Extracranial Vasculature Research Articles

Carotid surgery: the past is prologue. The John Homans lecture.

Carotid surgery: the past is prologue. The John Homans lecture.

When can magnetic resonance angiography replace contrast angiograms for vascular disease?

On the basis of the rapid proliferation of magnetic resonance methods, it seems likely that magnetic resonance angiography will obviate the need for invasive x-ray angiography in the initial screening of many patients with known or suspected vascular disease. As it relates to the stable patient with thoracic aortic disease, MRA has already replaced invasive contrast angiography and is now widely accepted as the gold standard. For abdominal aortic disease, MRA can best be considered a viable alternative, but developments need to be made before this can be considered a first-line approach. For the peripheral vasculature MRA has already assumed an important role but technical developments need to occur before this is more widely disseminated. Finally, in the extracranial cerebral vasculature, several centers are already performing therapeutic interventions based on noninvasive testing, most notably the combination of MRA and data from ultrasound-based techniques. The ultimate goal is to move as many diagnostic studies as possible into the noninvasive arena to reduce morbidity associated with straightforward diagnoses. In parallel, the invasive angiography suite will be used primarily for therapeutic work and for the occasional diagnostic study in which noninvasive testing fails to reveal a clear-cut diagnosis. Cardiovascular specialists need to assume a leadership role in developing and applying this technology to help improve the care of the large number of patients with vascular diseases.

Angioplasty in the Extracranial and Intracranial Vasculature

Angioplasty in the Extracranial and Intracranial Vasculature

Three-dimensional reconstruction of human carotid arteries from images obtained during noninvasive B-mode ultrasound examination

Previous investigators have demonstrated that B-mode ultrasonography can provide high resolution images of the carotid arteries. When combined with Doppler flow measurements, quantitative estimates of luminal narrowing may also be obtained. B-mode imaging is limited, however, in its ability to provide a composite view of the vessel wall, lumen and plaque. Spatial relations between structures visualized in individual frames must be inferred from repeated transducer passes over the designated site, or repeated review of recorded images, followed by a “mind's eye” reconstruction. Three-dimensional (3-D) reconstruction of serially recorded cross-sectional images from current B-mode systems represents a possible solution to this limited spatial display that preserves detail regarding vessel wall pathology. Accordingly, computer-based automated 3-D reconstruction was used to generate a tangible format with which to assess and compare serially and transcutaneously recorded 2-dimensional (2-D) B-mode images of the carotid arteries. One or more timed sweep recordings of the 2-D B-mode examination were obtained from 5 patients for 3-D reconstruction. In all cases, satisfactory 3-D reconstruction was accomplished in three 3-D formats: cylindrical, sagittal and lumen cast. Sagittal 3-D reconstruction provided information regarding pathologic alterations within the arterial wall. Experience with the cylindrical mode suggests that this 3-D format, particularly when the reconstructed vascular segment is hemisected, is optimally suited for those cases in which direct inspection of luminal topography is of special interest. The lumen cast display, used with a recently validated edgedetection algorithm, may enhance the use of B-mode ultrasound for assessment of luminal crosssectional area. This preliminary experience suggests that 3-D reconstruction may supplement in a meaningful way noninvasively recorded conventional B-mode images of the extracranial vasculature.

Stroke secondary to carotid occlusion in a young man with nephrotic syndrome: Case description and review of the literature

We report a case of hemispheric stroke and death secondary to thrombosis of the internal carotid artery in a young adult with minimal-change nephrotic syndrome. Thrombotic complications are common in patients with nephrotic syndrome and may be due to a hypercoagulable state. To our knowledge, this is the first report of cerebral infarction due to thrombosis in the extracranial vasculature in a patient with nephrotic syndrome. We review previous reports of cerebral infarction in association with nephrotic syndrome and discuss possible mechanisms of hypercoagulability in this setting.

