CVD Risk Prediction with Carotid Ultrasound

Use of carotid ultrasound to measure carotid intima-media thickness (carotid IMT, or CIMT) and to detect carotid plaques is a non-invasive, safe, well-validated, reproducible technique for quantifying the burden of subclinical vascular disease and assessing CVD risk. This test is increasingly is being used as clinical tool. Six consensus statements or guidelines have addressed carotid ultrasound for CVD risk assessment (1-6). We and others have demonstrated that measurement of CIMT is feasible in a clinical setting and can help re-classify intermediate risk patients without CVD (7-10). The American Society of Echocardiography (ASE) recently published a consensus statement regarding the clinical use of carotid ultrasound to identify subclinical vascular disease and evaluate cardiovascular disease risk (6). This document addresses issues of standardization and will help improve the availability of experienced clinical laboratories that can perform high-quality CIMT studies. It provides several recommendations for the optimal use of carotid ultrasound to assess subclinical vascular disease and CVD risk (6).

Clinicians who plan to use carotid ultrasound to evaluate CVD risk are encouraged to read the ASE consensus statement in detail, and to pay special attention to the recommendations on patient selection, scanning technique, study interpretation, reporting, training and certification (6). Highlights of the ASE Consensus Statement on use of carotid ultrasound for CVD risk assessment include the following recommendations and statements:

• There are 9 published prospective studies with >1000 asymptomatic participants that examined CIMT and CVD risk. Each study demonstrated that CIMT was significantly associated with risk for myocardial infarction, stroke, death from coronary heart disease, or a combination of these events.
  
  
  • In most of these studies, CIMT predicted future CVD events independent of traditional risk factors.
  • Furthermore, 9 large studies demonstrated similar or greater predictive power for carotid plaque and CVD.
    
    
• This test can be useful for refining CVD risk assessment in the following types of patients, provided they do not already have conditions that indicate high CVD risk (such as established CVD or risk equivalent conditions):
  
  
  • Intermediate CVD risk (ie, 6%-20% 10-year risk of myocardial infarction or coronary heart disease death);
  • Family history of premature CVD in a first-degree relative;
  • Individuals <60 years old with severe abnormalities in a single risk factor who otherwise would not be candidates for pharmacotherapy; or
  • Women younger than 60 years old with ≥2 CVD risk factors.
    
    
• This test can be considered if the level of the aggressiveness of therapy is uncertain and additional information about the burden of subclinical vascular disease or future CVD risk is needed.
  
  
• Imaging should not be performed unless the results would be expected to alter therapy.
  
  
• Outcome data regarding the ability of a management strategy that includes CIMT or plaque screening tests to improve CVD outcomes are limited to changes in patient or physician behavior that would be expected to reduce CVD risk. More research in this area is needed.
  
  
• CVD risk assessment, carotid ultrasound imaging and measurement should follow the protocol from a large epidemiological study that reported CIMT values in percentiles by age, sex, and race/ethnicity.
  
  
• The recommended carotid ultrasound scanning protocol is described in detail.
  
  
  • CIMT measurements should be limited to the far wall of the common carotid artery.
  • The extracranial carotid arteries should be scanned thoroughly for the presence of carotid plaque.
    
  
  
• Carotid plaque is defined as
  • Focal wall thickening that is at least 50% greater than that of the surrounding vessel wall, or
  • A focal region with CIMT >1.5 mm that protrudes into the lumen and that is distinct from the adjacent boundary.
    
    
• Increased CVD risk is signified by
  • The presence of carotid plaque, or
  • CIMT ≥75th percentile for age, sex, race
    
    
• Recommendations also are provided for
  • Interpretation of studies
  • Reporting
  • Training and certification for readers and scanners

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References

1. Greenland P, Abrams J, Aurigemma GP, Bond MG, Clark LT, Criqui MH, et al. Prevention Conference V: Beyond secondary prevention: identifying the high-risk patient for primary prevention: noninvasive tests of atherosclerotic burden: Writing Group III. Circulation 2000;101:E16-E22.
2. Third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation 2002;106:3143-421.
3. Taylor AJ, Merz CN, Udelson JE. 34th Bethesda conference: executive summary–can atherosclerosis imaging techniques improve the detection of patients at risk for ischemic heart disease? J Am Coll Cardiol 2003;41:1860-2.
4. Roman MJ, Naqvi TZ, Gardin JM, Gerhard-Herman M, Jaff M, Mohler E. Clinical application of noninvasive vascular ultrasound in cardiovascular risk stratification: a report from the American Society of Echocardiography and the Society of Vascular Medicine and Biology. J Am Soc Echocardiogr 2006;19:943-54.
5. Graham I, Atar D, Borch-Johnsen K, et al European guidelines on cardiovascular disease prevention in clinical practice: executive summary: Fourth Joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice. Eur Heart J 2007 28: 2375-2414.
6. Stein JH, Korcarz CE, Hurst RT, Lonn E, Kendall CB, Mohler ER, Najjar S, Rembold CM, Post WS. Use of carotid ultrasound to identify subclinical vascular disease and evaluate cardiovascular disease risk: A consensus statement from the American Society of Echocardiography Carotid Intima-Media Thickness Task Force. Journal of the American Society of Echocardiography 2008; 21:93-111.
7. Stein JH, Fraizer MC, Aeschlimann SE, Nelson-Worel J, McBride PE, Douglas PS. Individualizing coronary risk assessment using carotid intima media thickness measurements to estimate vascular age. Clin Cardiol 2004;27:388-92.
8. Gepner AD, Keevil JG, Wyman RA, Korcarz CE, Aeschlimann SE, Busse KL, et al. Use of carotid intima-media thickness and vascular age to modify cardiovascular risk prediction. J Am Soc Echocardiogr 2006;19:1170-4.
9. Bard RL, Kalsi H, Rubenfire M, Wakefield T, Fex B, Rajagopalan S, et al. Effect of carotid atherosclerosis screening on risk stratification during primary cardiovascular disease prevention. Am J Cardiol 2004;93: 1030-2.
10. Rembold KE, Ayers CR, Wills MB, Rembold CM. Usefulness of carotid intimal medial thickness and flow-mediated dilation in a preventive cardiovascular practice. Am J Cardiol 2003;91:1475-7.

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Last updated September 19, 2008