1337644 - Role of wall shear stress and peak systolic velocity changes derived using 4D Flow MRI in the assessment of activity in diseased vascular segments in Takayasu’s aorto-arteritis.

The diagnosis of Takayasu’s arteritis is difficult due to presence of only nonspecific systemic symptoms, such as fever and general weakness, during the early phase of the disease (1). Newer MRI techniques like 4D flow have shown promise in evaluation of vascular hemodynamics in pathologies like aortic aneurysms and dissection. However, the utility of non-contrast 4D flow MRI in detection of disease activity in Takayasu’s arteritis has not been reported yet. 

4D flow derived wall shear stress (WSS) is an indicator for impact of flow alterations on endothelial cell and extracellular matrix function(2). Pulse wave velocity and peak systolic velocity (PSV) are markers of arterial stiffness(2).  In this novel study, we intend to evaluate the role of axial and circumferential WSS and PSV in the assessment of activity in diseased segments of Takayasu’s arteritis and correlate them with the normal segments.

Methods:

This was a cross-sectional observational study which included prospectively enrolled patients with clinical diagnosis of Takayasu’s arteritis as per the 1990 ACR criteria. All patients underwent CE-CT/MRA followed by 4D flow MRI. Active disease showed concentric vessel wall thickening, narrowing, with delayed enhancement. A non-contrast 4D-flow sequence was planned covering the aorta. Quantitative assessment of parameters- axial and circumferential WSS, and PSV was done at the involved and normal aortic segments. The data was analysed using Stata v17.

Results:

A total number of 30 patients (4 males, 26 female, average age- years) were enrolled based on the inclusion criteria. Diseased and non-affected segments were evaluated in all patients for imaging parameters as well as 4D flow MRI parameters. All the patients had at least one diseased segment with post-contrast enhancement. Average axial WSS and PSV were significantly higher in the actively diseased segments, 0. 23+/-0.12 Pa; p=0.05, and 118.2+/-38.08 cm/sec, p= 0.0019, as compared to the normal segments 0.167+/-0.072 Pa and 92.71+/-36.84 cm/sec respectively. However, the average circumferential WSS was not significantly different in the diseased segments (0.07+/-0.09 Pa) and normal segments (0.06+/-0.08 Pa, p=0.2235). Spearman correlation coefficient revealed the independent ability of both axial WSS and PSV at the narrowest segment in predicting disease activity (p=0.002). Also, there was a strong positive correlation between increased PSV and increased axial WSS in actively diseased vascular segments of aorta (r= 0.3988, p= 0.0291). According to the ROC curve analysis, the cut-off of axial WSS of 0.17 Pa had a sensitivity of 63.33% and specificity of 56.67% in predicting the presence of disease activity, where as a PSV of >/= 91.3cm/sec had a sensitivity of 70% and specificity of 66.67% in predicting the disease activity.

Conclusion:

There is significant correlation between increased axial WSS and PSV in predicting disease activity  in Takayasu’s arteritis independently and also when combined together.