Hypoperfusion Intensity Ratio Predicts Infarct Progression and Functional Outcome in the DEFUSE 2 Cohort

Abstract

Background and Purpose We evaluate associations between the severity of magnetic resonance perfusion-weighted imaging abnormalities, as assessed by the hypoperfusion intensity ratio (HIR), on infarct progression and functional outcome in the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution Study 2 (DEFUSE 2). Methods Diffusion-weighted magnetic resonance imaging and perfusion-weighted imaging lesion volumes were determined with the RAPID software program. HIR was defined as the proportion of TMax >6 s lesion volume with a Tmax >10 s delay and was dichotomized based on its median value (0.4) into low versus high subgroups as well as quartiles. Final infarct volumes were assessed at day 5. Initial infarct growth velocity was calculated as the baseline diffusion-weighted imaging (DWI) lesion volume divided by the delay from symptom onset to baseline magnetic resonance imaging. Total Infarct growth was determined by the difference between final infarct and baseline DWI volumes. Collateral flow was assessed on conventional angiography and dichotomized into good and poor flow. Good functional outcome was defined as modified Rankin Scale ≤2 at 90 days. Results Ninety-nine patients were included; baseline DWI, perfusion-weighted imaging, and final infarct volumes increased with HIR quartiles (P<0.01). A high HIR predicted poor collaterals with an area under the curve of 0.73. Initial infarct growth velocity and total infarct growth were greater among patients with a high HIR (P<0.001). After adjustment for age, DWI volume, and reperfusion, a low HIR was associated with good functional outcome: odds ratio=4.4 (95% CI, 1.3–14.3); P=0.014. Conclusions HIR can be easily assessed on automatically processed perfusion maps and predicts the rate of collateral flow, infarct growth, and clinical outcome.

Predictive Value of the Velocity of Collateral Filling in Patients with Acute Ischemic Stroke

“…This is further emphasized by a recent study showing that a small proportion of tissue with Tmax values ≥ 10 seconds within tissue with a Tmax value of ≥ 4 seconds is associated with decreased infarct growth. 30 Thus, our results may indicate the importance of the collateral filling velocity in the assessment of dynamic angiographies and may further stress probabilistic approaches taking into account the distribution of parameter values in the assessment of CT perfusion. It would, however, be desirable to investigate the influence of the morphologic extent in a larger sample and to assess the total extent of collaterals in a more quantitative way as these may be factors that have led to an underestimation of the impact of the morphologic extent in our sample.…”

Reperfusion Within 6 Hours Outperforms Recanalization in Predicting Penumbra Salvage, Lesion Growth, Final Infarct, and Clinical Outcome

“…During the entire cohort, median and percentage DWI lesion reversal volume were 5.4 mL (2.7-11.8) and 43% (22-72), respectively. Reperfused patients had a higher percentage of DWI lesion reversal than those without reperfusion: 68% (33-89) versus 24% (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31), respectively (P=0.002). No significant difference in volume of DWI lesion reversal was found between patients with or without reperfusion (P=0.14).…”

“…Similar HIRs were found to be related to angiographic and PWI-based collateral circulation grade in previous reports. [19][20][21] We compared the HIR in patients without early recanalization according to their acute reperfusion status.…”

MR Perfusion to Determine the Status of Collaterals in Patients with Acute Ischemic Stroke: A Look Beyond Time Maps

“…19 Later, Olivot et al 23 showed that a smaller hypoperfusion intensity ratio (defined as the proportion of Tmax Ͼ6-second lesion volume with a Tmax Ͼ10-second delay) was associated with good collateral status. Most interesting, in 2015, by applying a probabilistic method, Lee et al 14 showed that good collaterals were associated with more severe delayed perfusion with a Tmax of 16 -22 seconds.…”

“…This finding is interesting and somewhat different from prior reports in which a better association between good collateral status and a smaller volume of severe hypoperfusion has been shown using Tmax Ͼ 6 seconds. 12,13,23 This may be explained by intrinsic technical differences between Bayesian-estimated ATD and singular value decomposition-estimated Tmax.…”