While several recent publications have “raised the possibility” of this link, none have had an appropriate control group, noted Dr. Merkler of the department of neurology, Weill Cornell Medicine. “Further elucidation of thrombotic mechanisms in patients with COVID-19 may yield better strategies to prevent disabling thrombotic complications like ischemic stroke,” he added.
An increased risk of stroke
The study included 1,916 adults with confirmed COVID-19 (median age 64 years) who were either hospitalized or visited an emergency department between March 4 and May 2, 2020. These cases were compared with a historical cohort of 1,486 patients (median age 62 years) who were hospitalized with laboratory-confirmed influenza A or B between January 1, 2016, and May 31, 2018.
Among the patients with COVID-19, a diagnosis of cerebrovascular disease during hospitalization, a brain computed tomography (CT), or brain magnetic resonance imaging (MRI) was an indication of possible ischemic stroke. These records were then independently reviewed by two board-certified attending neurologists (with a third resolving any disagreement) to adjudicate a final stroke diagnosis. In the influenza cohort, the Cornell Acute Stroke Academic Registry (CAESAR) was used to ascertain ischemic strokes.
The study identified 31 patients with stroke among the COVID-19 cohort (1.6%; 95% confidence interval, 1.1%-2.3%) and 3 in the influenza cohort (0.2%; 95% CI, 0.0%-0.6%). After adjustment for age, sex, and race, stroke risk was almost 8 times higher in the COVID-19 cohort (OR, 7.6; 95% CI, 2.3-25.2).
This association “persisted across multiple sensitivity analyses, with the magnitude of relative associations ranging from 4.0 to 9,” wrote the authors. “This included a sensitivity analysis that adjusted for the number of vascular risk factors and ICU admissions (OR, 4.6; 95% CI, 1.4-15.7).”
The median age of patients with COVID-19 and stroke was 69 years, and the median duration of COVID-19 symptom onset to stroke diagnosis was 16 days. Stroke symptoms were the presenting complaint in only 26% of the patients, while the remainder developing stroke while hospitalized, and more than a third (35%) of all strokes occurred in patients who were mechanically ventilated with severe COVID-19. Inpatient mortality was considerably higher among patients with COVID-19 with stroke versus without (32% vs. 14%; P = .003).
In patients with COVID-19 “most ischemic strokes occurred in older age groups, those with traditional stroke risk factors, and people of color,” wrote the authors. “We also noted that initial plasma D-dimer levels were nearly 3-fold higher in those who received a diagnosis of ischemic stroke than in those who did not” (1.930 mcg/mL vs. 0.682 mcg/mL).
The authors suggested several possible explanations for the elevated risk of stroke in COVID-19. Acute viral illnesses are known to trigger inflammation, and COVID-19 in particular is associated with “a vigorous inflammatory response accompanied by coagulopathy, with elevated D-dimer levels and the frequent presence of antiphospholipid antibodies,” they wrote. The infection is also associated with more severe respiratory syndrome compared with influenza, as well as a heightened risk for complications such as atrial arrhythmias, myocardial infarction, heart failure, myocarditis, and venous thromboses, all of which likely contribute to the risk of ischemic stroke.”