Can simple echocardiographic measures reduce the number of cardiac magnetic resonance imaging studies to diagnose right ventricular enlargement in congenital heart disease?

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 thresholds, thereby reducing the need for CMR in some patients. Methods: Children with repaired tetralogy of Fallot, double-outlet right ventricle, or truncus arteriosus who underwent 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 ± 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.