Carotid plaque, intima media thickness, cardiovascular risk factors, and prevalent cardiovascular disease in men and women - The British Regional Heart Study

Background and Purpose-B-mode ultrasound is a noninvasive method of examini ng the walls of peripheral arteries and provides measures of the intima-med ia thickness (IMT) at various sites (common carotid artery, bifurcation, in ternal carotid artery) and of plaques that may indicate early presymptomati c disease. The reported associations between cardiovascular risk factors, c linical disease, IMT, and plaques are inconsistent. We sought to clarify th ese relationships in a large, representative sample of men and women living in 2 British towns. Methods-The study was performed during 1996 in 2 towns (Dewsbury and Maidst one) of the British Regional Heart Study that have an approximate to 2-fold difference in coronary heart disease risk. The male participants were draw n from the British Regional Heart Study and were recruited in 1978-1980 and form part of a national cohort study of 7735 men. A random sample of women of similar age to the men (55 to 77 years) was also selected from the age- sex register of the general practices used in the original survey. A wide r ange of data on social, lifestyle, and physiological factors, cardiovascula r disease symptoms, and diagnoses was collected. Measures of right and left common carotid IMT (IMTcca) and bifurcation IMT (IMTbif) were made, and th e arteries were examined for plaques 1.5 cm above and below the flow divide r. Results-Totals of 425 men and 375 women were surveyed (mean age, 66 years; range, 56 to 77 years). The mean (SD) IMTcca observed were 0.84 (0.21) and 0.75 (0.16) mm for men and women, respectively. The mean (SD) IMTbif were 1 .69 (0.61) and 1.50 (0.77) mm for men and women, respectively. The correlat ion between IMTcca and IMTbif was similar in men (r=0.36) and women (r=0.38 ). There were no differences in mean IMTcca or IMTbif between the 2 towns. Carotid plaques were very common, affecting 57% (n=239) of men and 58% (n=2 11) of women. Severe carotid plaques with flow disturbance were rare, affec ting 9 men (2%) and 6 women (1.6%). Plaques increased in prevalence with ag e, affecting 49% men and 39% of women aged <60 years and 65% and 75% of men and women, respectively, aged >70 years. Plaques were most common among me n in Dewsbury (79% affected) and least common among men in Maidstone (34% a ffected). IMTcca showed a different pattern of association with cardiovascu lar risk factors from IMTbif and was associated with age, SEP, and FEV, but not with social, lifestyle, or other physiological risk factors. IMTbif an d carotid plaques were associated with smoking, manual social class, and pl asma fibrinogen. IMTbif and carotid plaques were associated with symptoms a nd diagnoses of cardiovascular diseases. IMTbif associations with cardiovas cular risk factors and prevalent cardiovascular disease appeared to be expl ained by the presence of plaques in regression models and in analyses strat ified by plaque status. Conclusions-IMTcca, IMTbif, and plaque are correlated with each other but s how differing patterns of association with risk factors and prevalent disea se. IMTcca is strongly associated with risk factors for stroke and with pre valent stroke, whereas , and plaque are more directly associated with ische mic heart disease risk factors and prevalent ischemic heart disease. Our an alyses suggest that presence of plaque, rather than the thickness of IMTbif , appears to be the major criterion of high risk of disease, but confirmati on of these findings in other populations and in prospective studies is req uired. The association of fibrinogen with plaque appears to be similar to i ts association with incident cardiovascular disease. Further work elucidati ng the composition of plaques using ultrasound imaging would be helpful, an d more data, analyzed to distinguish plaque from IMTbif and IMTcca, are req uired to understand the significance of thicker IMT in the absence of plaqu e.