBBB or narrow (<120 ms) QRS complex morphology. LVEF response between groups was evaluated with log-binomial and linear regression. LVEF response within groups was evaluated using the paired Student t test. RESULTS In 102 subjects (70 with narrow QRS complex and 32 with LBBB), post-GDMT LVEF was >35% in 39 narrow QRS complex subjects (56%) and 2 LBBB subjects (6%) (P < .0001). The absolute difference between post-GDMT LVEF and initial LVEF was greater in the narrow QRS complex group (16.1% ± 14.6% vs. 3.3% ± 10.7%; P < .0001). Narrow QRS complex, referenced to LBBB, was significantly associated with post-GDMT LVEF >35% (relative risk 10.30; 95% confidence interval 2.63-40.27; P = .0008) and absolute difference between post-GDMT LVEF and initial LVEF (β = 16.296; standard error = 2.977; P < .0001) in final multivariable analyses. CRT super-response, defined as post-CRT LVEF ≥50%, was observed in 8 of LBBB subjects (35%) who received CRT. CONCLUSION GDMT did not significantly improve LVEF in new-onset LBBB-associated idiopathic NICM at 3 months. Most remained candidates for CRT, and a high percentage were super-responders. Optimal timing for CRT implantation requires further investigation.

Implantable and surface electrocardiography: complementary technologies

Combining information obtained from the surface electrocardiogram and implantable devices represents an emerging trend in electrocardiology. Important potential applications include ischemia detection and localization, continuous monitoring of cardiac cycle parameters, and telemedicine. This article presents an overview of these emerging applications, focusing on our recent studies that combine the electrograms obtained from body surface and implantable devices to reconstruct a full 12-lead electrocardiogram from the implanted device. These technologies have broad application for detection of ischemia, improvement of the accuracy of ischemic localization, and rhythm discrimination.

New‐onset left bundle branch block‐associated idiopathic nonischemic cardiomyopathy and time from diagnosis to cardiac resynchronization therapy: The NEOLITH II study

The optimal timing for cardiac resynchronization therapy (CRT) after diagnosis of new‐onset left bundle branch block (LBBB)‐associated idiopathic nonischemic cardiomyopathy (NICM) and treatment with guideline‐directed medical therapy (GDMT) is unknown. The purpose of this study was to describe relationships between time from diagnosis to CRT and outcomes in new‐onset LBBB‐associated idiopathic NICM with left ventricular ejection fraction (LVEF) ≤35%.

Prophylactic Lead Extraction at Implantable Cardioverter-Defibrillator Generator Change

Background—Current implantable cardiac devices have a finite battery life of ≈3 to 7 years for implantable cardioverter-defibrillators. It is current practice to reuse all properly functioning intravascular leads. We tested the hypothesis that a strategy of prophylactic lead removal at the time of device change would be superior under some conditions to the current practice of lead reuse. Methods and Results—Using currently available data and a Monte Carlo microsimulation trial, we calculated the risks of leaving an indwelling lead until extraction is indicated because of malfunction versus an aggressive management strategy of prophylactic serial extraction at time of generator change. With a serial lead exchange strategy of leads at generator change, there is reduced overall extraction-related mortality because of fewer late complications attributable to extraction of leads with high dwell time because of infection, recall, or subsequent lead failure. This finding is limited to young patients or those with high expected indwell time of lead. This trend reverses for leads with <40 years expected dwell time. Sensitivity analysis shows high dependence on extraction performance and device longevity. In all cases, serial extraction would be expected to lead to increased adverse events related to the more complex procedure. Conclusions—A strategy of serial lead extraction, given best available current parameters, yields a lower procedural mortality risk in the long-term management of indwelling implantable cardioverter-defibrillator leads in young patients (>40-year estimated dwell time) driven by high aggregate anticipated risk of lifetime lead complication.

