[Clinical and electrophysiological indications for permanent electrostimulation in sick sinus syndrome (author's transl)].

In 49 patients with sick sinus syndrome the following electrophysiological parameters were studied: sinus node recovery time and conduction time, atrial and AV nodal refractory periods, atrioventricular and intraventricular conduction. Moreover, pharmacological, vagal and sympathicomimetic stimulation were performed. These data were related to the clinical picture to establish any possible correlation leading to a more specific therapeutical choice. Patients were divided in two groups: group 1, with a prevalence of tachyarrhythmic symptoms and a lesser incidence of syncope, in which cases the sinus node function appeared to be only slightly affected. In group 2 small incidence of tachyarrhythmias and a clear prevalence of syncope with severe impairment of sinusal automaticity and/or sinoatrial conduction were present; AV and IV conduction disturbances were equally distributed in both groups. In more than 1/3 of the cases of the group I arrhythmias were succesfully treated with pharmacological therapy only, with Group 1 A antiarrhythmic agents in most cases. In the other cases of this Group and in all cases of Group II permanent electrical stimulation alone or together with drug therapy was necessary. Long term results with different therapeutical choices and, specifically, with the type of stimulation chosen in individual cases (sequential, rate-programmable ventricular, demand ventricular) are presented.