Collateral Blood Flow In Patients Research Articles

CT vascular territory mapping: a novel method to identify large vessel occlusion collateral

IntroductionThis descriptive study explores typical patterns of vascular territory mapping (VTM) in ischaemic stroke patients with proximal vessel occlusion. VTM is a novel process using CT perfusion that can identify the source and extent of collateral blood flow in patients with vessel occlusion. It functions by determining which vessel provides dominant blood flow to a brain voxel.MethodsA total of 167 consecutive patients were analysed from INSPIRE (International Stroke Perfusion Imaging Registry) with their CT perfusion reprocessed through VTM software. We explored the typical territory maps generated by this software relating to common large vessel occlusion location sites (ACA/MCA/PCA).Results/ConclusionIn the presence of occlusion, VTM demonstrated a reciprocal increase in collateral vessel territories.

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 s. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

Abstract 1122‐000181: Collateral Circulation in Ischemic Stroke is Not Determined by Anatomical Variants of the Cerebral Arteries

Introduction : In acute ischemic stroke, collateral circulation determines tissue fate and treatment results. The aim of this study was to evaluate the role of anatomical variations of the Circle of Willis (CoW) in formation of cerebral collateral blood flow in patients with acute M1 occlusion. Methods : This study was a retrospective assessment of radiological examinations of patients with stroke due to middle cerebral artery M1 segment occlusion. All patients underwent mechanical thrombectomy from January 2015 until March 2021. The anatomy of the CoW was assessed on initial CT‐angiography and DSA. CTA was utilized to grade cranial collateral vasculature status and cortical vein opacification score (COVES). Non‐contrast CT scans and ASPECTS scores (using RAPID software) were used to determine the ischemic area. Results : A total of 100 patients were included in the analysis (58 females and 42 males, mean age: 71.6 +/‐ 13.9). We classified the anatomy of the CoW according to its continuity as a full circle. Patients with fully continuous CoW (n = 19) had worse COVES scores than those with CoW incomplete at both anterior and posterior portion (n = 9) (89% vs 68% with COVES 0–2, p = 0.179). No statistically significant results were found when comparing the enhancement of collaterals between these two groups (p = 0.390). The COVES scores were similar for patients with complete and incomplete anterior portions of CoW (77% vs 80% with COVES 0–2, p = 0.812). Patients with incomplete posterior portions of CoW had lower COVES scores than those with complete (80% vs 67% with COVES 0–2, p = 0.206). No statistically significant differences were discovered when comparing different types of the posterior communicating artery (adult, transitional and fetal). Analysis of ischemic areas determined as ASPECTS scores pre‐ and post‐thrombectomy yielded no significant differences between any of the groups. Conclusions : Although certain variants of the CoW have been reported to increase the risk of ischemic stroke, our results show that the anatomy of CoW has no large effect on collateral blood flow during acute M1 occlusion. We presume that the greater role is played by pial arterioles than anatomical variants of major cerebral arteries in cerebral collateral circulation formation. Detailed knowledge about the factors that influence collateral blood flow is crucial as it may aid in identification of patients prone to worse outcomes of ischemic stroke. Anatomical variants of CoW do not play a major role in formation of cerebral collaterals.

Abstract P321: The Cerebral Collateral Cascade: Rethinking the Assessment of Vascular Pathways in Acute Ischemic Stroke Patients

Background and Purpose: Robust collateral blood flow in patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO) has been correlated with favorable outcomes. Collaterals are commonly assessed by the number of arteries present on non-invasive CT angiography (CTA) overlying ischemic brain, but blood transit from these arteries through the brain tissue and the venous drainage is not assessed by this technique. We hypothesized that a comprehensive imaging analysis of the cerebral collateral cascade (CCC) would predict clinical and radiological outcomes in patients with AIS-LVO patients. Materials and Methods: Multicenter retrospective cohort study of AIS-LVO patients undergoing thrombectomy triage. CCC was determined on pre-treatment imaging by scoring for pial arterial collaterals, tissue-level collaterals (TLC), and venous outflow. Pial arterial collaterals were determined by CTA (Tan scale), TLC were assessed on CT perfusion data using the Hypoperfusion Intensity Ratio, and venous egress was assessed on CTA using the cortical vein opacification score system. 3 groups were defined: CCC+ (good pial collaterals, TLC, and venous perfusion), CCC- (poor pial collaterals, TLC, and venous perfusion) and CCCmixed (reminder of patients). Primary outcome was a good functional outcome (modified Rankin Scale [mRS] 0-2 at 90 days). Secondary outcome was final infarct volume. Results: 647 patients met inclusion criteria: 176 CCC+, 345 CCCmixed and 126 CCC-. Multivariate ordinal logistic regression showed that CCC+ predicted good functional outcomes (mRS 0-2: OR=20.8 [95% CI 9.3-46.8]; p<0.001) compared to CCC- and CCCmixed. CCCmixed (β: 27.1, SE: 7.7; p<0.001) and CCC- (β: 86.6, SE: 9.9; p<0.001) profiles were associated with higher final infarct volumes after treatment compared to CCC+. Conclusion: Comprehensive assessment of the collateral blood flow cascade in AIS-LVO patients is a strong predictor of clinical and radiological outcomes in AIS-LVO patients.

