Flow-sensitive four-dimensional magnetic resonance imaging facilitates the quantitative analysis of systemic-to-pulmonary collateral flow in patients with univentricular hearts

Abstract

Background Systemic-to-pulmonary collateral flow (SPCF) may constitute a risk factor for increased morbidity and mortality in patients with single-ventricle physiology (SV). However, clinical research is limited by the complexity of multi-site two-dimensional (2D) cardiovascular magnetic resonance (CMR) flow assessment. We sought to validate four-dimensional flow (4D-flow) for concise quantification of SPCF in patients with SV. Methods 29 patients with SV physiology prospectively underwent CMR (1.5T) to quantify SPCF (n=14 bidirectional cavopulmonary connection [BCPC], age 2.9±1.3 years; and n=15 Fontan, 14.4±5.9 years) and 20 healthy volunteers (age, 28.7±13.1 years) served as controls. Five 2D-flow measurements (ascending aorta, superior/inferior caval veins, right/left pulmonary arteries) were performed and SPCF (=aortic minus caval flows) was calculated and compared with 4D-flow measurements and calculations. Additionally, 4D-flow measurements were used to calculate SPCF as pulmonary venous minus pulmonary arterial flow. Results The comparison between 4D-flow and 2D-flow showed good Bland-Altman agreement for all individual vessels (mean bias, 0.05±0.24 l/min/m2), calculated SPCF (-0.02 ±0.18 l/min/m2), low intra and inter-observer variance (ICC>0.95[0.91-0.97]) and significantly shorter 4D-flow acquisition-time (12:34min/17:28min,p<0.01). 4D-flow in patients versus controls revealed (1) good agreement between systemic versus pulmonary estimator for SPFC; (2) significant SPCF in patients (BCPC 0.79±0.45 l/min/ m2; Fontan 0.62±0.82 l/min/m2) and not in controls (0.01+0.16 l/min/m2) and (3) inverse relation of right/ left pulmonary artery perfusion and right/left SPCF (Pearson=-0.47,p=0.01). Conclusions