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.

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.

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.

Stiffness of occipital-cervical constructs: beam theory.

Objective: The purpose of this study is to show that stiffness of an occipital-cervical construct can be predicted based on rod geometry and material.

Materials And Methods: Various rod-plate implants were tested as previously reported biomechanical studies of occipital-cervical fixation with the exception that no spine was used. A testing frame that holds paired contoured rods and plates to the same position as in the biomechanical testing protocol for occipital-cervical fixation was tested in the flexion-extension direction on a servo-hydraulic testing machine.

A method to measure cervical spine motion over extended periods of time.

Study Design: System validation study.

Objective: To develop and validate a motion sensor system for measuring cervical spine motion over extended time periods.

Summary Of Background Data: Many studies using different methodologies have tried to estimate cervical spine motion.

The effect of stretch rate and activation state on skeletal muscle force in the anatomical range.

Background: The effects of stretch rate and activation state on muscle mechanics require further clarification. This subject is of particular interest because of the role of skeletal muscle undergoing eccentric contractions in musculoskeletal injuries.

Methods: The present study investigated the force-displacement behavior of rabbit tibialis anterior muscle at three stretch rates (2.

Biomechanics of occipitocervical fixation.

Study Design: A human cadaveric biomechanical study comparing occipital fixation techniques.

Objectives: To compare ranges of motion between midline and lateral occipital fixation and between rigid and nonrigid occipital fixation of an unstable craniocervical spine.

Summary Of Background Data: New fixation techniques using rods and screws increase surgical choice on where fixation is placed onto the occiput.