The impact of body weight on the diagnosis of aortic dilation-misdiagnosis in overweight and underweight groups.

BACKGROUND: Body surface area (BSA)-indexed Z-scores are used to assess the ascending aorta (AAo) and diagnose aortic dilation (AoD) in children. BSA is directly related to body weight and corresponds to body mass index (BMI). We hypothesized extremes in BMI alter interpretation of aortic size in pediatric patients with AoD.

METHODS: We reviewed all echocardiograms with a diagnosis of AoD performed at our institution from January 2013 through June 2013. Those with an age <2 or >20 years, history of aortic root surgery, or inadequate images were excluded. The aorta was measured by standard methods at the sinus of Valsalva, sinotubular junction, and proximal AAo. Using subject age, height, and gender, hypothetical weights for each subject were calculated to provide BMIs corresponding to the 5th, 50th, 85th, and 95th percentiles. The derived weights were then used to determine hypothetical BSA, and Z-scores were calculated for the subject's aortic diameters in each BMI group.

RESULTS: A total of 153 patients met inclusion criteria. Mean age was 11.1±4.6 years (68% male). Mean height was 142.7±27.9 cm, mean weight 44.6±24.8 kg, and mean true BMI was the 62nd centile. Significant differences in all aortic dimension Z-scores were found among normal and underweight, overweight, and obese BMI groups (P<.001 for all comparisons), respectively.

CONCLUSION: Using current recommended methods, AoD will be missed in overweight and obese patients and overdiagnosed in underweight patients. For children of normal weight, a Z-score based on BSA may be reliable. As obesity rates increase, weight-independent Z-scores must be developed.