Aim. To study the possibilities of instrumental research methods in relation to the earliest detection of cardiovascular events in oncohematological patients receiving antitumor immunochemotherapy, as well as to determine the requirements for documenting adverse events.Material and methods. For the study, 63 patients were prospectively selected with a diagnosis of indolent non-Hodgkin lymphoma, who were indicated for antitumor immunochemotherapy. The patients were examined in three stages (before treatment, after 3 and 6 cycles of therapy) and divided into 2 groups by simple randomization. Cardiovascular toxicity in the main group of patients was assessed using 3D transthoracic echocardiography, analysis of left ventricular (LV) global longitudinal systolic strain and electrocardiography. The control group underwent a standard 3D echocardiography with analysis of LV ejection fraction. Clinical manifestations of cardiovascular events were assessed in all patients during treatment.Results. According to the study, significant changes were obtained in LV ejection fraction on the third visit — a decrease from 58,9±1,07 to 48,1±0,73% (p<0,05) and from 57,7±1,13 to 49,4±0,58% (p<0,05) in patients of the main and control groups and global longitudinal LV strain from |21,1±1,18 to |14,0±1,61 |% (p<0,05) in patients of the main group. A mixed clinical phenotype of cardiovascular toxicity was the most common among all patients. An integrated approach to the early diagnosis of cardiovascular events makes it possible to identify a larger percentage of patients with subclinical myocardial dysfunction.Conclusion. The long period of latent cardiovascular toxicity emphasizes the need for early verification of cardiovascular complications of antitumor therapy and expansion of the established paraclinical diagnostic minimum. In addition, taking into account the accumulated experience, recommendations are presented for the preparation of medical documentation in order to ensure the safety and quality of care.