Body Composition Abnormalities in Adults with a Fontan Circulation

Abstract

Background and methods: The Fontan circulation exists with no subpulmonary ventricular pump. We aimed to characterise body composition in this setting and to explore possible pathophysiological associations. Participants were recruited for dual x-ray absorptiometry (DXA), cardiopulmonary exercise testing, echocardiography and biochemical assessment. Results: Twenty-eight people with a Fontan circulation (26 ± 7 years) were recruited. All were NYHA Class I/II with 46% males. Skeletal muscle mass (relative appendicular lean mass Z-score) was reduced (−1.49 ± 1.10, p ≤ 0.001); 68% had muscle mass deficits (Z-score <−1), 39% were in sarcopenic range (Z-score <−2) and only 32% had normal muscle mass (Z-score ≥−1). Skeletal muscle mass correlated with % predicted oxygen pulse (stroke volume surrogate, r = 0.50, p = 0.007), % predicted maximum handgrip strength (r = 0.53, p = 0.004), systolic function (r = 0.42, p = 0.024) and was inversely related with haemoglobin (r = −0.39, p = 0.038), likely reflecting reduced oxygen saturations, which result in compensatory erythrocytosis. Appendicular lean mass was independently associated with peak VO2 (β = 73 mL/min, p ≤ 0.001). Overall, by DXA, only 50% had normal range adiposity, 14% had moderate adiposity, 32% had high adiposity, and 4% had low adiposity. In contrast, 32% had above normal range BMI. The level of agreement between BMI and DXA for adiposity categorisation was only fair (kw = 0.53). Conclusion: Young adults with a Fontan circulation have a body composition profile characterised by skeletal muscle deficiency and are predisposed to increased adiposity, which is underestimated by BMI. Superior skeletal muscle mass, which is independently related with peak exercise capacity, is associated with lower haemoglobin levels and greater systolic function.