Can Simple Echocardiographic Measures Reduce the Number of Cardiac Magnetic Resonance Imaging Studies to Diagnose Right Ventricular Enlargement in Congenital Heart Disease? Mohammed H. Alghamdi, MD, Lars Grosse-Wortmann, MD, Nauman Ahmad, MD, Luc Mertens, MD, PhD, and Mark K. Friedberg, MD, Toronto, Ontario, Canada; Riyadh, Saudi Arabia Background: Right ventricular (RV) enlargement is used as a criterion for the treatment of RV outflow tract dysfunction in patients with congenital heart disease. Although RV volumes are most accurately measured by cardiac magnetic resonance (CMR), CMR is a limited resource. The aim of this study was to investigate whether simple echocardiographic measurements can adequately predict RV volumes below clinical thresh- olds, thereby reducing the need for CMR in some patients. Methods: Children with repaired tetralogy of Fallot, double-outlet right ventricle, or truncus arteriosus who under- went CMR and echocardiography within a 4-week interval were retrospectively studied. From the four-chamber view, indexed RV lateral wall length, indexed RV end-diastolic perimeter length, and indexed RV end-diastolic area (RVEDAi), were measured. Results were compared with CMR indexed RV volume. The sensitivity and specifity of echocardiographic threshold values predicting RV volumes < 170 mL/m 2 were determined. Results: Fifty-one children (mean age, 12.7 6 3.5 years; 25 male, 26 female) were reviewed. RVEDAi was correlated with CMR indexed RV volume (r = 0.60, P < .0001). Indexed RV end-diastolic perimeter length and indexed RV lateral wall length were not correlated with CMR. RVEDAi < 20 cm 2 /m 2 had 100% specificity to predict indexed RV volume # 170 mL/m 2 (area under the curve, 0.79), reducing the need for CMR in 15 of 51 patients (29%). A threshold RVEDAi of 22 cm 2 /m 2 would reduce the need for CMR in 21 of 51 patients (41%) at the expense of one false-negative result. The coefficients of variation were 14.7% for intraobserver variability and 9.6% for interobserver variability. Conclusions: The specificity of echocardiography-measured RVEDAi can be set to predict RV volumes below a 170 mL/m 2 threshold in 100% of cases. This may reduce the need for CMR to determine RV volumes in $25% of patients with congenital heart disease, potentially reducing patient burden and costs. (J Am Soc Echocardiogr 2012;25:518-23.) Keywords: Pediatrics, Right ventricle, Echocardiography, Cardiac magnetic resonance imaging Right ventricular (RV) enlargement is an indication for surgical or catheter pulmonary valve replacement or repair for RV outflow tract dysfunction in children with congenital heart disease (CHD). 1 Cardiac magnetic resonance (CMR) is currently the most accepted method to quantify RV volumes. 2-4 However, CMR is relatively expensive, with limited availability in some centers. Although two-dimensional (2D) echocardiography is not sufficiently accurate to determine RV volumes for clinical decision making, it remains the most widely available modality for initial screening and serial follow-up. 5 In patients who are otherwise asymptomatic but appear to have significant RV enlargement on the basis of echocardiography, clinicians are faced with the decision whether to perform CMR for the accurate determination of RV volumes. However, echocardio- graphic criteria to guide the need for more accurate RV volume quan- tification by CMR are lacking. RV enlargement by echocardiography is often suspected by subjective assessment, albeit with suboptimal interobserver variability. 6 Current guidelines rely mainly on linear measurements of the RV body from the apical four-chamber view and the RV outflow tract from the parasternal short-axis view. 7 However, these methods correlate weakly with RV size measured by CMR in children with CHD. 8 Measurement of RV area from the apical four-chamber view correlates better with RV volumes measured by CMR 9,10 and is readily measured using commercially available digital platforms. We hypothesized that although 2D echocardiographic measure- ments are inadequate to determine absolute RV volumes, simple 2D echocardiographic indices can adequately predict RV volumes From the Labatt Family Heart Centre (M.H.A., L.G.-W., N.A., L.M., M.K.F.) and the Department of Diagnostic Imaging (L.G.-W.), The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada; and King Fahad Cardiac Centre, King Saud University, Riyadh, Saudi Arabia (M.H.A.). Reprint requests: Mark K. Friedberg, MD, The Labatt Family Heart Center, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada (E-mail: mark.friedberg@sickkids.ca). 0894-7317/$36.00 Copyright 2012 by the American Society of Echocardiography. doi:10.1016/j.echo.2012.01.023 518