Feeling the Force: Measurements of Platelet Contraction and Their Diagnostic Implications.

In addition to the classical biological and biochemical framework, blood clots can also be considered as active biomaterials composed of dynamically contracting platelets, nascent polymeric fibrin that functions as a matrix scaffold, and entrapped blood cells. As platelets sense, rearrange, and apply forces to the surrounding microenvironment, they dramatically change the material properties of the nascent clot, increasing its stiffness by an order of magnitude. Hence, the mechanical properties of blood clots are intricately tied to the forces applied by individual platelets. Research has also shown that the pathophysiological changes in clot mechanical properties are associated with bleeding and clotting disorders, cancer, stroke, ischemic heart disease, and more. By approaching the study of hemostasis and thrombosis from a biophysical and mechanical perspective, important insights have been made into how the mechanics of clotting and the forces applied by platelets are linked to various diseases. This review will familiarize the reader with a mechanics framework that is contextualized with relevant biology. The review also includes a discussion of relevant tools used to study platelet forces either directly or indirectly, and finally, concludes with a summary of potential links between clotting forces and disease.

A case report of primary pericardial sarcoma.

Background: Primary pericardial sarcomas are extremely rare malignancies. In this case of primary pericardial synovial sarcoma, we discuss the initial steps to work-up pericardial effusions and review features that warrant more detailed investigation. Case summary: A 29-year-old male with no relevant past medical history presents with a few weeks of fatigue, dyspnoea, orthopnoea, leg swelling, and back pain. Transthoracic echocardiogram revealed pericardial effusion for which pericardiocentesis and drain placement were done. He was discharged with a diagnosis of post-viral pericarditis. He returned 5 months later with worsening symptoms. Advanced imaging with cardiac magnetic resonance imaging (CMR) showed heterogeneous pericardial mass later revealed to be a high-grade synovial sarcoma on biopsy. The patient was started on a doxorubicin-based chemotherapy regimen, but due to kidney dysfunction and multi-organ failure, he was transitioned to palliative care measures. Discussion: Transthoracic echocardiogram and computed tomography are often the initial tests of choice for pericardial effusions with pericardiocentesis recommended for effusions with tamponade physiology, for moderate-to-large effusions, or if there is concern for infection/neoplasm. Due to improved tissue characterization and spatial resolution, CMR and positron emission tomography should also be considered for atypical or recurrent pericardial effusions to assess for less common aetiologies such as malignancy.