Free-running 5D flow yielded the most accurate maximum velocity compared to echocardiography, despite underestimating net flow volumes relative to standard 2D flow by 4-17 ml per beat.
Do 5D and 4D flow imaging provide comparable net flow volumes and maximum velocity measurements to standard 2D flow and TTE in patients with congenital heart disease?
5D flow CMR provides comparable net flow volumes to 2D flow with superior internal agreement and yields the most accurate maximum velocity compared to TTE in congenital heart disease patients.
Absolute Event Rate: 0% vs 0%
Flow quantification by cardiac magnetic resonance (CMR) is essential for diagnosis-making and follow-up in patients with congenital heart disease (CHD). Standard 2D phase contrast (2D flow) sequences require, however, precise image plane prescription resulting in long exam times. Free-breathing 3D whole-heart flow sequences (4D flow) offer faster acquisition but require respiratory navigation rendering exam duration unpredictable. Free-running radial, fully self-gated, respiratory and cardiac motion-resolved 5D flow promises ease-of-use and stable scan duration. This study compared net flow volumes (NFV) between 2D, 4D and 5D flow and maximum velocity (Vmax) to transthoracic echocardiography (TTE). CHD patients were scanned on a 1.5 T scanner. 2D flow was performed in the ascending (AAo), descending aorta, main (MPA), right, and left pulmonary arteries, superior vena cava, and pulmonary veins. By a prototype whole-heart free-running 3D radial phase contrast CMR sequence end-expiratory 5D flow images were obtained. Finally, 4D flow data were collected. 3D vessel segmentation was performed for 4D and 5D flow datasets. NFV were compared between 2D, 4D and 5D flow and Vmax to transthoracic echocardiography (TTE). 59 CHD patients (median age 28, IQR 17.5, 42% women) with right- and/or left-sided CHD were included. Scan duration did not differ significantly between methods. 4D and 5D flow underestimated NFV relative to 2D flow by 4-17 ml per beat which was more prominent for 4D flow and smaller vessels. Internal agreement was best for 4D flow, followed by 5D flow, while 2D flow showed the largest variability: MPA vs AAo (bias ml, 95% LOA): 2D flow: -4.84 (-34.18, 24.5), 4D flow -0.84 (-17.85, 16.18), 5D flow -6.4 (-28.53, 15.73). 2D and 4D but not 5D flow underestimated Vmax compared to TTE: AAo: TTE 120±46; 2D 108±36; 4D 107±36; 5D 115±40 cm/s; p<0.03 TTE vs 2D and 4D flow; p=0.253 TTE vs 5D flow). 4D and 5D flow provided measurements comparable to 2D flow. Despite systematic underestimation of NFV, internal agreement of whole heart methods was superior while scan time did not increase significantly. 5D flow yielded the most accurate Vmax compared to TTE, supporting its potential for comprehensive non-invasive hemodynamic evaluation.
Dirbach et al. (Sun,) reported a other. Free-running 5D flow yielded the most accurate maximum velocity compared to echocardiography, despite underestimating net flow volumes relative to standard 2D flow by 4-17 ml per beat.
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