Background: Mechanical work is traditionally defined by the pressure–volume loop, but its invasive nature limits routine clinical use. The myocardial work index (MWI) has emerged as a non-invasive alternative, combining strain and estimated pressure to assess cardiac performance. However, MWI does not account for ventricular geometry and treats the ventricle as a dimensionless chamber. According to Laplace’s law, wall stress and the true myocardial load depend on both pressure and ventricular geometry. Therefore, this study aims to develop and evaluate a geometry-informed myocardial work framework that provides a more physiologically representative estimate of mechanical energy expenditure. Method: In this proof-of-concept study, mechanical work was calculated using the one-fiber model of the left ventricle (LV) with Laplace-based geometric correction, integrating fiber stress over strain to derive the tension-adjusted myocardial work (TAMW) model. Strain was obtained from speckle tracking echocardiography along with pressure data while LV volumes and wall geometry were obtained from cardiac MRI. Two acute myocarditis patients with compact and dilated ventricles were analyzed, comparing cumulative and instantaneous work between MWI and TAMW. Performance gaps were quantified as the percentage difference in peak cumulative work. Results: Conventional MWI differed substantially between two cases (2576 vs. 1795 mmHg%, performance gap: 33.3%) whereas TAMW reduced this discrepancy to 7.5% (10,806 vs. 9789 mmHg%). TAMW also highlighted differences in temporal distribution of instantaneous work relative to MWI, reflecting the influence of ventricular geometry on contraction dynamics. Conclusions: TAMW incorporates the influence of geometry in the myocardial work framework revealing a more physiologically consistent reflection of myocardial effort across different ventricular geometries.

Background: Cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE) is an important marker of myocardial injury in acute myocarditis (AM). Although echocardiographic myocardial work (MWI) provides a non-invasive assessment of left ventricular (LV) mechanics, conventional MWI does not account for ventricular geometry or temporal distribution of myocardial work. These factors may provide additional physiological information relevant to myocardial injury. Objective: To investigate the association of conventional and geometry- and timing-informed myocardial work measures with LGE-defined injury in AM in a preliminary proof-of-concept study. Methods: In this retrospective, single-center study, 41 patients with AM underwent echocardiography and CMR within ±10 days. Conventional segmental MWI was derived from pressure-strain loops. Tension-adjusted myocardial work (TAMW) incorporated ventricular geometry using CMR-derived ventricular volume and wall volume into the myocardial work estimation. Front Loading Index (FLI) and Back Loading Index (BLI) quantified the relative contribution of constructive work during the initial and final 20% of the ejection phase, respectively. Associations between myocardial work indicators and segmental LGE were assessed using Spearman correlation and linear mixed-effects (LME) models with patient-specific random intercepts. Multiple comparisons were addressed using Holm correction. Additional analyses examined segmental localization, within- and between-patient variability, patient-specific slopes and the influence of extreme observations. Results: Spearman correlations between LGE and MWI ($\rho$ = −0.09, p = 0.01) and TAMW ($\rho$ = −0.06, p = 0.08) were weak. In LME analysis, greater LGE was associated with lower MWI (β = −2.57, 95% CI −4.71 to −0.42, Holm-adjusted p = 0.038) and lower TAMW (β = −11.09, 95% CI −21.24 to −0.94, Holm-adjusted p = 0.038). Exploratory model comparison using LGE as the common outcome showed comparable model support for standardized MWI and TAMW (AIC = 6264.7 and 6265.7 respectively; ΔAIC = 0.97). FLI was not significantly associated with LGE in the LME analysis (β = −0.00021, 95% CI: −0.000558 to 0.000147, Holm-adjusted p = 0.253), whereas BLI showed a significant positive association with LGE (β = 0.000127, 95% CI: 0.000065 to 0.000190, Holm-adjusted p < 0.001) The BLI association was not maintained after accounting for segmental localization. Conclusions: In this preliminary proof-of-concept, MWI and TAMW showed weak inverse associations with segmental LGE in the primary analysis, while BLI demonstrated an exploratory positive association with LGE and FLI was not independently associated with LGE. These findings demonstrate the feasibility of incorporating ventricular geometry and temporal distribution into myocardial work assessment but do not establish superiority or incremental value over conventional MWI. Further prospective studies are required to determine the reproducibility, physiological significance, and clinical utility of these additional dimensions.