InSight Ultrasound Specialists, Inc.

Medical Support of Ultrasound Carotid IMT Measurements

Some of the most respected medical associations in the U.S. have recommended IMT measurement as a valuable indicator of cardiovascular risk and a likely indicator of future coronary events.

Below are just a few excerpts from a vast body of clinial studies and papers regarding the utilization of Carotid IMT measurements as a powerful additional tool to improve stratification of heart attack and stroke risk, especially in the low to intermediate risk population.

In 2002, the president of the American Society of Echocardiography had this to say about IMT exams:

"This test has been a mainstay of epidemiologic investigations of coronary and cerebrovascular disease for decades. Excellent data document the validity of using carotid findings to predict the state of the coronary circulation, and carotid IMT both detects patients with current disease as well as accurately predicts future cardiac and cerebrovascular events. Carotid IMT measurements have been proven to provide incremental data to traditional risk prediction based on clinical data."

    
"ASE President's Message." Journal of the American Society of Echocardiography, June 2002.

(Circulation. 2000;101:111.)
© 2000 American Heart Association, Inc.

AHA Scientific Statement

Prevention Conference V
Beyond Secondary Prevention : Identifying the High-Risk Patient for Primary Prevention : Executive Summary

Sidney C. Smith, Jr, MD; Philip Greenland, MD; Scott M. Grundy, MD, PhD

Conclusions:

"Carotid artery B-mode ultrasound imaging is a safe, noninvasive, and relatively inexpensive means of assessing subclinical atherosclerosis. The technique can measure IMT, an operational measure of atherosclerosis, in a valid and reliable manner. The severity of carotid IMT is an independent predictor of transient cerebral ischemia, stroke, and coronary events such as myocardial infarction. The writing group concluded that in asymptomatic individuals older than 45 years of age, carefully performed carotid ultrasound examination with IMT measurement can add incremental information to traditional risk factor assessment. In experienced laboratories, this test can now be considered for further clarification of CHD risk assessment at the request of a physician."

(Circulation. 2001;104:2815.)
© 2001 American Heart Association, Inc.

Clinical Investigation and Reports

Carotid Intimal-Medial Thickness Is Related to Cardiovascular Risk Factors Measured From Childhood Through Middle Age
The Muscatine Study

Patricia H. Davis, MD; Jeffrey D. Dawson, ScD; Ward A. Riley, PhD; Ronald M. Lauer, MD

Conclusions— Higher carotid IMT in young and middle-aged adults is associated with childhood and current cardiovascular risk factors, as well as risk factor load.

Carotid Wall Thickness is Predictive of Incident Clinical Stroke: The Atherosclerosis Risk in Communities (ARIC) Study

Lloyd E. Chambless¹, Aaron R. Folsom², Limin X. Clegg³, A. Richey Sharrett⁴, Eyal Shahar², F. Javier Nieto⁵, Wayne D. Rosamond⁶ and Greg Evans⁷

¹Department of Biostatistics, School of Public Health, University of North Carolina Chapel Hill, NC
²Division of Epidemiology, School of Public Health, University of Minnesota Minneapolis, MN
³National Cancer Institute Bethesda, MD
⁴National Heart, Lung, and Blood Institute Bethesda, MD
⁵Division of Epidemiology, School of Hygiene and Public Health, Johns Hopkins University Baltimore, MD
⁶Division of Epidemiology, School of Public Health, University of North Carolina Chapel Hill, NC
⁷Department of Public Health, Bowman Gray School of Medicine Winston-Salem, NC

Reprint requests to Dr. Lloyd E. Chambless, Department of Biostatistics, University of North Carolina School of Public Health, Chapel Hill, NC 27514.



Few studies have determined whether carotid artery intima-media thickness (IMT) is associated prospectively with risk of first ischemic stroke. In the Atherosclerosis Risk in Communities Study, carotid IMT, an index of generalized atherosclerosis, was defined as the mean of IMT measured by B-mode ultrasonography at six sites of the carotid arteries. The authors assessed the relation of mean IMT to stroke incidence over 6–9 years' follow-up (1987–1995) among 7,865 women and 6,349 men aged 45–64 years without prior stroke at baseline in four US communities. There were 90 incident ischemic stroke events for women and 109 for men. In sex-specific Cox proportional hazards models adjusting only for age, race, and community, the hazard rate ratios comparing extreme mean IMT values (1 mm) to values less than 0.6 mm were 8.5 for women (95% confidence interval: 3.5, 20.7) and 3.6 for men (95% confidence interval: 1.5, 9.2). The relation was graded, and models with cubic splines indicated significant nonlinearity, with hazards increasing more rapidly at lower IMTs than at higher IMTs. Thus, models using linear IMT values substantially underestimate the strength of the association at lower IMTs. The strength of the association was reduced by the inclusion of putative stroke risk factors, but it remained elevated at higher IMTs. Hence, mean carotid IMT is a noninvasive predictor of future ischemic stroke incidence. Am J Epidemiol 2000;151:478–87