Activation of εPKC reduces reperfusion arrhythmias and improves recovery from ischemia: optical mapping of activation patterns in the isolated guinea-pig heart.

Unlabelled: Pervious biochemical and hemodynamic studies have highlighted the important role of εPKC in cardioprotection during ischemic preconditioning. However, little is known about the electrophysiological consequences of εPKC modulation in ischemic hearts. Membrane permeable peptide εPKC selective activator and inhibitor were used to investigate the role of εPKC modulation in reperfusion arrhythmias.

Improved activation time assignment of unipolar electrograms from ischemic canine epicardium.

Aims: The present study attempts to develop an objective, statistically based set of criteria for activation time determination from unipolar electrograms (U-EGMs) using a standard of activation related to biophysical theory.

Methods: A high-resolution assembly of U-EGMs obtained from the epicardial surface of the canine postinfarction heart were analyzed in order to achieve the best prediction of local versus distant activation. An activation time standard (ATS) consisted of three properties: (1) propagation of activation, evidenced by a linear temporal shift of waveforms from closely spaced U-EGMs with little or no decay in amplitude; (2) cycle length-dependent changes of those propagating waveforms; and (3) evidence of electrotonic deflections, seen as nonpropagating potentials having decaying amplitude with distance.

Spatial dispersion of repolarization is a key factor in the arrhythmogenicity of long QT syndrome.

Introduction: The occurrence of significant spatial dispersion of repolarization in vivo as it relates to the mechanism of arrhythmia formation in the long QT syndrome (LQTS) continues to be questioned.

Methods And Results: We investigated a guinea pig model of LQT3 using anthopleurin-A (AP-A) to study the contribution of rate-dependent spatial dispersion of repolarization in the intact heart to the arrhythmogenicity of LQTS. Optical action potentials were measured using potentiometric fluorescent dye di-4ANEPPS in Langendorff-perfused hearts with induced AV block.

Mechanism of discordant T wave alternans in the in vivo heart.

Introduction: Compared to concordant T wave alternans (CA), discordant T wave alternans (DA) may be associated with an increased dispersion of repolarization (DR) and a greater propensity to develop reentrant ventricular tachyarrhythmias. The electrophysiologic mechanisms of DA in the in vivo heart are not well understood.

Methods And Results: The mechanisms of DA were investigated in the canine anthopleurin-A surrogate model of long QT3 syndrome using tridimensional analysis of activation and repolarization patterns from 256 to 384 unipolar electrograms.

Electrophysiological mechanism of enhanced susceptibility of hypertrophied heart to acquired torsade de pointes arrhythmias: tridimensional mapping of activation and recovery patterns.

Background: Cardiac hypertrophy is associated with increased incidence of sudden death and susceptibility to proarrhythmic effects of antiarrhythmic agents. However, the in vivo electrophysiologic mechanism of the arrhythmias has not been investigated in detail.

Methods And Results: Dose-dependent susceptibility to Torsade de Pointes (TdP) by class III drug dofetilide, 3, 10, and 30 microg/kg, was compared in 6 control dogs (C) and in 5 dogs 6 to 8 weeks after induction of complete atrioventricular block (AVB) that resulted in ventricular hypertrophy (H).