PET/CMR may help in accurate detection of left atrial appendage thrombus: Study

USA: PET/CMR of [64Cu] FBP8 may identify both acute and older platelet-poor thrombi with high accuracy, finds a new study. Moreover integrated PET/CMR approach provides useful information on the biological properties of left atrial appendage such as fibrin and methemoglobin content.

The study was published in the journal JACC: Cardiovascular Imaging on 13th October 2021.

Detecting thrombus in the left atrial appendage (LAA) is critical in stroke prevention and is presently done through transesophageal echocardiography (TEE). David Izquierdo-Garci and team aimed to detect and characterize LAA thrombus in humans using combined positron emission tomography (PET)/cardiac magnetic resonance (CMR) of a fibrin-binding radiotracer, [64Cu]FBP8.

In 8 healthy subjects, the metabolism and pharmacokinetics of [64Cu] FBP8 were investigated. Patients with atrial fibrillation and recent TEEs of the LAA (positive n = 12; negative n = 12) were injected with [64Cu] FBP8 and scanned with PET/CMR, including measuring the LAA's longitudinal magnetic relaxation time (T1).

SUV max values in the LAA were considerably greater in individuals with clots in the LAA than in those who did not have clots in the LAA. According to the researchers, an SUV max threshold of 2.6 produced a sensitivity of 100 percent and a specificity of 84 percent when reviewed by a radiologist with 15 years of expertise. Furthermore, the blood clots caused by the occlusion device implantation were quite visible. All of the blood clots in these individuals were restricted to the LAA, which was behind the device, and there was no indication of contact between the LAA and the left atrium on pictures. An examination of cardiac MRI with T1 mapping in individuals with positive ultrasound tests indicated the presence of a hyperintense signal consistent with LAA blood clots.

In conclusion, the combined PET/MRI technique offered valuable information on the biological features of blood clots, such as fibrin and methemoglobin, a clot consequence. More research is needed to assess the sensitivity of Cu-64 FBP8 for chronic thrombi (those lasting more than 10 weeks), the value of adding a gadolinium-based contrast agent to aid identification, and the embolic danger of these fibrin-poor organised thrombi.

Reference:

Izquierdo-Garcia, D., Désogère, P., Philip, A. L., Mekkaoui, C., Weiner, R. B., Catalano, O. A., Iris Chen, Y.-C., DeFaria Yeh, D., Mansour, M., Catana, C., Caravan, P., & Sosnovik, D. E. (2021). Detection and Characterization of Thrombosis in Humans Using Fibrin-Targeted Positron Emission Tomography and Magnetic Resonance. In JACC: Cardiovascular Imaging. Elsevier BV. https://doi.org/10.1016/j.jcmg.2021.08.009