Determinants of the distribution and severity of hypoperfusion in patients with ischemic stroke

Abstract

Background: In acute cerebral ischemia, two variables characterize the extent of hypoperfusion: the volume of hypoperfused tissue and the intensity of hypoperfusion within these regions. We evaluated the determinants of the intensity of hypoperfusion within oligemic regions among patients who were eligible for recanalization therapy for acute ischemic stroke.

Methods: We analyzed data, including pretreatment diffusion-weighted imaging (DWI) and perfusion-weighted imaging, on 119 patients with acute middle cerebral artery infarctions. The intensity of hypoperfusion within oligemic regions was characterized by the hypoperfusion intensity ratio (HIR), defined as the volume of tissue with severe hypoperfusion (Tmax > or = 8 seconds) divided by the volume of tissue with any hypoperfusion (Tmax > or = 2 seconds). Based on the DWI data, we divided the patients into four stroke phenotypes: large cortical, small (< 1 cm diameter) cortical, border-zone, and deep pattern.

Results: The mean (SD) volume of severe hypoperfusion was 54.6 (52.5) mL, and that of any hypoperfusion was 140.8 (81.3) mL. The HIR ranged widely, from 0.002 to 0.974, with a median of 0.35 (interquartile range 0.13-0.60). The volume of any hypoperfusion did not predict the intensity of hypoperfusion within the affected region (r = 0.10, p = 0.284). Angiographic collateral flow grade was associated with HIRs (p value for trend = 0.019) and differed among DWI lesion patterns. In multivariate analysis, diastolic pressure on admission (odds ratio 0.959, 95% CI 0.922-0.998) and DWI pattern of deep infarcts (odds ratio 18.004 compared with large cortical pattern, 95% CI 1.855-173.807) were independently associated with a low HIR.

Conclusions: The intensity of hypoperfusion within an oligemic field is largely independent of the size of the oligemia region. Predictors of lesser intensity of hypoperfusion are lower diastolic blood pressure and presence of a deep diffusion-weighted imaging lesion pattern.

Figure 1 Selection of patients *Wrong location of measurement of arterial input function (AIF) on the volume of hypoperfusion. DWI = diffusion-weighted imaging; MCA = middle cerebral artery; MR = magnetic resonance.

Figure 2 Perfusion-weighted imaging findings in different diffusion-weighted imaging lesion patterns (A) Large cortical pattern, (B) predominantly deep, (C) border-zone, and (D) multiple small cortical pattern.

Figure 3 Relationship between diffusion-weighted imaging (DWI) lesion patterns, collateral flow, and hypoperfusion intensity ratios