Intervention versus standard medical treatment in patients with symptomatic occlusion of the internal carotid artery: a randomised oxygen-15 PET study.

BACKGROUND: The aim of this randomised pilot study was to investigate the haemodynamic effects measured by oxygen-15 positron emission tomography (PET) of interventional treatment consisting of either endarterectomy or endovascular treatment of stenosed cerebropetal arteries, or tapering of antihypertensive medication in comparison with standard medical treatment alone in patients with symptomatic internal carotid artery (ICA) occlusion. METHODS: Twenty-three patients with symptomatic ICA occlusion underwent PET scanning at baseline and after 3 months. Twelve patients were randomised to intervention (either endarterectomy or endovascular treatment of stenosed cerebropetal arteries, or tapering of antihypertensive medication) and 11 to standard medical treatment alone. Primary outcome was a change in cerebral blood flow (CBF), cerebral blood volume (CBV) and/or oxygen extraction fraction (OEF) after 3 months measured by PET. RESULTS: There were no differences in changes in CBF, CBV or OEF between the two groups. Only patients with compromised perfusion at presentation showed a borderline significant increase in CBF of 2.8 mL/min/100 mL (95% confidence interval 0.0 to 5.7) after intervention (n = 7). CONCLUSION: This pilot study shows that in patients with symptomatic ICA occlusion, oxygen-15 PET did not detect differences in improvement of CBF, CBV or OEF between interventional and standard treatment.

Day-to-day test-retest variability of CBF, CMRO2, and OEF measurements using dynamic 15O PET studies.

PURPOSE: We assessed test-retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF) measurements derived from dynamic (15)O positron emission tomography (PET) scans. PROCEDURES: In seven healthy volunteers, complete test-retest (15)O PET studies were obtained; test-retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO(2) in arterial flow territories were calculated. RESULTS: Whole-brain test-retest coefficients of variation for CBF, CBV, CMRO(2), and OEF were 8.8%, 13.8%, 5.3%, and 9.3%, respectively. Test-retest variability of CBV left-to-right ratios was <7.4% across all territories. Corresponding values for CBF, CMRO(2), and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively. CONCLUSIONS: The test-retest variability of CMRO(2) measurements derived from dynamic (15)O PET scans is comparable to within-session test-retest variability derived from steady-state (15)O PET scans. Excellent regional test-retest variability was observed for CBF, CMRO(2), and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF.

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.

Predictors of patency of excimer laser-assisted nonocclusive extracranial-to-intracranial bypasses.

OBJECT: Excimer laser-assisted nonocclusive anastomosis (ELANA) is a technique that can be used for extracranial-to-intracranial (EC-IC) bypasses, without the necessity of temporary occlusion of the donor or recipient artery. Information on predictors of patency of EC-IC bypasses in general and the ELANA bypass in particular is sparse. The authors studied 159 ELANA EC-IC bypasses to find predictors of patency. METHODS: From a prospective database of patients who underwent EC-IC bypass surgery, 143 consecutive patients who underwent a total of 159 ELANA bypasses were studied. The associations of patient characteristics, surgical aspects, and technical aspects specific to the ELANA technique with intraoperative and postoperative bypass patency were studied using logistic regression analysis. RESULTS: At the end of the operation, 146 (92%) of the 159 bypasses were patent. A first attempt to create a bypass was almost 8 times more likely (OR 7.6, 95% CI 2.1-27.5; p = 0.02) to result in a patent bypass than a second attempt. Administration of a small amount of heparin during the operation was also associated with bypass patency (OR 5.2, 95% CI 1.1-24.9; p = 0.04). One hundred twenty-three (77%) of the 159 bypasses were functional at patency assessments during the 1st month after the operation. Older age (OR 1.043 for every year of increase in age, 95% CI 1.010-1.076; p = 0.01), male sex (OR 2.9, 95% CI 1.3-6.5; p = 0.01), and high intraoperative bypass flow (OR 1.017 for every milliliter per minute increase in flow, 95% CI 1.004-1.030; p = 0.01) were associated with postoperative bypass patency. CONCLUSIONS: Attempts to create a second EC-IC ELANA bypass after the first one are more likely to fail, whereas administration of heparin to the patient during the procedure increases the intraoperative bypass patency rate. Postoperative patency results are better in male and in older patients. Intraoperative bypass flow measurements are essential because high bypass flow is an important determinant of postoperative patency.