Abstract TP61: Could Fazekas Score Serve as a Predictor of Functional Outcomes in ELVO Patients Undergoing Mechanical Thrombectomy?

Objective: To evaluate the association between cerebral small vessel disease (CSVD) burden and degree of disability based on modified Rankin Score at 90 days, in patients presenting with emergent large vessel occlusion (ELVO) within 6 hours of last known well. Methods: We conducted a retrospective analysis of all patients presenting with an ELVO between May 2016 and July 2018. Patients with a TICI score of 2b or 3 were included and evaluated for CSVD burden as quantified by white matter hyperintensities in the non-affected hemisphere, on T2-FLAIR MRI using the Fazekas score (0-3). 90-day modified Rankin Scale scores (mRS, range 0-6) and patient information was collected from the Houston Methodist Hospital Outcomes Based Prospective Endpoints in Stroke (HOPES) registry. Results: 138 patients were evaluated, TICI 2b/3 was achieved in 114, and 84 patients were able to undergo MRI. Factors excluding patients from MRI included: medical instability, implantable devices, and death. All 84 patients were successfully re-evaluated at 90 days and divided into two cohorts, functionally independent (mRS 0-2) and functional dependent/deceased (mRS 3-6). Among the 84 patients, 37 (mean age 69.4y [SD, 14.5]; 54% female) were determined to be functionally independent (14, mRS 0; 19, mRS 1; 4, mRS 2) with the average Fazekas score for each subclass and the cohort; (mRS 0, 1.07; mRS 1, 0.89; mRS 2, 1; 0.97). The remaining 47 patients (mean age 71.1y [SD, 15.8]; 55% female) were determined to have a significant degree of disability, or were deceased (8, mRS 3; 10, mRS 4; 15, mRS 5; 14, mRS 6). Average Fazekas scores were (mRS 3, 1.75; mRS 4, 1.90; mRS 5, 2.13; mRS 6, 1.93; 1.96). Potentially confounding variables, including the use of intravenous alteplase (78% vs. 76%), and door to groin puncture time (204m [SD, 74m] vs. 206m [SD, 54m]) were found to be non-significant contributors. Conclusion: Based on our analytical cohort of ELVO patients undergoing thrombectomy, CSVD burden, classified by Fazekas score on T2-FLAIR MRI, was found to correlate with worse 90-day mRS. These results may be explained by potentially poor cerebrovascular reserve and diminished collateral blood flow in patients with greater CVSD burden.

Abstract TP127: Impact of Smoking on Collateral Blood Flow in Patients With Acute Ischemic Stroke With Large Cerebral Artery Embolic Occlusion

Introduction: Good collateral flow is associated with improved outcomes in acute embolic stroke. There is compelling data linking smoking to all types of stroke, with current smokers at a higher risk than former or never smokers. Smoking has, however, been shown to promote collaterals in coronary vascular bed in humans. It is unknown if there is a similar effect in cerebral collateral flow. We aimed to investigate if cigarette smoking was positively associated with collateral blood flow in a homogenous cohort of patients with acute large vessel occlusive embolic stroke. Methods: We identified all patients aged ≥18 with acute ischemic stroke showing embolic occlusion of ICA terminus/M1 MCA on admission CT angiography (CTA), between 2008 to 2018, through an institutional database. Patients with chronic occlusions and stenotic lesions were excluded. Individual CTAs were independently reviewed by two trained investigators to calculate collateral scores of the affected hemisphere using the modified Tan scale (0-4) as a reference. Details of cigarette smoking history were obtained from the electronic medical records. Patients were grouped into smokers (former and current smokers) and never smokers. Odds ratios (OR) and their 95% confidence intervals (CI) were estimated, and all tests were considered significant when P<0.05. Results: Of the 612 patients identified through the database, 429/612 patients (mean age 71±16 years, 45% [194/429] women) satisfied the inclusion criteria. 64.8% (278/429) had a positive history of smoking with an average of 47±12 pack-years. There was a significant association between good collateral scores (≥2) with smoking history (OR 1.74 CI 1.17-2.61, P=0.006). This trend remained significant even after comparing raw collateral scores (0-4) ( P=0.006, Spearman’s ρ=0.22). However, number of pack-years and collateral scores exhibited no statistically significant relationship (P=0.6). Conclusions: Our study shows that patients who have ever smoked have higher intracranial collateral vessel scores in the event of an acute embolic stroke. Increased impedance and reduced cerebral blood flow resulting from cigarette smoking may stimulate collateral recruitment in cerebral pial circulation, similar to the effect in coronary bed.

