CHANGES IN ELECTROCARDIOGRAPHIC INDICATORS OF DEPOLARIZATION AND REPOLARIZATION DURING CHEMOTHERAPY OF BREAST CANCER WITH DOXORUBICIN

Aim. To study changes in electrocardiographic parameters of the myocardium in patients with verified breast cancer (BC) after completion of chemotherapy (CT) with doxorubicin. Material and methods. The study included 100 patients with a confirmed diagnosis of breast cancer who were treated at the healthcare institution “Grodno University Clinic” (Grodno, Belarus). A number of electrocardiographic parameters of the myocardium were measured in patients before and after chemotherapy using electrocardiography and Holter monitoring. Based on the echocardiography data and the selected threshold value for the relative decrease in GLS (more than 12%), the subjects were divided into two subgroups: those with the presence of cardiotoxicity – CTx+ (n=19) and those without it – CTx- (n=81). Results. An increase in electrocardiographic parameters of depolarization and repolarization (P, P-Q, QRSc, J-Tc, Tpic-Tendc, Q-Tc, Q-Tdc – p<0.001; p<0.001; p=0.005; p=0.023; p=0.009; p<0.001; p=0.006, respectively), as well as in the number of supraventricular extrasystoles (p<0.001) in the general group before and after chemotherapy was detected. The J-Tc and Q-Tc intervals (longer in the CTx- subgroup compared to the CTx+ subgroup: p=0.033 and p=0.037, respectively), the number and total time of sinus tachycardia episodes (p=0.011 and p=0.010, respectively) after chemotherapy differed statistically significantly in the cardiotoxicity subgroups. Conclusions. During chemotherapy with doxorubicin, an increase in the duration of the J-Tc and Q-Tc intervals was observed, the number and duration of episodes of sinus tachycardia also increased. Assessment of the dynamics of these indicators at the stages before/after chemotherapy can provide additional information about the state of the myocardium even before identifying functional disorders by echocardiography.