EFFECT OF COVID-19 VACCINATION ON CARDIAC ELECTROMECHANICAL FUNCTIONS: ELECTROCARDIOGRAPHIC AND ECHOCARDIOGRAPHIC EVALUATION IN YOUNG HEALTHY INDIVIDUALS

Introduction: The cardiac safety of BNT162b2 mRNA vaccination has been questioned due to rare reports of vaccine-associated myocarditis, particularly in young individuals. This study aimed to evaluate the long-term effects of BNT162b2 mRNA vaccination on electrocardiographic repolarization parameters and echocardiographic cardiac function in young healthy adults. Methods: This prospective cross-sectional study included 200 healthy individuals aged 18–45 years. Participants who had received two or three doses of BNT162b2 at least two years prior to enrollment were assigned to the vaccinated group (n=112), while unvaccinated individuals constituted the control group (n=88). Standard 12-lead electrocardiography and transthoracic echocardiography were performed. Electrocardiographic repolarization indices and diastolic function parameters were compared between groups. Given the significant sex imbalance, sex-adjusted analyses were performed using analysis of covariance. Results: P-wave dispersion (46.2 ± 6.8 vs. 45.7 ± 7.1 ms, p=0.61), QT dispersion (38.4 ± 8.9 vs. 38.1 ± 9.3 ms, p=0.86), QTc dispersion (44.9 ± 10.3 vs. 46.8 ± 11.2 ms, p=0.27), and frontal QRS–T angle (33.6 ± 25.0 vs. 30.9 ± 12.2°, p=0.78) did not differ significantly between vaccinated and unvaccinated participants. After adjustment for sex, vaccination status was not independently associated with P-wave dispersion (adjusted p=0.333) or QTc dispersion (adjusted p=0.559). Although lateral e′ velocity (13.20 ± 2.40 vs. 12.23 ± 1.57 cm/s, p=0.008) and deceleration time (203.9 ± 25.9 vs. 194.6 ± 17.9 ms, p=0.017) were higher in the vaccinated group, these differences remained within established physiological reference ranges. Left ventricular systolic function (LVEF: 64.3 ± 2.3% vs. 64.6 ± 2.5%, p=0.23) and other diastolic parameters were largely comparable between groups, with all values remaining within normal physiological reference ranges. Conclusions: In young healthy adults evaluated at least two years after vaccination, BNT162b2 mRNA vaccination was not associated with clinically meaningful long-term alterations in cardiac repolarization or diastolic function. These findings support the long-term cardiac safety of the vaccine in this population.