The presence of one or more first-degree relatives with a history of premature coronary heart disease (CHD) is an independent risk factor for CHD. Nasir and colleagues investigated the strength of association between coronary artery calcification, as measured by electron beam tomography, and a sibling or parental history of premature CHD.
A consecutive sample of physician-referred patients presenting to one electron beam tomography facility between July 1999 and June 2003 were evaluated for inclusion in the study. Patients were excluded if they reported a history of previous myocardial infarction, coronary or peripheral arterial revascularization, or current symptoms of chest discomfort. The study group consisted of 8,549 patients; 69 percent were men and the average age was 52 years.
In addition to self-reporting sibling and parental histories of premature coronary heart disease (defined in this study as a fatal or non-fatal myocardial infarction and/or coronary revascularization before 55 years of age), the study population provided information on demographics, medications, physical activity, and other coronary risk factors such as tobacco use, hyperlipidemia, and diabetes. The amount of coronary artery plaque noted on electron beam tomography screening was measured according to a standardized coronary artery calcification score, which was subsequently classified into one of five categories.
Multivariable logistic regression was used to analyze the strength of association between self-reported family history and categories of calcification scores. There was no significant association between the calcification score and a positive family history in a first-degree relative 55 years or older. However, increasing calcification scores were strongly associated with parental and sibling histories of premature CHD, with the sibling history being more significant. The authors conclude that these data support recommendations to include a family history of premature CHD in the coronary risk assessment for subclinical atherosclerosis. In addition, they suggest paying particular attention to the sibling family history because it seems to confer a higher level of risk than the parental history. Key limitations of this study include its reliance on self-reporting of family histories (as opposed to chart reviews) and its physician-referred rather than randomly selected population.
editor’s note: This study’s conclusion begs the question of whether coronary artery calcification measured by electron beam tomography is a valid marker of subclinical atherosclerosis and, as such, correlates with patient-oriented outcomes such as cardiovascular and all-cause mortality. A recent prospective study1 of 5,635 adults between 30 and 76 years of age who underwent electron beam tomography screening and were then followed for an average of three years for the occurrence of death, myocardial infarction, or coronary revascularization determined that the presence of coronary artery calcifications at baseline significantly increased the relative risk for any of these events (RR = 10.5 in men, 2.6 in women) compared with traditional coronary risk factors such as diabetes (RR = 1.98 in men, no association in women) and tobacco use (RR = 1.4 in men, no association in women). In an editorial2 in the same issue, O’Donnell comments that although the family history is sometimes limited by inaccurate reporting, it remains a vastly underused tool for estimating hereditary coronary risk.—k.l.