Calcification and endothelialization of thrombi in acute stroke.

We report chronic histopathological features in thrombi mechanically retrieved from five acute ischemic stroke patients with a median age of 68 years and a median pretreatment National Institutes of Health Stroke Scale score of 13. Early endothelialization occurred over and within the thrombus, and calcifications were seen, in addition to the usual acute laminar fibrin, intervening red blood cells, and neutrophils. The effectiveness of tissue plasminogen activator in clot dissolution might be affected by these features, if extensive. Thrombus composition could critically determine the success of chemical thrombolysis. Our results should stimulate the development of imaging modalities to determine thrombus composition.