Clinical effects of oral theophylline in sick sinus syndrome.

In 17 patients with symptomatic sinus bradycardia (age: 66 +/- 11 years), a resting electrocardiogram, a 24-hour Holter recording, and a treadmill test were performed both before and after administration of slow-release theophylline (700 mg daily). The drug increased resting heart rate (46 +/- 7 versus 62 +/- 18 beats/min, p less than 0.01), mean 24-hour rate (51 +/- 6 versus 64 +/- 16 beats/min, p less than 0.01), and minimal 24-hour heart rate (36 +/- 6 versus 43 +/- 10 beats/min, p less than 0.05). Cardiac pauses greater than 2.5 seconds were present in four patients during control recording, and disappeared after theophylline. The daily number of premature supraventricular and ventricular beats increased slightly after the drug. Exercise heart rate was higher after theophylline than during the control test (p less than 0.01). Thirteen patients were followed for a period of 17 +/- 3 months. Suppression of symptoms was achieved in 12 patients. Asthenia and easy fatigue were reduced markedly by the drug. During long-term therapy, the sinus rate was similar to that observed at the steady-state evaluation. In 3 of the 17 patients theophylline had to be discontinued because of gastric intolerance (in two at the end of the steady-state evaluation and in one during long-term therapy). These data suggest that oral theophylline can represent an effective therapy in some patients with symptomatic sinus bradycardia.