Noninvasive xenon-133 measurements of cerebral blood flow using stationary detectors compared with dynamic emission tomography.

Repeated bedside measurements of CBF have been made possible by the recent development of a mobile unit with 10 stationary detectors using the intravenous xenon-133 method. To evaluate this technique, comparative CBF studies at rest and following the application of a cerebral vasodilatory stimulus (acetazolamide, 1 g i.v.) were performed with the mobile equipment and with xenon-133 single-photon emission inhalation tomography in patients with cerebrovascular disease. The CBF level and the flow response to acetazolamide as determined with the two methods were well correlated, although at low flow levels the stationary detectors yielded somewhat lower CBF values than did emission tomography. Considering the side-to-side asymmetry, an excellent correlation was obtained. Using the initial slope index, the stationary detectors revealed quantitatively 83% of the interhemispheric asymmetry and 63% of the asymmetry in the middle cerebral artery territory shown with the tomograph. As illustrated by a case history, the nontomographic CBF unit used in this study may provide reliable and useful information in patients with occlusive cerebrovascular disease by performing repeated CBF studies and challenging the cerebral circulation with acetazolamide.

Asymptomatic carotid lesions after endarterectomy of contralateral carotid artery. Five-year follow-up study and prognosis.

Of 185 patients who consecutively underwent carotid endarterectomy five years ago, 135 had a patent asymptomatic contralateral internal carotid artery (ICA). During follow-up (median, 59 months), 36 patients developed new neurologic symptoms (18 strokes and 18 transient ischemic attacks). Thirteen patients developed symptoms referable to the territory of the previously asymptomatic ICA (five strokes and eight transient ischemic attacks). Using life-table analysis, the annual stroke rate was estimated to be 1% and 2.2% considering the previously asymptomatic and symptomatic ICA, respectively. Separating patients according to the degree of stenosis on the preoperative angiogram and according to the presence of ulceration revealed a significantly higher incidence of neurologic events and strokes in patients with stenoses exceeding 50% and/or patients with obvious ulcerations. Although the risk of stroke without warning was increased in these subgroups, we did not consider the risk high enough to warrant prophylactic endarterectomy. An exception enough to warrant prophylactic endarterectomy. An exception may be the patient with a more than 90% stenosis.

Cerebral hyperperfusion following carotid endarterectomy.

Serial measurements of cerebral blood flow (CBF) were performed in 56 patients before and one to four times after uncomplicated carotid endarterectomy. The findings were related to the ratio between internal carotid artery (ICA) and common carotid artery (CCA) mean pressures. Within the 1st postoperative day CBF increased by a median of 37% in the ipsilateral and 33% in the contralateral hemisphere. Later recordings showed a gradual return of CBF toward the preoperative level. Sixteen patients with an ICA/CCA pressure ratio below 0.7 showed a significantly more pronounced and longer-lasting flow increase than did 40 patients with a ratio above this level. On Day 1, the median CBF increase in the ipsilateral hemisphere was 61% and 24% in the two groups, respectively (p less than 0.01). A significant improvement in side-to-side asymmetry, resulting from a higher gain in the ipsilateral hemisphere, occurred in the low pressure ratio group, while the hemispheric asymmetry on average was unchanged in the high pressure ratio group. This relative hyperemia was most pronounced 2 to 4 days following reconstruction. The marked hyperemia, absolute as well as relative, in patients with a low ICA/CCA pressure ratio suggests a temporary impairment of autoregulation. Special care should be taken to avoid postoperative hypertension in such patients, who typically have preoperative hypoperfusion, to avoid the occurrence of cerebral edema or hemorrhage.

Hemodynamically significant stenosis of the internal carotid artery treated with endarterectomy. Case report.

