Abstract 3007: What Perfusion Parameters Best Define Ischemic Penumbra in Patients with TIA and Minor Stroke; Data from the VISION study
Background: Patients with TIA and minor ischemic (MIS) stroke are at high risk for clinical and radiographic deterioration. Acute Perfusion-Diffusion (PWI-DWI) mismatch have been used to identify those at risk for early deterioration. However, optimal perfusion thresholds for ischemic penumbra have not been defined in TIA/MIS patients. We aimed to determine the interrater reliability of different perfusion measurements and the optimal values that predict DWI lesion expansion in patients with TIA/MIS.
Methods: Patients with minor stroke (NIH Stroke Scale ≤3) and TIA were prospectively enrolled and imaged within 24 hours of symptom onset. All patients had follow-up imaging at day 30. Raw perfusion images were used to generate maps of time to peak of the impulse response (Tmax), cerebral blood flow (CBF) and cerebral blood volume (CBV). DWI and PWI volumes were measured with planimetric and thresholding techniques by two independent groups of readers (1 group with a single experienced rater and a second group with 2 inexperienced raters) and 95% confidence intervals were calculated. Infarct progression (FLAIR 30 vol-DWI Acute vol) was a priori defined as growth of at least 2.5 ml.
Results: At baseline 55.2% of the 116 patients included had DWI lesions and 42.2% had PWI deficits. The inter-rater reliability for assessment of hypoperfused regions was excellent for all Tmax thresholds (Tmax+2s (Intraclass Correlation Coefficient (ICC)=0.996 [0.994, 0.997], Tmax+4s(0.99 [0.985, 0.993], Tmax+6s (0.998 [0.998, 0.999] and Tmax+8s(0.996 [0.994, 0.997]). The interrater agreement was very good for assessment of regions with reduced CBF (ICC=0.84[0.78-0.89] and moderate for evaluation of regions with low CBV (ICC=0.43 [0.27, 0.57]). 18.1% of patients had evidence of radiographic progression on follow-up. Mismatch volumes (PWI-DWI) calculated using Tmax+4s predicted infarct expansion (R=0.8, [0.21-0.28], P<0.001). In contrast, mismatch volumes calculated with CBF did not predict infarct expansion (R=0.04, [-0.31,0.50] P=0.66). A mismatch volume (Tmax+4s-DWI) of ≥10 ml predicted infarct progression with 81% sensitivity and 92% specificity (AUC =0.85, [0.74-0.97]).
Conclusion: In patients with TIA/MIS, penumbral patterns are common. Application of perfusion thresholds produced Tmax maps with excellent intra-rater reliability. Mismatch volume calculated as Tmax+4s-DWI volume reliably predicted infarct expansion. Objective PWI-DWI mismatch definitions such as these may be useful for acute reperfusion treatment decision making in patients with minor ischemic symptoms
- © 2012 by American Heart Association, Inc.