2.3 The vicious circle: stroke–heart syndrome
Due to the extremely wide prevalence of COVID-19, the management of stroke cannot be ignored. The presence of a true relationship between COVID-19 and stroke remained to be determined. Although the number of stroke hospitalizations had declined, the evidence was available that COVID-19 infection itself may cause a stroke. It was worth noting that, without excluding the possibility of the virus directly invading the nervous system, heart injury seemed to be an important feature of this disease. The impairment of cardiac function occurs in 20-30% of hospitalized COVID-19 patients [15]. In a pooled analysis, the cerebrovascular disease was found to be associated with a 2.5-fold increase in the severity of COVID-19 [16]. In addition, medical records from three hospitals in Wuhan indicated that 5.9% of the patients had COVID-19 infection complicated with stroke, and these patients were older, with more CVD complications, and more severe pneumonia. Stroke mechanisms in these cases might include hypercoagulable state caused by critical illness and cardiogenic embolism caused by virus-related heart damage [17]. The expression of ACE2 on vascular smooth muscle cells may also be a potential target for SARS-CoV-2 infection. The pathological analysis of COVID-19 patients documented the presence of microvascular inflammation and microthrombosis in the lungs and other affected organs [18]. Importantly, many incidences of sudden death and severe non-fatal cardiac events after the stroke may result from the interaction between cardiovascular and nervous systems [19]. Therefore, considering the possibility that COVID-19 may promote cardiac and microvascular thrombosis at various levels, the incidence of a stroke may increase with the thrombus entering the brain in COVID-19 patients. Thus, the vicious cycle in which the heart function is affected by brain damage should be considered by clinicians.