Magnetic Resonance Imaging-Based Psoas Muscle Volume as an Additional Risk Factor for Fontan Failure: A Prospective...

Sarcopenia is prevalent in patients with Fontan circulation and may contribute to functional decline and adverse outcomes. It is commonly assessed using the cross-sectional area of the psoas muscle (PMA), although volumetric assessment of psoas muscle volume (PMV) may better capture true muscle mass. The ability of PMA versus PMV to differentiate patients with Fontan circulation from healthy controls and to provide incremental prognostic information remains incompletely defined.

In this prospective study, abdominopelvic magnetic resonance imaging was used to quantify PMA and PMV in 70 patients with Fontan circulation and 51 healthy controls with similar age and sex distribution. PMA at the fourth lumbar level and total PMV were indexed to body surface area. Group differences were assessed using nonparametric testing. Prognostic associations were evaluated using multivariable logistic regression.

Male patients with Fontan circulation had lower PMV and PMA indexed to body surface area than healthy male patients (P=0.029 and P=0.008, respectively), while no significant differences were observed among female patients (PMV indexed to body surface area, P=0.073; PMA indexed to body surface area, P=0.135). In multivariable analysis, Fontan-associated liver disease, lower serum total protein, and oxygen saturation were independently associated with Fontan failure. PMV indexed to body surface area demonstrated a modest inverse association with Fontan failure and modestly improved model discrimination when added to the clinical base model (cross-validated area under the receiver operating characteristic curve, 0.84 versus 0.81), whereas PMA indexed to body surface area did not improve predictive performance.

PMV indexed to body surface area may provide incremental prognostic information and serve as an adjunctive imaging biomarker of sarcopenia in Fontan circulation, although its independent predictive value for adverse outcomes requires further validation in larger cohorts.