Predictors of atrial flutter with 1 : 1 conduction in patients treated with class I antiarrhythmic drugs for atrial tachyarrhythmias

Objectives: The purpose of the study was to look for the predictor factors of atrial proarrhythmic effects of class I antiarrhythmic drugs. Background : Class I anti arrhythmic drugs may induce or exacerbate cardiac arrhythmia s. The predictors of ventricular proarrhythmia are known. The predictors of atrial flutter with 1:1 conduction are unknown. Methods: Clinical history, EGG, signal-averaged EGG (SAECG) and electrophysiologic study were analyse d in 24 cases of 1:1 atrial flutter with class I AA drugs and in 100 contro l patients without history of 1:1 atrial flutter with class I AA drugs. Res ults: The ages of patients varied from 46 to 78 years. Underlying heart dis ease was present in nine patients. The surface EGG revealed the presence of a short PR interval (PR <0.13 ms), visible in leads V5, V6 in eight (35%) patients with normal P wave duration; in other patients with prolonged P wa ve duration, PR seemed normaL On SAECG recording, there was a pseudofusion between P wave and QRS complex. The electrophysiologic study revealed some signs indicating a rapid AV nodal conduction (short AH interval or rate of 2nd degree AV block at atrial pacing > 200 beats/mm) in 19 of the 23 studie d patients. All patients, except one, had at least one sign indicating a ra pid AV nodal conduction (short PR and/or P wave-QRS complex continuity on S AECG). In the control group, seven patients (7%) had a short PR interval (P <0.01) and 11 (11%) had a pseudofusion between P wave and QRS complex on S AECG (P <0.001). The P wave-QRS complex pseudofusion on SAECG had a sensiti vity of 100% and a specificity of 89% for the prediction of an atrial proar rhythmic effect with class I antiarrhythmic drug. Conclusion: We recommend avoiding class I AA drugs in patients with a short PR interval on surface E GG and to record SAECG in those with apparently normal PR interval to detec t a continuity between P wave and QRS complex, which could indicate a rapid AV nodal conduction, predisposing to 1: 1 atrial flutter with the drug. (C ) 2001 Elsevier Science Ireland Ltd. All rights reserved.