An Echocardiographic Measurement of Superior Vena Cava to Inferior Vena Cava Distance in Patients <20 Years of Age With Idiopathic Dilated Cardiomyopathy

In normal pediatric echocardiograms, the distance from the junction of superior vena cava (SVC) and right atrium to inferior vena cava (IVC) and right atrium is linearly related to height. We examine this relation in children listed for heart transplant with idiopathic dilated cardiomyopathy (IDC) compared with the previously defined normal distribution of SVC-IVC to improve matching of heart sizes. Measurements of SVC-IVC and left ventricular end-diastolic diameter in 55 pediatric patients with IDC were correlated with height, weight, and body surface area. Regression analyses were performed to find the best-fit equation and correlation coefficient. Generalized linear modeling compared SVC-IVC in patients with IDC with normal SVC-IVC values from 254 patients. There was a strong linear relation in patients with IDC between SVC-IVC and height (R2 = 0.84) and a logarithmic relation to weight (R2 = 0.80). Left ventricular end-diastolic diameter did not correlate with SVC-IVC or any other parameter. In 87% of patients with IDC, SVC-IVC was over 2 SDs above predicted normal values (mean z-score = 4.3 ± 2.1). In conclusion, predicted SVC-IVC in patients with IDC was different from published norms (p <0.001). SVC-IVC in pediatric patients with IDC, although linearly related to height, is consistently above normal values.