Feasibility, reproducibility and diagnostic performance of non-invasive myocardial work in Fontan circulation

Background Patients with Fontan circulation are prone to progressive ventricular dysfunction, which may not be detected by conventional systolic indices. Non-invasive myocardial work (MW), integrating strain and afterload, may provide a more sensitive assessment of ventricular performance. Purpose To evaluate feasibility, reproducibility, and diagnostic performance of MW indices in Fontan patients compared with matched healthy controls. Methods In this single-centre observational study, 70 Fontan patients (21±9 years; 53% male) underwent echocardiography with speckle-tracking analysis. Age-, sex-, body size-, and blood pressure–matched healthy subjects served as controls. Global longitudinal strain (GLS) and MW parameters—myocardial work index (MWI), constructive work (MCW), wasted work (MWW), and work efficiency (MWE)—were derived using vendor software and brachial cuff blood pressure. Reproducibility was assessed using intraclass correlation coefficients (ICC). Diagnostic performance was evaluated by ROC analysis. Results MW analysis was feasible in 86% of Fontan studies. Compared with controls, Fontan patients showed significantly reduced MWI (1162±364 vs 1777±240 mmHg%, P<0.001), GLS (−13.9±3.1% vs −21.2±1.5%, P<0.001), 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). MWI remained impaired despite preserved EF/FAC. Inter-observer reproducibility was excellent for MWI (ICC 0.957) and good–excellent for GLS (ICC 0.898). GLS (AUC 0.988) and MWI (AUC 0.925) showed excellent discrimination. Conclusion Non-invasive MW is feasible and reproducible in Fontan circulation and detects impaired ventricular work even with preserved conventional systolic function, supporting its role in identifying subclinical dysfunction and refining longitudinal surveillance.