Ischemic Stroke Appears to Be More in Common in COVID-19 Vs. Influenza

Ischemic strokes are elevated with respiratory viral illnesses, but a new study determines that is even more the case in patients with severe COVID-19. Find out the different in risks in the two patient groups and why researchers posit that COVID is more likely to result in a severe vascular side effect.

NEW YORK – Respiratory viral illnesses, such as influenza, are known to increase the risk of stroke in some cases. A recent study looked at whether that risk is further elevated in patients with COVID-19.

The study in JAMA Neurology sought to compare the rate of ischemic stroke between patients with COVID-19 and patients with influenza.

Weill Cornell Medicine-led researchers conducted the retrospective cohort study at two academic hospitals in New York City. Included were adult patients with emergency department visits or hospitalizations with COVID-19 from March 4, 2020, through May 2, 2020.

A comparison cohort included adults with emergency department visits or hospitalizations with influenza A/B from January 1, 2016, through May 31, 2018 – which spanned moderate and severe influenza seasons.

Researchers report that a panel of neurologists determined the primary outcome of acute ischemic stroke and its clinical characteristics, mechanisms, and outcomes. The study team then compared the proportion of patients with COVID-19 with ischemic stroke vs the proportion among patients with influenza.

Overall, among 1,916 patients with emergency department visits or hospitalizations with COVID-19, 31 (1.6%; 95% CI, 1.1%-2.3%) had an acute ischemic stroke. The median age of patients with stroke was 69 years (interquartile range, 66-78 years); 18 (58%) were men. In eight cases, stroke was the reason for hospital presentation.

In comparison, three of 1,486 patients with influenza (0.2%; 95% CI, 0.0%-0.6%) had an acute ischemic stroke.

After adjustment for age, sex, and race, researchers determined that the likelihood of stroke was higher with COVID-19 infection than with influenza infection (odds ratio, 7.6; 95% CI, 2.3-25.2). The association was found to persist across sensitivity analyses adjusting for vascular risk factors, viral symptomatology, and intensive care unit admission.

Researchers also write that patients with COVID-19 infection who experienced an ischemic stroke were considerably more likely to die than patients with COVID-19 infection who did not experience an ischemic stroke.

“In this retrospective cohort study from two New York City academic hospitals, approximately 1.6% of adults with COVID-19 who visited the emergency department or were hospitalized experienced ischemic stroke, a higher rate of stroke compared with a cohort of patients with influenza,” according to the authors, who called for additional studies are needed to confirm these findings and to investigate possible thrombotic mechanisms associated with COVID-19.

In positing reasons for their results, researchers note that it has been established that acute viral infections, including influenza, act as triggers that increase the short-term risk of ischemic stroke and other arterial thrombotic events, such as myocardial infarction, with implicated mechanisms including inflammation, prothrombotic coagulopathy, and endothelial injury. Especially with COVID-19 infection, the authors explain, a vigorous inflammatory response occurs accompanied by coagulopathy, with elevated D-dimer levels and the frequent presence of antiphospholipid antibodies, which might be related to the high prevalence of thromboses in those patients.

“Second, patients with COVID-19 infection are at heightened risk for medical complications, such as atrial arrhythmias, myocardial infarction, heart failure, myocarditis, and venous thromboses, all of which likely contribute to the risk of ischemic stroke,” they write. “Additionally, COVID-19 infection may on average result in a more severe respiratory syndrome than influenza infection, and this greater severity of illness may in part account for the greater rate of stroke seen in patients with COVID-19, especially regarding its associations with the cardiovascular and coagulation systems.”

Another theory is related to the higher rate of baseline stroke risk factors, such as hypertension, diabetes, and coronary artery disease, in COVID-19 patients compared to those with the flu. Researchers point out, however, that “even when adjusting for the number of vascular risk factors, we identified a higher risk of ischemic stroke with Covid-19 vs with influenza. How these and other unidentified factors unique to COVID-19 may play a role in the excess risk of stroke beyond the risk observed with other viral infections requires further investigation.”

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