Pacemaker therapy in sino-atrial block complicated by paroxysmal tachycardia.

Pacemakers were implanted in 10 of 14 patients with dizziness and syncopal episodes of long duration, due to sino-atrial block.Paroxysmal supraventricular tachycardia, notably atrial fibrillation, had occurred in 6 patients.Medical treatment was unsatisfactory in 3 of these and pacemaker therapy was given.This abolished both syncope and paroxysmal tachycardia.Sino- atrial block and supraventricular tachycardia are probably not only different expressions of the same pathological process; a functional relation seems likely.Sino-atrial block may, on rare occasions, cause syncopal episodes which can be pre- vented by pacemaker therapy.Another complication is paroxysmal, rapid, supra- ventricular rhythms, notably atrial fibrillation.Treatment is then difficult.Cardio-accelerator drugs, such as atropine or isoprenaline, may precipitate tachycardia, while antiarrhythmic agents, such as quinidine, digitalis, or propranolol, can accentuate bradycardia and cause syncope.A logical approach seems to be the combination of pacemaker to prevent bradycardia, and antiarrhythmic drugs in sufficient doses to prevent tachycardia.Suc- cessful use of the pacemaker was reported by Cohen, Kahn, and Donoso (I967) in a patient with chronic sinus and nodal bradycardia and paroxysmal atrial flutter.The purpose of this paper is to show that sino-atrial block can quite often be associ- ated with paroxysmal atrial fibrillation, and that pacemaker therapy may prevent both syncope and fibrillation.Patients and methods During the past 4 years sino-atrial block was the main diagnosis in I4 patients admitted to the Section of Cardiology, Medical Department, Central Hospital, Trondheim.Neither patients with recent myocardial infarction nor those whose symptomless sino-atrial block was dis- covered accidentally, were included.A summary of clinical data is shown in the Table.Ages varied from 47 to 76 years.One patient had a history