Assessment of collateral blood flow in patients with distal branch occlusion of the middle cerebral artery

PurposeAim of this study was to evaluate the collateral blood flow between more distal branches of the middle cerebral artery (MCA) in the case of peripheral MCA branch occlusion on dynamic 4D angiograms. We sought to individually predict the finally resulting infarction volume with regard to the extent of collateral blood flow. MethodsOverall, 35 acute ischemic stroke patients with peripheral MCA branch occlusion were included. Volumes of the ischemic infarctions and perfusion deficits were measured on diffusion-weighted images DWI and time-to-peak TTP (> 4 s). Collateral flow on 4D MR angiograms were classified as previously specified. ResultsOn DWI, the ischemic lesions had a mean volume of 3.4 ± 15.1 mL while the mean volume on TTP (> 4 s) was significantly larger 22.0 ± 18.1 mL (P < 0.001). On dynamic 4D angiograms we observed grade 1 in 8 (22.9%), grade 2 in 4 (11.4%), grade 3 in 10 (28.6%), and grade 4 in 13 (37.1%) patients. In comparison to patients with better collateralization (grade 3–4) patients with less sufficient collateralization (grade 0–2) demonstrated larger infarction volumes on initial (11.1 mL (IQR 2.9–35.5) vs. 2.1 mL (IQR 0.5–4.5), P = 0.03) and follow-up DWI (15.5 mL (IQR 12.6–23.3) vs. 1.9 mL (IQR 0.5–4.5), P = 0.03) with prominent infarction growth (7.4 mL (IQR 2.6–10.1) vs. 0.9 mL (IQR 0.2–2.6), P = 0.08). ConclusionsIn the majority of cases with distal MCA branch occlusion a good collateral blood flow has been observed. Nevertheless, in approximately one quarter of patients an insufficient collateral blood flow has been detected that was associated with substantial infarction growth.

A protective role of early collateral blood flow in patients with ST-segment elevation myocardial infarction

Conflict persists regarding whether the presence of early collateral blood flow to the infarct-related artery has an effective role in reducing infarct size and improving myocardial salvage in patients with ST-segment elevation myocardial infarction (STEMI). We sought to investigate the impact of the collateral circulation on myocardial salvage and infarct size in STEMI patients. In 306 patients who were diagnosed with STEMI and underwent cardiac magnetic resonance within 1 week after revascularization, initial collateral flow to the infarct-related artery was assessed by coronary angiography. Using cardiac magnetic resonance imaging, myocardial infarct size and salvage were measured. Among 247 patients with preprocedural Thrombolysis in Myocardial Infarction flow 0/1, 54 (22%) patients had good collaterals (Rentrop grade ≥ 2, Collateral Connection Score ≥ 2). Infarct size and area at risk were significantly smaller in patients with good collaterals than those with poor collaterals (infarct size: 17.1 ± 10.1 %LV vs 21.8 ± 10.5 %LV, P = .003, area at risk: 33.8 ± 16.8 %LV vs 38.8 ± 15.5 %LV, P = .039). There was a significant difference of myocardial salvage index between 2 groups (50.9% ± 15.0% vs 43.8% ± 18.5%, P = .005). Poor collateralization was an independent predictor for large infarct size (odd ratio 2.48 [1.28-4.80], P = .007). In patients with STEMI, the presence of well-developed collaterals to occluded coronary artery from the noninfarct vessel and its extent were independently associated with reduced infarct burden and improved myocardial salvage. Our results help explain why MI patients with well-developed collateralization have reduced mortality and morbidity.

