The thickness of the carotid artery wall, as measured by ultrasound, is a good predictor of heart attack and stroke in asymptomatic, elderly individuals, according to a new report (New England Journal of Medicine 1999;340:14-22).
Researchers from the multicentre Cardiovascular Health Study Collaborative Research Group enrolled 5858 subjects, 4476 of whom had no previous history of cardiovascular disease, into an observational study. Sixty per cent of the subjects were women, 15% black, and the remainder white. Their average age was 72 years.
The investigators measured the intimal and medial wall thickness of the common carotid and internal carotid arteries in the study subjects and then followed them for an average of 6.2 years, recording the rate of myocardial infarcts and strokes.
Although researchers monitored and recorded the health, lifestyle, and diet of the subjects, diagnosis and treatment of heart disease were left to the patient’s own doctors. The researchers divided the study participants into five groups, according to the thickness of their carotid arteries.
The investigators found a direct relation between carotid arterial wall thickness and cardiovascular event risk. A nearly fivefold increase in stroke or heart attack rates occurred in people with the thickest carotid arteries compared with those with the thinnest. Participants with the thinnest carotid artery walls had 40 cardiovascular events compared with 184 in those with the thickest walls.
The relative risk of stroke or heart attack for the fifth with the greatest wall thickness compared with the lowest fifth was 3.87. Moreover, this relation proved stable even when traditional cardiovascular risk factors of age, sex, blood pressure, cholesterol levels, smoking, and diabetes were controlled for.
Although it is reasonable to assume that arterial wall thickness would reflect risk of cardiovascular morbidity, this is the first study to confirm such an assumption. Arterial walls thicken both as a result of deposition of cholesterol and atherosclerotic plaque and in response to wall stress, as in hypertension.
Ultrasonography can detect arterial wall thickening, and the carotid arteries are easily accessible. Currently, carotid artery ultrasonography is used to detect carotid artery stenosis in patients presenting with stroke or transient ischaemic attack. Those with stenoses of over 80% may be referred for endarterectomy.
Figure.
Carotid artery: thin walls predict heart disease