Aging shifts the heart’s hidden energy waste from filling to pumping, echocardiography study finds

Every heartbeat wastes a measurable sliver of energy. As blood swirls, collides, and redirects itself inside the left ventricle, viscous dissipation converts part of the heart’s mechanical work into heat, a quantity researchers call intraventricular energy loss. A new retrospective observational study from Dokkyo Medical University Nikko Medical Center, published in Cardiovascular Ultrasound, reports that in healthy adults this wasted energy does not rise uniformly with age. Instead, it shifts dramatically across the cardiac cycle: systolic energy loss climbs steeply in older participants, while diastolic energy loss remains statistically unchanged.

The technique behind the measurement, vector flow mapping, reconstructs intraventricular velocity vector fields from standard color Doppler echocardiographic images. By incorporating cardiac chamber geometry and applying the continuity equation, the software estimates the viscous dissipation of kinetic energy caused by flow disturbance, vortex interaction, and flow redirection. Because conventional indices such as left ventricular ejection fraction capture how much blood the heart pumps but say little about how efficiently the blood moves inside the chamber, energy loss offers a complementary window on intraventricular flow organization that standard echocardiography cannot provide.

The study included 41 healthy adults aged 20 to 90 who underwent routine transthoracic echocardiography between April 2025 and April 2026. All had a left ventricular ejection fraction of at least 50 percent, sinus rhythm, and no known organic heart disease, including ischemic, valvular, cardiomyopathic, or congenital conditions. From 48 initially screened examinations performed by a single experienced sonographer on an ARIETTA850 system, seven were excluded because insufficient color Doppler image quality made vector flow mapping infeasible. The remaining participants were stratified into a younger group under 65 years of age (n = 16, mean age 44 ± 10 years) and an elderly group of 65 or older (n = 25, mean age 77 ± 6 years).

Offline analysis used dedicated software on archived DICOM images from standard apical long-axis views, acquired at frame rates of 30 to 50 frames per second with aliasing velocities of 50 to 70 cm/s. Analysts manually defined landmark points at the mitral annulus, aortic annulus, and left ventricular apex, after which the endocardial border was traced automatically and visually adjusted when necessary. Mean energy loss, normalized per unit area to reduce dependence on ventricular size, was computed frame by frame across three consecutive cardiac cycles, with a three-frame smoothing process applied in the time domain to damp outliers. Cardiac phases were defined using synchronized phonocardiographic recordings together with valvular events on echocardiography: diastole began at the onset of the second heart sound, and systole was anchored to mitral valve closure.

The headline result concerns the phase split of energy dissipation. Maximum mean energy loss was significantly higher in the elderly group (14.4 ± 7.9 vs. 9.6 ± 5.1 J/(m³·s), p = 0.024), and mean systolic energy loss was markedly increased (10.9 ± 6.5 vs. 3.9 ± 1.7 J/(m³·s), p < 0.001). Mean diastolic energy loss, by contrast, showed no significant difference between groups (9.6 ± 4.3 vs. 7.8 ± 4.6 J/(m³·s), p = 0.106). In younger participants, diastolic energy loss predominated: the diastolic-to-systolic energy loss ratio was 2.7 ± 1.9 in the young group versus 1.0 ± 0.3 in the elderly group (p = 0.012), and the corresponding diastolic-to-systolic area-under-the-curve ratio fell from 2.6 ± 1.4 to 1.2 ± 0.4 (p < 0.001). Aging, in other words, preferentially augments systolic energy dissipation rather than raising energy loss evenly throughout the cycle.

To check that the difference was not simply a byproduct of smaller hearts or lower output in older participants, the researchers normalized systolic energy loss by stroke volume and by cardiac output. Both normalized indices remained significantly higher in the elderly group (Mean ELS/SV: 0.22 ± 0.16 vs. 0.06 ± 0.03, p < 0.001; Mean ELS/CO: 3.18 ± 2.18 vs. 0.99 ± 0.48, p < 0.001), indicating that the age-related difference persisted after accounting for per-beat and per-minute hemodynamic output. Normalization by stroke volume reflects energetic efficiency per beat, while normalization by cardiac output represents energetic cost relative to overall hemodynamic output.

