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[Arrhythmogenic effect of ajmaline on the atrial level].

The aim of this study was to determine whether an antiarrhythmic, Ajmaline, could have proarrhythmic effects on the atrium and to compare the results with those of other antiarrhythmic drugs. A total of 1950 patients without cardiac failure or recent (less than 6 weeks) myocardial infarction were given 1 mg/kg of Ajmaline intravenously during electrophysiological investigation. A proarrhythmic effect was defined as the occurrence of supraventricular tachycardia (SVT) in a patient without this arrhythmia before the test or the facilitation of its induction. Fifty five patients developed SVT (mainly atrial tachyarrhythmias: 48 cases, and some junctional tachycardia: 7 cases) which occurred spontaneously in 22 patients and during fixed atrial pacing in 33 patients. Fifteen patients developed ventricular tachycardia (VT). The predisposing factors for the development of SVT were: a previous history suggesting spontaneous SVT (28 patients; 51 p. 100); sinoatrial block (14 patients--the only abnormality in 10 cases). Seventeen patients had none of these factors but 8 had known cardiac pathology and the other 9 were relatively elderly patients (79 years). Twelve of the patients developing VT had known cardiac disease, bundle branch block in 12 cases and previous VT in 6 cases. In conclusion, proarrhythmic effects of Ajmaline are infrequent if its contraindications are respected, but they do exist at both atrial (2.8 p. 100) and ventricular levels (0.8 p. 100): the risk factors are comparable: previous spontaneous arrhythmias or ECG changes (SA block at the atrial and bundle branch block at the ventricular level).