Thrombus Characteristics Are Related to Collaterals and Angioarchitecture in Acute Stroke.

BACKGROUND: We have theorized that clots with stasis are longer. We therefore explored the relationship between thrombus imaging characteristics on noncontrast computed tomography (NCCT) and magnetic resonance imaging (MRI) with clot length and pial collaterals on baseline computed tomography angiography (CTA). METHODS: Prospective study of acute ischemic stroke patients (2005-2009) from Keimyung University. Patients with known stroke symptom onset time, baseline CTA, MRI, and with M1-Middle Cerebral Artery (MCA)±intracranial internal carotid artery (ICA) occlusions were included. Clot length and pial collaterals were measured on baseline CTA. RESULTS: A total of 104 patients (mean age 65.1±12.28 years, 56.7% male, median baseline National Institutes of Health Stroke Scale 13) with intracranial ICA + MCA (n=50) or isolated M1-MCA (n=54) occlusions were included. Hyperdense sign on NCCT had a median clot length of 42.3 mm versus 29.5 mm when hyperdense negative (p=0.02). Clots showing blooming artifact on gradient recall echo MRI had a median length of 39.1 mm versus 24.5 mm without blooming (p=0.005). Patients with poor baseline collaterals on CTA had longer clots than those with intermediate/good collaterals (median clot length 49.4 mm vs 34.9 mm vs 20.5 mm respectively, p<0.001). In censored logistic regression modeling, clot length was an independent predictor of hyperdense sign (p=0.05) and of the presence of blooming artifact (p=0.006). CONCLUSIONS: Clot length and baseline collateral status are independent predictors of clot hyperdensity on NCCT and blooming artifact on gradient recall echo. Longer clots are more likely to be hyperdense and to bloom more, probably because portions of these clots are freshly formed locally due to of stasis of blood around the original clot. This stasis could be because of poor collaterals and inefficient angio-architecture within the cerebral arterial tree.

Occult anterograde flow is an under-recognized but crucial predictor of early recanalization with intravenous tissue-type plasminogen activator.

BACKGROUND AND PURPOSE: Thrombolysis depends on the ability of blood and thrombolytic agents to permeate thrombus. We devised a novel technique to quantify blood permeating through thrombi and determine whether this parameter predicts early recanalization with intravenous tissue-type plasminogen activator. METHODS: Intravenous tissue-type plasminogen activator-treated patients with stroke and complete occlusion on computed tomographic angiography were analyzed using perfusion computed tomography and a delay insensitive algorithm. We generated maps that measure delay in arrival time of contrast within the intracranial arterial tree (T0 maps). A positive sloped regression line of T0 values measured along artery silhouette distal to thrombus was defined as marker of permeable thrombus (occult anterograde flow). Median T0 values at proximal and distal thrombus interface were measured. Early recanalization was assessed on first angiography of subsequent intra-arterial procedure or on a 4-hour computed tomographic angiography. RESULTS: Of 66 patients, occult anterograde flow was detected in 17 (25.8%). Early recanalization was more in patients with occult anterograde flow versus not (66.7 versus 29.7%; P=0.031). Median T0 value (in s) at distal thrombus interface (1.5 versus 3.8; P=0.006) and difference in median T0 value between proximal and distal thrombus interface (1.3 versus 3.7; P=0.014) were less in early recanalizers versus in nonrecanalizers. In multivariable analysis, patients with occult anterograde flow and T0 value difference between proximal and distal thrombus interface ≤2 s recanalized most (71.4%; odds ratio, 12.15; 95% confidence interval, 2.05-71.91), whereas patients with retrograde flow and T0 value difference >2 s recanalized least (25.9%; odds ratio, 1). CONCLUSIONS: Occult anterograde flow through thrombus can be assessed by perfusion computed tomography T0 maps and predicts early recanalization with intravenous tissue-type plasminogen activator robustly.

Multiphase CT Angiography: A New Tool for the Imaging Triage of Patients with Acute Ischemic Stroke.

PURPOSE: To describe the use of an imaging selection tool, multiphase computed tomographic (CT) angiography, in patients with acute ischemic stroke (AIS) and to demonstrate its interrater reliability and ability to help determine clinical outcome. MATERIALS AND METHODS: The local ethics board approved this study. Data are from the pilot phase of PRoveIT, a prospective observational study analyzing utility of multimodal imaging in the triage of patients with AIS. Patients underwent baseline unenhanced CT, single-phase CT angiography of the head and neck, multiphase CT angiography, and perfusion CT. Multiphase CT angiography generates time-resolved images of pial arteries. Pial arterial filling was scored on a six-point ordinal scale, and interrater reliability was tested. Clinical outcomes included a 50% or greater decrease in National Institutes of Health Stroke Scale (NIHSS) over 24 hours and 90-day modified Rankin Scale (mRS) score of 0-2. The ability to predict clinical outcomes was compared between single-phase CT angiography, multiphase CT angiography, and perfusion CT by using receiver operating curve analysis, Akaike information criterion (AIC), and Bayesian information criterion (BIC). RESULTS: A total of 147 patients were included. Interrater reliability for multiphase CT angiography is excellent (n = 30, κ = 0.81, P < .001). At receiver operating characteristic curve analysis, the ability to predict clinical outcome is modest (C statistic = 0.56, 95% confidence interval [CI]: 0.52, 0.63 for ≥50% decrease in NIHSS over 24 hours; C statistic = 0.6, 95% CI: 0.53, 0.68 for 90-day mRS score of 0-2) but better than that of models using single-phase CT angiography and perfusion CT (P < .05 overall). With AIC and BIC, models that use multiphase CT angiography are better than models that use single-phase CT angiography and perfusion CT for a decrease of 50% or more in NIHSS over 24 hours (AIC = 166, BIC = 171.7; values were lowest for multiphase CT angiography) and a 90-day mRS score of 0-2 (AIC = 132.1, BIC = 137.4; values were lowest for multiphase CT angiography). CONCLUSION: Multiphase CT angiography is a reliable tool for imaging selection in patients with AIS.