Impact of collateral flow on tissue fate in acute ischaemic stroke

Abstract

Background: Collaterals may sustain penumbra prior to recanalisation yet the influence of baseline collateral flow on infarct growth following endovascular therapy remains unknown.

Methods: Consecutive patients underwent serial diffusion and perfusion MRI before and after endovascular therapy for acute cerebral ischaemia. We assessed the relationship between MRI diffusion and perfusion lesion indices, angiographic collateral grade and infarct growth. Tmax perfusion lesion maps were generated and diffusion-perfusion mismatch regions were divided into Tmax >or=4 s (severe delay) and Tmax >or=2 but <4 s (mild delay).

Results: Among 44 patients, collateral grade was poor in 7 (15.9%), intermediate in 20 (45.5%) and good in 17 (38.6%) patients. Although diffusion-perfusion mismatch volume was not different depending on the collateral grade, patients with good collaterals had larger areas of milder perfusion delay than those with poor collaterals (p = 0.005). Among 32 patients who underwent day 3-5 post-treatment MRIs, the degree of pretreatment collateral circulation (r = -0.476, p = 0.006) and volume of diffusion-perfusion mismatch (r = 0.371, p = 0.037) were correlated with infarct growth. Greatest infarct growth occurred in patients with both non-recanalisation and poor collaterals. Multiple regression analysis revealed that pretreatment collateral grade was independently associated with infarct growth.

Conclusion: Our data suggest that angiographic collateral grade and penumbral volume interactively shape tissue fate in patients undergoing endovascular recanalisation therapy. These angiographic and MRI parameters provide complementary information about residual blood flow that may help guide treatment decision making in acute cerebral ischaemia.

Figure 1

Volumes of diffusion weighted imaging (DWI), penumbra and “benign oligaemia” of 44 patients with acute middle cerebral artery infarctions.

Figure 2

Impact of angiographic collateral grade on infarct growth. Displayed are scattered plots of (A) pretreatment diffusion–perfusion mismatch volume versus infarct growth and (B) the degree of recanalisation after treatment versus infarct growth. Filled diamonds indicate patients with good collaterals (grade 4), grey diamonds those with intermediate collaterals (grade 2–3) and open diamonds those with poor collaterals (grade 0–1). (C) Pretreatment diffusion and perfusion MRI findings and final diffusion weighted imaging (DWI) findings of patients with (i) recanalisation (Thrombolysis in Myocardial Infarction scale (TIMI) 2) but poor collaterals (grade 1), (ii) recanalisation (TIMI 3) but good collaterals (grade 4) and (iii) minimal recanalisation (TIMI 1) but good collaterals (grade 4). The initial DWI lesion volume, time to peak (TTP) delayed perfusion volume and mismatch area was similar among the patients. However, the patient with good collaterals showed minimal/no marked infarct growth, regardless of the occurrence of recanalisation, whereas infarct growth with clinical deterioration was observed in the patient with poor collaterals.