Advanced imaging can identify ischaemic stroke patients for intra-arterial thrombectomy >6 hours from symptom onset

According to a study conducted by the University of Hong Kong (HKU) and Queen Mary Hospital (QMH) since mid-2018, advanced imaging can identify patients with acute ischaemic stroke for intra-arterial thrombectomy even beyond 6 hours from symptom onset.

Intra-arterial mechanical thrombectomy is the standard treatment for ischaemic stroke caused by occlusion of major intracranial arteries. In a randomized controlled trial involving 500 acute ischaemic stroke patients, the rate of functional independence (modified Rankin score, 0–2) was higher with intra-arterial treatment (eg, mechanical thrombectomy) plus usual care vs usual care alone (32.6 vs 19.1 percent) within 6 hours after symptom onset. [N Engl J Med 2015;372:11-20]

“Although 6 hours is a reference cut-off time, penumbra [ie, salvageable brain tissue] may still be found in patients with acute ischaemic stroke beyond 6 hours from symptom onset,” the researchers pointed out.

In the study, the researchers used advanced imaging scans (eg, CT perfusion) and artificial intelligence software (RapidAI) to assess patients’ salvageable brain volume and identify those eligible for intra-arterial mechanical thrombectomy at QMH – the first hospital in Hong Kong to provide 24/7 thrombectomy services since 2018.

During the study period, intra-arterial mechanical thrombectomy was performed in 415 patients with acute ischaemic stroke. Among 360 patients (87 percent) treated within 6 hours after symptom onset, 43.5 percent achieved functional independence at 90 days after the procedure.

The remaining 55 patients (13 percent; mean age, 70 years) underwent intra-arterial mechanical thrombectomy >6 hours after symptom onset. Among these patients, the mean time from stroke onset to thrombectomy was 9 hours (maximum time, 22 hours). After treatment, >90 percent of patients had improvement in cerebral vascular occlusion and reduction in brain cell necrosis. Notably, 36 percent of patients achieved functional independence 90 days after treatment. No increased risk of severe complications or death was reported.

“Advanced imaging technology can be useful for identifying patients eligible for endovascular treatment, [potentially] extending the golden period for stroke treatment from 6 to 24 hours,” highlighted Dr Edward Chu of the Department of Diagnostic Radiology, HKU.

“Early stroke diagnosis remains important. Implementing a prehospital ambulance notification system facilitates timely patient transfer to a stroke service centre, which helps optimize treatment outcomes,” reminded Dr Koon-Ho Chan of the Department of Medicine, HKU.

Perfusion scan showing salvageable brain volume in an 80-year-old female with wake-up stroke