Right Ventricular Restrictive Physiology Is Associated With Right Ventricular Direct Flow From 4D Flow CMR

Abstract

Background: Right ventricular restrictive physiology (RVRP) is a common occurrence in repaired tetralogy of Fallot (rTOF). The relationship of RVRP with biventricular blood flow components and kinetic energy (KE) from 4-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is unclear.

Objectives: The purpose of this study was to investigate the association of 4D flow CMR parameters with RVRP in rTOF patients.

Methods: A total of 103 rTOF patients and 62 age and sex-matched healthy control subjects were prospectively recruited. All participants underwent CMR (cine, 2-dimensional phase-contrast, and 4D flow sequences), and cardiopulmonary exercise test in adult populations. RVRP was identified from pulmonary artery flow curve using 2-dimensional phase-contrast images. Biventricular flow components (direct flow, retained inflow, delayed ejection flow, and residual volume) and KE parameters normalized to end-diastolic volume (KEi_EDV) were analyzed encompassing global, peak systolic, average systolic, average diastolic, peak E-wave, and peak A-wave.

Results: Compared with control subjects, rTOF patients had significantly lower RV direct flow and higher RV residual volume (both P < 0.001). All RV KEi_EDV parameters, except peak A-wave, were higher in rTOF patients. In rTOF patients, 70 of 103 (68%) had RVRP, with increasing RV direct flow (27% vs 20%; P = 0.002) and RV peak E-wave KEi_EDV (28.4 vs 20.7μJ/mL; P = 0.015) and decreasing RV residual volume (37% vs 42%; P = 0.039) than rTOF without RVRP. Exercise capacity was impaired in rTOF, although comparable between RVRP subgroups. Multivariable analysis revealed RV direct flow was an independent predictor of RVRP (OR: 1.158; 95% CI: 1.074-1.249; P < 0.001).

Conclusions: RVRP is associated with dilated RV, higher pulmonary regurgitation, and higher RV direct flow. (Integrated Computational modeling of Right Heart Mechanics and Blood Flow Dynamics in Congenital Heart Disease; NCT03217240).

Keywords: 4D flow CMR; flow component; kinetic energy; repaired tetralogy of Fallot; right ventricular restrictive physiology.

Graphical abstract

Figure 1

Illustration of Parameters From 2D Phase-Contrast and 4D Flow CMR Segmentation of 2D phase-contrast main pulmonary artery borders was performed throughout the cardiac cycle (first row), and can generate the resultant pulmonary flow curve in MASS software (second row). Using 4D flow analysis, the 4 flow components for left ventricle (LV) and right ventricle (RV) can be calculated and displayed using pie plot (third row), and also the biventricular kinetic energy (KE) curves. We presented these in 1 healthy control (left panel), repaired tetralogy of Fallot (rTOF) without right ventricular restrictive physiology (RVRP) (middle panel) and rTOF with RVRP (right panel). KEi_EDV = kinetic energy normalized to end-diastolic volume; PRF = pulmonary regurgitant fraction.

Figure 2

Bar Plot Comparisons of RV 4D Flow Parameters Kruskal-Wallis nonparametric 1-way analysis of variance analysis was used to compare the 3 subgroups, with post hoc pairwise comparisons. In the event of a significant Kruskal-Wallis test without any correction, only raw P values were reported. Comparisons of RV direct flow (first row), RV residual volume (second row), RV peak E-wave KEi_EDV (third row) and KE discordance (last row) among control, rTOF without and with RVRP for pediatric and adult subjects were given on the left panel and right panel, respectively. RVRP (−) = rTOF without RVRP; RVRP (+) = rTOF with RVRP; other abbreviations as in Figure 1.

Central Illustration

Right Ventricular Direct Flow Associated With Right Ventricular Restrictive Physiology in Repaired Tetralogy of Fallot (A) A total of 103 patients with rTOF and 62 healthy control subjects were included in the study. (B) Patients with RVRP have greater PR volume and PR fraction; smaller LV cavity; greater LV ejection fraction; greater RV stroke volume index, RV ejection fraction, RVEDV/LVEDV ratio, and RV direct flow; and smaller RV residual volume. (C) Patients with RVRP have increased RV direct flow, deceased residual volume, and increased peak E-wave KEi_EDV compared with patients without RVRP. (D) On multivariable binary logistic analysis, RV direct flow was independently associated with RVRP (OR: 1.158). CMR = cardiovascular magnetic resonance; CPET = cardiopulmonary exercise test; LV = left ventricle; LVEDV = left ventricular end-diastolic volume; KEi_EDV = kinetic energy normalized to end-diastolic volume; PR = pulmonary regurgitation; rTOF = repaired Tetralogy of Fallot; RV = right ventricle; RVEDV = right ventricular end-diastolic volume; RVRP(−) = rTOF without RVRP; RVRP(+) = rTOF with RVRP.