BACKGROUND Bradyarrhythmias are typically treated with permanent pacemakers (PM). The elimination of bradyarrhythmia by PM implantation improves the patient's quality of life and prognosis, but it can also result in a number of sequalae. It is still unclear how PM implantation affects the hemostasis system's parameters and how such parameters relate to different consequences after PM placement. OBJECTIVE To assess the blood coagulation factor activity in PM patients throughout the perioperative period. METHODS Patients treated in the Department of Surgical Therapy of Cardiac Arrhythmias and Pacing at the Ryazan State "Regional Clinical Cardiology Dispensary" from April 2020 to December 2021 were included in the study. Before surgery, 7 and 30 d after PM placement, peripheral venous blood samples were withdrawn to measure the level of blood coagulation factor I (FI) and the activity of blood coagulation factors II (FII), V (FV), VII (FVII), VIII (FVIII), IX (FIX), X (FX), XI (FXI), XII (FXII). We used an automatic coagulometer Sysmex CA 660 (Sysmex Europe, Germany) and reagents from Siemens (Siemens Healthcare Diagnostics Products GmbH, Germany). RESULTS The study included 146 patients. The activity of factors FV [147.7 (102.1-247.55)% vs 103.85 (60-161.6)% vs 81.8 (67.15-130.65)%, P = 0.002], FVIII [80.4 (60.15-106.25)% vs 70.3 (48.5-89.1)% vs 63.7 (41.6-88.25)%, P = 0.039], FIX [86.2 (70.75-102.95)% vs 75.4 (59.2-88.3)% vs 73.9 (56.45-93.05)%, P = 0.014], FX [188.9 (99.3-308.18)% vs 158.9 (83.3-230)% vs 127.2 (95.25-209.35)%, P = 0.022], FXI [82.6 (63.9-103.6)% vs 69.75 (53.8-97.6)% vs 67.3 (54.25-98.05)%, P = 0.002], FXII [87.6 (67.15-102.3)% vs 78.9 (63.4-97.05)% vs 81.2 (62.15-97.4)%, P < 0.001] decreased at 7 and 30 d after surgery; FII activity [157.9 (109.7-245.25)% vs 130 (86.8-192.5)% vs 144.8 (103.31-185.6)%, P = 0.021] decreased at 7 d and increased at 30 d postoperatively. There were no statistically significant changes in the FVII activity within 30 d after PM placement [182.2 (85.1-344.8)% vs 157.2 (99.1-259)% vs 108.9 (74.9-219.8)%, P = 0.128]. Subgroup analysis revealed similar changes only in patients on anticoagulant therapy. FXII activity decreased in patients on antiplatelet therapy [82 (65.8-101.9)% vs 79.9 (63.3-97.1)% vs 89.7 (75.7-102.5)%, P = 0.01] 7 d after surgery, returning to baseline values at 30 d postoperatively. CONCLUSIONS PM placement and anticoagulant therapy were associated with decreased activity of clotting factors FV, FVIII, FIX, FX, FXI, FXII in the postoperative period. FVII activity did not decrease within 30 d after PM placement, which may indicate endothelial injury caused by lead placement.