12-lead surface electrocardiogram reconstruction from implanted device electrograms

AIM Reconstruction of the surface electrocardiogram (EKG) from voltage recordings from implanted leads is not performed by current pacemakers or cardioverter-defibrillators. We investigated the feasibility and accuracy of reconstruction of a full 12-lead surface EKG from an implanted biventricular device. METHODS AND RESULTS We applied three techniques for surface EKG reconstruction from multiple intracardiac (IC) vector recordings from implanted cardiac leads: single fixed dipole modelling via exact solution, exhaustive best-fit solution, and time-independent association using a transfer matrix. Recordings were performed at biventricular generator change in 10 patients. Overdetermined projection transformation resulted in high fidelity surface EKG reproduction for left-sided implanted devices (correlation coefficient 0.84+/-0.13) with computationally lightweight reconstruction. CONCLUSION After individual post-implantation correlation with the surface EKG, reconstruction using a time-independent transfer matrix accurately reproduces the surface EKG, is free from gating requirements, and retains validity during aberrant depolarization. These findings have significant implications for further study relating IC electrogram to surface tracings. The techniques may be used for real-time or remote monitoring and diagnosis of rhythm disturbances, cardiac ischaemia, and lead integrity and stability.

Insights into Atrioventricular Nodal Function from Patients Displaying Dual Conduction Properties: Interactive and Orthogonal Pathways

Background—There is a significant variability observed in the conduction properties of the atrioventricular node. In a subset of hearts, impulse transmission tends to fall into two distinct conduction regions, termed the slow and fast pathway, and a further subset are capable of dual conduction of a single input stimulus, termed double firing. Methods and Results—In this article, we closely characterize two distinct responses in patients with double firing properties of the atrioventricular node, separating these into discrete types: those with slow and fast pathway interaction and interdependence (interactive), and those with independent pathway properties (orthogonal). We use novel mathematical techniques to evaluate the relative decrement and unique properties of conduction during the overlapping slow and fast pathway conduction zones. Conclusions—Our analysis demonstrates two distinct patterns of pathway conduction in double firing patients, termed interactive and orthogonal. We show parallel overlapping segments of slow and fast pathway decremental conduction curves in interactive pathways, with no such findings with orthogonal conduction. These findings suggest anatomic correlates of pathway conduction, with interactive pathways likely having a common distal segment and orthogonal pathways able to independently activate downstream structures.

Arrhythmia care in a value-based environment: Past, present, and future: Developed and endorsed by the Heart Rhythm Society (HRS)

Fred M. Kusumoto, MD, FHRS (Chair), Steven C. Hao, MD, FHRS (Coach), David J. Slotwiner, MD, FHRS (Coach), Jim W. Cheung, MD, FHRS, Jonathan C. Hsu, MD, FHRS, Marcin Kowalski, MD, FHRS, Ruth A. Madden, MPH, RN, Pamela K. Mason, MD, FHRS, G. Stuart Mendenhall, MD, FHRS, Devi G. Nair, MD, FHRS, Javed M. Nasir, MD, FHRS, Josh R. Silverstein, MD, Brad Sutton, MD, MBA, Khaldoun G. Tarakji, MD, MPH, FHRS, Gaurav A. Upadhyay, MD, FHRS, Emily P. Zeitler, MD, MHS From the Department of Cardiovascular Disease, Mayo Clinic, Jacksonville, Florida, Sutter Pacific Medical Foundation, San Francisco, California, NewYork-Presbyterian/Queens, New York, New York, Weill Cornell Medical College, Cardiology Division, New York, New York, Weill Cornell Medicine, Cardiology, New York, New York, Cardiac Electrophysiology Section, University of California, San Diego, La Jolla, California, Staten Island University, Hospital Northwell Health System New York, New York, Cleveland Clinic, Cleveland, Ohio, University of Virginia Health System, Charlottesville, Virginia, University of Pittsburgh, Pittsburgh, Pennsylvania, St. Bernards Heart & Vascular Center, Jonesboro, Arkansas, Cardiac Electrophysiology and Arrhythmia Service, Stanford University, Stanford, California, Mount Carmel Columbus Cardiology Consultants, New Albany, Ohio, University of Louisville, Louisville, Kentucky, Cleveland Clinic, Cleveland, Ohio, University of Chicago Medical Center, Chicago, Illinois, and Duke University Hospital, Durham, North Carolina.