J. Lacy Sturdivant

Head-to-head comparison of arrhythmia discrimination performance of subcutaneous and transvenous ICD arrhythmia detection algorithms: The START study

Arrhythmia Detection with S‐ICD Versus Transvenous ICDs.

A Prospective Comparison of AV Delay Programming Methods for Hemodynamic Optimization during Cardiac Resynchronization Therapy

Introduction: There are several methods for programming the optimal AV delay (AVD) during cardiac resynchronization therapy (CRT). These include Doppler echocardiographic measurements of mitral inflow or aortic outflow velocities, an arbitrarily fixed AVD, and calculations based on intracardiac electrogram (EGM) intervals. The present study was designed to compare the acute effects of AVD programming methods during CRT.

Implantable Cardioverter-Defibrillator Therapy for Primary Prevention of Sudden Death After Alcohol Septal Ablation of Hypertrophic Cardiomyopathy

OBJECTIVES The purpose of this study was to examine the effects of alcohol septal ablation (ASA) on ventricular arrhythmias among patients with obstructive hypertrophic cardiomyopathy (HCM), as measured by appropriate implantable cardioverter-defibrillator (ICD) discharges. BACKGROUND Alcohol septal ablation is an effective therapy for patients with symptomatic HCM. However, concern has been raised that ASA may be proarrhythmic secondary to the iatrogenic scar created during the procedure. The impact of ASA on ventricular arrhythmias has not been well described. METHODS This prospective study included 123 consecutive patients with obstructive HCM who underwent ASA and had an ICD implanted for primary prevention of sudden cardiac death (SCD). The ICDs were implanted based on commonly accepted risk factors for SCD in the HCM population. Data from ICD interrogations during routine follow-up were collected. RESULTS Nine appropriate ICD shocks were recorded over a mean follow-up of 2.9 years in the cohort, which had a mean of 1.5 +/- 0.9 risk factors for SCD. Using Kaplan-Meier survival analysis, the estimated annual event rate was 2.8% over 3-year follow-up. There were no significant differences in the incidence of risk factors between patients who did and did not receive appropriate shocks. CONCLUSIONS The annual rate of appropriate ICD discharges after ASA is low and less than that reported previously for primary prevention of SCD in HCM. This suggests that ASA is not proarrhythmic. Traditional SCD risk factors did not predict ICD shocks in this cohort.

Safety of Continuous Anticoagulation With Dabigatran During Implantation of Cardiac Rhythm Devices

The perioperative bleeding risk associated with therapeutic anticoagulation at cardiac implantable electronic device implantation has previously been demonstrated to vary by the specific anticoagulant used. Although uninterrupted anticoagulation with warfarin appears to be safe, heparin products have been shown to increase the risk of perioperative bleeding. However, the risk associated with cardiac implantable electronic device implantation with anticoagulation using dabigatran, a novel oral direct thrombin inhibitor, is not known. We performed a prospective observational study of patients receiving dabigatran for anticoagulation who underwent cardiac implantable electronic device implantation from June 2011 through May 2012. The study end points included thromboembolic and bleeding complications within 30 days of surgery. Major bleeding complications were defined as bleeding requiring surgical intervention, prolongation of hospitalization, and discontinuation of the anticoagulant or transfusion of blood products within 30 days of surgery. Minor bleeding complications included the development of a hematoma not requiring additional intervention. The thrombotic end points included stroke, transient ischemic attack, myocardial infarction, pulmonary embolism, and deep vein thrombosis. A total of 25 patients were identified for inclusion. During the index hospitalization, no thromboembolic or bleeding complications developed. No major bleeding complications occurred within 30 days of surgery. One minor bleeding event (4%) occurred within 30 days of surgery in 1 patient who was also receiving dual antiplatelet therapy. In conclusion, although no thromboembolic or major bleeding events were observed, additional studies are required to define the optimal antithrombotic management in the perioperative period.

Randomized comparison of defibrillation thresholds from the right ventricular apex and outflow tract

BACKGROUND Implantable cardioverter-defibrillator (ICD) leads are traditionally placed in the right ventricular apex (RVA), in part because this is considered the preferred vector for minimizing defibrillation threshold (DFT). However, if adequate DFT safety margins are attainable, ICD leads placed in the right ventricular outflow tract (RVOT) might confer advantages if frequent ventricular pacing is anticipated. OBJECTIVE The purpose of this study was to compare RVA with RVOT transvenous ICD lead position on DFT. METHODS This was a prospective, randomized, crossover study of RVA versus RVOT DFT in 33 patients undergoing left pectoral ICD placement. A binary search algorithm was used to measure DFT, with initial lead position tested in randomized order. The relationship between RVOT position and DFT was assessed by evaluation of the distance between RVA and RVOT. RESULTS The study population had a mean age of 59 ± 12 years and ejection fraction of 33% ± 14%. Mean DFT in the RVA was 9.8 ± 7.3 J versus 10.8 ± 7.2 J in the RVOT (P = .53), with no correlation between RVOT location and DFT. CONCLUSION The study found no evidence that ICD lead placement in the RVOT is associated with significantly higher DFT than lead placement in the RVA.

