Comparing transthoracic echocardiography, 2D and 4D flow cardiovascular magnetic resonance for quantitative valve assessment after percutaneous pulmonary valve implantation

Abstract Aim To compare transthoracic echocardiography (TTE), 2D and 4D flow cardiovascular magnetic resonance (CMR) for the evaluation of valve function and flow measurements after percutaneous pulmonary valve implantation (PPVI). Methods In this multicentre exploratory observational study, 29 patients who underwent PPVI were planned for TTE and CMR with 2D and 4D flow measurements after PPVI. Peak velocity was measured with all techniques. Net and regurgitating flow measurements were measured with CMR distal to the transcatheter pulmonary valve (TPV). Results Median peak velocity of the transcatheter pulmonary valve (TPV) with TTE was 2.5 (2.0-3.1) m/s, with 2D flow CMR 2.3 (2.0-3.2) m/s, and with 4D flow 2.3 (2.0-3.0) m/s. There was a good correlation for the peak velocity of the TPV between TTE and 2D flow CMR (r=0.68, p<0.001) and a moderate correlation for peak velocity between TTE and 4D flow CMR (r=0.56, p=0.003), and between 2D flow and 4D flow CMR (r=0.56, p=0.006). For peak velocity measurements, no proportional bias was observed between the three imaging techniques. For the CMR flow measurements, a strong correlation was observed between 2D and 4D flow CMR, for both net flow (r=0.87, p<0.001) and regurgitation fraction (r=0.96, p<0.001) of the TPV. Net flow through the left pulmonary artery correlated strongly between 2D and 4D flow CMR (r=0.85, p<0.001), and there was a good correlation for the right pulmonary artery (r=0.65, p<0.01). For net flow measurements of the TPV, we found an underestimation of flow measurements at higher flow rates with 4D flow CMR, compared to 2D flow CMR. Conclusion TTE, 2D and 4D flow CMR are all feasible and reliable imaging techniques after PPVI, concordant in predominantly mild-to-moderate stenosis. These findings strengthen the use of 2D and 4D flow CMR as a tool for post-PPVI assessment, despite stent induced artifacts, although reliability in more advanced valve dysfunction remains uncertain.