Actovegin in treatment of critical limb ischemia

The problem of distal occlusion of the lower limbs cannot be currently considered solved due to too large number (40%) of postoperative amputations. Only surgical way of disease management seems impossible. Thus multidisciplinary approach is necessary. To determine the effectiveness of actovegin in treatment of critical ischemia of lower extremities. The study included 60 patients (34 men, 26 women, mean age - 69.5 ± 7.2 years) with confirmed atherosclerosis obliterans (critical limb ischemia stage III-IV with necrotic processes within the toes). Patients in the control group (n=30) received standard medical therapy including pentoxifylline (15 ml), rheopolyglukin (400.0 ml), antiplatelet agents (in some cases with dual antiplatelet therapy), low molecular weight heparins in prophylactic doses, statins. In the main group (n=30) actovegin in a daily dose of 1200 mg intravenously for 15 days, followed by 1200 mg in tablet form (2 tablets 3 times per day) for 15 days was added. Primary, 15-, 30- and 60-day pain-free walking distance and microcirculation using polarography and laser Doppler imaging were assessed in all patients. Cytological and histological studies were applied for double control of therapy's effectiveness. The reliability of the results of microcirculation investigation was achieved using an index of regional tissue perfusion. Statistically significant improvement of transcutaneous oxygen tension has not been received in the control group. In the main group therapy with actovegin improved skin perfusion 35% by the 15th day and activated microcirculation 12.8% followed by increased tissue oxygenation. Positive effect of actovegin on the development of collateral blood flow in patients with distal occlusion of the lower limbs is convincingly proven.

Arterial spin labeling magnetic resonance perfusion imaging in cerebral ischemia

Arterial spin labeling (ASL) is a noninvasive magnetic resonance perfusion imaging method for visualizing and quantifying whole-brain perfusion that does not require exogenous contrast agents. The goal of this review article is to explain the principles of ASL perfusion imaging and review the strengths and limitations of different ASL methods. There are several different approaches that vary mainly on the basis of the technique that is used to label the inflowing arterial blood. These methods can be used to assess perfusion at brain tissue level or the perfusion territories of the brain feeding arteries. In patients with acute ischemic stroke, ASL can be of clinical value by detecting brain regions with hypoperfusion and perfusion-diffusion mismatch. ASL has been used to detect decreased perfusion, delayed arrival of the arterial blood bolus and assessment of collateral blood flow in patients with extracranial large artery disease and moyamoya disease. Recent evidence indicates that perfusion and territorial perfusion imaging of the brain feeding arteries with ASL can help to assess the extent of hemodynamic compromise and to customize medicinal and surgical treatment, both in patients with acute and with chronic cerebrovascular disease.

Clinical evaluation of aortic coarctation with 4D flow MR imaging

To show that 4D Flow is a clinically viable tool for evaluation of collateral blood flow and demonstration of distorted blood flow patterns in patients with treated and untreated aortic coarctation. Time-resolved, 3D phase contrast magnetic resonance imaging (MRI) (4D Flow) was used to assess blood flow in the thoracic aorta of 34 individuals: 26 patients with coarctation (22 after surgery or stent placement) and eight healthy volunteers. Direct comparison of blood flow calculated with 2D and 4D phase contrast data at standard levels for analysis in coarctation patients showed good correlation and agreement (correlation coefficient r = 0.99, limits of agreement = -20% to 20% for collateral blood flow calculations). Abnormal blood flow patterns were demonstrated at peak systole with 4D Flow visualization techniques in the descending thoracic aorta of patients but not volunteers. Marked helical flow was seen in 9 of 13 patients with angulated aortic arch geometries after coarctation repair. Vortical flow was seen in regions of poststenotic dilation. 4D Flow is a fast and reliable means of evaluating collateral blood flow in patients with aortic coarctation in order to establish hemodynamic significance. It also can detect distorted blood flow patterns in the descending aorta after coarctation repair.

Arterial spin labeling perfusion MRI at multiple delay times: a correlative study with H(2)(15)O positron emission tomography in patients with symptomatic carotid artery occlusion.

Arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) with image acquisition at multiple inversion times is a noninvasive ASL technique able to compensate for spatial heterogeneities in transit times caused by collateral blood flow in patients with severe stenosis of the cerebropetal blood vessels. Our aim was to compare ASL-MRI and H(2)(15)O positron emission tomography (PET), the gold standard for cerebral blood flow (CBF) assessment, in patients with a symptomatic internal carotid artery (ICA) occlusion. Fourteen patients (63+/-14 years) with a symptomatic ICA occlusion underwent both ASL-MRI and H(2)(15)O PET. The ASL-MRI was performed using a pulsed STAR labeling technique at multiple inversion times within 7 days of the PET. The CBF was measured in the gray-matter of the anterior, middle and posterior cerebral artery, and white-matter. Both PET and ASL-MRI showed a significantly decreased CBF in the gray-matter of the middle cerebral artery in the hemisphere ipsilateral to the ICA occlusion. The average gray-matter CBF measured with ASL-MRI (71.8+/-4.3 mL/min/100 g) was higher (P<0.01) than measured with H(2)(15)O PET (43.1+/-1.0 mL/min/100 g). In conclusion, ASL-MRI at multiple TIs is capable of depicting areas of regions with low CBF in patients with an occlusion of the ICA, although a systematic overestimation of CBF relative to H(2)(15)O PET was noted.

The influence of genotype on vascular endothelial growth factor and regulation of myocardial collateral blood flow in patients with acute and chronic coronary heart disease

The influence of genotype on vascular endothelial growth factor and regulation of myocardial collateral blood flow in patients with acute and chronic coronary heart disease

The influence of genotype on vascular endothelial growth factor and regulation of myocardial collateral blood flow in patients with acute and chronic coronary heart disease

Objective: To test the hypothesis that mutations in the vascular endothelial growth factor (VEGF) gene are associated with plasma concentration of VEGF and subsequently the ability to influence coronary collateral arteries in patients with coronary heart disease (CHD). Methods: Blood samples from patients with chronic ischemic heart disease (n=53) and acute coronary syndrome (n=61) were analysed. Coronary collaterals were scored from diagnostic biplane coronary angiograms. Results: The plasma concentration of VEGF was increased in patients with acute compared to chronic CHD (p=0.01). The genotype frequencies differed significantly from Hardy-Weinberg equilibrium in three of 15 examined loci. Four new mutations in addition to the already described were identified. The VEGF haplotype did not seem to predict plasma VEGF concentration (p=0.5). There was an association between the genotype in locus VEGF-1154 and coronary collateral size (p=0.03) and a significant association between the VEGF plasma concentration and the collateral size (p=0.03). Conclusion: VEGF plasma concentration seems related to coronary collateral function in patients with CHD. The results did not support the hypothesis that polymorphisms in the untranslated region of the VEGF gene were associated with the concentration of circulating VEGF. Increased understanding of VEGF in the regulation of myocardial collateral flow may lead to new therapies in CHD.

Phosphodiesterase-5 inhibitors decrease collateral blood flow in patients with portal hypertension

Phosphodiesterase-5 inhibitors decrease collateral blood flow in patients with portal hypertension

Collateral blood flow between left coronary artery bypass grafts and chronically occluded right coronary circulation in patients with triple vessel disease. Observations during complete revascularisation of beating hearts

Preoperative measurements of collateral blood flow in patients with triple vessel disease and chronic occlusions of the right coronary artery do not, currently, ascertain the need to revascularise an occluded right coronary artery. We performed direct measurements of flow across left coronary bypass grafts to determine their contributions to collateral blood flow. Collateral blood flow was scored preoperatively according to Rentrop in 13 patients with triple vessel disease and chronic occlusions of the right coronary artery who underwent complete, off-pump, surgical revascularisation. The transit-time flow through the left coronary grafts was measured before and after unclamping of the right coronary artery bypass graft. Unclamping of the right coronary artery bypass graft was associated with a 5.9+/-6.9ml/min (mean+/-SD) decrease in flow across the left circumflex territory (P=0.009), which was proportional to the preoperative Rentrop score (P=0.007). No significant change was observed in flow across the graft to the left anterior descending artery. Grafts to the left circumflex system are the only grafts that supply a significant, albeit modest amount of collateral blood flow to chronically occluded right coronary artery. These observations confirm that (1) most collateral flow after revascularisation is supplied by the native network, and (2) revascularisation of an occluded right coronary artery is fully justified.

