Electrophysiologic evaluation of extrinsic and intrinsic sinus node dysfunction.

Electrophysiologic investigation was done for ten patients with clinical and ECG criteria for sick sinus syndrome (SSS). Sinus node function was assessed through corrected sinus node recovery time (CSNRT) and sinoatrial conduction time (SACT), before and after autonomic blockade (AB) with propranolol 0.2 mg/kg and atropine 0.04 mg/kg, given intravenously. Four patients having electrophysiologic parameter in normal range before AB were not considered as SSS. In three patients extrinsic sinus node dysfunction (SND) was found, the pathologic values of CSNRT and SACT being normal after AB, and in one patient with sinus bradycardia, the sinus node function was difficult to be appreciated. In two patients only intrinsic SND was found and, in consequence, pacemaker device was implanted.