Four-dimensional flow cardiovascular magnetic resonance in tetralogy of Fallot: a systematic review

Abstract

Background: Patients with repaired Tetralogy of Fallot (rTOF) often develop cardiovascular dysfunction and require regular imaging to evaluate deterioration and time interventions such as pulmonary valve replacement. Four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) enables detailed assessment of flow characteristics in all chambers and great vessels. We performed a systematic review of intra-cardiac 4D flow applications in rTOF patients, to examine clinical utility and highlight optimal methods for evaluating rTOF patients.

Methods: A comprehensive literature search was undertaken in March 2020 on Google Scholar and Scopus. A modified version of the Critical Appraisal Skills Programme (CASP) tool was used to assess and score the applicability of each study. Important clinical outcomes were assessed including similarities and differences.

Results: Of the 635 articles identified, 26 studies met eligibility for systematic review. None of these were below 59% applicability on the modified CASP score. Studies could be broadly classified into four groups: (i) pilot studies, (ii) development of new acquisition methods, (iii) validation and (vi) identification of novel flow features. Quantitative comparison with other modalities included 2D phase contrast CMR (13 studies) and echocardiography (4 studies). The 4D flow study applications included stroke volume (18/26;69%), regurgitant fraction (16/26;62%), relative branch pulmonary artery flow(4/26;15%), systolic peak velocity (9/26;35%), systemic/pulmonary total flow ratio (6/26;23%), end diastolic and end systolic volume (5/26;19%), kinetic energy (5/26;19%) and vorticity (2/26;8%).

Conclusions: 4D flow CMR shows potential in rTOF assessment, particularly in retrospective valve tracking for flow evaluation, velocity profiling, intra-cardiac kinetic energy quantification, and vortex visualization. Protocols should be targeted to pathology. Prospective, randomized, multi-centered studies are required to validate these new characteristics and establish their clinical use.

Keywords: 4D flow; Cardiovascular magnetic resonance; Tetralogy of Fallot.

Fig. 1

Flow diagram showing the stages of the systematic review process (adapted from Moher et al. [16])

Fig. 2

Participants age demographic profile. * estimated from mean ± 2*s.d

Fig. 3

4D flow analysis applications. (A) manually placed seed positions; (B) particle streamline visualization of the ascending aorta; (C) main pulmonary and branches forward flow; (D) main pulmonary artery regurgitation; (E) flow analysis: Net flow across cardiac cycle; (F) 3D vortex core extraction in the right ventricle; (G) 2D visualization of vortices in the right ventricle; (H) kinetic energy mapping from Kanski et al. JCMR (2015) 17:111 DOI 10.1186/s12968-015-0211-4 used under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/)