Despite changing recommendations, aspirin is widely used to prevent vascular events such as myocardial infarction and stroke. Studies showed that 15% to 40% of patients with ischemic stroke are already taking aspirin at the stroke time. During an observational study, the authors investigated functional outcome, thrombus burden, early neurologic deterioration (END), and hemorrhagic transformation in aspirin users versus nonusers. Thrombus burden was determined by the susceptibility vessel sign (SVS), and functional outcome was assessed at 3 months. Patients who received thrombolysis or thrombectomy were excluded.

Overall, 5,700 patients (mean age, 67 years; 41% women) were included in the multicenter registry, and 15.9% had documented aspirin use within the seven days before stroke. Because of imbalances between aspirin users and nonusers, the authors used propensity adjustment before analysis. Compared with nonuse, pre-stroke aspirin use was associated with a 30% smaller infarct volume and a 45% lower rate of atherosclerotic stroke.

In addition, aspirin users had an 85% lower occurrence of the SVS, indicating a smaller thrombus burden. Among those with cardioembolic stroke, aspirin users had a lower rate of END than nonusers. The favourable functional outcome was 30% more common in aspirin users than nonusers. Rates of haemorrhagic transformation did not differ between aspirin users and nonusers.