J. Marcus Wharton

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

OBJECTIVESnThe 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.nnnBACKGROUNDnAlcohol 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.nnnMETHODSnThis 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.nnnRESULTSnNine 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.nnnCONCLUSIONSnThe 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

BACKGROUNDnImplantable 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.nnnOBJECTIVEnThe purpose of this study was to compare RVA with RVOT transvenous ICD lead position on DFT.nnnMETHODSnThis 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.nnnRESULTSnThe 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.nnnCONCLUSIONnThe 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.u2002Background: 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 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.

Plasma Profiles of Matrix Metalloproteinases and Tissue Inhibitors of the Metalloproteinases Predict Recurrence of Atrial Fibrillation Following Cardioversion

Atrial fibrosis is considered to contribute to atrial fibrillation (AF) recurrence following cardioversion. This study tested the hypothesis that circulating levels of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) can predict AF recurrence postcardioversion. Precardioversion plasma samples (nu2009=u200982) were assayed for MMPs (eight types), TIMPs (all four types), N-terminus pro B-type natriuretic peptide, and high-sensitivity C-reactive protein levels. Patients were followed for AF recurrence postcardioversion. Despite 100xa0% restoration of sinus rhythm, 36 (44xa0%) reverted to AF within 3xa0months. Left atrial volume was increased in patients in whom AF recurred. Precardioversion MMP-9 was higher and TIMP-4 lower with AF recurrence. MMP-9, MMP-3, and TIMP-4 independently predicted AF recurrence. In multivariate analysis, combination of MMP-9, MMP-3, and TIMP-4 increased prediction of AF recurrence. Circulating levels of MMPs and TIMPs predict AF recurrence postcardioversion and may be used in a novel biomarker panel to guide AF stratification and therapy.

Role of Transesophageal Echocardiography Among Patients With Atrial Fibrillation Undergoing Electrophysiology Testing

External or internal shocks administered to terminate ventricular arrhythmias as a part of electrophysiology or implantable cardioverter-defibrillator testing, can inadvertently cardiovert atrial fibrillation (AF). Moreover, anticoagulation therapy is often withheld in these patients in anticipation of an invasive procedure. The risk of embolic events during these procedures has not been well described. Accordingly, the present study was a prospective evaluation of the incidence of left atrial (LA) thrombus and AF cardioversion among patients undergoing ventricular arrhythmia assessment. Transesophageal echocardiography was routinely performed on 44 consecutive patients in AF with subtherapeutic anticoagulation undergoing electrophysiology or implantable cardioverter-defibrillator testing. Arrhythmia induction was not performed when LA thrombus was present. The incidence and clinical predictors of thrombus, the inadvertent cardioversion of AF, and adverse events related to the procedure were assessed during the subsequent 4 to 6 weeks. Left atrial thrombus was observed in 12 patients (27%). Sinus rhythm was restored in 29 patients (91%), at least transiently, who underwent testing with a shock delivered. No adverse neurologic or hemorrhagic complications were observed. Univariate analysis identified no predictors of LA thrombus or cardioversion to sinus rhythm. In conclusion, LA thrombus and cardioversion to sinus rhythm are common among patients with AF undergoing an evaluation of ventricular arrhythmias. Transesophageal echocardiography performed before the procedure in patients with subtherapeutic anticoagulation is warranted to minimize embolic complications. This strategy appears to be a safe method to guide diagnostic testing in this patient population.

THE EFFECT OF LEFT VENTRICULAR SENSING ELECTRODE POSITION ON ELECTRICAL DELAY IN CARDIAC RESYNCHRONIZATION THERAPY

Positioning left ventricular leads by anatomic guidance only has little effect on cardiac resynchronization therapy (CRT) outcomes with the exception of worse responses in apical locations. However, pacing at sites of electrical or mechanical delay is associated with better outcomes. The advent of