Introduction. Currently, about one million pacemakers are implanted in the world in one year. Two-chamber pacemakers are considered the most physiological, since they allow you to maintain atrioventricular synchronization constantly. The question of the effect of constant pacing, B-blockers and antiarrhythmic drugs on the electrophysiological properties of the heart remains unresolved to the end, and the degree of influence of the drug trimetazidine dihydrochloride on the activity of the sinus node is practically not covered in the world literature. Aim. The aim of the study is to study the effect of trimetazidine dihydrochloride on the activity of the sinus node under conditions of constant pacing in various modes and to determine the effect of pacemaker on the activity of the sinus node. Material and methods. The electrophysiological properties of the cardiac conduction system were evaluated by the frequency of atrial contractions, by the number of atrial contractions upon admission according to an electrocardiogram, 24–48 hours after implantation of an electrocardiostimulator, 6–8 hours after taking the drug trimetazidine dihydrochloride, 30, 90, 180 days after taking the drug and 30 days after discontinuation of the studied drug. We examined 100 patients. To compare the effectiveness of the drug trimetazidine dihydrochloride on the activity of the sinoatrial node, all patients were divided into two groups: 1) patients without therapy of concomitant diseases (B-blockers, antiarrhythmic drugs), but receiving the studied drug (38 (38%) patients); 2) patients with concomitant disease therapy (B-blockers, antiarrhythmic drugs) and also receiving the studied drug (62 (62%) patients). Results. The following results were obtained – exchange therapy improves the electrophysiological properties of the sinoatrial node in the first group. The total increase in the frequency of atrial contractions is 3.04% (p = 0.022570210). There were no improvements in the second group, but it is worth noting that exchange therapy reduces the negative effect of B-blockers and antiarrhythmic drugs, since after its cancellation, after 180 days of admission, a decrease in the average frequency of atrial contractions was revealed by 2.73% (p = 0).019969538, which is even less than the initial value at admission by 3.42% (p = 0.02796553). Сonclusion. The appointment of trimetazidine dihydrochloride begins to have a positive effect on the activity of the sinus node after 6–8 hours after administration and reaches its maximum effect after 3 weeks. A similar pattern is observed with respect to the average number of own atrial complexes. The pacemaker had no effect on the sinus node in the studied time period for 6 months.