Atrial fibrillation (AF) with a rapid ventricular response was induced
by intravenous (IV) aminophylline during treatment for symptomatic pu
lmonary disease in three patients who had no evidence of underlying he
art disease or previous cardiac arrhythmia. Serum theophylline concent
ration was therapeutic in two patients and toxic in the third. Previou
s reports of AF related to aminophylline have underscored its associat
ion with toxic serum theophylline concentration. Conversion to sinus r
hythm occurred at a time interval (9-14 hours) appropriate to the seru
m decay of aminophylline, after its cessation. A shortened atrial refr
actory period and dispersed recovery of excitability consequent to ami
nophylline may engender multiple reentrant circuits and lead to AF. IV
diltiazem was more effective than digoxin in the ventricular rate con
trol of AF prior to conversion to sinus rhythm.