Repeated cerebral blood flow (CBF) measurements with xenon-133 inhalation and single photon emission tomography were performed in a patient suffering a minor stroke with subsequent orthostatic-provoked transient ischemic attacks (TIA's). Angiography revealed a thread-like internal carotid artery and an occluded external carotid artery on the side of the ischemic neurological symptoms. Computerized tomography and technetium-99m-pertechnetate brain scintigraphy 2 weeks after stroke were both normal. Before reconstructive vascular surgery, resting CBF showed a hypoperfused area corresponding to the clinical symptoms. Diamox (acetazolamide, 1 gm) increased CBF by 24% in the unaffected hemisphere, whereas even a slight decrease in flow ("steal") was seen in the maximally affected region. In contrast, theophylline (220 mg) reduced CBF in the unaffected hemisphere and caused a slight increase in the previously maximally hypoperfused area ("inverse steal"). After surgery, the flow pattern practically normalized and the TIA's disappeared. The CBF measurements before surgery and also after the injection of the vasoactive drugs indicated that focal hemodynamic insufficiency elicited the TIA's, and pointed at a low mean arterial blood pressure of about 35 mm Hg in the affected hemisphere. The perioperative finding of a mean blood pressure in the internal carotid artery of 31 mm Hg on the symptomatic side confirmed that the brain tissue had a severely reduced perfusion pressure. On clamping the artery, a stump pressure of 22 mm Hg and electroencephalogram flattening was noted, so a temporary internal shunt was inserted. The findings demonstrate that preoperative CBF measurements, including studies of the regional vasoreactivity, may identify patients with hemodynamic TIA's. These patients are at particular risk of developing cerebral ischemia during carotid endarterectomy, as any further compromise of the inflow may precipitate frank ischemia.

Measurement of cerebral blood flow by intravenous xenon-133 technique and a mobile system. Reproducibility using the Obrist model compared to total curve analysis.

The recent development of a mobile 10 detector unit, using i.v. Xenon-133 technique, has made it possible to perform repeated bedside measurements of cerebral blood flow (CBF). Test-retest studies were carried out in 38 atherosclerotic subjects, in order to evaluate the reproducibility of CBF level and side-to-side asymmetry. Data were analysed according to the Obrist model and the results compared with those obtained using a model correcting for the air passage artifact. Reproducibility was of the same order of magnitude as reported using stationary equipment. The side-to-side CBF asymmetry was considerably more reproducible than CBF level. Using a single detector instead of five regional values averaged as the hemispheric flow increased standard deviation of CBF level by 10-20%, while the variation in asymmetry was doubled. In optimal measuring conditions the two models revealed no significant differences, but in low flow situations the artifact model yielded significantly more stable results. The present apparatus, equipped with 3-5 detectors covering each hemisphere, offers the opportunity of performing serial CBF measurements in situations not otherwise feasible.

Evaluation of the regional cerebral vasodilatory capacity before carotid endarterectomy by the acetazolamide test.

To estimate the regional perfusion pressure and possibly the stump pressure during carotid endarterectomy, cerebral blood flow (CBF) measurements including a vasodilatory test were performed preoperatively. CBF was measured by 133Xe inhalation and emission tomography. An intravenous dose of 1g acetazolamide (Diamox) was used as cerebral vasodilator. Thirty-six patients with a clinical history of previous strokes (9 cases) or transient ischaemic attacks (27 cases) were studied. Nine of the patients showed occlusion of the contralateral internal carotid artery (ICA). The percent flow increase induced by Diamox in the ipsilateral hemisphere correlated to the ICA pressure was measured before clamping (n = 32, r = 0.55, p less than 0.001). In 12 of the 36 patients, Diamox caused a significant change in the flow distribution indicating a restricted regional vasodilatory capacity and a reduced regional perfusion pressure. In addition, these 12 patients showed a low stump pressure (less than 50 mmHg). However, 8 additional patients had uniform CBF increases at the Diamox test, but showed low stump pressures. It is concluded, that preoperative tests of the cerebral vasodilational capacity can be used to identify most patients with a low ICA pressure, and a substantial fraction of patients that will develop a low stump pressure upon ICA clamping during operation. In these patients with abnormal Diamox tests surgical reconstruction is particularly indicated, but, at the same time the perioperative risks are presumably highest in this group.

Carotid artery disease and low cerebral perfusion pressure: symptomatology, operative risk and outcome.

