The autonomous nervous system influence on sinus node (SN) in both physiological and pathological states is the most important factor determining its function. There are only few publications about autonomous nervous system action on electrophysiological properties of the human heart (ventricles), specially in patients with different types of sick sinus syndrome (SSS). Electrocardiograms of 113 patients (pts) with coronary heart disease, suspected for SSS, recorded during transesophageal atrial pacing before and after pharmacological denervation of the heart, were analysed. For heart denervation propranolol (0.2 mg/kg body weights) and atropine (0.04 mg/kg body weights) intravenously were used. We analysed sinus cycle length (P-P), QT interval and QTc (QT interval corrected according to Bazett's formula) during both sinus and paced rhythm (100 bpm), before and after denervation of the heart. During clinical observations (including Holter monitoring) and after electrophysiological testing we excluded SSS in 28 pts (group A) and confirmed diagnosis of SSS in 85 pts (group B). Group B was divided in two parts; pts with normal (group B1) and abnormal (group B2) intrinsic properties of the SN. Group B1 included 23 pts (15 men and 8 woman from 36 to 74, mean 53 +/- 9) with normal sinus cycle length after denervation (according to Joses's formula) and maximal, corrected sinus node recovery time after denervation less than 422 ms. Group B2 included remaining 62 pts (26 men and 36 woman from 36 to 80, mean 59 +/- 9). In groups A and B1 denervation of the heart shortens P--P, QT, QT100 and QTc100 significantly. Only QTc in A and B1 and all parameters in group B2 didn't change significantly.(ABSTRACT TRUNCATED AT 250 WORDS)