Assessment of the contribution of the external carotid artery to brain perfusion in patients with internal carotid artery occlusion.

BACKGROUND AND PURPOSE: The purpose of this study was to prospectively investigate the contribution of the ipsilateral external carotid artery (ECA) to cerebral perfusion in patients with internal carotid artery occlusion. METHODS: Institutional Review Board approval and informed consent were obtained. Thirty functionally independent patients (24 men, 6 women; mean age, 63 years) with an angiographically proven unilateral internal carotid artery occlusion and transient or minor disabling ischemic attacks ipsilateral to the side of the internal carotid artery occlusion were included. Grading of ECA collateral flow was performed with intraarterial digital subtraction angiography. The contribution of the ECA to regional cerebral blood flow was assessed with selective arterial spin labeling MRI. Differences in regional cerebral blood flow were analyzed with Student t test. RESULTS: Twenty percent of the patients had ECA Grade 0 collateral flow (no filling of ophthalmic artery), 20% Grade 1 (filling of carotid siphon), and 60% Grade 2 (filling of anterior and/or middle cerebral artery) as demonstrated on digital subtraction angiography. Although in the Grade 1 group, the ECA supplied a smaller region of the brain compared with the Grade 2 group, the mean regional cerebral blood flow of the perfusion territory supplied by the ECA is similar (P=0.70) in the Grade 1 group (mean+/-SD 57+/-16 mL/min/100 g) and the Grade 2 group (60+/-12 mL/min/100g). CONCLUSIONS: In patients with symptomatic internal carotid artery occlusion, focal brain regions may strongly depend on the contribution to cerebral perfusion of the ECA ipsilateral to the side of the internal carotid artery occlusion, even in patients with limited ECA collateral supply as demonstrated on digital subtraction angiography.

Sutureless nonocclusive bypass surgery in combination with an expanded polytetrafluoroethylene graft. Laboratory investigation.

OBJECT: Cerebral aneurysms that cannot be treated by clip or coil placement can be treated with high-flow bypass surgery using techniques such as the excimer laser-assisted nonocclusive anastomosis (ELANA). To simplify the technique, a sutureless ELANA (SELANA) was developed in combination with an expanded polytetrafluoroethylene (ePTFE) graft. METHODS: In 18 rabbits a bypass was constructed on the abdominal aorta using the SELANA technique with an ePTFE graft, resulting in 18 bypasses and 36 anastomoses. Short-term effects were analyzed in the first 2 weeks and at 2 and 3 months after the procedure. Patency was evaluated using quantitative ultrasound flowmetry. The anastomotic sites were studied using scanning electron microscopy. RESULTS: Construction of the bypass using the SELANA technique was easier and faster (15-25 minutes) compared with bypasses made with the ELANA technique (> 90 minutes). At the end of follow-up, 16 of 18 bypasses were patent. Of 36 SELANA anastomoses, 32 could be completed without short temporary occlusion of the recipient vessel. Scanning electron microscopy showed complete coverage of all anastomoses with neointimal repair tissue after 10 days. CONCLUSIONS: The SELANA technique provides further advantages over the conventional ELANA technique in ease of use and shortening of procedure time. The patency rate in this series was 89% and neointima repair tissue at the anastomosis site was complete after 10 days. Further experimental studies of the long-term patency and safety of this technique are necessary before clinical application.

The excimer laser-assisted nonocclusive anastomosis practice model: development and application of a tool for practicing microvascular anastomosis techniques.

OBJECTIVE: To practice microsurgical skills, several experimental models are available that diminish the need for experimental animals. We defined criteria with which such models should comply, and we tested whether the models described in literature, as well as our own practice model, comply with these criteria. METHODS: We defined the criteria to which these models should comply, and we performed a literature search on microvascular practice models. During the development of the Excimer laser-assisted nonocclusive anastomosis technique, we designed our own Excimer laser-assisted nonocclusive anastomosis Practice Model (EPM) according to those criteria, and we compared that model with the models described in the literature. RESULTS: All practice models could be categorized into three groups: beginner, moderate, and advanced. Our EPM complies with almost all criteria defined in the beginner and moderate groups and has much in common with the models that are categorized in the advanced group. CONCLUSION: In consideration of the methods to learn microvascular surgical techniques, the EPM can be used for a very long time before the need for living animals arises. This last aspect remains an inescapable condition for practicing microsurgical skills. However, with use of the EPM or another practice model, the amount of experimental animals can be drastically reduced.