Operative treatment of nonspecific aortoarteritis (Takayasu's arteritis)

Operative treatment of nonspecific aortoarteritis remains controversial and little information is available on the results of reconstruction of extracranial cerebral vasculature in this disease. Our experience with 25 patients with histologically proven symptomatic disease treated during a 4-year period is presented. The aortic arch and its branches were involved in 12 patients and 13 had disease affecting the descending aorta and its tributaries. Patients with cerebrovascular disease had aneurysms, minor stroke, or intermittent neurologic dysfunction. Descending aortic involvement resulted either in symptomatic or ruptured aneurysm and renovascular hypertension. Operative treatment of cerebrovascular disease comprised aortic arch (three patients), carotid (three patients), or subclavian artery reconstruction (six patients). Descending aortic reconstruction comprised thoracoabdominal (four patients) or infrarenal (five patients) aneurysmorrhaphy, abdominal aortic replacement with bilateral renal artery reconstruction (two patients), and nephrectomy (two patients). One early postoperative death occurred because of stroke. Twenty-four survivors have been observed between 3 and 42 months. No deaths or further neurologic episodes have occurred during this period and three of five hypertensive patients were cured. We conclude that symptomatic aortoarteritis, including cerebrovascular disease, may be treated by standard operative techniques with rewarding results.

Digital Subtraction Arteriography

Digital subtraction arteriography (DSA) allows visualization of both the intracranial and extracranial vasculature following an intravenous injection of contrast medium. One hundred consecutive patients were evaluated using this modality. In 32, DSA was compared with conventional arteriography. The degree of internal carotid artery stenosis and/or occlusion shown by DSA was confirmed by conventional arteriography in 27 cases (84%). Abnormalities of the extracranial vasculature was demonstrated by DSA in 60% of patients with suspected cerebrovascular disease. Digital subtraction arteriography demonstrated significant stenosis or occlusion of the carotid arteries in 30% of patients in whom Doppler and radionuclide studies were normal. Digital subtraction arteriography is useful in evaluation of the extracranial vasculature in a variety of clinical conditions. In some instances it serves as a substitute for conventional arteriography. However, its exact place in evaluation of extracranial vasculature disease remains to be defined.

Digital Subtraction Angiography in the Evaluation of Cerebrovascular Disease

Intravenous DSA provides a safe, accurate, and cost-effective means of examining the extracranial and intracranial vasculature on an inpatient or outpatient basis. Intra-arterial DSA provides better spatial resolution than IV-DSA and has advantages over conventional film-screen angiography. The authors demonstrate the applications and limitations of this revolutionary diagnostic technique.

Cerebrovascular actions of prostaglandins

The actions of prostaglandins (PGs) on the cerebral circulation appear to present special problems for the investigator because the anatomy and physiology of this circulation differ significantly from other vascular beds. The anastomoses of the cerebral circulation with the extracranial vasculature vary greatly from species to species and are not easily isolated for study. Cerebral vessels are encased in a bony structure; the resistance arterioles are embedded in the gelatinous brain and are devoid of adventitia (Baker and Iannone, 1959). Also, the brain is without lymphatics and its capillaries are devoid of fenestra and clefts and do not manifest pinocytosis, but do contain numerous mitochondria (Oldendorf, 1975). Despite an abundant innervation, the function of the nerve supply to the cerebral vasculature is in question (Heistad and Marcus, 1978). Techniques for studying the cerebral circulation which have been used in other vascular beds are angiography, clearance techniques and topical application. The latter is possible after craniotomy by application through cannulae inserted into the subarachnoid space, or by means of additions to tissue chambers. The methods used to study the pharmacodynamic actions of prostaglandins discussed herein are presented schematically in Fig. 1. The results obtained with arachidonic acid and its derivatives, the prostanoids, are listed in Table 1. The terms prostanoid and prostaglandins are used interchangeably in this article.

Simultaneous measurement of internal and external carotid blood flow in the monkey. An approach to the study of migraine mechanisms.

