Histopathological Profile of Thrombi Differs Depending on Pathogenesis of Embolic Cerebral Infarction and Evidence of Intracardiac Thrombus

Background and Objectives: Determining the etiopathogenesis of stroke is a cornerstone for correct secondary prophylaxis, however, in up to 40% the precise source of embolism cannot be determined. The aim of our study was to investigate histopathological differences of emboli retrieved during mechanical thrombectomy, and to investigate how radiological findings and ischemic stroke outcomes correlate with histopathological profile of thrombi. Materials and Methods: In total 40 stroke patients were included in the study. Histopathological examination was performed using Hematoxylin and Eosin staining. Subsequently, on the basis of hematoxylin-andeosin staining, the percentage and area of erythrocytes, leukocytes, and fibrin in investigated thrombi were measured. Thrombi were stained immunohistochemically, according to manufacturer`s instructions. The results were compared in supposed etiopathological stroke subtype groups as cardioembolic, atheroembolic and cryptogenic. Correlation between histopathology of thrombi and stroke
outcomes, as well as radiological findings, that is hyperdense artery sign and presence of thrombi in left atrium appendage on nonenhanced thoracic Computed Tomography, was also performed. Results: There were 26 cardioembolic thrombi, 7 atheroembolic and 7 cryptogenic thrombi. Atheroembolic thrombi had a higher percentage of the fibrin area versus total thrombi area than cryptogenic thrombi (p=0.038) and similar tendency comparing with cardioembolic thrombi (p=0.099). Cryptogenic thrombi had statistically lower
fibrin/leukocytes ratio than atheroembolic thrombi (p=0,026). As to radiological findings, hyperdense artery sign did not correlate with any specific histopathological composition of thrombi, but patients with CT visualized thrombus in the heart had larger erythrocyte area in thrombus than those without mentioned finding (p=0.047). The ischemic stroke outcome in patients after performed mechanical thrombectomy did not correlate with thrombus histopathology. Conclusion: We found partial histologic similarities of cryptogenic thrombi with cardioembolic thrombi. Therefore patients with cryptogenic stroke should probably undergo extensive cardiac examination including long-term heart rhythm monitoring.