Structure, mechanical properties, and modeling of cyclically compressed pulmonary emboli.

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 distinctive structure and composition of arterial and venous thrombi and pulmonary emboli.

Although arterial and venous thromboembolic disorders are among the most frequent causes of mortality and morbidity, there has been little description of how the composition of thrombi and emboli depends on their vascular origin and age. We quantified the structure and composition of arterial and venous thrombi and pulmonary emboli using high-resolution scanning electron microscopy. Arterial thrombi contained a surprisingly large amount of fibrin, in addition to platelets. The composition of pulmonary emboli mirrored the most distal part of venous thrombi from which they originated, which differed from the structure of the body and head of the same thrombi. All thrombi and emboli contained few biconcave red blood cells but many polyhedrocytes or related forms of compressed red blood cells, demonstrating that these structures are a signature of clot contraction in vivo. Polyhedrocytes and intermediate forms comprised the major constituents of venous thrombi and pulmonary emboli. The structures within all of the thrombi and emboli were very tightly packed, in contrast to clots formed in vitro. There are distinctive, reproducible differences among arterial and venous thrombi and emboli related to their origin, destination and duration, which may have clinical implications for the understanding and treatment of thrombotic disorders.

A Patient With Parenteral Nutrition-Dependent Short Bowel Syndrome and Cardiovascular Disease With 4-Year Exposure to Teduglutide.

Clinical trials of the glucagon-like peptide 2 analogue teduglutide resulted in approval of the drug by the Food and Drug Administration in 2012 as a treatment for parenteral nutrition-dependent short bowel syndrome in adults. This report presents the case study of a man with short bowel syndrome caused by portal vein thrombosis who had 4 years exposure to the drug at the time of his death due to cardiovascular disease.

Consensus Guidelines for Practical Competencies in Anatomic Pathology and Laboratory Medicine for the Undifferentiated Graduating Medical Student.

The practice of pathology is not generally addressed in the undergraduate medical school curriculum. It is desirable to develop practical pathology competencies in the fields of anatomic pathology and laboratory medicine for every graduating medical student to facilitate (1) instruction in effective utilization of these services for optimal patient care, (2) recognition of the role of pathologists and laboratory scientists as consultants, and (3) exposure to the field of pathology as a possible career choice. A national committee was formed, including experts in anatomic pathology and/or laboratory medicine and in medical education. Suggested practical pathology competencies were developed in 9 subspecialty domains based on literature review and committee deliberations. The competencies were distributed in the form of a survey in late 2012 through the first half of 2013 to the medical education community for feedback, which was subjected to quantitative and qualitative analysis. An approval rate of ≥80% constituted consensus for adoption of a competency, with additional inclusions/modifications considered following committee review of comments. The survey included 79 proposed competencies. There were 265 respondents, the majority being pathologists. Seventy-two percent (57 of 79) of the competencies were approved by ≥80% of respondents. Numerous comments (N = 503) provided a robust resource for qualitative analysis. Following committee review, 71 competencies (including 27 modified and 3 new competencies) were considered to be essential for undifferentiated graduating medical students. Guidelines for practical pathology competencies have been developed, with the hope that they will be implemented in undergraduate medical school curricula.

The integration of pathology into the clinical years of undergraduate medical education: a survey and review of the literature.

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.