Reduced myocardial work in Fontan circulation: feasibility, reproducibility, and diagnostic performance

To evaluate the feasibility, reproducibility, and diagnostic performance of non-invasive myocardial work (MW) indices in patients with Fontan circulation compared with matched healthy controls.

In this single-centre observational study, echocardiography and speckle-tracking analysis were performed in 70 Fontan patients (mean age 21 ± 9 years; 53% male) and age/sex/body size/blood pressure-matched controls. Global longitudinal strain (GLS) and MW indices-myocardial work index (MWI), constructive work (MCW), wasted work (MWW), and work efficiency (MWE)-were derived using vendor software and brachial cuff blood pressure. MW analysis was feasible in 86% of Fontan examinations. Compared with controls, Fontan patients had significantly lower MWI (1162 ± 364 vs. 1777 ± 240 mmHg%, P < 0.001), GLS (-13.9 ± 3.1% vs. -21.2 ± 1.5%, P < 0.001), and EF/FAC (58.9 ± 4.5% vs. 63.3 ± 3.9%, P = 0.002). MCW (1554 ± 450 vs. 2102 ± 221 mmHg%, P < 0.001) and MWE (90 ± 6% vs. 96 ± 2%, P < 0.001) were also reduced. MWI remained lower than controls even in Fontan patients with preserved EF/FAC. Inter-rater reliability was excellent for MWI (ICC 0.957; 95% CI 0.838-0.989) and good-excellent for GLS (ICC 0.898; 95% CI 0.641-0.974). Receiver operating characteristic analysis showed excellent discrimination for GLS (AUC 0.988) and MWI (AUC 0.925), and good discrimination for MCW (AUC 0.902) and MWE (AUC 0.795).

Non-invasive MW indices are feasible and highly reproducible in Fontan circulation and identify reduced ventricular work and efficiency, including in patients with preserved conventional systolic measures. MW may provide a sensitive marker of subclinical myocardial dysfunction and support longitudinal follow-up in this population.