Experimental study of cryofreezing energy applications on the ventricular myocardium using sheep hearts.

Background: Cryofreezing energy has been utilized to abolish arrhythmogenic substrates of various kinds of tachyarrhythmias. However, systematic electrophysiological and histological investigations of cryothermia have never been performed. The aim of this study was to clarify those aspects using sheep beating hearts.

Sotalol and a broken heart.

An 82-year-old woman with persistent atrial fibrillation underwent successful electrical cardioversion and was begun on sotalol. After 3 days of in-hospital observation she had only mild lengthening of the QT interval. Two weeks later in clinic, the day after her husband's unexpected death, she was noted to have profound QT interval prolongation.

Implantable cardiac defibrillator lead failure or myopotential oversensing? An approach to the diagnosis of noise on lead electrograms.

The appearance of noise on electrograms (EGMs) recorded from the lead of an implantable cardioverter-defibrillator (ICD) may be owing to oversensing of myopotentials, insulation breach, conductor coil fracture, loose set screw, or electromagnetic interference from an external source. The extraneous noise may lead to inappropriate shocks or inhibition of pacing. We describe two cases of pectoral myopotentials oversensing in patients with ICD and an approach to distinguish among the various extraneous noises recorded on EGMs.

Catheter cryoablation of supraventricular tachycardia: results of the multicenter prospective "frosty" trial.

Objective: To study the safety, efficacy, and mapping utility of a new cryoablation catheter.

Background: The CryoCath Technologies Freezor catheter has been used successfully for cryoablation of supraventricular tachycardia (SVT), but has not been evaluated in a large clinical trial.

Methods: A multicenter clinical trial to evaluate the safety, efficacy, and cryomapping utility of this cryoablation catheter was conducted in 166 subjects.

Impact of changing activation sequence on bipolar electrogram amplitude for voltage mapping of left ventricular infarcts causing ventricular tachycardia.

Introduction: Wavefront direction is a determinant of bipolar electrogram amplitude that could influence identification of low amplitude regions indicating infarction or scar.

Methods: To assess the importance of activation sequence on electrogram amplitude 11 patients with prior infarction and ventricular tachycardia were studied. At 819 left ventricular sites bipolar electrograms were recorded during atrial pacing and ventricular pacing, followed by unipolar pacing with a stimulus of 10 mA at 2 ms.

Catheter cryoablation of cardiac arrhythmias.

Purpose Of Review: The purpose of the review is to provide an update on the safety and efficacy of catheter cryoablation.

Recent Findings: Catheter cryoablation is a safe and clinically effective method for ablation of atrioventricular nodal reentrant supraventricular tachycardia. Although the acute procedural success rate of catheter cryoablation for this arrhythmia may be slightly lower than that reported for radiofrequency ablation, it has an excellent safety profile, with no reported instances of inadvertent atrioventricular block requiring implantation of a permanent pacemaker.

Identification of the ventricular tachycardia isthmus after infarction by pace mapping.

Background: Ventricular tachycardia (VT) isthmuses can be defined by fixed or functional block. During sinus rhythm, pace mapping near the exit of an isthmus should produce a QRS similar to that of VT. Pace mapping at sites proximal to the exit may produce a similar QRS with a longer stimulus-to-QRS interval (S-QRS).

Assessment of radiofrequency ablation effect from unipolar pacing threshold.

Methods for determining if an ablation lesion has been created by RF current application are limited, but needed. This study sought to determine if a change in pacing threshold at the ablation site might be used to assess creation of an ablation lesion. Peak-to-peak amplitude of the bipolar electrogram (EGM) and the unipolar pacing threshold were determined before and after creation of RF lesions using irrigated tip (63 lesions in 11 patients) or conventional ablation catheters (33 lesions in 9 patients) in infarct scars for ablation of ventricular tachycardia.

Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.

Introduction: The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.

Methods And Results: The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.

Comparison of arrhythmia recurrence in patients presenting with ventricular fibrillation versus ventricular tachycardia in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial.

Because many episodes of ventricular fibrillation (VF) are believed to be triggered by ventricular tachycardia (VT), patients who present with VT or VF are usually grouped together in discussions of natural history and treatment. However, there are significant differences in the clinical profiles of these 2 patient groups, and some studies have suggested differences in their response to therapy. We examined arrhythmias occurring spontaneously in 449 patients assigned to implantable cardioverter-defibrillator (ICD) therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial to determine whether patients who receive an ICD after VT have arrhythmias during follow-up that are different from patients who present with VF.

Relationship of slow conduction detected by pace-mapping to ventricular tachycardia re-entry circuit sites after infarction.

Objectives: This study sought to characterize the relationship of conduction delays detected by pace-mapping, evident as a stimulus to QRS interval (S-QRS) delay >or=40 ms, to ventricular tachycardia (VT) re-entry circuit isthmuses defined by entrainment and ablation.

Background: Areas of slow conduction and block in old infarcts cause re-entrant VT.

Methods: In 12 patients with VT after infarction, pace-mapping was performed at 890 sites.

Quality of life in the antiarrhythmics versus implantable defibrillators trial: impact of therapy and influence of adverse symptoms and defibrillator shocks.

Background: Implantable cardioverter defibrillator (ICD) use reduces mortality in patients with serious ventricular arrhythmias compared with antiarrhythmic drug (AAD) use. However, the relative impact of these therapies on self-perceived quality of life (QoL) is unknown.

Methods And Results: Three self-administered instruments were used to measure generic and disease-specific QoL in Antiarrhythmics Versus Implantable Defibrillators trial participants.