COVID-19-Associated Nonocclusive Fibrin Microthrombi in the Heart.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its resultant clinical presentation, coronavirus disease 2019 (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 individuals with COVID-19 undergoing postmortem evaluation is provided, with 4 aims: (1) describe the pathological spectrum of the myocardium; (2) compare with an alternate viral illness; (3) investigate angiotensin-converting enzyme 2 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 nonvirally mediated deaths (n=6). Salient information was abstracted from the medical record. Light microscopic findings were recorded. An angiotensin-converting enzyme 2 immunohistochemical H-score was compared across cases. Viral detection encompassed SARS-CoV-2 immunohistochemistry, ultrastructural examination, and droplet digital polymerase chain reaction. RESULTS: Male sex was more common in the COVID-19 group (P=0.05). Nonocclusive 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, whereas 1 case of cleared COVID-19 showed extensive disease. Arteriolar angiotensin-converting enzyme 2 endothelial expression was lower in COVID-19 cases than in controls (P=0.004). Angiotensin-converting enzyme 2 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 nonspecific staining, whereas ultrastructural examination and droplet digital polymerase chain reaction were negative for viral presence. Four patients (26.7%) with COVID-19 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 patients with active and cleared COVID-19 but is usually limited in extent. Histological features of resolved infection are variable. Cardiac amyloidosis may be an additional risk factor for severe disease.

Neuropathology of COVID-19: a spectrum of vascular and acute disseminated encephalomyelitis (ADEM)-like pathology.

We report the neuropathological findings of a patient who died from complications of COVID-19. The decedent was initially hospitalized for surgical management of underlying coronary artery disease. He developed post-operative complications and was evaluated with chest imaging studies. The chest computed tomography (CT) imaging results were indicative of COVID-19 and he was subsequently tested for SARS-CoV-2, which was positive. His condition worsened and he died after more than 2 weeks of hospitalization and aggressive treatment. The autopsy revealed a range of neuropathological lesions, with features resembling both vascular and demyelinating etiologies. Hemorrhagic white matter lesions were present throughout the cerebral hemispheres with surrounding axonal injury and macrophages. The subcortical white matter had scattered clusters of macrophages, a range of associated axonal injury, and a perivascular acute disseminated encephalomyelitis (ADEM)-like appearance. Additional white matter lesions included focal microscopic areas of necrosis with central loss of white matter and marked axonal injury. Rare neocortical organizing microscopic infarcts were also identified. Imaging and clinical reports have demonstrated central nervous system complications in patients' with COVID-19, but there is a gap in our understanding of the neuropathology. The lesions described in this case provide insight into the potential parainfectious processes affecting COVID-19 patients, which may direct clinical management and ongoing research into the disease. The clinical course of the patient also illustrates that during prolonged hospitalizations neurological complications of COVID may develop, which are particularly difficult to evaluate and appreciate in the critically ill.