Evaluating CMR

Evaluating CHD risk

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Absolute CHD risk is defined as the probability of developing CHD over a specific period of time. The latest Framingham report by Wilson et al. (8) estimates absolute CHD risk over the next 10 years. The absolute CHD risk estimates in the Framingham risk equation are based on a non-proportional hazard Weibull accelerated failure time model (parametric model) and a Cox proportional hazard regression model (semiparametric model) (18). Prediction models include age, sex, blood pressure, total or LDL cholesterol, HDL cholesterol, smoking, and diabetes. Points are assigned for values of all these risk factors and the 10 year risk for CHD is calculated (to calculate your 10 year CHD risk, go to http://www.nhlbi.nih.gov/about/framingham/riskabs.htm). The Framingham report defines low risk as the risk for CHD at any age that is conferred by a combination of all the following parameters: blood pressure <120/<80 mm Hg, total cholesterol between 4.1 to 5.2 mmol/l (160 to 199 mg/dl) or LDL cholesterol between 2.6 to 3.3 mmol/l  (100 to 129 mg/dl), and HDL cholesterol >1.2 mmol/l  (>45 mg/dl) for men or >1.4 mmol/l (>55 mg/dl) for women, in a nonsmoking person without diabetes. This definition of low risk has been validated in a follow-up study of 350,000 participants of the Multiple Risk Factor Intervention Trial (19), which found that major risk factor levels higher than those above were linked to excess mortality from CHD.

The Framingham Heart Study also used sex-specific equations to predict CHD. Before Framingham, CHD was mainly considered a male disease. At the time, the Framingham Heart Study was one of the few prospective studies to include women and therefore allowed CHD risk factors and prevalence to be compared in both men and women (20, 21).

Reference

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8. Wilson PW, D'Agostino RB, Levy D, et al. Prediction of coronary heart disease using risk factor categories. Circulation 1998; 97: 1837-47.

18. Odell PM, Anderson KM and Kannel WB. New models for predicting cardiovascular events. J Clin Epidemiol 1994; 47: 583-92.

19. Stamler J, Wentworth D and Neaton JD. Is relationship between serum cholesterol and risk of premature death from coronary heart disease continuous and graded? Findings in 356,222 primary screenees of the Multiple Risk Factor Intervention Trial (MRFIT). JAMA 1986; 256: 2823-8.

20. Kannel WB and Wilson PW. Risk factors that attenuate the female coronary disease advantage. Arch Intern Med 1995; 155: 57-61. 21. Castelli WP. Cardiovascular disease in women. Am J Obstet Gynecol 1988; 158: 1553-60, 66-7.

21. Castelli WP. Cardiovascular disease in women. Am J Obstet Gynecol 1988; 158: 1553-60, 66-7.

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