P0417 - Two Dimensional Assessment of Right Ventricle in Repaired Tetralogy of Fallot – a Novel Approach to Older Technique

Introduction: In repaired tetralogy of Fallot (rTOF), progressive right ventricular (RV) enlargement and dysfunction lead to poor outcomes. Currently, the evaluation of RV has limitations, especially in pediatric patients. While cardiac magnetic resonance (CMR) imaging is considered gold standard, it has significant barriers including cost, accessibility and need for sedation in pediatric patients. Newer echocardiographic techniques like 3D and strain are not readily available and need additional expertise. Two-dimensional (2D) echocardiogram remains the most accessible, practical and commonly utilized tool for serial RV assessment. However, there are limitations of traditional echocardiographic RV assessment due to its complex geometry and location. Our study aims to assess novel 2D echocardiographic measurements of RV volume to improve its diagnostic and clinical utility in comparison to CMR and exercise test.

Methods: This is a retrospective study of rTOF patients who underwent clinically indicated CMR and echocardiogram within 6 months followed by exercise tests. Clinical, echocardiographic, exercise test, and CMR data were collected. By echocardiogram, RV end-diastolic and end-systolic length in parasternal long (PSL) axis and 4-chamber view were measured in addition to traditional measurements per American Society of Echocardiography (ASE) guidelines. RV end-diastolic volume (RVEDV) and RV end-systolic volume (RVESV) were calculated using 5/9(area in 4-chamber view*length in PSL) based on regression analysis equation.

Results: Forty-five patients with 66 CMR/echocardiogram/exercise test sets were included. Mean age was 13.8 years (range 6.1 to 19.7 years). Echocardiographic RVEDV and RVESV by our method had strong correlation with respective CMR parameters (r = 0.82 and 0.77; p=<0.0001), and moderate correlation with peak oxygen pulse (0.62 and 0.49; p=<0.0001) and CMR left ventricular EF (-0.40 and-0.42; p=0.001). However, traditional measurements such as tricuspid annular plane systolic excursion (TAPSE) and fractional area change (FAC) had no significant correlation. Also, ASE guideline measurements of 4-chamber RV basal and mid-cavity dimensions had weak correlation. Subsequent RV outflow interventions were performed in 62% cases. Mean echocardiographic RVEDV and RVESV were significantly higher and EF lower in those requiring interventions. By ROC analysis, indexed echocardiographic RVEDV of 93 ml/m2 had 92% sensitivity and 50% specificity (area under curve 0.75 (p=0.001)) in predicting CMR RV/LV EDV ratio > 2:1, which is considered an early indicator for pulmonary valve replacement in a few studies. The echocardiographic RV volumes had excellent inter-observer agreement with intraclass correlation coefficient of 0.96-0.98.

Conclusion: This study demonstrates that our novel echocardiographic RV measurements have strong correlation with equivalent CMR values, and are better than traditional echocardiographic parameters. Their association with exercise tests suggests potential clinical value, warranting further longitudinal prospective studies to validate these findings. While echocardiogram will not replace CMR, these 2D measurements would be useful in pediatric population in predicting the RV volume, progression, and timing of CMR.