CMR-Flow

1355653 - Pulmonary regurgitation is associated with blood kinetic energy discordance in pediatric repaired tetralogy of Fallot: A 4D flow CMR study

Friday, January 27, 2023

3:25 PM – 3:40 PM

Location: Silver Pearl 1

Presenting Author(s)

LZ

Liang Zhong, PhD

Professor
National Heart Centre Singapore，Duke-NUS Medical School, National University of Singapore
Singapore, Singapore

Primary Author(s)

XZ

Xiaodan Zhao, PhD

Research Assistant
National Heart Centre Singapore, Singapore

Co-Author(s)

LiWei Hu, MSc

Research Assistant
Shanghai Children's Medical Center
Shanghai, Shanghai, China (People's Republic)
RO

Rong-Zhen Ouyang, MD

Pediatric radiologist
Shanghai Children’s Medical Center, China (People's Republic)
SL

Shuang Leng, PhD

Research Fellow
National Heart Centre Singapore, Singapore
RT

Ru-San Tan, MD

Clin Assoc Prof, Senior Consultant
National Heart Centre Singapore
Singapore, Singapore
JB

Jen Bryant, MSc, Phd, FSCMR

Senior Principal Radiographer / Manager
National Heart Centre Singapore
JA

John C. Allen, PhD

Adjunct Assistant Professor
Duke University Medical Center, United States
Marina Hughes, PhD

Professor
University of East Anglia
Norwich, England, United Kingdom
PG

Pankaj Garg, PhD

Associate Professor of Cardiovascular Medicine
University of East Anglia, United Kingdom
Rv

Rob J. J. van der Geest, PhD

Associate Professor
Leiden University Medical Center
Leiden, Zuid-Holland, Netherlands
JT

Ju Le Tan, MBBS

Clin Assoc Prof, Senior Consultant
National Heart Centre Singapore, Singapore
YZ

Yu-Min Zhong, MD, PhD

Pediatric radiologist
Shanghai Children’s Medical Center
SHANGHAI, Shanghai, China (People's Republic)

Background: Pulmonary regurgitation (PR) after repaired tetralogy of Fallot (rTOF) is a common sequela that can disrupt intracardiac blood flow kinetics, leading to altered wall stress, adverse right ventricular (RV) remodeling, and interventricular mechanical discordance. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows quantification of biventricular blood flow and blood kinetic energy (KE). In this study, we used 4D flow CMR to measure a novel metric blood KE discordance―ratio of KE between the RV and left ventricle (LV)―in pediatric rTOF subjects and evaluated its association with standard ventricular functional indexes and PR severity.

Methods: Forty pediatric rTOF (age 7±4 years; 16 females) and 15 control subjects (age 9±3 years; 7 females) underwent prospective cine and 4D flow CMR acquisitions (3.0T, GE). All images were analyzed using MASS (Version 2022EXP, The Netherlands). PR fraction (PRF) was calculated from 4D flow curve generated at a trans-axial slice located at the pulmonary trunk. Intraventricular KE per voxel was computed as KE=1/2*ρ_blood*V_voxel*v_voxel, where ρ_bloodrepresents blood density (1.06 g/cm³); V_voxeland v_voxel, voxel volume and velocity, respectively. From time-resolved KE curves for all voxels within both ventricles^1,2, values of mean intraventricular KE averaged over all systolic time points and normalized to end-diastolic volume (EDV), KEi_EDV (unit μJ/ml), were extracted. Blood KE discordance was defined as the ratio of RV-to-LV mean systolic KEi_EDV. From cine CMR images, biventricular EDV, end-systolic volumes (ESV) and ejection function (EF) were calculated using Simpson’s method; and peak lateral mitral (MAPSE) and tricuspid annular plane systolic excursions (TAPSE) measured on the four-chamber view using feature tracking^3-5. Mechanical discordance was defined as the difference in time-to-peak (ms) between TAPSE and MAPSE.

Results: Compared with controls, rTOF subjects (mean PRF 31.6±11.1%) had significantly larger RV volumes, lower TAPSE, higher mechanical (23 vs. 0 ms, P=0.032) and blood KE discordances (2.29 vs. 1.20, P < 0.001) (Table 1). For discriminating rTOF from controls, blood KE discordance and TAPSE shared similar C statistics (0.927 vs. 0.995, Delong’s P=0.066) that were superior to RVEDV (0.535), RVESV (0.520), and RVEF (0.537) on receiver operating characteristic analyses. Blood KE discordance was correlated with PRF (R=0.517, P< 0.001) and TAPSE (R=-0.369, P< 0.01). On multivariable analysis, only PRF was independently associated with blood KE discordance (ˆβ=0.031, P < 0.001).

Conclusion: 4D flow-assessed blood KE discordance was independently associated with PR severity, but not other RV volume and functional parameters. In our cohort of pediatric rTOF with preserved RV ejection fraction, it was significantly increased, suggesting that it is an early marker of the hemodynamic consequence of PR. The prognostic implication of this novel parameter will require longitudinal investigation.