Quantitative assessment of systolic and diastolic left ventricular energy loss using vector flow mapping in healthy participants: a retrospective observational study

Abstract

Energy loss (EL) derived from vector flow mapping (VFM) is an indicator of intraventricular flow efficiency in the left ventricle. However, standardized reference values in adults have not been established. Furthermore, the clinical significance of systolic and diastolic EL assessments has not been fully explored. Therefore, we aimed to separately quantify VFM-derived EL during systole and diastole in healthy participants, and to clarify age-related differences. This single-center retrospective observational study included 41 healthy participants (young group < 65-years-old, n = 16; elderly group ≥ 65-years-old, n = 25) who underwent transthoracic echocardiography between April 2025 and April 2026. VFM was used to quantify maximum mean EL, mean systolic EL (Mean ELS), mean diastolic EL (Mean ELD), the diastolic-to-systolic EL ratio (ELD/ELS), and the ratio of the diastolic to systolic EL area under the time curve (AUCD/AUCS). In addition, EL indices normalized by stroke volume (SV), cardiac output (CO), mitral inflow velocities (E and A waves), and myocardial relaxation index (e′) were evaluated. Statistical analyses were conducted using the Shapiro–Wilk test, independent t-test, Mann–Whitney U test, and Fisher’s exact test. The maximum mean EL and Mean ELS were significantly higher in the elderly group than in the younger group, whereas no significant difference was observed in Mean ELD. In phase-based comparisons, the ELD/ELS and AUC ratios were significantly lower in the elderly group. Among the normalized EL parameters, Mean ELS/SV and Mean ELS/CO remained significantly higher in the elderly group, indicating that age-related differences in EL persisted after normalization. VFM-derived EL exhibits age-related, phase-dependent changes characterized by a selective increase in systolic EL and altered phase distribution in healthy participants. Separate assessment of systolic and diastolic EL may provide insights into left ventricular flow efficiency beyond conventional echocardiographic indices. jRCT1030250395 (Registration date: 29 September 2025).