The most common cause of myocardial necrosis in patient undergoing COVID-19 infection is microthrombi. These microthrombi resulted quite different in composition vs. thrombi obtained from COVID-19 negative patients and thrombi obtained from infected patients with ACS.
Myocardial injury is common in patients hospitalized for COVID-19 and has worse prognosis. Regardless its frequency, the mechanism and the kind of myocardial damage associated to COVID-19 remains uncertain.
This is a systematic pathological analysis of 40 hearts of patients that died when hospitalized for COVID-19. It was carried out to identify the pathological mechanisms behind myocardial injury.
Hearts were divided according to presence of absence of acute myocyte necrosis and the cause behind it.
Of the 40 hearts, 14 (35%) had evidence of necrosis, mainly in the left ventricle. Compared against necrosis-free subjects, those with clear heart injury were most frequently women, with chronic kidney failure and shorter symptom onset to hospitalization time.
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The presence of obstructive coronary disease (>75% lesions) resulted similar between patients with and without injury.
A small percentage of patients presenting myocardial injury (21.4%) reached the definition of microscopic MI (necrosis in area > 1 cm2) while the remaining vast majority showed small necrotic areas spread out.
Thrombi were found in most patients with necrosis (78.6%), but with a small percentage in the epicardial arteries (14.2%). In the rest, thrombi were found in the capillaries, arterioles, and small muscle arteries.
Microthrombi in patient with COVID-19 presented significantly more fibrine and terminal fragments of the C5b-9 complement compared against intra myocardial thrombi of negative patients or the aspirated material of conventional STEMI patients (irrespective of COVID infection).
Conclusion
The most frequent physiopathological cause of myocardial necrosis in dead COVID patients is microthrombi. They are different in constitution to that of non-infected patients, and STEMI patients, be them infected or not.
Antithrombotic measures should be assessed to counteract the effect of COVID 19 to the heart.
Original Title: Microthrombis As A Major Cause of Cardiac Injury in COVID-19: A Pathologic Study.
Reference: Dario Pellegrini et al. Circulation. 2021 Mar 9;143(10):1031-1042. DOI: 10.1161/CIRCULATIONAHA.120.051828.
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