Symptomatic improvement in a patient with sick sinus syndrome after the onset of stable atrial flutter.

A patient with sick sinus syndrome (SSS) presented with episodic lightheadedness and weakness. The electrocardiographic features were marked supraventricular bradyarrhythmias and paroxysmal atrial flutter. The symptoms lasted for four years and disappeared with the onset of stable atrial flutter which has persisted for the past seven years. Over the 11-year period of observation, there has been progressive involvement of the His-Purkinje system manifested by the development of left anterior fascicular block, right bundle-branch block, and prolongation of the HV conduction time. The patient has refused pacemaker implantation. In the absence of angina and in the presence of a normal heart size, the etiology of his SSS is postulated to be idiopathic fibrosis of his conduction system.