Publications by authors named "O Osadchii"
Background: The aim of this simulation was to examine the utility of a novel ECG-based index of cardiac action potential (AP) triangulation, the Tstart-to-Tpeak (TsTp) interval-to-JTstart (JTs) interval ratio, for assessment of changes in AP profile imposed through variations in the duration of the plateau phase and the phase 3 repolarization.
Methods: ECGs were simulated using a realistic rabbit model based on experimental data. The AP plateau was measured at APD30, and the phase 3 was assessed as APD90-to-APD30 difference (AP durations at 90 % and 30 % repolarization, respectively).
New Findings: What is the central question of this study? Can the triangular appearance of ventricular action potential, indicating proarrhythmic profile of antiarrhythmic agent, be approximated by specific changes on an electrocardiogram (ECG)? What are the main finding and its importance? The triangulation of the ventricular action potential seen when antiarrhythmic drugs induce a greater lengthening of the late repolarization compared to the initial repolarization in epicardium is closely approximated by a greater prolongation of the T wave upslope relative to the interval between the J point and the start of the T wave (the JT interval) on the ECG. These findings may improve the power of ECG assessments in predicting the drug-induced arrhythmia resulting from slowed phase 3 repolarization.
Abstract: Antiarrhythmic drugs prescribed to treat atrial fibrillation can occasionally precipitate ventricular tachyarrhythmia through a prominent slowing of the phase 3 repolarization.
New Findings: What is the central question of this study? Can antiarrhythmic drug effects on repolarization, conduction time and excitation wavelength in premature beats be determined by prior cardiac activation frequency? What is the main finding and its importance? In premature beats induced after a series of cardiac activations at a slow rate, antiarrhythmics prolong repolarization but evoke little or no conduction delay, thus increasing the excitation wavelength, which indicates an antiarrhythmic effect. Fast prior activation rate attenuates prolongation of repolarization, while amplifying the conduction delay induced by drugs, which translates into the reduced excitation wavelength, indicating proarrhythmia. These findings suggest that a sudden increase in heart rate can shape adverse pharmacological profiles in patients with ventricular ectopy.
View Article and Find Full Text PDFNew Findings: What is the central question of this study? Are modifications in the restitution of ventricular action potential duration induced by antiarrhythmic drugs the same when assessed with premature extrastimulus application at variable coupling intervals (the standard stimulation protocol) and with steady state pacing at variable rates (the dynamic stimulation protocol)? What is the main finding and its importance? With class I and class III antiarrhythmics, the effects on electrical restitution determined with the standard stimulation protocol dissociate from those obtained during dynamic pacing. These findings indicate a limited value of the electrical restitution assessments based on extrasystolic stimulations alone, as performed in the clinical studies, in estimating the outcomes of antiarrhythmic drug therapies.
Abstract: A steep slope of the ventricular action potential duration (APD) to diastolic interval (DI) relationships (the electrical restitution) can precipitate tachyarrhythmia, whereas a flattened slope is antiarrhythmic.
New Findings: What is the central question of this study? Is the slowed conduction upon premature ventricular activations during clinical electrophysiological testing attributable to the prolonged activation latency, or increased impulse propagation time, or both? What is the main finding and its importance? Prolonged activation latency at the stimulation site is the critical determinant of conduction slowing and associated changes in the ventricular response intervals in premature beats initiated during phase 3 repolarization in perfused guinea-pig heart. These relations are likely to have an effect on arrhythmia induction and termination independently of the presence of ventricular conduction defects or the proximity of the stimulation site to the re-entrant circuit.
Abstract: During cardiac electrophysiological testing, slowed conduction upon premature ventricular activation can limit the delivery of the closely coupled impulses from the stimulation site to the region of tachycardia origin.