Comparison of fixed tilt and tuned defibrillation waveforms: the PROMISE study.

Background: All modern defibrillation systems use biphasic shock waveforms. Typically a fixed tilt waveform is used for implantable defibrillators (ICDs), but a tuned waveform with duration based on shock impedance may be superior based on theoretical calculations.

Objective: The objective of this study was to compare defibrillation efficacy of fixed tilt and tuned waveforms.

Efficacy of tuned waveforms based on different membrane time constants on defibrillation thresholds: primary results from the POWER trial.

Background: The efficacy of tuned defibrillation waveforms versus the nominal fixed-tilt waveform has been previously studied. However, the optimal membrane time constant for tuning was not known. The POWER (Pulsewidth Optimized Waveform Evaluation tRial) trial was designed to determine the optimal membrane time constant for programming "tuned" biphasic waveforms.

Does defibrillation threshold increase as left ventricular ejection fraction decreases?

Aims: Advanced cardiac disease, entailing more hypertrophy, fibrosis, scarring, dilatation and conduction delays, poses the question of whether defibrillation thresholds (DFTs) increase as left ventricular ejection fraction (LVEF) decreases. This question has been approached indirectly or insufficiently in previous studies. In this study we add and expand on our previous work, stratifying DFT for various LVEF ranges.

Long-term changes in high-voltage impedance of defibrillating leads.

Background: The maturation of the high-voltage impedance (HVLI) of defibrillating leads has not been explored thoroughly. Since impedance influences the charge, current, and energy delivered to the heart in both fixed pulse-width and fixed tilt implantable cardioverter-defibrillator (ICD) waveforms, changes in HVLI might have an effect on the defibrillation threshold. This analysis examined the maturation of defibrillation lead HVLI.

Performance of dedicated versus integrated bipolar defibrillator leads with CRT-defibrillators: results from a Prospective Multicenter Study.

Introduction: Right ventricular (RV) anodal stimulation may occur in cardiac resynchronization therapy defibrillators (CRT-D) when left ventricular (LV) pacing is configured between the LV lead and an electrode on the RV defibrillator lead. RV defibrillator leads can have a dedicated proximal pacing ring electrode (dedicated bipolar) or utilize the distal shocking coil as the proximal pacing electrode (integrated bipolar). This study compares the performance of integrated versus dedicated leads with respect to anodal stimulation incidence, sensing, and inappropriate ventricular tachyarrhythmia detection in patients implanted with CRT-D.

Real-time percutaneous optical imaging of anatomical structures in the heart through blood using a catheter-based infrared imaging system.

The ability to optically image structures and instrumentation within the heart during procedures is limited by the presence of blood in the field. The goal of our research was to design, develop, and evaluate technology for a catheter-based optical imaging system that enables intracardiac and intravascular visualization in real time through blood. Based on Mie optical scattering theory, imaging through blood using infrared light was theoretically feasible, but scattering in the near-infrared wavelengths (1100 to 1300 nm) generated substantial noise in the image despite relatively low absorption.

Optimization of superior vena cava coil position and usage for transvenous defibrillation.

Background: Prior studies of active pectoral implantable defibrillator (ICD) lead systems demonstrated a lowering of defibrillation thresholds (DFTs) with the addition of a superior vena cava (SVC) coil. These studies were done on fixed-tilt waveforms where a large reduction in impedance leads to large phase duration changes.

Objective: The present study was designed to evaluate the SVC coil benefit and intercoil spacing on DFTs with a "tuned" waveform.

Atrial overdrive pacing and incidence of heart failure-related adverse events in permanently paced patients.

Background: Atrial overdrive pacing algorithms may be effective in preventing or suppressing atrial fibrillation (AF). However, the maintenance of a heart rate incessantly faster than spontaneous could induce left ventricular (LV) dysfunction and promote heart failure (HF) on the long term.

Objective: This post hoc analysis examined the effects of a new overdrive algorithm on the incidence of HF-related adverse events in 411 patients enrolled in the ADOPT-A trial.

Successful catheter ablation of electrical storm after myocardial infarction.

Background: We report on 4 patients (aged 57 to 77 years; 3 men) who developed drug-refractory, repetitive ventricular tachyarrhythmias after acute myocardial infarction (MI). All episodes of ventricular arrhythmias were triggered by monomorphic ventricular premature beats (VPBs) with a right bundle-branch block morphology (RBBB).

Methods And Results: Left ventricular (LV) mapping was performed to attempt radiofrequency (RF) ablation of the triggering VPBs.

A new pacemaker algorithm for the treatment of atrial fibrillation: results of the Atrial Dynamic Overdrive Pacing Trial (ADOPT).

Objectives: The Atrial Dynamic Overdrive Pacing Trial (ADOPT) was a single blind, randomized, controlled study to evaluate the efficacy and safety of the atrial fibrillation (AF) Suppression Algorithm (St. Jude Medical Cardiac Rhythm Management Division, Sylmar, California) in patients with sick sinus syndrome and AF.

Background: This algorithm increases the pacing rate when the native rhythm emerges and periodically reduces the rate to search for intrinsic atrial activity.