Exploratory correlation analysis reinforced the pattern. Age correlated positively with mean systolic energy loss (Spearman r = 0.692, p < 0.001) and negatively with both the diastolic-to-systolic energy loss ratio (r = −0.613, p < 0.001) and the diastolic-to-systolic AUC ratio (r = −0.509, p < 0.001), consistent with a progressive shift of energy dissipation from filling toward ejection as people age.

The hemodynamic context matters for interpreting these numbers. Baseline echocardiography showed the expected age-related signature: the elderly group had significantly smaller left ventricular end-diastolic and end-systolic volumes (84 ± 21 vs. 105 ± 17 mL, p = 0.002; 30 ± 9 vs. 40 ± 8 mL, p < 0.001), a slightly higher ejection fraction (65 ± 11 vs. 62 ± 4%, p = 0.016), lower early diastolic inflow velocity (E wave 63 ± 11 vs. 80 ± 25 cm/s, p = 0.024), higher late diastolic velocity (A wave 90 ± 13 vs. 53 ± 13 cm/s, p < 0.001), a reduced E/A ratio (0.7 ± 0.2 vs. 1.6 ± 0.5, p < 0.001), lower tissue Doppler e′ velocity (5.9 ± 1.3 vs. 9.5 ± 2.1 cm/s, p < 0.001), a higher E/e′ ratio (10.9 ± 2.1 vs. 8.2 ± 3.1, p = 0.002), and lower stroke volume (54 ± 13 vs. 65 ± 12 mL, p = 0.004). Cardiac output did not differ significantly. Despite preserved ejection fraction in both groups, the older hearts were dissipating far more energy during ejection.

The authors place this finding in a broader physiological framework. Systolic energy loss reflects the efficiency of blood ejection and flow organization within the left ventricular outflow tract, whereas diastolic energy loss represents the energetic cost of vortex formation and ventricular filling. Prior work links systolic energy loss to systolic blood pressure and left ventricular mass index, supporting a connection with afterload-related ventricular stress, and pressure-overload-related increases in systolic energy loss have also been reported for the right ventricle. Disease states dominated by filling dynamics, such as aortic regurgitation, instead show selective increases in diastolic energy loss. Against that backdrop, the selective systolic elevation seen in healthy aging suggests that aging modifies the phase distribution of intraventricular energy dissipation rather than uniformly degrading diastolic energetics, and that systolic and diastolic energy loss carry distinct hemodynamic determinants.

The study’s authors are careful about scope. This was a single-center, cross-sectional pilot study with a small sample, which limits generalizability and precludes causal inference. Only healthy adults were included, so the observed age-related changes cannot be directly extrapolated to patients with cardiovascular disease, and the clinical significance of phase-specific energy loss has not yet been validated in outcome-based or longitudinal studies. Because vector flow mapping reconstructs velocities from a single two-dimensional apical plane, it assumes out-of-plane flow components are small and may not fully capture the inherently three-dimensional complexity of intraventricular flow, although the same apical long-axis view was used consistently for all participants and the approach has been validated in a left ventricular phantom model. Color Doppler frame rates of 30 to 50 per second also limit temporal resolution. The authors note that energy loss is only one aspect of flow dynamics and that complementary parameters such as vorticity, vortex strength, washout efficiency, and vortex formation time may add further information. Larger, prospective studies with longitudinal follow-up and clinical endpoints, they conclude, are needed to confirm whether phase-specific energy loss measurement can move from a research curiosity to a clinically useful index of left ventricular flow efficiency beyond conventional echocardiographic indices.

Subject of Research: Age-related changes in systolic and diastolic left ventricular energy loss measured by vector flow mapping in healthy adults

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

Article References: Otani, N., Noma, H., Takahashi, H., Toyoda, S., Yasu, T., & Maejima, Y. (2026). Quantitative assessment of systolic and diastolic left ventricular energy loss using vector flow mapping in healthy participants: a retrospective observational study. Cardiovascular Ultrasound, 24(1), Article 15. https://doi.org/10.1186/s12947-026-00378-2

Image Credits: AI Generated

DOI: 10.1186/s12947-026-00378-2

Keywords: vector flow mapping, energy loss, left ventricle, echocardiography, aging, diastolic function, systolic function, intraventricular flow, hemodynamics, healthy adults, cardiac efficiency, observational study