**6. Natriuretic peptides**

Natriuretic peptides represent a change of intracardial pressure, especially atrial pressure, and thus is also used as an important cardiac function indicator. These include Brain-type natriuretic peptide (BNP), NT-proBNP, and mid-regional pro atrial natriuretic peptide. Nartiuretic peptides are trigger by hemodynamic stress and heart failure, intracardiac filling pressures, end diastolic wall stress, and hypoxemia. In patients who are not critically ill, BNP/pro-BNP elevations have a high positive predictive value for heart failure. However, in patients who are critically ill, the elevations are likely in the presence of hemodynamic stress and heart failure. Several studies have identified heart failure as a significant manifestation of COVID-19. Heart failure in COVID-19 patients is postulated to occur as a result of the severe immune system reaction and cytokine storm [6, 7]. The virus downregulates the angiotensin-converting enzyme 2 (ACE2), leading to increased levels of angiotensin II. Further, this causes increased inflammation, thrombosis, and hypertension. Abnormalities NT-proBNP, were associated with higher in-hospital mortality in all patients and in severe patients. Studies were done to estimate the cumulative in-hospital mortality among patients severe COVID-19 patients. The mortality rates were the highest with elevated hs-cTnI and NT-proBNP, followed by elevated NT-proBNP and normal

hs-cTnI, elevated hs-cTnI and normal NT-proBNP, and normal hs-cTnI and NT-proBNP. The combination of these two cardiac markers together was found

#### *COVID-19 and Cardiac Enzymes DOI: http://dx.doi.org/10.5772/intechopen.101402*

to be more valuable than cardiac troponin alone in determining the prognosis of COVID-19 patients. There has been one retrospective study that reported a correlation between first and peak BNP values to predict the need for mechanical ventilation and mortality respectively. Pro-BNP levels elevated above 167.5 pg./mL are associated with an increased risk of mortality in patients receiving mechanical ventilation. Furthermore, along with the strong association of mortality in patients admitted to the hospital with COVID-19, the elevation of natriuretic peptides could be used as an early indicator for the presence of left and right ventricular systolic dysfunction independently. Identification of ventricular systolic dysfunction, if a treatable dysregulation, will help in decreased mortality and improved outcomes in patients.
