New consensus statement on carotid intima-media thickness measurement

Atherosclerosis is a systemic vascular disease that begins in childhood. Eventually, it may progress to myocardial infarction and other vascular events. The modification of traditional risk factors has been shown to reduce risk. Clinical tools such as the Framingham Risk Score assist clinicians in placing patients into low-, intermediate- and high-risk categories. One limitation of the Framingham Risk Score, however, is that it estimates 10-year risk and not lifetime risk. In addition, it does not identify increased risk due to family history. Finally, even with the aggressive management of traditional risk factors, residual risk may remain.

Carotid intima-media thickness measurement by B-mode ultrasound is being used more frequently as a clinical tool to screen for subclinical atherosclerosis. In 2000, the American Heart Association Prevention Conference V suggested that carotid intima-media thickness measurement may be included in cardiovascular risk assessment. This spring, the American Society of Echocardiography Carotid Intima Media Thickness Task Force released a consensus statement* on carotid intima-media thickness measurement endorsed by the Society for Vascular Medicine.

The Task Force advised that carotid intima-media thickness be considered in patients at intermediate cardiovascular risk who do not already have cardiovascular disease or cardiovascular disease risk equivalents. Additional situations where carotid intima-media thickness measurement may be appropriate included: those with a family history of premature CVD in a first-degree relative; individuals aged younger than 60 years with severe abnormalities in a single risk factor who would not otherwise be candidates for therapy (such as familial hypercholesterolemia); and women aged younger than 60 with two or more CVD risk factors. They recommended against carotid intima-media thickness measurement if atherosclerotic vascular disease is already present or if the information would not change management.

One concern about carotid intima-media thickness measurement has been about the reliability and reproducibility of results. The authors made suggestions on imaging technique and protocol to maximize accuracy. The distal 1 cm of the far wall of both common carotid arteries should be measured with a semi-automated border detection program. The values should be compared to data obtained from large epidemiologic studies. They also recommended screening for carotid plaque. Individuals with a carotid intima-media thickness measurement greater than the 75th percentile for age and gender are at increased future cardiovascular risk.

Some endocrinologists, including myself, have already been using carotid intima-media thickness measurement to further identify patients at increased cardiovascular risk. I consider it similar to the use of DXA in those who may be at risk for fragility fracture. Although not every individual with high carotid intima-media thickness (or low bone mass) will go on to experience an event, both carotid intima-media thickness measurement and DXA provide us information on which patients should be treated more aggressively. However, no matter whether we are managing cardiovascular disease or bone disease, risk factors beyond carotid intima-media thickness measurement and DXA must not be ignored. The most important difference is that DXA has been validated and accepted as a routine screening tool covered by insurers whereas carotid intima-media thickness measurement has not.

*J Am Soc Echocardiogr. 2008;21:93-111.