Abstract 79: Chronic and Acute Hypertension in Ischemic Stroke Are Distinct Markers of Impaired Collateral Circulation

Impact of Acute and Chronic Hypertension on Changes in Pial Collateral Tone In Vivo During Transient Ischemia

We investigated vasoconstrictive responses of pial collaterals in vivo at baseline and during transient middle cerebral artery occlusion during chronic hypertension. A cranial window was used to measure diameter of leptomeningeal anastomoses (pial collaterals) in male Wistar (n=8) and spontaneously hypertensive rats (SHRs; n=8) using video dimensional analysis. Middle cerebral artery occlusion was induced by remote filament for 2 hours with 2 hours reperfusion. Phenylephrine was infused during ischemia as a pressor therapy. Active diameters of pial collaterals were significantly smaller in SHRs versus Wistar (14.1±1.5 versus 21.6±2.8 µm; P<0.01); however, passive diameters were similar (25.0±2.9 versus 25.0±2.6 µm; P>0.05). Basal tone of pial collaterals before occlusion was 42±5% in SHRs versus 15±4% in Wistar (P<0.01). Tone decreased in both Wistar and SHRs during occlusion but remained higher in SHRs (9±2% versus 29±4%; P<0.05). Phenylephrine increased blood pressure in both groups but had little effect on leptomeningeal anastomoses diameters. Reperfusion caused vasoconstriction of pial collaterals, increasing tone from 8±1% to 20±5% in Wistar and 29±5% to 44±5% in SHRs (P<0.01). Higher tone in pial collaterals from SHRs basally and during occlusion/reperfusion could limit flow to the penumbra and promote evolution of infarction. Sustained elevated tone of pial collaterals from SHRs with phenylephrine suggests pressor therapy may not be appropriate during chronic hypertension.

Leukoaraiosis and collateral blood flow in stroke patients with anterior circulation large vessel occlusion

Background

Leukoaraiosis and collateral blood flow are processes that involve small vessels, the former related to flow within the deep perforating arterioles and the latter involving the small, cortical pial-pial connections, both of which are independently used to predict cerebrovascular events and treatment outcomes. The aim of this study was to investigate their relationship to each other.

Methods

We retrospectively reviewed patients who underwent mechanical thrombectomy for stroke with pre-procedural CT imaging within 24 hours of the onset of symptoms. Leukoaraiosis was graded by the total Fazekas score on non-contrast CT, periventricular white matter (PVWM) and deep white matter (DWM) scores, both ranging from 0 to 3. Collateral cerebral blood flow was measured by the American Society of Interventional and Therapeutic Radiology/Society of Interventional Radiology (ASITN/SIR) collateral scale.

Results

178 patients were included with a mean age of 67.6±14.8 years. We found an inverse relationship between total Fazekas score and collateral flow (p<0.0001). Among patients with good collaterals, 75.1% had total Fazekas scores of 0–2, compared with 36.6% of patients with moderate collaterals and 32.7% of patients with poor collaterals with total Fazekas scores of 0–2. Mean Fazekas scores were 1.6±1.5, 3.1±1.5 and 3.4±1.6 for good, moderate and poor collaterals, respectively (p<0.0001). On multivariate analysis, total Fazekas score was the only variable independently associated with collateral status (p<0.0001).

Conclusions

Increasing severity of leukoaraiosis is associated with poor collateral grade among ischemic stroke patients with anterior circulation large vessel occlusion. These findings suggest that leukoaraiosis may be a marker for global cerebrovascular dysfunction.

Detrimental Effect of Chronic Hypertension on Leptomeningeal Collateral Flow in Acute Ischemic Stroke

Background and Purpose- We aimed to evaluate the effect of chronic hypertension on acute leptomeningeal collateral flow in patients with large-vessel ischemic stroke using digital subtraction angiography, which is the gold standard for the assessment of collateral circulation. Methods- Of the consecutive ischemic stroke patients from October 2011 to December 2017 seen in our institution, patients with acute occlusion of the M1 segment of the middle cerebral artery confirmed on initial digital subtraction angiography were enrolled. Chronic hypertension was defined as its documentation before the index stroke or as the administration of antihypertensive medications before onset. Angiographic leptomeningeal collateral flow was evaluated according to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology Collateral Flow Grading System and dichotomized the findings into excellent (grade 3-4) or poor (grade 0-2) collateral status for analysis. Results- Of the 3759 consecutive ischemic stroke patients, 100 patients were analyzed. Thirty-nine patients (39%) had poor collateral status. Patients with poor collateral status were older, more frequently male, and had chronic hypertension more frequently, shorter time from onset to angiography, and higher admission systolic blood pressure than those with excellent collateral status. Multivariable logistic analysis with prespecified covariates showed a significantly positive association between chronic hypertension and poor collateral status (odds ratio, 2.80; 95% CI, 1.08-7.70; P=0.034). This association was independent of admission systolic blood pressure. The proportion of patients with poor collateral status increased in a stepwise manner in patients without chronic hypertension, hypertensive patients with premorbid antihypertensive medications, and hypertensive patients without antihypertensive medications ( P for trend <0.001). Conclusions- Our data suggest that chronic hypertension has a detrimental effect on acute leptomeningeal collateral flow in patients with cerebral large-vessel occlusion. Clinical Trial Registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT02251665.