Real-Time Estimation of Core Infarct in Angiography Using Collateral Flow

Abstract

Background and Purpose: In order to attribute a diagnostic value to angiographic runs performed before revascularization, we aimed at developing a regional evaluation of leptomeningeal collateral flow that can be used to detect and predict infarction when performing stroke endovascular procedures. Materials and Methods: We evaluated all consecutive patients treated for occlusions in the anterior circulation in our center between 2009 and 2013, with MRI imaging performed before the endovascular procedure. Two readers performed an evaluation of collateral circulation in 5 cortical regions based on the vascular anatomy. Regional scores were correlated with the presence of infarction in the same cortical sector on pretreatment and follow-up imaging. Global collateral scores for each patient were correlated with infarct volumes. Results: In 89 patients with 408 cortical regions, we found a significant correlation between the degree of zonal collateral flow and the absence of infarction in the same zone on pretreatment imaging. In a subgroup of 37 recanalized patients (Thrombolysis in Cerebral Infarction scale 3) with 173 cortical zones, retrograde collateral flow to the proximal M4 segment predicted the absence of infarction within the same zone on follow-up imaging (positive predictive value 88.7%). We found good inter-rater agreement for the presence of collateral flow to the M4 proximal segment or further - k = 0.77 (p = 0.05, 95% CI 0.66-0.88). Global collateral scores correlated with infarct volume on initial imaging; all patients with scores ≥4 had infarct volumes ≤70 ml, whereas all patients with global collateral scores ≤1 had infarct volumes ≥70 ml. Conclusion: Anatomic collateral flow evaluation using the angiographic runs performed during stroke endovascular procedures can provide a real-time estimation of the volume and location of core infarct. For each cortical region, good collateral flow is associated with the absence of infarct on pre-treatment imaging, and is predictive of the absence of infarct on follow-up imaging in recanalized patients.

The diagnostic reliability and validity of noninvasive imaging modalities to assess leptomeningeal collateral flow for ischemic stroke patients

“…The interobserver agreement of FLAIR ranged from 0.58 to 0.86 [8,9,31–33] . For patients receiving thrombolysis or endovascular treatment, [9,32,33] the interobserver agreement of Flair ranged from 0.75 to 0.86.…”

“…For patients receiving thrombolysis or endovascular treatment, [9,32,33] the interobserver agreement of Flair ranged from 0.75 to 0.86. For systems of different grades, the interobserver agreement of FLAIR was 0.86 for the 2-point system [33] ; the interobserver agreement of FLAIR ranged from 0.77 to 0.87 for the system of >5 points [9,31] . FLAIR showed an AUC of 0.82, indicating a good diagnostic performance of this modality [9] …”

“…[4] In clinical practice, noninvasive methods with simple operation and wide application, such as CT angiography (CTA) and MRI-fluid attenuated inversion recovery (FLAIR), have also been introduced to assess LMF. [3,[5][6][7][8][9] Normally the effectiveness of an imaging method should be evaluated by its validity and reliability. The validity indicates the veracity of a method.…”

“…The application of digital subtraction angiography (DSA), the golden standard to assess LMF, is limited by its invasiveness and complexity, as well as the patient's or the hospital's condition [4] . In clinical practice, noninvasive methods with simple operation and wide application, such as CT angiography (CTA) and MRI-fluid attenuated inversion recovery (FLAIR), have also been introduced to assess LMF [3,5–9] . Normally the effectiveness of an imaging method should be evaluated by its validity and reliability.…”

“…The reliability, which refers to the agreement reached between different observers or at difference times by the same observers, indicates the stability and credibility of a method. However, the effectiveness of these noninvasive methods in assessing LMF was uncertain, [5][6][7][8][9] and the different grading systems of these methods further intensify the uncertainty. [5][6][7][8][9] A review published in 2012 showed the difference in reliability among the different imaging methods.…”