Intracardiac Flow Analysis of the Right Ventricle in Pediatric Patients With Repaired Tetralogy of Fallot Using a Novel Color Doppler Velocity Reconstruction

Background: Repaired tetralogy of Fallot (RTOF) patients will develop right ventricular (RV) dysfunction from chronic pulmonary regurgitation (PR). Cardiac magnetic resonance sequences such as four-dimensional flow can demonstrate altered vorticity and flow energy loss (FEL); however, they are not as available as conventional echocardiography (echo). The study determined whether a novel, vendor-independent Doppler velocity reconstruction (DoVeR) could measure RV intracardiac flow in conventional echo of RTOF patients. The primary hypothesis was that DoVeR could detect increased vorticity and diastolic FEL in RTOF patients.

Methods: Repaired tetralogy of Fallot patients with echo were retrospectively paired with age-/size-matched controls. Doppler velocity reconstruction employed the stream function-vorticity equation to approximate intracardiac flow fields from color Doppler. A velocity field of the right ventricle was reconstructed from the apical 4-chamber view. Vortex strength (VS, area integral of vorticity) and FEL were derived from DoVeR. Cardiac magnetic resonance and exercise stress parameters (performed within 1 year of echo) were collected for analysis.

Results: Twenty RTOF patients and age-matched controls were included in the study. Mean regurgitant fraction was 40.5% ± 7.6%, and indexed RV end-diastolic volume was 158 ± 36 mL/m. Repaired tetralogy of Fallot patients had higher total, mean diastolic, and peak diastolic VS (P = .0013, P = .0012, P = .0032, respectively) and higher total, mean diastolic, and peak diastolic body surface area-indexed FEL (P = .0016, P = .0022, P < .001, respectively). Peak diastolic indexed FEL and peak diastolic VS had weak-to-moderate negative correlation with RV ejection fraction (r = -0.52 [P = .019] and r = -0.49 [P = .030], respectively) and left ventricular ejection fraction (r = -0.47 [P = .034] and r = -0.64 [P = .002], respectively). Mean diastolic indexed FEL and VS had moderate-to-strong negative correlation with percent predicted maximal oxygen consumption (r = -0.69 [P = .012] and r = -0.75 [P = .006], respectively).

Conclusions: DoVeR can detect alterations to intracardiac flow in RTOF patients from conventional color Doppler imaging. Echo-based measures of diastolic VS and FEL correlated with ventricular function. DoVeR has the potential to provide serial evaluation of abnormal flow dynamics in RTOF patients.