Direct internal carotid artery blood pressure measurements in patients undergoing carotid endarterectomy identified 49 patients, among 239 consecutive cases (21%), who had a reduction in perfusion pressure of 20% or more. The clinical history, objective findings and angiographic data were compared with those of a control group of a further 49 patients selected from the remaining patients operated on over the same period. The two groups were compared for short- and long-term outcome of surgery. We were unable to delineate a symptomatic neurological profile that identified patients with low perfusion pressures. Surgery in patients with low perfusion pressures seemed to be associated with an increased complication rate (12% versus 4%), although this was not statistically significant. Definite postoperative improvements in persisting neurological deficits were observed only in one patient. Long-term results were equal in the two groups with an annual stroke risk of 3%.

[Ergotism in migraine. Peripheral vascular complications in 14 patients with migraine]. / Ergotisme ved migraene. Perifere kredsløbskomplikationer hos 14 patienter med migraene.

The general occurrence of subclinical ergotism with reduced peripheral systolic blood pressures in patients taking ergotaminepreparations regularly for migraine and the frequent occurrence of milder symptoms indicates that severe ischaemia of the extremities is not as rare a complication as would appear from the few case reports published. The 14 cases reported here constitute the largest series published of migraine patients with acute ergotism. The patients, all women, were admitted to a vascular department over a period of 14 years. They suffered from severe ischaemia of one or more extremities after consumption of varying doses of ergotamine tartrate. Ten patients had previously exhibited symptoms of acute or chronic ergotism, but only eight were admitted with this diagnosis. Liver enzyme tests were abnormal in five out of six patients examined, while three patients had ECG signs of myocardial ischaemia, regressing during treatment. At the beginning of the period, hyperbaric oxygen at 3 ATAB was the standard treatment. Since 1980, the treatment of choice has been continous i.v. nitroglycerine infusion for 24 hours. Nine patients experienced prolonged postischaemic symptoms; one patient required a forefoot amputation and four patients had permanent ischaemic muscular damage. Increased bioavailability of ergotamine due to hepatic vasospasm is suggested as a cause of sudden reduced tolerance to ergotamine. Peripheral systolic pressures and liver function tests should be controlled in patients taking ergotamine regularly. Subclinical ergotism over a prolonged period may facilitate development of occlusive peripheral vascular disease.

[Neurologic complications in connection with the surgical treatment of 577 cases of carotid artery stenosis]. / Neurologiske komplikationer i relation til kirurgisk behandling af 577 a. carotis stenoser.

During the period January 1982 till June 1988, 536 patients underwent 577 carotid thrombendartectomies in the Department of Vascular Surgery RK in the University Hospital in Copenhagen. Preoperatively, 270 patients (47%) had experienced transient ischaemic attacks (TIA), 247 (43%) had experienced stroke (APC) and 19 (3%) had non-focal symptoms while 41 (7%) had asymptomatic stenoses. Postoperatively, 17 (2.9%) patients developed TIA, 22 (3.8%) developed slight neurological symptoms and 40 (7%) had more severe neurological complications and six of these (1%) died. None of the patients died from other causes during the first month. The frequency of complications had no relationship to the preoperative focal symptoms, but in patients with non-focal symptoms this was 37%. The degree of stenosis of the contralateral internal carotid artery (ICA) was correlated positively with the occurrence of severe neurological complications which were observed in 5% without contralateral ICA changes, in 7% with stenoses and in 20% with contralateral ICA occlusion. Patients with cerebral infarction developed complications significantly more frequently (20%) than patients with normal CT scans. The risk was also found to be increased in cases with a high pressure gradient across the stenosis and low pressure peripherally in the occluded artery (stump pressure). Follow-up examination of the 73 patients with complications on average 39 months after operation revealed that 37 patients (6.4%) had severe neurological symptoms resulting either from the operation or subsequent APC; seven patients required complete nursing care (1.2%) and 17 patients died during the period of observation. On follow-up examination, 15 patients had been occupationally active for at least 1.5 years.