Tridimensional activation patterns of acquired torsade-de-pointes tachycardias in dogs with chronic AV-block.

Background: Dogs with chronic AV block exposed to type-III antiarrhythmic agents develop polymorphic ventricular tachycardias (PVT). Controversy exists regarding PVT mechanism and underlying pathophysiology.

Methods And Results: In dogs with acute (n = 10, AAVB) or chronic AV block (n = 14, CAVB, 62 +/- 5 days after AV-node ablation) 60 pins (12 mm long, 4 bipolar electrodes) were inserted into both ventricles.

Biventricular hypertrophy in dogs with chronic AV block: effects of cyclosporin A on morphology and electrophysiology.

Chronic atrioventricular (AV) block (CAVB) and biventricular hypertrophy in dogs increase susceptibility to drug-induced polymorphic ventricular tachycardia (PVT). In various rodent models, cyclosporin A (CsA) prevented hypertrophy. A similar effect in the CAVB model would allow us to determine whether hypertrophy represents an epiphenomenon, the cause of electrophysiological changes, and/or the anatomic substrate for PVTs.

Effects of acute ischemia, early extrabeats and propafenone on complex activation patterns in intact and ischemic canine hearts.

Although, sodium channel blockers have the ability to suppress nonsustained ventricular arrhythmias, an excessive drug-associated arrhythmic death rate has been reported in patients with coronary heart disease (CHD). Sodium channel blockers should prevent initiation of reentry activation by reducing directional differences in cardiac conduction (anisotropy). However, in vitro data demonstrated, that reduction of membrane excitability, e.

Refractory patterns and susceptibility to drug-induced polymorphic ventricular tachycardias in dogs with chronic atrioventricular block: relation to the type of anesthesia.

Controversy exists as to the homogeneity of repolarization throughout the canine ventricular wall in vivo. The type of anesthesia has been shown to affect regional differences in monophasic action potential duration and the inducibility of polymorphic ventricular tachycardias (PVTs) in normal canine hearts. This study was conducted to determine refractory patterns and arrhythmia susceptibility in relation to halothane or pentobarbital anesthesia in dogs with chronic atrioventricular block and biventricular hypertrophy.

Suppression of atrial fibrillation by multisite and septal pacing in a novel experimental model.

Objectives: To evaluate the preventive efficacy of multisite and septal atrial pacing in an experimental model.

Methods: Sterile right atrial pericarditis was induced in 12 foxhounds to provide an anatomical substrate for atrial fibrillation (AF). As a trigger mechanism, atrial extrasystoles were simulated by constant asynchronous pacing at a cycle length of 1000 ms from randomly selected right or left atrial electrodes, using a biatrial epicardial multielectrode with 128 bipoles.

Variability of Holter electrocardiographic findings in patients fulfilling the noninvasive MADIT criteria. Multicenter Automatic Defibrillator Implantation Trial.

In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the non-invasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF < or = 0.

Effects of the I(Kr)-blocking agent dofetilide and of the I(Ks)-blocking agent chromanol 293b on regional disparity of left ventricular repolarization in the intact canine heart.

Recent in vitro studies have described regional differences of ion current expression and function, possibly accounting for reduced homogeneity of repolarization in the heart. In 11 intact canine hearts regional disparity of repolarization was determined at baseline and after administration of the I(Kr) blocking agent dofetilide (30 microg/kg) and the I(Ks)-blocking agent chromanol 293b (10 mg/kg). Effective refractory periods (ERPs) were determined through up to 10 needle electrodes inserted into basal, midwall and apical regions of the left ventricular wall using the extrastimulus technique (cycle length [CL] 300 and 850 ms).