Morphological signs of the intravital contraction (retraction) of thrombotic emboli

Aim. To establish whether contraction (retraction) of thrombi and thrombotic emboli occurs in vivo using structural signs of blood clot compression, such as compressive deformation of erythrocytes and redistribution of fibrin on the surface of a clot.

Methods. Three postmortem pulmonary thrombotic emboli were examined by scanning electron microscopy and light microscopy after staining with hematoxylin and eosin as well as with Mallory’s method.

Results. In 2 studied pulmonary emboli, extracted 7 and 15 hours after patients’ death, polyhedral erythrocytes (polyhedrocytes) were revealed that were formed as a result of mechanical deformation under the action of contractile forces generated by activated platelets. In addition, the uneven distribution of fibrin within the emboli was found with displacement of fibrin to the periphery of the emboli, which is characteristic for contracted blood clot. In the first and the «oldest» clot extracted 38 hours after the patient’s death, the described contraction signs were absent, which was likely related to the postmortem autolysis or intravital pathological impairment of contraction.

Conclusion. Thrombotic emboli ex vivo have morphological signs of contraction, suggesting intravital compression of the primary thrombi and/or thrombotic emboli, which might be an important pathogenetic mechanism for modulation of impaired blood flow at the sites of thrombotic occlusion of a vessel; the presence or absence of compressed erythrocytes inside and predominant location of fibrin on the periphery of a thrombus or embolus can potentially serve as additional pathomorphological criteria of death coming prescription.