Key result
Class Ic antiarrhythmic drugs increased atrial refractoriness and wavelength index in a tachycardia-dependent manner in patients with paroxysmal atrial fibrillation.
Why the study?
Do class Ic antiarrhythmic drugs alter atrial refractoriness, conduction delay, and wavelength index in patients with paroxysmal atrial fibrillation?
Do class Ic antiarrhythmic drugs alter atrial refractoriness, conduction delay, and wavelength index in patients with paroxysmal atrial fibrillation?
Class Ic antiarrhythmic drugs may reduce atrial vulnerability in paroxysmal AF by increasing the wavelength of the reentrant circuit during rapid heart rates.
May support Class Ic use for rate-dependent wavelength prolongation in paroxysmal AF; extends mechanistic data but remains hypothesis-generating.
While class Ic antiarrhythmic drugs are effective in treating patients with atrial fibrillation, their mechanism of action is poorly understood. We performed electrophysiological studies before and after their administration to 22 patients with paroxysmal atrial fibrillation. Atrial refractoriness, maximal interatrial conduction delay and the wavelength index were measured at two basic cycle lengths (600 or 400 ms). Both drugs studied increased atrial refractoriness and wavelength index. Flecainide reduced the maximal interatrial conduction delay, but pilsicainide did not. Each drug increased the wavelength index in a tachycardia-dependent manner. Class Ic drugs may reduce atrial vulnerability by increasing the wavelength of the reentrant circuit during periods of rapid heart rate.
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Kumagai et al. (1998) studied paroxysmal atrial fibrillation (n=22). Class Ic antiarrhythmic drugs (flecainide and pilsicainide) vs. Baseline (before administration) was evaluated on Atrial refractoriness, maximal interatrial conduction delay, and wavelength index. Class Ic antiarrhythmic drugs increased atrial refractoriness and wavelength index in a tachycardia-dependent manner in patients with paroxysmal atrial fibrillation.
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