The Effects of Coronary Artery Remodeling on the Developments of Collateral Blood Flow in Patients with Acute Myocardial Infarction Treated with Primary Angioplasty

Background: The relation between pressure-derived fractional collateral flow (PDCF) and coronary arterial remodeling remains uncertain in acute myocardial infarction. Methods: We evaluated the effect of arterial remodeling on the development of PDCF in 72 patients with first acute myocardial infarction (pain onset 1.0 and nonpositive remodeling as a RI ≤1.0. Using a 0.014-in. fiber optic pressure moni- toring guide wire, the PDCF index was measured by simultaneous measurement of mean aorta pressure (Pao), distal coronary pressure during the balloon occlusion (Pocc), and central venous pressure (CVP): PDCF index= 100×(Pocc-CVP)/(Pao-CVP). Sufficient collateral was defined as PDCF index >24% and insufficient collateral as PDCF index ≤24%. Results: The RI was 1.04±0.15 in the lesions with sufficient collateral and 1.03±0.16 in the lesions with insufficient collateral (p=0.812). There was no significant difference in the frequency of positive remodeling between the 2 groups (55% vs. 54%, respectively, p=0.966). The PDCF index was 20±11% and 20± 9% in positive and nonpositive remodeling, respectively (p=0.891). There was no significant correlation between RI and PDCF index (r=0.027, p=0.823). Conclusions: The pattern of coronary arterial remodeling might not influence the development of collateral blood flow in patients with acute myocardial infarction treated with primary

Collateral flow and ischemic brain lesions in patients with unilateral carotid artery occlusion.

To investigate the association between ischemic brain lesions and intracranial collateral blood flow in patients with unilateral occlusion of the internal carotid artery (ICA). Sixty-eight consecutive patients were included. Ischemic lesions on MRI were identified on hard copies, and volume measurements of the lesions were performed on an MR workstation. Intracranial collateral pathways were studied with MR angiography, digital subtraction angiography, and transcranial Doppler sonography. The presence of collateral flow via the anterior communicating artery (ACoA) was associated with a reduction in prevalence (p = 0.01) and volume (p = 0.008) of internal border zone infarcts in the hemisphere ipsilateral to the occluded ICA. Absence of collateral blood flow via the circle of Willis was associated with an increase in prevalence (p = 0.007) and volume (p = 0.005) of internal border zone infarcts. No association between any collateral flow pattern in the circle of Willis and periventricular lesions or lacunar, territorial, or external border zone infarcts was found. No association between collateral flow via the ophthalmic artery or leptomeningeal vessels with any type of ischemic lesion was found. Collateral flow via the ACoA is associated with a reduction of the prevalence and volume of internal border zone lesions but not with any other type of ischemic lesion. The presence of a functional posterior communicating artery or secondary collateral pathways is not associated with the prevalence of any type of ischemic lesion.

Intravascular β-Radiation May Acutely Increase Coronary Collateral Blood Flow in Patients With Coronary Artery Disease

To the Editor: Intravascular irradiation effectively reduces neointimal proliferation after coronary interventions. Scheinert et al1 showed that vasoconstriction is a frequent reaction of coronary arteries after high-dose intracoronary β-radiation, necessitating repetitive administration of vasodilators. Unfortunately, these authors did not study the effects of β-radiation on the microcirculation and small resistance vessels. To examine the acute effects of intravascular β-irradiation on the coronary collateral blood flow, we studied 7 patients with stable angina, 4 with in-stent restenosis, and 3 with de novo lesions while they were undergoing angioplasty and intracoronary β-irradiation. Eight control patients, 2 with in-stent restenosis and 6 with de novo lesions, underwent balloon angioplasty without intracoronary β-irradiation. All patients underwent a minimum …

Echo-Enhanced Transcranial Color-Coded Duplexsonography to Study Collateral Blood Flow in Patients with Symptomatic Obstructions of the Internal Carotid Artery and Limited Acoustic Bone Windows

We prospectively evaluated 30 consecutive patients with echo-enhanced transcranial color-coded duplexsonography (TCCD) and correlative transfemoral digital subtraction angiography to assess the diagnostic efficacy of echo-enhanced TCCD for evaluation of collateral pathways through the circle of Willis in patients with limited acoustic bone windows and critical symptomatic carotid disease. Echo-enhanced TCCD detected collateral blood flow through the anterior communicating artery in 16 of 18 patients (sensitivity 89%, 95% CI 65–99%) and was false positive in one out of 12 patients without collateral flow (specificity 92%, 95% CI 59–100%). For the posterior communicating artery, sensitivity was 11/14 (79%, 95% CI 49–95%) and specificity was 15/16 (94%, 95% CI 70–100%). Echo-enhanced TCCD enables to study collateral blood flow through the communicating arteries of the circle of Willis with high sensitivity and specificity in patients with obstructions of the internal carotid artery and limited acoustic bone windows.