Background: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and its resultant clinical presentation, COVID-19, is an emergent cause of mortality worldwide. Cardiac complications secondary to this infection are common; however, the underlying mechanisms of such remain unclear. A detailed cardiac evaluation of a series of COVID-19 individuals undergoing postmortem evaluation is provided, with four aims: 1) describe the pathologic spectrum of the myocardium; 2) compare to an alternate viral illness; 3) investigate angiotensin converting enzyme 2 (ACE2) expression; and 4) provide the first description of the cardiac findings in patients with cleared infection. Methods: Study cases were identified from institutional files and included COVID-19 (n=15; 12 active, 3 cleared), influenza A/B (n=6), and non-virally mediated deaths (n=6). Salient information was abstracted from the medical record. Light microscopic findings were recorded. An ACE2 immunohistochemical H-score was compared across cases. Viral detection encompassed SARS-CoV-2 immunohistochemistry, ultrastructural examination, and droplet digital polymerase chain reaction (ddPCR). Results: Male sex was more common in the COVID-19 group (p=0.05). Non-occlusive fibrin microthrombi (without ischemic injury) were identified in 16 cases (12 COVID-19, 2 influenza, and 2 controls), and were more common in the active COVID-19 cohort (p=0.006). Four active COVID-19 cases showed focal myocarditis, while one case of cleared COVID-19 showed extensive disease. Arteriolar ACE2 endothelial expression was lower in COVID-19 cases versus controls (p=0.004). ACE2 myocardial expression did not differ by disease category, sex, age or number of patient comorbidities (p=0.69, p=1.00, p=0.46, p=0.65, respectively). SARS-CoV-2 immunohistochemistry showed non-specific staining, while ultrastructural examination and ddPCR were negative for viral presence. Four (26.7%) COVID-19 patients had underlying cardiac amyloidosis. Cases with cleared infection had variable presentations. Conclusions: This detailed histopathologic, immunohistochemical, ultrastructural and molecular cardiac series showed no definitive evidence of direct myocardial infection. COVID-19 cases frequently have cardiac fibrin microthrombi, without universal acute ischemic injury. Moreover, myocarditis is present in 33.3% of active and cleared COVID-19 patients, but is usually limited in extent. Histologic features of resolved infection are variable. Cardiac amyloidosis may be an additional risk factor for severe disease.

Context: Respiratory failure appears to be the ultimate mechanism of death in most patients with severe COVID-19 infection. Studies of postmortem COVID-19 lungs largely report diffuse alveolar damage (DAD) and capillary fibrin thrombi, but we have also observed other patterns. Objective: To report demographic and radiographic features along with macroscopic, microscopic, and microbiologic postmortem lung findings in patients with COVID-19 infections. Design: Patients with confirmed COVID-19 infection and postmortem examination (3/2020–5/2020) were included. Clinical findings were abstracted from medical records. Lungs were microscopically reviewed independently by 4 thoracic pathologists. Imaging studies were reviewed by a thoracic radiologist. Results: Eight patients (7 men, 87.5%; median age of 79 years, range, 69–96) died within a median of 17 days (range, 6–100) from onset of symptoms. The median lung weight was 1,220 g (range, 960–1,760); consolidations were found in 5 of 8 (62.5%) patients; gross thromboemboli were noted in one of 8 (12.5%) patient. Histologically, all patients had acute bronchopneumonia, 6 of 8 (75%) patients had also DAD. Two of 8 (25%) patients had aspiration pneumonia in addition. Thromboemboli, usually scattered and rare, were identified in 5 of 8 (62.5%) patients in small vessels and in two of these patients also in pulmonary arteries. Four of (50%) patients had perivascular chronic inflammation. Postmortem bacterial lung cultures were positive in 4 of 8 (50%) patients. Imaging studies (available in 4 patients) were typical (N=2, 50%), indeterminate (N=1, 25%), or negative (N=1, 25%) for COVID-19 infection. Conclusions: Our study shows that patients infected with COVID-19 not only have DAD but also commonly have acute bronchopneumonia and aspiration pneumonia. These findings are important for management of these patients.

To cite this article: Depasse F., Gerotziafas G. T., Busson J., Van Dreden P., Samama M.M. Assessment of three chromogenic and one clotting assays for the measurement of synthetic pentasaccharide fondaparinux (Arixtra Synthetic pentasaccharide fondaparinux (Arixtra 1) is the ®rst indirect (antithrombin-dependent) synthetic speci®c factor (F)Xa inhibitor approved in several countries for the prevention of deep vein thrombosis (DVT) in major orthopedic surgery. In addition, ongoing clinical trials aim to prove its ef®cacy for the treatment of DVT and in coronary heart disease (for review see [1,2]). Fondaparinux plasma concentrations obtained in patients treated at prophylactic and therapeutic doses range from 0.1 to 0.5 mg mL À1 and from 0.6 to 1.5 mg mL À1, respectively; in healthy volunteers, the subcutaneous injection of the established prophylactic dose (2.5 mg) is associated with plasma levels at 0.34 AE 0.04 mg mL À1 [3±5]. Although no coagulation monitoring is advocated, accurate assays dedicated to anti-Xa activity measurement should be available. This could be useful in practical use at least in some particular groups of patients, e.g. with renal impairment, during pregnancy, body weight < 50 kg as recommended for LMWHs or in the elderly. Nevertheless, no special assay has been developed for this purpose and the commercial available assays are designed for either unfractionated or low molecular weight heparins. The aim of this work was to evaluate the possibility of using commercially available assays. Three different chromogenic and one clotting assays for the measurement of fondaparinux anti-Xa activity in plasma were evaluated.Normal pool plasma (Normapool 1 , Hyphen BioMed, Neuville sur Oise, France) was spiked with increasing amounts of fondaparinux (Sano®, Paris, France) in order to obtain plasma concentrations ranging from 0 to 10 mg mL À1 . The antithrombin activity level was measured in this range of concentrations using the Berichrom 1 Heparin was used with addition of exogenous bovine antithrombin as provided with the assay and without addition of exogenous antithrombin. In addition to the results expressed in LMWH anti-Xa IU mL À1 , results were registered as raw data, i.e. optical density variation per minute (DOD min À1 ) and clotting time for the chromogenic and the clotting assays, respectively. FXa inhibition for the chromogenic assays was calculated by reporting the DDO min À1 of the considered sample to the DDO min À1 of the normal pool plasma free of fondaparinux considered as baseline. A statistical analysis was performed using an analysis of variance (ANOVA, F-test).All the antithrombin activity levels measured remained in the normal range and were not signi®cantly affected by the addition of fondaparinux.Results expressed in LMWH anti-Xa IU/mL differed signi®cantly (P < 0.01) from an assay to another for the same fondaparinux plasma concentration, e.g. (mean AE SD, n 10) 0.93 AE 0.03 IU mL A linear relationship was obtained for fondaparinux plasma concentrations ranging from 0 up ...