Clinical relevance and practical implications of trials of perfusion and angiographic imaging in patients with acute ischaemic stroke: a multicentre cohort imaging study

Abstract

Background: In randomised trials testing treatments for acute ischaemic stroke, imaging markers of tissue reperfusion and arterial recanalisation may provide early response indicators.

Objective: To determine the predictive value of structural, perfusion and angiographic imaging for early and late clinical outcomes and assess practicalities in three comprehensive stroke centres.

Methods: We recruited patients with potentially disabling stroke in three stroke centres, performed magnetic resonance (MR) or CT, including perfusion and angiography imaging, within 6 h, at 72 h and 1 month after stroke. We assessed the National Institutes of Health Stroke Scale (NIHSS) score serially and functional outcome at 3 months, tested associations between clinical variables and structural imaging, several perfusion parameters and angiography.

Results: Among 83 patients, median age 71 (maximum 89), median NIHSS 7 (range 1-30), 38 (46%) received alteplase, 41 (49%) had died or were dependent at 3 months. Most baseline imaging was CT (76%); follow-up was MR (79%) despite both being available acutely. At presentation, perfusion lesion size varied considerably between parameters (p<0.0001); 40 (48%) had arterial occlusion. Arterial occlusion and baseline perfusion lesion extent were both associated with baseline NIHSS (p<0.0001). Recanalisation by 72 h was associated with 1 month NIHSS (p=0.0007) and 3 month functional outcome (p=0.048), whereas tissue reperfusion, using even the best perfusion parameter, was not (p=0.11, p=0.08, respectively).

Conclusion: Early recanalisation on angiography appeared to predict clinical outcome more directly than did tissue reperfusion. Acute assessment with CT and follow-up with MR was practical and feasible, did not preclude image analysis, and would enhance trial recruitment and generalisability of results.

Keywords: Stroke.

Figure 1

Extent of the perfusion lesion at baseline according to various perfusion parameters as quantified by the ASPECTS score. Shaded areas represent the IQR; horizontal line within the shaded area is the median, point marked within the shaded area is the mean. Where not shown separately, the median has the same value as the upper quartile: ASPECTS=10. ASPECTS, Alberta Stroke Program Early CT Score; ATF, arrival time fitted; CBF, cerebral blood flow; CBV, cerebral blood volume, MTT, mean transit time; raw data, lesion as seen on preprocessed perfusion image; TTP, time to peak; Tmax, time to peak of the residue function.

Figure 2

Perfusion lesions and mismatch rates by perfusion parameter. Mismatch defined as a perfusion lesion >20% larger than the structural lesion. CBF, cerebral blood flow; CBV, cerebral blood volume; Tmax, time to peak of the residue function, a measure of mean transit time.

Figure 3

Proportions of patients with/without a perfusion defect (on Tmax) and/or arterial obstruction within 6 h, at 72 h and 30 days after stroke. Numbers on bars are numbers of patients. Tmax, time to peak of the residue function, a measure of mean transit time.