Objectives-Dissipative energy loss derived from vector flow mapping represents the viscous dissipation of turbulent blood flow. We aimed to determine the left ventricular (LV) energy loss in patients with end-stage renal disease (ESRD). Methods-Patients with ESRD and a preserved LV ejection fraction, who consisted of a group receiving peritoneal dialysis, a group receiving hemodialysis, and a group receiving preparation for dialysis initiation, were examined by echocardiography; a group of healthy control participants were examined as well. Vector flow mapping analysis was then performed from the apical 4-chamber view to calculate the energy loss during diastole and systole in the left ventricle. Results-Conventional transthoracic echocardiography and LV energy loss calculations were successfully performed in 63 cases and 50 controls. The patients with ESRD had significantly higher diastolic energy loss [median (interquartile range), 71.73 (46.08-106.75) versus 23.32 (17.17-29.26) mW/m; P < .001] and higher systolic energy loss [25.28 (19.03-33.93) versus 12.52 (9.35-16.47) mW/m; P < .001]. A significant difference in diastolic energy loss between the peritoneal dialysis and preparation groups was found [54.92 (39.28-89.94) versus 84.82 (62.58-171.4) mW/m; P = .04]. In patients with ESRD, the log-transformed diastolic energy loss had a significant association with the peak early diastolic transmitral flow velocity (P=.011), peak early diastolic transmitral flow velocity-to-peak early diastolic mitral annular flow velocity ratio (P = .001), LV mass index (P = .017), and heart rate (P = .003). Conclusions-Impaired blood flow efficiency was detected in patients with ESRD by using dissipative energy loss derived from vector flow mapping. The energy loss value could be a novel parameter for evaluating the ventricular workload of uremic hearts in terms of fluid mechanics.