Out of a pacemaker population of 392 patients, 90 (23%) have been found to have sinoatrial syndrome. Their ages ranged from 22 to 86 years, and averaged 66 for men and 70 for women. The male-to-female ratio was 1 : 1.6. Before pacemaker implantation, syncopal attacks had occurred in 54 %, dizziness without syncope in 31 % and tachyarrhythmias in 57 %. Atrial or paroxysmal supraventricular tachycardia had been recorded in 33 %, atrial fibrillation or flutter in 28 %, and ventricular tachycardia in 11%. First and/or second degree AV block was found in 36%. Coronary heart disease was present in 61% and 20% had had myocardial infarction. Cardiomyopathy and previous carditis were other associated heart diseases. Sinoatrial syndrome was the only manifestation of heart disease in 20%. Follow-up time after pacemaker implantation ranged from 3 months to 7 years, mean 23 months. Syncopal attacks were stopped in 48 of 49 patients, dizziness was relieved in all 28 patients and tachyarrhythmias were controlled by combined drug treatment in 43 of 51 patients. Nineteen patients died during the follow-up, most of them of cerebrovascular events or myocardial infarction. Associated coronary heart disease was especially frequent in this group. The death of one patient was caused by a run-away pacemaker. Other pacing failures were due to electrode movement or premature battery exhaustion. There was no mortality associated with pacemaker implantations or replacements. These results strongly support the view that pacemaker treatment most effectively controls symptoms of sinoatrial syndrome when drug treatment fails.

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One hundred and seventy-five patients with atrial fibrillation treated for the first time with DC shock were divided into two groups according to year of birth. Group I received a long-acting quinidine bisulphate preparation, the dosage of which was adjusted to give serum levels of 1-3 mg./l. Side-effects were rare with this dosage. The lack of controlled data on the value of prophylactic quinidine prompted the present study. Subjects and methodsOur study comprised all the patients of three departments of medicine of the University Central Hospital, Helsinki, who were referred for the first time for electric conversion of their atrial fibrillaReceived I6 June I969.

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