title: Electrophysiologic effects of theophylline in young patients with recurrent symptomatic bradyarrhythmias.
abstract: In this study, both acute electrophysiologic actions of intravenously administered theophylline and clinical effects of chronic oral theophylline therapy were assessed in 10 young patients (aged 9 to 41 years) without clinically significant cardiac disease, in whom recurrent symptoms of syncope and dizziness were attributed to transient bradyarrhythmias (sinus pauses, marked sinus bradycardia or paroxysmal atrioventricular [AV] block). Intravenous theophylline infusion (serum concentration range 9.5 to 12.0 mg/liter) shortened means sinus cycle length (control 973 +/- 285 ms versus theophylline 880 +/- 226 ms, p less than 0.005) and decreased both the estimated sinoatrial conduction time (control 169 +/- 56.0 ms versus theophylline 143 +/- 55.3 ms, p less than 0.05) and the maximum corrected sinus node recovery time (control 442 +/- 251.0 ms versus theophylline 255 +/- 146.2 ms, p less than 0.05). In addition, theophylline infusion shortened the minimum atrial paced cycle length with sustained 1:1 AV conduction (control 414 +/- 86 ms versus theophylline 379 +/- 97 ms, p less than 0.05) and consistently reduced AV node functional refractory periods. Subsequent chronic oral theophylline therapy (serum levels 9 to 12 mg/liter) was tolerated in 8 patients (80%). During a follow-up of 5 to 24 months, suppression of symptoms was achieved in 6 of the 8 patients. Thus, theophylline exhibits positive chronotropic and dromotropic effects in man at serum concentrations in the usual therapeutic range (10 to 15 mg/liter). Furthermore, suppression of symptoms during follow-up suggests that theophylline treatment may be a useful therapeutic consideration in some patients with recurrent symptomatic bradyarrhythmias.
mesh_terms: D000293:Adolescent; D000328:Adult; D001283:Atrioventricular Node / Q000187:drug effects; D001919:Bradycardia / Q000188:drug therapy* / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial / Q000379:methods; D002986:Clinical Trials as Topic; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D007263:Infusions, Parenteral; D008297:Male; D012008:Recurrence; D012849:Sinoatrial Node / Q000187:drug effects; D013575:Syncope / Q000188:drug therapy / Q000503:physiopathology; D013806:Theophylline / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D013806:Theophylline