Dromotropic effects of oral theophylline in patients with atrial fibrillation and a slow ventricular response

Theophylline increases sinus rate, but as yet its use has not been investigated in patients with chronic atrioventricular conduction disturbances. Resting electrocardiogram, 24-h Holter recording and treadmill test were performed in 17 patients with chronic atrial fibrillation and a slow ventricular response not related to drugs (age: 75 ± 8 years). Then slow-release theophylline was administered (700 mg daily) and after 5 days these investigations were repeated with the same methods. Theophylline increased mean resting heart rate (51 ± 6 versus 67 ± 13 beats · min ^-1, P <0.01), mean 24-h heart rate (51 ± 6 versus 68 ± 14 beats · min ^-1, P -1, P <0.01). Cardiac pauses >2.5 s were present in 13 patients during control recording; after theophylline they disappeared in 11 and markedly decreased in the remaining two. The longest R-R interval decreased in all patients (3218 ± 943 versus 2121 ± 518 ms, P <0.01). The daily number of wide QRS complexes increased in 16 out of 17 patients (428 ± 752 versus 1146 ± 1464 ms, P <0.01). Exercise heart rate, evaluated at the end of first and second stage, was higher after theophylline than during control test (P <0.01). These data suggest that oral theophylline can represent a valid therapy in most patients with atrial fibrillation and a slow ventricular response.