Background
By the end of January 2021, SARS-CoV-2, the causative virus of COVID-19, had infected over 100 million and killed over 2 million people internationally.1 Hypertension has been recognised as the most common comorbidity among patients hospitalised with COVID-19.2–4 However, it remains unclear whether hypertension is an independent risk factor for mortality or whether the presence of hypertension is a marker of other factors that confer an adverse prognosis such as advanced age, coronary artery disease, heart failure and renal disease. This has important implications for identifying patients at high risk of adverse outcomes and for prioritising the management of comorbidities in patients with and at risk of COVID-19. The primary aim of this study was therefore to assess whether hypertension is independently linked with increased mortality from COVID-19.
Additionally, there has been conjecture about the effects of ACE inhibitors and angiotensin receptor blockers (ARBs) on COVID-19 prognosis in light of the fact that the virus responsible for COVID-19, SARS-CoV-2, binds to the ACE2 receptor in order to enter host cells.5 With the potential upregulation of ACE2, secondary to ACE inhibitor and ARB use,6 7 there exists a possible risk of increased viral entry into host cells. However, on the other hand, previous animal studies have suggested that ACE2 may have protective effects against acute respiratory distress syndrome.8 Initial observational data on this matter have been conflicting.9 10 Therefore, the secondary aim of this study was to assess the impact of ACE inhibitors and ARBs on mortality in patients with a background of hypertension admitted to hospital with COVID-19.
Australia provides a unique context to investigate these questions. Healthcare resources have been overwhelmed internationally,11–13 requiring stricter rationalisation of access to intensive care units (ICUs) in many regions and rapid construction of new hospitals in some settings. The extent to which this pandemic context has confounded the results of international clinical studies investigating COVID-19 outcomes is unknown. Australia has maintained control of COVID-19 case numbers such that hospital systems been able to maintain a high level of supportive care to all patients as required. The current manuscript presents analysis of the Australian Cardiovascular COVID-19 (AUS-COVID) Registry, which is the largest Australian multicentre COVID-19 cardiovascular registry of hospitalised patients.