Internal and external carotid blood flow was simultaneously measured in monkeys. The experimental technique, which was validated by observations on response of the intracranial and extracranial vasculature to CO2 inhalation, hypertension, sympathetic stimulation, and the cerebral vasodilator, papaverine, appears to be an improved approach to the study of migraine mechanisms in the animal model. lntracarotid serotonin was shown by this method to constrict both the internal and external carotid arteries. This effect was prevented by intracarotid methysergide, which itself produced only a transient constriction of the same vessels.

CEREBRAL PROTECTION DURING CAROTID ENDARTERECTOMY

Carotid endarterectomy has assumed an increasingly important role in the definitive management of patients with cerebrovascular insufficiency syndromes whose lesions are located in the extracranial vasculature. With proper selection of cases and careful attention to details of intraoperative management, endarterectomy can be performed with low morbidity and with operative mortality approaching 1%. Since no unnecessary risks should be taken in these patients, especially those with transient cerebral ischemic attacks and asymptomatic carotid bruits, some method of monitoring the adequacy of cerebral blood flow or a reliable means of cerebral protection during endarterectomy must be employed if strokes are to be prevented and aggravation of neurological deficits is to be avoided. Elsewhere in this issue (p 1023) White and associates report on the anesthetic management for carotid artery surgery. Their regimen includes hypercapnia, general anesthesia with halothane, spontaneous respiration, maintenance of each patient's normal blood pressure using phenylephrine if necessary, and

Endarterectomy of the totally occluded carotid artery for stroke. Results in 100 operations.

CAROTID endarterectomy continues to play an increasingly important role in the definitive management of patients with cerebrovascular insufficiency syndromes when the obstructing lesions are located in the extracranial vasculature. If the atherosclerotic plaque is only partially occlusive and the distal internal carotid is patent on the arteriogram, restoration of cerebral blood flow by surgical reconstruction is almost uniformly successful. This is not the case, however, if the internal carotid is totally occluded. 1 A considerable difference of opinion exists in the literature regarding the advisability of operation on the totally occluded carotid. Some authors believe that exploration is not worthwhile, 2,3 but others are liberal in exploring both the acutely and chronically occluded internal carotid. 4 It is the purpose of this paper to record our experiences with the management of totally occluded carotid arteries based on an analysis of clinical results in patients subjected to endarterectomy over a ten-year

CEREBRAL ANGIOGRAPHY IN THE EVALUATION OF PATIENTS WITH CEREBROVASCULAR DISEASE

Accurate visualization of all of the extracranial and intracranial vasculature, including serial studies for evaluation of collaterals and circulatory physiology is essential before undertaking any therapeutic measures for patients with evidence of ischemic cerebrovascular disease. The methods now at our command make it possible to identify vascular lesions in 80 per cent of patients with cerebrovascular disease. In order to achieve a complete picture of extra-or intracranial circulation one must obtain excellent contrast filling and technically good films of the entire brachiocephalic arterial tree. Films must be obtained in rapid succession and must be taken during a period of time long enough to make visible not only the anatomy but the physiology of flow and collateral circulation. The techniques of angiography used at New York University Medical Center include right and left percutaneous brachial angiography and left carotid angiography. Biplane films of the origins of the vessels and their course in the neck are taken in the oblique projection during the brachial examination. Biplane head and neck films are obtained during both brachial and carotid angiograms. Extracranial stenoses and occlusions are readily identified. Such lesions are most commonly found at the common carotid bifurcation and at the vertebral artery origin. Intracranial stenoses and occlusions may occur in conjunction with extracranial disease or independently. Collateral channels of every conceivable type have been seen. An understanding of the alteration of flow caused by the formation of collateral beds is basic to an understanding of ischemic phenomena. Acute major vascular occlusions are often associated with edema of the involved hemisphere, and in such instances these findings suggest a grave prognosis. Although the status of surgical and medical therapy is not entirely clear at this point, it is probable that surgical removal of certain stenotic lesions in particular cases of stenotic cerebrovascular disease may offer a more favorable prognosis. It is imperative that the study of the entire intra- and extracranial circulation be completed before a rationale for therapy can be developed.