Abstract Background Hematopoietic stem cell transplant (HSCT) represents a potentially curative approach for various hematologic cancers and bone marrow disorders. Advancements in safety and efficacy have broadened the application of HSCT to older individuals and those with concurrent medical conditions predisposing them to cardiovascular (CV) issues. Despite the significant survival benefits offered by HSCT, it is accompanied by both short- and long-term complications, leading to considerable morbidity and mortality. CV complications, including heart failure, arrhythmias, acute thrombosis, pulmonary hypertension, and pericardial effusions, are among the potential adverse events following HSCT. Aim for the present registry is to determine how much CV complications are related to short-term survival in patients after HSCT. Methods Observational, monocentric cohort study consecutively enrolling all patients undergoing HSCT from 2019 to 2023. Inclusion criteria was >18 years, autologous or allogeneic HSCT, and written informed consent for the participation in the study. All patients underwent a complete cardiological examination, including 12-lead ECG, echocardiography, and cardiac biomarkers, before HSCT, and after 2,6 and 12-months. CV-related adverse events were defined as systolic dysfunction (even asymptomatic), thromboembolism (both VTE and PE), stroke, arrhythmias, pericarditis and hypertensive crises. Results 91 patients (34% female; mean age 54 +/- 12 years) were followed-up for a median of 2 years after HSCT. Major risk factors' prevalence was overall low (hypertension 28%, dyslipidaemia 33%, diabetes 9%, and only 11 patients (12%) had a positive history for CV events (6 atrial fibrillation, 4 coronary heart disease, 1 stroke) before HSCT. During follow-up, 26 patients (29%) experienced at least one CV-related adverse event, of which 7 (8%) were serious enough to require an hospital admission. CV adverse events included 5 new heart failure diagnosis, 5 new atrial fibrillation diagnosis, 10 episodes of VTE/PE, 4 pericarditis, one stroke and one hypertensive crisis. Twenty of all CV-related adverse events were reported within the first six months after HSCT (77%). Having a CV-related AE within the first six months after HSCT is associated with an increased risk of all-cause death (39% vs. 17%; log-rank p=.01; Figure 1). Conclusions CV-related adverse events are common in patients undergoing HSCT and strikes an overall young and healthy population. Having a CV-related adverse event in the six months following HSCT is a heavy prognostic factor for all-cause mortality. Therefore, an optimal prevention strategy including arrhythmia monitoring, echocardiographic follow-up and guideline-driven thromboembolic prophilaxis could improve patients' survival after HSCT.Figure 1