Sinoatrial node (SAN) function depends on its intrinsic properties and on regulatory influences of autonomic nervous system. Disturbances in these both factors are responsible for intrinsic and extrinsic SAN dysfunction (SAND), respectively. Heart rate variability (HRV) is a reliable noninvasive marker of cardiovascular autonomic control. We examined 120 patients (pts) with syncope, palpitations and/or bradycardia (< 40 bpm during daily activity). In these patients, after one-minute oesophageal-ECG recording for HRV assessment, rapid continuous and programmed premature transesophageal left atrial pacing (TAP) were performed. Regarding the results of TAP, pts were divided into two groups: group I included 57 subjects with negative TAP, and group II consisted of 63 pts with positive TAP (SAND). We analysed two HRV parameters: variation ratio (VR, %) and maximal difference of any two consecutive sinus cycle lengths (DSCL, ms). The following TAP variables were calculated: corrected sinus node recovery time (CSNRT), second pause time (SPT) and calculated sinoatrial conduction time after Strauss (SACT). RESULTS: Mean DSCL was significantly shorter in group I (106 +/- 96) than in gr. II (151 +/- 169) (p < 0.05). Similarly behaved VR values. In SAND-pts with abnormal CSNRT or SPT we observed significantly greater VR and DSCL. This correlation was not confirmed in respect to SACT. We corroborated the significant coincidence of high HRV (VR < 20.0 and DSCL > 100) with pathologic CSNRT or SPT, but not with SACT.(ABSTRACT TRUNCATED AT 250 WORDS)