Detection of repolarization alternans with an implantable cardioverter defibrillator lead in a porcine model.

Mechanistic links have been suggested between repolarization alternans (RPA) and the onset of ventricular tachycardia (VT) and/or fibrillation. Endocardial detection of RPA may, therefore, be an important step in future device-based treatments of arrhythmias. Here, we investigate if RPA could be detected during acute ischemia using an implantable cardioverter defibrillator (ICD) lead (tip to distal coil) located in the right ventricular apex.

Significance of adenosine-induced atrioventricular block in patients with unexplained syncope.

Objectives: The purpose of this study was to test whether a prolonged (>/=6 seconds) period of AV block in response to adenosine triphosphate (ATP) identifies additional patients at risk for bradycardia who may benefit from pacemaker implantation.

Background: Bradycardia is a common etiology for syncope in patients without underlying structural heart disease. Conventional testing using electrophysiologic and tilt table studies often fail to identify patients prone to episodes of symptomatic bradycardia.

Usefulness of prolonged QRS duration to identify high-risk ischemic cardiomyopathy patients with syncope and inducible ventricular tachycardia.

We evaluated 61 consecutive patients who had coronary artery disease, decreased left ventricular function, and syncope and underwent implantation of a cardioverter-defibrillator because sustained ventricular tachycardia was inducible at electrophysiologic testing. During a follow-up of 3.0 +/- 1.

Single-stage adenosine tilt testing in patients with unexplained syncope.

Introduction: We previously have shown that a 3-minute single-stage adenosine tilt test has a diagnostic yield comparable to a two-stage protocol consisting of a 30-minute drug-free tilt followed by a 15-minute isoproterenol tilt. In this study, we sought to further define the clinical utility of adenosine tilt testing in patients with unexplained syncope by prospectively evaluating test specificity and determining predictors of a positive test response.

Methods And Results: The specificity of single-stage adenosine tilt testing was determined using 30 control subjects.

An update on electrical cardioversion of atrial fibrillation.

Atrial fibrillation is the most frequently encountered sustained arrhythmia in clinical practice. Electrical cardioversion of atrial fibrillation using damped sine wave shocks has been a mainstay of therapy for nearly 4 decades; its limitation remains a failure rate that approaches 20%. Although several alternatives have been proposed, including delivering 720 J shocks using dual monophasic defibrillators, ibutilide pretreatment and internal cardioversion, each of these approaches has significant limitations, which preclude its routine use.