Data processing and analysis
In each epicardial lead, activation time (AT) and end of repolarization
time (RT) were determined as dV/dt minimum during QRS-complex and dV/dt
maximum during T-wave, respectively, in respect to a QRS-complex onset.
As a surrogate for action potential duration, activation-repolarization
interval (ARI) was calculated as the difference between RT and AT.
Average duration of ARI from all leads was used in analysis. A time of
epicardial activation breakthrough reflecting the duration of conduction
via conduction system was taken as the minimal AT throughout all
epicardial leads. A duration of epicardial activation serving as an
indirect estimate for activation of ventricular contractile myocardium
was calculated as the difference between the maximal and minimal ATs
throughout all epicardial leads. The maximal epicardial AT was used as a
measure of total duration of ventricular activation. Dispersion of
repolarization (DOR), a prerequisite for the unilateral conduction
block, was taken as the difference between the maximal and minimal
values of RTs. The inducibility of episodes of ventricular tachycardia
and/or ventricular fibrillation (VT/VF) induced by burst pacing was
analyzed.