Skeletal Muscle Index Z-score—A Novel Method to Evaluate Malnutrition Level in Pediatric Heart Failure Patients?

Abstract

Malnutrition in children is defined by international guidelines as the age-adjusted Z-score for weight or BMI. However, weights can be misleading in children with HF because of fluid retention leading to misclassification of malnutrition level. We sought to estimate the prevalence of sarcopenic malnutrition in pediatric HF patients by quantifying objectively muscle wasting (sarcopenia) relative to age-adjusted normative data for children. All children listed for HT between 2012 and 2017 who underwent thoracic CT as part of transplant surgical planning were identified using a hospital database. The skeletal muscle index (SMI) was defined as the cross-sectional area of skeletal muscle at L3 index to patient, a known predictor of total muscle mass. Age adjusted Z-scores were calculated using normative data from the University of Michigan. Mild, moderate and severe were defined by cut-off Z-scores of -2 and -3, respectively. Among 28 children listed for HT, the median age was 10 (IQR 6, 13) years, the median weight was 26 (18, 40) kg, 39% were female, 82% had congenital heart disease. By ASPEN guidelines, the prevalence of mild, moderate and severe malnutrition was 14%, 29% and 25%. The median SMI was 39 cm2/m2 (Z-score, -1.7); the prevalence of sarcopenia by Z-score was 36%, 25% and 10% (figure) (P<0.01). SMI Z-score classified a larger percentage of children as mildly or moderately malnourished, and fewer children as severe. However, sarcopenia was profound in 11% of subjects. Muscle wasting is common in children with advanced heart failure and can be profound. Conventional definitions for malnutrition in children may misclassify malnutrition severity in children with HF. Normative curves may be helpful for understanding the severity of muscle wasting in children with HF, and may help to guide nutritional replacement.