Objective: The role of renin–angiotensin–aldosterone system (RAAS) blockers during the coronavirus disease 2019 (COVID-19) pandemic is a matter of controversies. Studies based on in-hospital exposure have suggested a beneficial effect of these drugs, unlike those based on chronic exposure. We aimed to analyse RAAS blocker prescription before and during hospital stay in patients with COVID-19, and the corresponding outcomes, to explain these discrepant results. Methods: In a retrospective cohort study conducted in 347 patients hospitalized for COVID-19 (Bichat Hospital, Paris, France, 23 January–29 April 2020), RAAS blocker exposure, as well as timing and reason for treatment modifications, were collected. The association between exposure and mortality within 30 days of hospital admission was analysed using logistic regression analysis adjusted for age, sex, and comorbidities. Results: Median age was 61 [interquartile range, 51–72] years, 209 (60%) were male, 169 (49%) had a history of treated hypertension, and 117 (34%) received a RAAS blocker prior to hospitalization. RAAS blockers were discontinued within the first 7 days of hospital admission in 33% of previously treated patients (mostly driven by severity of the disease), with a corresponding mortality rate of 33%. Mortality was 8% when treatment was maintained or introduced, and 12% in patients never exposed. Adjusted odds ratios for association between exposure and mortality were 0.62 (95% confidence interval 0.25–1.48) based on chronic exposure and 0.25 (0.09–0.65) based on in-hospital exposure. Conclusion: A ‘healthy user-sick stopper’ bias influences RAAS blocker prescription after hospital admission for COVID-19, and explains the seemingly favourable outcome associated with in-hospital treatment.

Since December 2019, the coronavirus 2019 (COVID-19) pandemic has rapidly spread and overwhelmed healthcare systems worldwide, urging physicians to understand how to manage this novel infection. Early in the pandemic, more severe forms of COVID-19 have been observed in patients with cardiovascular comorbidities, who are often treated with renin-angiotensin aldosterone system (RAAS)-blockers, such as angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs), but whether these are indeed independent risk factors is unknown. The cellular receptor for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the membrane-bound angiotensin converting enzyme 2 (ACE2), as for SARS-CoV(-1). Experimental data suggest that expression of ACE2 may be increased by RAAS-blockers, raising concerns that these drugs may facilitate viral cell entry. On the other hand, ACE2 is a key counter-regulator of the RAAS, by degrading angiotensin II into angiotensin (1-7), and may thereby mediate beneficial effects in COVID-19. These considerations have raised concerns about the management of these drugs, and early comments shed vivid controversy among physicians. This review will describe the homeostatic balance between ACE-angiotensin II and ACE2-angiotensin (1-7) and summarize the pathophysiological rationale underlying the debated role of the RAAS and its modulators in the context of the pandemic. In addition, we will review available evidence investigating the impact of RAAS blockers on the course and prognosis of COVID-19 and discuss why retrospective observational studies should be interpreted with caution. These considerations highlight the importance of solid evidence-based data in order to guide physicians in the management of RAAS-interfering drugs in the general population as well as in patients with more or less severe forms of SARS-CoV-2 infection.