Ultrasound elastography monitoring reveals a decline in shear wave attenuation and clot viscosity after recombinant tissue plasminogen activator treatment of blood clots

Abstract

Deep vein thrombosis is one of the leading causes of disability and serious illness and can become fatal. The lytic recombinant tissue plasminogen activator (rt-PA) is the main drug used for clot lysis and rapid normalization of venous blood flow. Less than 40% of patients who receive rt-PA treatment have improved blood flow. In this study, we quantitatively monitor the rt-PA treatment in in-vitro blood clots with ultrasound elastography. An acoustic radiation force imaging sequence was implemented on a research ultrasound system to remotely generate shear waves inside the blood clot samples. Porcine blood samples from two different pigs were bought from a local slaughterhouse. Clots of varying viscoelasticity were prepared by allowing different coagulation time between 30 min to 3 days in borosilicate glass pipettes. The clots were then embedded in gelatin-agar phantoms to perform ultrasound measurements. Another batch of clots from the same blood samples was treated with rt-PA drug for 30 min, and ultrasound measurements were performed after treatment. In 11 samples, variations in SW speed before and after rt-PA treatment were not found to be statistically significant (>0.05). However, SW attenuation and clot viscosity declined significantly after rt-PA treatment by 33.49% ± 31.07% (<0.05) and 33.33% ± 35.72% (<0.05). The results indicate that SW attenuation and viscosity can be used to monitor DVT treatment, and clot viscosity may emerge as an important biomarker for clot staging.