Recanalization of a chronically occluded coronary artery results in the improvement of various clinical parameters in patients with coronary artery disease. Increase of parasympathetic activity due to such procedure could be another argument for attempting recanalization. The aim of the study was to evaluate direct effects of recanalization of a chronically occluded coronary artery on the autonomic nervous system activity in patients with single-vessel coronary artery disease. MATERIAL AND METHODS: Forty patients aged 57 +/- 10 (36-73 years), scheduled for recanalization of a chronically occluded coronary artery were included into the study. Left ventricular ejection fraction (LVEF), mean heart period (MHP), baroreflex sensitivity (BRS) and short-term heart rate variability indices (SDNN, pNN50, RMSSD, TP, LFnu, HFnu, LF/HF) were analyzed one day before (El) and one day after (E2) the procedure. RESULTS: Statistically significant increase of LVEF in E2 in comparison to E1 (53 +/- 7 and 50 +/- 8%, respectively; p=0.005) and borderline decrease in BRS (4.2 +/- 3.6 and 5.8 +/- 4.6 ms/mm Hg, p=0.06) were found in the studied group. Statistically significant decrease in BRS was found in a subgroup of patients with initial value of BRS > 3 ms/ mm Hg (5.8 +/- 4.3 and 9.2 +/- 4.0 ms/mm Hg, p=0.02) one day after the procedure. Of the HRV indices, only borderline decrease in pNN50 was noted (1.4 +/- 1.7 and 3.8 +/- 5.6%, p=0.09). No other differences of HRV, or MHP, were found. CONCLUSION: Despite the increase of LVEF recanalization of a chronically occluded coronary artery leads to the decrease of BRS and pNN50 as a result of sympathetic activation one day after the procedure in the majority of patients. These changes in BRS were more profound and reached statistical significance in patients in whom baroreflex sensitivity was initially well preserved.