Progressive loss of bone mass in children with Fontan circulation

Objective We investigated bone mineral density (BMD) at different ages after the Fontan completion, and we evaluated the relationship between BMD, vitamin D levels, and pertinent patient variables. Methods A cross-sectional sample of 64 patients was examined with dual-energy X-ray absorptiometry (DXA) scans to determine BMD. Of these patients, 24 were also examined with BoneXpert software to determine bone mass density (BMX), expressed as the bone health index (BHI). Blood samples from all patients were analyzed. Patients were divided into three different age groups; A: 4-9 years old (n = 22), B: 10-15 years old (n = 21), and C: 16-18 years old (n = 21). Results Overall, BMD z scores were (mean +/- SD): -1.0 +/- 1.3 for the lumbar spine and -0.2 +/- 1.2 for the total body. Groups B and C had significantly lower z score values compared to group A. Of patients in group C, 35% had z score values <=-2 SD of the mean of the healthy population. There was no difference related to systemic ventricular anatomy (left or right); however, patients with lateral tunnels had lower BMD than patients with extra cardiac conduits. Overall, the BHI z score was (mean +/- SD): -1.2 +/- 0.9, but low BMX did not correlate with low BMD. The 25-hydroxy vitamin D level was 58 +/- 30 nmol/L. Vitamin D levels decreased with age: in group C, 33.3% of patients exhibited vitamin D deficiencies. Vitamin D levels were not correlated with bone mineral densities. Conclusion BMD levels decreased with age in patients with Fontan circulation. Different bone components were involved. Vitamin D levels also decreased with age, but they were not consistently associated with bone mineral densities. The single factor most predictive of low BMD was a lateral tunnel Fontan, compared to an extra cardiac Fontan.