Haemodynamic Effects of Carotid Artery Stenosis

Abstract

Mental Illness-Shepherd et al. MEDBCAL JOURNAL 1363 and for the detection of causal associations among these complex conditions. At the same time the study underlines the need to extend and refine available techniques of measurement. Even with carefully defined criteria of illness the wide variation between practitioners' prevalence rates points to two potent groups of factors. The first of these relates to the ecological differences between practices and can be offset by paying regard to the size and representativeness of the sample of participating doctors. The second relates to the doctor, his attitudes, and his interactions with his patients ; for psychiatric illness, as we have shown, they constitute a major source of variation. SummaryThis paper reports on a general practice survey of psychiatric morbidity carried out in the Greater London area. The sickness experience of nearly 15,000 patients on the lists of 80 practitioners was studied over a period of one year. It was shown that minor psychiatric disorders, classified according to a predetermined schema, were diagnosed in 14% of the population at risk. Neurotic illness was most prevalent among middle-aged females and proved to be an important cause of chronic illness. The reasons for interpractice variation in recorded morbidity are discussed.We are grateful to the following general practitioners, whose cooperation made this study possible. (1957, 1961) found a high incidence in a post-mortem series of patients who had had a cerebrovascular accident, but they did not study any control subjects; they suggested that extracranial arterial disease was a common cause of cerebral infarction through its direct effect on cerebral blood flow. Schwartz and Mitchell (1961) showed that atherosclerosis of these arteries, as with atherosclerosis elsewhere, correlated well with age, that it was common even in patients without cerebrovascular accidents, and that a correlation between cerebral infarction and extracranial atherosclerosis could be due largely to the fact that both were correlated with age. The occlusive lesions described by these authors varied from small plaques scarcely narrowing the arterial lumen to complete occlusion of one or more of the extracranial arteries. The incomplete lesions were classified, according to the percentage reduction of the normal lumen, into mild or moderate (less than 50% reduction) or severe (more than 50% reduction); no evidence is available to assess the possible effects of such stenosis on cerebral blood flow.Alteration of calibre may be of importance either directly, by its effect on cerebrovascular resistance, or indirectly, producing turbulent conditions of flow which might predispose to local platelet aggregation. In this paper we are concerned with the effect of narrowing of carotid arteries on their hydraulic resistance only, and report experiments designed to determine the approximate dimensions and hydraulic resistance of the minimum narrowing which has a detectable effect on blood flow through the artery. We...

Auscultation of cervical and ocular bruits in extracranial carotid occlusive disease: a clinical and angiographic study.

“…Two millimeters was selected as the cut-off point because hemodynamic changes may occur at this degree of stenosis. 8 Forty-four of the patients were investigated for symptomatic carotid disease (TIAs or stroke), 5 patients had asymptomatic carotid bruit, and 1 patient had carotid disease discovered incidentally at the time of subarachnoid hemorrhage evaluation.…”

Amount of smoking independently predicts carotid artery atherosclerosis severity.

“…1 " 3 The causal mechanism relating carotid plaque to ischemic stroke has been thought to be flow restriction, 4 embolism, 5 or both. 6 Because cigarette smoking has been found to be a significant predictor of extracranial carotid atherosclerosis among patients referred for cerebrovascular evaluation, 6 -8 in representative samples of community populations, 910 and in pairs of identical twins who are discordant for smoking, 1112 we investigated in this study the independent effect of the level of cigarette use on carotid plaque thickness among smokers after controlling for age, history of hypertension, and history of diabetes.…”

Stroke-in-progression.

“…Extension of thrombus Except for embolization, the consequences of accretions of thrombotic material on a thrombus in situ short of occlusion of the arterial lumen are poorly documented. However it may be presumed that reduction of the arterial lumen by 80-90% decreases blood flow 29 - 30 thereby possibly aggravating brain ischemia. On the other hand the development of antero a/o retrograde thrombus (secondary thrombus, stagnation thrombus) has been found nearly always to follow arterial occlusion due either to atherosclerotic thrombosis or cardiac embolism.…”