Study of Electrophysiological Properties of Atrioventricular Node in Permanent Cardiac Pacing under Influence of Trimetazidine Dihydrochloride

INTRODUCTION: Dual-chamber cardiac pacing permits to maintain permanent atrial-ventricular synchronization. Physiological sequence of propagation of the impulse from atria to ventricles is provided with an artificial delay analogous to delay of propagation of excitation through the atrioventricular (AV) node of a heathy individual. The delay interval is formed so that to minimize stimulation of the right ventricle. This preserves the left ventricular ejection fraction, reduces the risk of development of the chronic heart failure (CHF) and of atrial fibrillation, and increases functional abilities of the patient. On the other hand, critical increase in the atrioventricular delay leads to pacemaker syndrome: impairment of circulation function, shortness of breath, reduced tolerance to exercise, dizziness, syncopal state. The question of the influence of the permanent electrical pacing on the AV node conduction remains unsolved. AIM: To study the effect of trimetazidine dihydrochloride on the AV node conduction in conditions of permanent cardiac pacing, to determine the effect of cardiac pacing on the AV node in the studied time period. MATERIALS AND METHODS: The study involved 86 patients. The AV node activity was assessed by antegrade intraoperative determination of Wenckebach point on the basis of electrocardiography data in 24–48 hours after pacemaker implantation, in 6–8 hours, 7, 14, 9 and 180 days after intake of trimetazidine dihydrochloride and in 7, 14, 21 and 30 days after its cancellation. To compare the extent of influence of the studied drug on the AV node activity, the patients were divided to three groups depending on the basic pathology: group 1 ― patients with the sick sinus node syndrome (n = 38, 44.2%); group 2 ― patients with II degree AV block (n = 25, 29.1%); group 3 ― patients with III degree AV block (n = 23, 26.7%). RESULTS: Trimetazidine dihydrochloride improved the electrophysiological properties of the AV node in the first and second groups: increase in the mean value of Wenckebach point antegrade in the first group was in total 3.26% (р = 0.022), in the second group 4.68% (р = 0.001). In the third group of patients no improvement was noted, but it should be said that under the action of this drug, in 4 of 23 patients with III degree AV block, antegrade AV conduction appeared (р = 0.236). CONCLUSION: Trimetazidine dihydrochloride has a positive effect on the AV node activity as early as in 6–8 hours of intake, which reaches maximum in 3 weeks. Cardiac pacing had no effect on AV node within the follow-up period (6 months).