Distinct Pharmacologic Substrate in Lidocaine-Sensitive, Repetitive Atrial Tachycardia

Lidocaine-sensitive, repetitive atrial tachycardia is an uncommon arrhythmia. The electrophysiologic substrate is still unknown, and the pharmacologic responses have not been fully explored. The aim of this study was to investigate the effects of intravenous adenosine and verapamil in patients with lidocaine-sensitive atrial tachycardia. In 9 patients with repetitive uniform atrial tachycardia, the response to intravenous adenosine (12 mg), lidocaine (1 mg/kg body weight), and verapamil (10 mg) were sequentially investigated. Simultaneous 12-lead electrocardiogram (ECG) was recorded at baseline and continuously monitored thereafter. Tracings were obtained at regularly timed intervals right after the administration of each drug to evaluate changes in the arrhythmia characteristics. Repetitive atrial tachycardia was abolished by intravenous lidocaine in the 9 patients within the first 2 minutes after the end of injection. Adenosine suppressed the arrhythmia in 2 patients and shortened the runs of atrial ectopic activity in 1 patient, while verapamil was effective in 2 patients, 1 of them insensitive to adenosine and the other 1 sensitive to this agent. In 5 patients, the arrhythmia was abolished by radiofrequency ablation at different sites of the right atrium. Lidocaine-sensitive atrial tachycardia may eventually be also suppressed by adenosine and/or verapamil. This suggests that this enigmatic arrhythmia may be caused by different underlying electrophysiologic substrates and that at least in some cases, delayed afterdepolarizations seem to play a determining role.