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

Aims 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. Methods and Results 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). ROC 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). Conclusion 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.