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1086 Accurate quantification of simultaneous mitral and tricuspid blood flow using 3D velocity-encoded MRI with retrospective valve tracking
Journal of Cardiovascular Magnetic Resonance volume 10, Article number: A211 (2008)
In valvular disease, surgical decision-making regarding timing and type of intervention is based on the severity of the regurgitation through the particular atria-ventricular valve. Conventional one-directional (1-dir) velocity-encoded (VE) MRI is routinely used for flow assessment over the mitral (MV) and tricuspid valve (TV), but this technique has been shown to be inaccurate and correlation between 1-dir VE MRI MV- and TV-flow measurement is weak.
Validation of three-dimensional (3D) 3-dir VE MRI with retrospective valve tracking during offline analysis for simultaneous MV and TV-flow assessment in phantoms and volunteers without valve regurgitation. The MRI technique is also applied to twenty heart failure patients with valve regurgitation.
MRI was performed on a 1.5 T Gyroscan ACS/NT15 (Philips, Best, the Netherlands). A 3D 3-dir VE MRI sequence (3D volume scan with slab thickness 48 mm, acquisition voxel size 2.9 × 3.8 × 4.0 mm3, velocity sensitivity 150 cm/s in all directions, with 30 phases reconstructed during one average cardiac cycle, with free breathing in vivo) was designed and tested in stationary flow phantoms and in a phantom simulating harmonic left ventricular filling. Echo Planar Imaging (EPI) was used for accelerating the acquisition (EPI factor 5, in vivo scan time <5 min).
In ten volunteers without valvular regurgitation, MV and TV-flow was assessed with this 3D 3-dir VE MRI sequence. MV and TV-flow were reformatted offline using the left and right ventricular cine 2- and 4-chamber views (in 30 corresponding phases/cardiac cycle) as orthogonal guides for the respective planning of the valvular planes (Figure 1). Analysis was repeated by two observers to test intra- and inter-observer variation. 1-dir VE MRI at MV and TV was performed for comparison. Systolic aortic flow measured with 1-dir VE MRI was used as the standard of reference.
Finally, MV and TV-flow was assessed in twenty patients with ischemic heart failure and MV and/or TV regurgition.
Validation in phantoms showed less than 5% error in flow quantification for either 3D VE MRI or 1-dir VE MRI. In volunteers, a significant bias was found for 1-dir VE MRI for both MV (over-estimation 11 ml/cycle) and TV (over-estimation 12 ml/cycle) compared to the aortic flow volume, while 3D VE MRI showed no bias and small confidence intervals. Correlation with aortic flow volume was strong for 3D VE MRI (r = 0.96 for MV, r = 0.88 for TV) and strong between MV and TV (r = 0.91). Correlation with aortic flow volume was weak for 1-dir VE MRI (r = 0.80 for MV, r = 0.22 for TV) and weak between MV and TV (r = 0.34). Coefficient of variation for 3D VE MRI was <4% for intra- and <8% for inter-observer analysis. In patients (mean regurgitant fraction for MV = 13%, for TV = 10%), correlation between MV- and TV-flow volume for 3D VE MRI was strong (r = 0.97) and there was no significant bias. Figure 2 shows the correlation between the flow volume measured at MV and TV using 3D 3-dir VE MRI in these twenty patients.
Although correlation for MV- and TV-flow with aortic flow was also good, these showed significant bias due to the aortic valve regurgitation that was present in several cases.
3D VE MRI provides the true trans-valvular MV and TV-flow in a single acquisition in less than 5 minutes scan time. Regurgitation through atrio-ventricular valves can be accurately quantified, providing essential information for surgical decision-making.
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Westenberg, J.J., Roes, S.D., de Roos, A. et al. 1086 Accurate quantification of simultaneous mitral and tricuspid blood flow using 3D velocity-encoded MRI with retrospective valve tracking. J Cardiovasc Magn Reson 10 (Suppl 1), A211 (2008). https://doi.org/10.1186/1532-429X-10-S1-A211
- Tricuspid Valve
- Echo Planar Image
- Left Ventricular Filling
- Valve Regurgitation
- Aortic Flow