Electrophysiologic effects of intravenous carocainide

The electrophysiological properties of carocainide a new Class I antiarrhythmic agent (Delalande Research Centre) were studied after intravenous injection of 3.5 mg/kg in 5 minutes in 16 patients aged 24 to 66 years. Five minutes after the injection there was a significant increase (p less than 0.01) in the HV (+/- 12.8 +/- 10.5 msec), AH (+ 21.8 +/- 14 msec) and PR intervals (+ 43.8 +/- 24.2 msec) and in the duration of QRS (+ 20.6 +/- 9.9 msec). The anterograde and retrograde Wenckebach points were decreased (-42 +/- 43 bpm and - 52 +/- 36 bpm respectively, p less than 0.05). All these effects reverted progressively 20 minutes after injection and disappeared by the 40th minute, which corresponds to the pharmaco-kinetic profile of the patient. There were no changes in blood pressure, sinus node function or refractory periods except for the retrograde refractory periods which were prolonged (+ 87 +/- 41 msec). Atrial fibrillation was induced in 2 patients and atrial flutter in 2 others by the extrastimulus technique. These arrhythmias could not be reproduced in these 4 patients during the 40 minutes after injection of carocainide. Five other patients with reciprocating nodal tachycardia induced by atrial extrastimuli had their arrhythmia interrupted by the carocainide injection. We conclude that carocainide acts mainly on atrio-ventricular and intra-ventricular conduction. The results obtained in patients with tachycardias suggest that the product is effective in atrial arrhythmias and paroxysmal junctional tachycardia.