Artificial Stroke Clots: How Wide is the Gap to the Real World?

Especially since the establishment of mechanical thrombectomy as part of standard stroke therapy, artificial thrombi have become important in the training of interventionalists as well as for the development and testing of devices. So far, these in vitro clots have lacked direct comparisons with ex vivo thrombi. We therefore compared the histologic appearance of dynamically produced clots with that of stroke thrombi acquired during mechanical recanalization.

Thrombi of 145 consecutive patients with stroke with large-vessel occlusions were histologically compared with 10 artificial clots, dynamically created from human blood and pig's blood using a Chandler loop system. Quantified FP/RBC ratios (fibrin/platelets divided by red blood cell fraction) and white blood cell (WBC) fractions were identified and compared between artificial (human and pig) and ex vivo thrombi obtained from patients with various stroke causes.

There were no significant differences in the analysis of FP/RBC ratios between artificial thrombi and ex vivo thrombi (P = 0.42) or in the more precise analyses considering etiologic subgroups. Distinct differences were observed for the WBC fraction, with lower values in artificial thrombi (median, 1.34%) than in ex vivo thrombi (median, 5%) (P < 0.001).

The main clot components, FP and RBC, are presumably the most influential factors for clot stability and mechanical resistance. Similarities between artificially generated and ex vivo stroke clots (and when considering different stroke subgroups) support the usefulness of these artificial thrombi in the pre-evaluation of thrombus extraction devices and as appropriate training material.