[Choice of a class I intravenous anti-arrhythmic drug in severe ventricular arrhythmias]

In the choice of a Class I intravenous antiarhythmic medication for the treatment of threatening ventricular extrasystoles, one must take into account the speed of action of the product, its effects on hemodynamics and conduction as well as its efficacy. The rapidity of action implies the ability to reach, without delay, a therapeutic plasma level which will depend upon the distribution volume and the dose injected. An effective plasma level may be quickly reached following the intravenous administration of lidocain, disopyramide, lorcainide, tocainide and flecainide. All antiarhythmic medications have an unfavorable effect on hemodynamics; xylocain and ajmaline seem to depress the least the left ventricular function, followed by lorcainide. Unfavorable effects on the atrio-ventricular conduction are observed with substances of type IC; the duration of QRS may be affected as well by antiarhythmic medications IA and IC, with a lengthening of QT being mostly noted type IA medications. Comparison of the efficacy of antiarhythmic medications requires a strict methodology and the current data from the literature do not permit to assert with certainty the superiority of one antiarhythmic medication over the others.