Antiarrhythmic drug effects on premature beats are partly determined by prior cardiac activation frequency in perfused guinea-pig heart

Electrocardiographic marker of the cardiac action potential triangulation induced by antiarrhythmic drugs in perfused guinea-pig heart

NEW FINDINGS

What is the central question of this study? Can triangular appearance of ventricular action potential, indicating proarrhythmic profile of antiarrhythmic agent, be approximated by specific changes on ECG? What is 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_start interval) on 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. The latter results in the triangular shape of ventricular action potential, indicating high arrhythmic risks. However, clinically, the utilility of triangulation assessments for predicting arrhythmia is limited owing to the invasive nature of the ventricular action potential recordings. This study examined whether the triangulation effect can be detected indirectly from ECG analysis. Epicardial monophasic action potentials and ECG were simultaneously recorded in perfused guinea-pig hearts. With antiarrhythmics (dofetilide, quinidine, procainamide and flecainide), a prolongation of the initial repolarization seen in the action potential recordings was closely approximated by lengthening of the interval bewteen the J point and the start of the T wave (the JT_start interval) on ECG, whereas a prolongation of the late repolarization was paralleled by widening of the T wave upslope. Dofetilide, quinidine and procainamide induced a prominent slowing of the phase 3 repolarization in epicardium, leading to triangulation of the action potential. These effects were accompanied by a greater prolongation of the T wave upslope compared to the JT_start interval. Flecainide elicited a proportional prolongation of the initial and the late ventricular repolarization, and therefore failed to induce triangulation, based on analysis of both epicardial action potential and ECG profiles. Collectively, these findings suggest that the ratio between the durations of the T wave upslope and the JT_start interval may represent ECG metric of the ventricular action potential triangulation induced by antiarrhythmic drugs. This article is protected by copyright. All rights reserved.