Multi detector CT for differentiation of prosthetic valve thrombus from pannus

Multi detector CT for differentiation of prosthetic valve thrombus from pannus

Differentiation of prosthetic valve thrombus from pannus is often difficult by echocardiography. Both can cause abnormal masses and both can cause increase in the transvalvar gradients and leaflet thickness.

Multi detector computed tomogram (MDCT) is useful for this differentiation. Attenuation of signals as measured in Hounsfield units is lower for the thrombus compared to pannus. Pannus has attenuation values similar to the adjacent interventricular septum.

ECG (electrocardiogram) gated computed tomography (CT) also helps in the assessment of the dynamic function of the prosthetic valve in systole and diastole. Early hypoattenuated leaflet thickening indicative of subclinical prosthetic valve thrombosis was detected in 10% of cases in one study [1]. It was fully reversible on anticoagulation. The study used ECG triggered dual source CT angiography.

Computed tomography radiomic analysis can also be used to differentiate between thrombus and pannus. A retrospective study evaluated 39 periprosthetic masses in 34 patients with clinically suspected prosthetic valve obstruction who underwent redo surgery during which the cause of obstruction was confirmed and classified as thrombus, pannus or vegetation. Visual analysis from axial and valve dedicated CT views were done. Computed radiomic analysis of the periprosthetic masses were also done and advantage of radiomic score assessed. Radiomic score was significantly higher in those with pannus compared to thrombus and vegetation [2].

Radiomics aims at enhancing the existing data available to clinicians by advanced mathematical analysis. Mathematical extraction of spatial distribution of signal intensities and pixel interrelationships is used to quantify textural information using artificial intelligence [3].

References

1. Pache G, Schoechlin S, Blanke P, Dorfs S, Jander N, Arepalli CD, Gick M, Buettner HJ, Leipsic J, Langer M, Neumann FJ, Ruile P. Early hypo-attenuated leaflet thickening in balloon-expandable transcatheter aortic heart valves. Eur Heart J. 2016 Jul 21;37(28):2263-71.
2. Nam K, Suh YJ, Han K, Park SJ, Kim YJ, Choi BW. Value of Computed Tomography Radiomic Features for Differentiation of Periprosthetic Mass in Patients With Suspected Prosthetic Valve Obstruction. Circ Cardiovasc Imaging. 2019 Nov;12(11):e009496.
3. van Timmeren JE, Cester D, Tanadini-Lang S, Alkadhi H, Baessler B. Radiomics in medical imaging-“how-to” guide and critical reflection. Insights Imaging. 2020 Aug 12;11(1):91. doi: 10.1186/s13244-020-00887-2. PMID: 32785796; PMCID: PMC7423816.