Cardiovascular Magnetic Resonance-derived Tricuspid Annular Motion Indices in the Assessment of Right Ventricular Function in Patients with Repaired Tetralogy of Fallot

Shuang Leng1, Ru-San Tan2, Ju Le Tan2, Ping Chai3, Lynetto Teo3, Marielle V Fortier4, Teng Hong Tan4, Wen Ruan1, Xiaodan Zhao1, Ching Ching Ong5, Devinder Singh3, John C Allen6, Ghassan S Kassab7, James W Yip3, Liang Zhong2
1National Heart Centre Singapore, 2National Heart Centre Singapore; Duke-NUS Medical School Singapore, 3National University Heart Centre Singapore; Yong Loo Lin School of Medicine, National University of Singapore, 4KK Women’s and Children’s Hospital Singapore; Duke-NUS Medical School Singapore, 5National University Heart Centre Singapore, 6Duke-NUS Medical School Singapore, 7California Medical Innovations Institute

Abstract

Background: Quantitative assessment of tricuspid annular (TA) deformation is essential for patients with repaired tetralogy of Fallot (rTOF). Tissue Doppler imaging (TDI) is well-established technique that enables measurements of regional right ventricular (RV) myocardial velocities. However, the application of TDI depends on the angle of insonation and measures only the vector of motion that is parallel to the direction of the ultrasound beam. This study investigates the feasibility, reliability and clinical utility of cardiovascular magnetic resonance (CMR)-derived TA motion indices in the assessment of RV function.

Methods: An in-house developed program based on adaptive feature tracking is used to semi-automatically track the RV septal and free wall in 4-chamber CMR view. Four clinically useful indices are extracted: SmCMR, peak systolic velocity; EmCMR, peak early diastolic velocity; AmCMR, peak late diastolic velocity during atrial contraction; and TAPSECMR, TA plane systolic excursion. This method was applied in 81 rTOF patients and 52 normal controls that had undergone CMR scans. 56 out of the 81 rTOF patients had cardiopulmonary exercise testing (CPET).

Results: Analysis was feasible in all subjects and took < 1 minute per subject. In comparison to controls, patients with rTOF had significantly reduced SmCMR, AmCMR and TAPSECMR, and larger EmCMR/AmCMR ratio. TAPSECMR had better predictive performances for exercise capacity as measured by maximal oxygen consumption (VO2max) during CPET (Area under the curve (AUC) = 0.823) than RV end-systolic volume index (AUC = 0.718), end-diastolic volume index (AUC = 0.714) and ejection fraction (AUC = 0.447). On multivariate analysis, only TAPSECMR was independently associated with VO2max (β = -0.097, p < 0.001). In addition, the study showed high reproducibility for assessment of TA motion parameters on CMR.

Conclusions: CMR-based measurements overcome the limitation of angle dependency of TDI, thus effectively extending routine CMR's capability for RV systolic and diastolic function assessment.