Myocardial Dimensions in Children With Hypertrophic Cardiomyopathy: A Comparison Between Echocardiography and Cardiac Magnetic Resonance Imaging

Background: The primary mode of imaging in hypertrophic cardiomyopathy (HCM) is transthoracic echocardiography (TTE). However, in adults inadequate acoustic windows lead to poor quantification of myocardial thickness compared with cardiac magnetic resonance (CMR) imaging. In comparison, children have better acoustic windows and TTE measurements of wall thickness might be more accurate. The aim of this study was to assess the performance of TTE compared with CMR for the assessment of myocardial thickness in children with HCM. Methods: Nineteen children (median age, 12.7 years; range, 8.4-18.4 years) with known HCM were studied using TTE and CMR imaging on the same day. The left ventricle was measured off-line using the standard 16-segment model. Results: With CMR imaging 304 (19 x 16) segments were analyzable whereas only 263 were analyzable using echocardiography. Wall thickness measurements according to TTE were greater than those according to CMR imaging in the basal anterolateral, midventricular anterior and anterolateral and apical inferior, lateral and septal segments and smaller for the midventricular inferior and inferoseptal segments. Reproducibility of CMR and TTE measurements was assessed using the intraclass correlation coefficient (ICC). CMR measurements showed excellent intrareader (ICC, 0.929-0.991) and moderate inter-reader (ICC range, 0.512-0.991) reproducibility. TTE measurements revealed moderate intrareader (ICC, 0.575-0.942) and poor inter-reader (ICC range, -1.02 to 0.939) reproducibility. Conclusions: Echocardiography incompletely assesses circumferential myocardial thickness in a proportion of pediatric patients with HCM. Echocardiography under-and overestimates maximum wall thickness compared with CMR, depending on the location. Measurements using CMR are more reproducible than those obtained using echocardiography.