Defibrillation thresholds in hypertrophic cardiomyopathy.

Defibrillation Thresholds in Hypertrophic Cardiomyopathy. Background: Defibrillation threshold (DFT) testing is performed in part to ensure an adequate safety margin for the termination of spontaneous ventricular arrhythmias. Left ventricular mass is a predictor of high DFTs, so patients with hypertrophic cardiomyopathy (HCM) are often considered to be at risk for increased defibrillation energy requirements. However, there are little prospective data addressing this issue.

The effect of left ventricular electrical delay on the acute hemodynamic response with cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) improves hemodynamic function, as well as reduces hospitalizations and mortality among patients with systolic dysfunction, QRS prolongation, and heart failure. The magnitude of the hemodynamic response is associated with improved outcomes, so optimization of this parameter is a goal of therapy. The purpose of this study was to evaluate the effect of left ventricular (LV) electrical delay, as assessed by the QLV interval, on the acute hemodynamic response to CRT.

The Effect of Dofetilide on Ventricular Defibrillation Thresholds

Introduction: High defibrillation threshold (DFT) with an inadequate defibrillation safety margin remains an infrequent but troubling problem associated with defibrillator implantation. Dofetilide is a selective class III antiarrhythmic drug that reduces DFTs in a canine model. We hypothesized that dofetilide would reduce DFTs in humans, obviating the need for complex lead systems.

A prospective, randomized comparison of the acute hemodynamic effects of biventricular and left ventricular pacing with cardiac resynchronization therapy.

BACKGROUND Cardiac resynchronization therapy (CRT) is most commonly performed with biventricular (BiV) pacing. Left ventricular (LV) only pacing is an alternative pacing configuration for CRT, but comparative studies with BiV pacing have shown inconsistent results. This may be due to differences in LV activation pattern, which could be differentially affected by atriventricular (AV) programming or atrial pacing (AP). OBJECTIVE The purpose of this study was to compare AV optimization and the effect of atrial overdrive pacing on the acute hemodynamic response of LV and BiV CRT. METHODS This study included 28 patients undergoing CRT. At implant, invasive LV dP/dt was measured by a micromanometer catheter during BiV or LV pacing in atrial sensing (AS) and AP modes at five different AV delays (AVDs), tested in randomized order. RESULTS Compared with intrinsic rhythm, CRT with AS increased LV dP/dt by 12% ± 10% during LV pacing and by 11% ± 11% during BiV pacing (P = .15). With atrial overdrive pacing, CRT increased LV dP/dt by 17% ± 10% with LV pacing and by 17% ± 11% during BiV pacing (P = NS vs. LV; P <.001 vs. AS). The optimal AVD was significantly longer with AP (LV 202 ± 63 ms vs. 131 ± 42 ms during AS; BiV 195 ± 71 ms vs. 134 ± 43 ms during AS) but did not differ between LV and BiV pacing. CONCLUSION In this study, AP increases LV dP/dt during CRT but requires a substantially longer AVD. However, the optimal AVDs were similar for LV and BiV as were the magnitudes of the responses during CRT, suggesting that programmed AVDs are interchangeable in these two configurations.

Temporal stability of defibrillation thresholds with cardiac resynchronization therapy.

BACKGROUND Defibrillation thresholds (DFTs) are typically stable over time among patients with implantable cardioverter-defibrillators (ICDs). However, the impact of cardiac resynchronization therapy (CRT) on DFTs has not been studied systematically. OBJECTIVE This study prospectively evaluated the effect of CRT and left ventricular (LV) chamber reverse remodeling on DFTs. METHODS This prospective, multicenter study evaluated 54 cardiac resynchronization therapy defibrillator (CRT-D) patients. Echocardiography and DFTs were performed both at implantation and at 6 months after implantation. All patients received dual-coil leads and a CRT-D pulse generator. DFTs were measured using a binary search method and tuned biphasic waveforms, where the shock pulse widths were determined by the measured shock impedance. Echocardiograms were analyzed by an independent core laboratory with a responder defined as a decrease of left ventricular end systolic volume >15%. RESULTS The study cohort was 74% male, with a mean age of 68.7 ± 10.9 years. The baseline ejection fraction was 0.245 ± 0.076, and the mean New York Heart Association class was 2.9 ± 0.4. In CRT responders (n = 32) the mean DFT was 415.6 ± 108.1 V at implantation vs. 415.6 ± 124.7 V at 6 months (P = .9), and in nonresponders (n = 19) the mean DFT was 452.6 ± 102 V at implantation vs. 447.4 ± 112.4 V at 6 months (P = .8). There was no significant change in DFT peak voltage, delivered energy, or shock impedance over time. CONCLUSION DFTs were unchanged at 6 months in CRT patients with or without LV chamber reverse remodeling.