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Electrophysiologic effects of the new class III antiarrhythmic drug dofetilide compared to the class IA antiarrhythmic drug quinidine in experimental canine atrial flutter: role of dispersion of refractoriness in antiarrhythmic efficacy.

Abstract：

INTRODUCTION:Previous studies suggest that class III antiarrhythmic drugs are more effective in reentrant arrhythmias because they prolong refractoriness (ERP) and wavelength and reduce dispersion of refractoriness compared to Class IA antiarrhythmic drugs, which slow conduction velocity (CV) in addition to their effects on refractoriness. METHODS AND RESULTS:To test this hypothesis, the Class III drug dofetilide and the Class IA drug quinidine were studied in the experimental canine crush-injury model of atrial flutter, utilizing right atrial multipoint programmed stimulation and activation mapping. In seven dogs dofetilide prolonged ERP by 23%, slowed CV by 9% at 200-msec cycle length (P < 0.001) and by 39% at 150-msec cycle length (P < 0.001), and increased wavelength by 11% (P < 0.02). Dofetilide reduced dispersion of ERP by 20% (P = 0.003) and adjacent electrodes with ERP difference > or = 20 msec by 76% (P < 0.001). Dofetilide slowed atrial flutter by 37% (P = 0.003) prior to terminating and suppressing it in all dogs. In eight dogs quinidine prolonged ERP by 14% (P < 0.001), slowed CV by 14% at 200-msec length cycle (P < 0.001) and by 19% at 150-msec cycle length (P < 0.001), and reduced wavelength by 2% (P = NS). Quinidine did not reduce dispersion of refractoriness. Quinidine slowed atrial flutter by 57% (P < 0.001), terminating and suppressing it in only three dogs. Efficacy of dofetilide was greater than quinidine (P = 0.026) and correlated with reduced dispersion of ERP (r = -0.653, P = 0.01), reduced adjacent electrodes with ERP difference > or = 20 msec (r = -0.637, P = 0.012), and prolonged wavelength (r = 0.61, P = 0.018). Dofetilide and quinidine terminated atrial flutter by similar mechanisms. Myocardial fiber orientation was nonuniform around the crush injury. CONCLUSIONS:Antiarrhythmic efficacy of dofetilide was greater than that of quinidine and correlated with drug-induced prolongation of wavelength and reduction in dispersion of refractoriness, effects produced only by dofetilide.

journal_name

J Cardiovasc Electrophysiol

journal_title

Journal of cardiovascular electrophysiology

authors

Cha Y,Wales A,Wolf P,Shahrokni S,Sawhney N,Feld GK

doi

10.1111/j.1540-8167.1996.tb00594.x

subject

Has Abstract

pub_date

1996-09-01 00:00:00

pages

809-27

issue

eissn

1045-3873

issn

1540-8167

journal_volume

pub_type

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Electrophysiologic effects of the new class III antiarrhythmic drug dofetilide compared to the class IA antiarrhythmic drug quinidine in experimental canine atrial flutter: role of dispersion of refractoriness in antiarrhythmic efficacy.