Thrombosis is a fairly rare, yet dangerous complication of pacemaker implantation. It may occur in various time intervals after the actual implantation procedure. The risk factors are as follows: inflammation or injury, vein anomalies, arrhythmia, venous stenosis. The aim of the study was to assess the risk factors for venous thrombosis, determine the interrelationship between venous thrombosis and the level of select inflammatory and pro-thrombotic factors, as well as to evaluate the actual impact of pacemaker implantation procedure within a group of patients with permanent heart stimulation system. METHODS The study involved 48 patients with permanent heart stimulation system, divided into 2 groups. Group A (18 F, 20 M; mean age 71.7 +/- 13.6 years) consisted of patients who had up to 3 thrombotic risk factors, whereas group B (2 F, 8 M; mean age 71.6 +/- 7.5 years) comprised the patients with more than 5 thrombotic risk factors. All patients were subsequently followed up for 18 months. Prior to pacemaker implantation the following factors were assessed in each patient: specific indications for pacemaker implantation, overall clinical condition, coexisting diseases, history of tobacco smoking, medications used prior to the procedure (anti-platelet, anti-coagulation), history of thrombotic or infectious complications, previous temporary heart stimulation. A transthoracic echocardiogram (TTE) and an ultrasound examination of the veins in both upper extremities were carried out. The levels of: D-dimers, fibrinogen, interleukin-6 (IL-6), hsCRP, TF and PAI-1 were determined in the venous blood. During the pacemaker implantation procedure the actual access to the veins and possible venous anomalies were assessed. After the pacemaker implantation, the TTE and venous ultrasound examination were carried out after 6 and 12 months, blood analyses for up to 7 days after the implantation, and subsequently after 6 and 12 months. RESULTS Patients in group B had significantly lower left ventricle ejection fraction and larger left ventricle end diastolic diameter than group A patients. In 3 patients in group B (which made up 6.25% of the study population), symptomatic venous thrombosis occurred after a 12-month observation period (mean 13.06 months). Initially, the levels of IL-6, hsCRP, TF, PAI-1, fibrinogen and D-dimers were considerably higher in group B, in comparison to group A. In all patients the levels of the above referenced factors kept on increasing for up to 7 days after the procedure. In group A they subsequently decreased, whereas in group B they kept on growing. In group B a significant negative correlation was observed between the left ventricle ejection fraction and the inflammatory and thrombotic factors under study. The lower the ejection fraction, the higher actually were their values. CONCLUSIONS In patients with more than 5 thrombosis risk factors, the increased levels of IL-6, hsCRP, fibrinogen, D-dimers, TF and PAI-1 were observed. A pacemaker implantation procedure is believed to increase both thrombotic and inflammatory state in a patient for up to 7 days after the procedure. In patients prone to thrombosis, a negative correlation between the ejection fraction and the levels of hsCRP, D-dimers, TF and PAI-1 were observed.