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Pulmonary embolism occurs when blood flow to a part of the lungs is blocked by a venous thrombus that has traveled from the lower limbs. Little is known about the mechanical behavior of emboli under compressive forces from the surrounding musculature and blood pressure. We measured the stress-strain responses of human pulmonary emboli under cyclic compression, and showed that emboli exhibit a hysteretic stress-strain curve. The fibrin fibers and red blood cells (RBCs) are damaged during the compression process, causing irreversible changes in the structure of the emboli. We showed using electron and confocal microscopy that bundling of fibrin fibers occurs due to compression, and damage is accumulated as more cycles are applied. The stress-strain curves depend on embolus structure, such that variations in composition give quantitatively different responses. Emboli with a high fibrin component demonstrate higher normal stress compared to emboli that have a high RBC component. We compared the compression response of emboli to that of whole blood clots containing various volume fractions of RBCs, and found that RBCs rupture at a certain critical stress. We describe the hysteretic response characteristic of foams, using a model of phase transitions in which the compressed foam is segregated into coexisting rarefied and densified phases whose fractions change during compression. Our model takes account of the rupture of RBCs in the compressed emboli and stresses due to fluid flow through their small pores. Our results can help in classifying emboli as rich in fibrin or rich in red blood cells, and can help in understanding what responses to expect when stresses are applied to thrombi in vivo.

The introduction of Janus kinase (JAK) 1/2 inhibitor ruxolitinib into the armamentarium of myelofibrosis therapies has allowed to effectively control systemic symptoms, reduce splenomegaly, and imp...

Pathology as a basic science discipline traditionally is a component of the preclinical medical school curriculum. While there have been regional and nationwide surveys reporting on the curricular organization and instructional formats of preclinical pathology instruction, the extent of required pathology integration into the clinical medical school curriculum, particularly as it relates to practical issues of patient management, has not been studied. A survey soliciting information about required pathology programs in the clinical years was distributed to the members of the Undergraduate Medical Educators Section of the Association of Pathology Chairs (APC). A literature search of such programs was also performed. Thirty-seven respondents representing 30 medical schools (21% of the 140 Liaison Committee on Medical Education-accredited medical schools in the APC) described a total of 16 required pathology programs in the clinical years. An additional 10 programs were identified in the literature. Advantages of required pathology activities in the clinical years include educating medical students in effective utilization of anatomic and clinical pathology for patient care and exposing them to the practice of pathology. Reported challenges have been competition for curricular time in the clinical years, attitudinal resistance by clerkship directors, failure to recognize pathology as a clinical discipline, and insufficient number of faculty in pathology departments. By survey sample and literature review, there has been relatively little progress in the integration of required pathology exposure into the clinical years. Development of practice-related pathology competencies may facilitate introduction of such curricular programs in the future.