1.2 COVID-19 in the cardiovascular system
Because COVID-19 may affect the cardiovascular system at multiple levels, the virus infection may lead to myocardial damage and dysfunction, increasing the incidence of CVD in patients. The mechanism of COVID-19-induced heart damage was unclear, but it may involve the combined effects of direct viral damage, immune damage, and cytotoxic immune cell responses in the later stages of the infection [5]. Cardiac involvement was a documented complication of COVID-19 and was associated with a higher hospital mortality rate [6]. In a study on the impact of CVD complications on death outcomes, 35.3% of 187 enrolled patients had potential CVD. Moreover, the presence of myocardial injury was significantly related to the mortality rate among COVID-19 patients, and the prognosis was better in patients without myocardial injury [7]. In a patient with acute heart injury directly related to SARS-CoV-2 localized in the myocardium, a biopsy of myocardial intima documented low-grade myocardial inflammation, but no viral particles in myocardial cells were found [8]. Therefore, the onset and progression of COVID-19 may cause myocardial damage independently of the infection of the cardiac tissue by the virus. Although the specific mechanism remained unknown, it would be still necessary to pay attention to the protection of the cardiovascular system in COVID-19 patients during the treatment of the disease.