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Torrance, CA - A US research group has shown for the first time that there are differences in both coronary calcium and angiographic burden between patients of different ethnic origins, which persist after adjustment for classic cardiovascular risk factors.
Dr Matthew J Budoff (Harbor-UCLA Medical Center) and colleagues found that whites and Asian Americans have a higher atherosclerotic burden than blacks and Hispanics, with black patients having just half the risk of obstructive disease as compared with whites; they report their findings in the February 6, 2002 issue of the Journal of the American College of Cardiology.1
The researchers studied 782 patients (453 white, 108 black, 177 Hispanic, and 44 Asian) undergoing coronary angiography for clinical indications, the vast majority of whom were suspected to have coronary artery disease (CAD). Patients underwent electron beam tomography (EBT) - used to quantify the amount of coronary artery calcification (CAC) - within 3 months of angiography. An experienced reader without knowledge of the EBT results analyzed the angiograms. A 50% luminal narrowing in any coronary vessel defined a significant angiographic obstruction.
Racial differences in prevalence of coronary artery calcification and angiographic obstruction|
Race |
Angiographic obstruction |
Prevalence of CAC |
Mean calcium score |
|
Asian | 64% (p*=0.30) | 73% (p=0.06) | 365 (p=0.04) |
|
Black | 49% (p<0.001) | 62% (p<0.001) | 341 (p=0.002) |
|
Hispanic | 58% (p<0.01) | 71% (p<0.001) | 286 (p=0.0005) |
|
White | 71% | 84% | 478 |
After adjusting for hypertension, tobacco use, diabetes, age, gender, family history of premature heart disease, hypercholesterolemia, and use of statins, whites had a higher risk of angiographic disease (odds ratio 1.65) than all other races separately or combined (p=0.004). Blacks had only 0.48 times the risk of whites (p=0.0002); Hispanics 0.68 the risk of whites (p=0.07) and Asians 0.66 (p=0.25).
The sensitivity and specificity of EBT in detecting significant angiographic obstruction did not differ among the ethnic groups despite a different prevalence in CAC. The EBT-detected CAC correlated well with extent and prevalence of angiographic CAD across all ethnicities, "demonstrating a considerable similarity in calcifying stenotic lesions," the researchers note.
Lower prevalence of calcification in blacks likely due to lower disease
Budoff et al say that many epidemiologic reports suggest that the risks of cardiovascular disease differ between blacks and whites, but that "results are controversial and conflicting." They note that one other study of coronary calcium and ethnicity2 has been reported which found a lower prevalence of coronary calcium in blacks, "yet a similar or higher coronary event rate." But they say that no angiography, or other measure of disease, was performed in that trial "and the numbers of black subjects were excessively small."
"Our study, by use of angiography, suggests that the lower calcium prevalence is due to the lower prevalence of coronary atherosclerosis in blacks," the authors state. White patients are more likely to have significant CAD than blacks, and this finding "is similar to other studies of angiographic disease prevalence rates between the races, and it supports the hypothesis that the lower CCSs parallel the lower angiographic prevalence of disease in blacks."
The researchers say, however, that many questions still remain. Larger prospective studies of the natural history and progression of subclinical atherosclerosis in different ethnic groups - such as the Multi-Ethnic Study of Atherosclerosis (MESA) - "will provide more definitive answers to some of these questions." One of the aims of MESA, as reported by heartwire, is to observe any differences in how heart disease develops in different racial groups.
