CORRECT USE OF PROPAFENONE
The main electrophysiological property of Propafenone is a reduction in the upstroke velocity (phase 0) and amplitude of the monophasic action potential . This leads to a decrease of conduction velocity in all cardiac structures (atria, AV node, His Purkinje, ventricular myocardium). In the same structures there is a slight prolongation of the refractory period that becomes significant only at high heart rates. In the surface ECG, Propafenone increases both the PR interval (typically 11 to 22%) and QRS duration (typically 16 to 18%) in a dose dependent manner (Table 1). The QT interval is usually not affected. The increase in QTc that can sometimes be observed at high doses (up to 900 mg/day) is actually due to QRS lengthening, while the JT interval remains the same or is shorter. TABLE 1
Abbrev. â decrease á increase à no change In addition, Propafenone has a moderate anti-adrenergic effect (1), expressed by a reduction in exercise-induced tachycardia (2), the clinical importance of which is still under evaluation.
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