Breast Arterial Calcification

Circulation. 2017;135:499–501. DOI: 10.1161/CIRCULATIONAHA.116.025277 February 7, 2017 499 Tamar S. Polonsky, MD, MSCI Philip Greenland, MD A large proportion of cardiovascular events occur among women whose 10year estimated atherosclerotic cardiovascular disease risk is <7.5%, and thus guidelines would not routinely recommend statins for such patients before their events.1 Additional strategies beyond the measurement of traditional risk factors are therefore needed to identify women who might benefit from medical therapy, based on unexpected higher risk. Coronary artery calcium (CAC) seen on a noncontrast chest computed tomogram is the most potent marker of subclinical cardiovascular disease (CVD), and has been shown to enhance risk prediction in women.1 However, CAC testing is usually not covered by insurance companies, limiting its widespread use as a screening tool for subclinical CVD. Given that millions of women undergo mammograms each year, there has been growing interest in whether the presence of breast arterial calcification (BAC), which is easily detected on a standard mammogram, could help inform cardiovascular risk assessment. Unlike CAC, which represents calcification in the intima, BAC is found along the circumference of the media giving it a tram-track appearance when the burden is severe (Figure). Some studies of BAC described it simply as present versus absent, whereas others attempted to use a semiquantitative assessment based on the density and extent of calcium in each artery, and the number of arteries involved.2 BAC prevalence varies widely depending on the population’s age and comorbidities, ranging from 10% to 12% in healthier population-based cohort studies, to 60% to 70% among women >70 years of age or with chronic kidney disease.2 BAC is thought to develop primarily through pathways related to mineral metabolism and bone formation, but there may be a role for inflammation as well. Although traditional cardiovascular risk factors such as age, hypertension, and diabetes mellitus are associated with BAC presence, BAC has an inverse association with smoking, which is consistent with other studies of medial calcification.2 Reproductive factors such as parity and breastfeeding are also associated with BAC.2 Several observational studies have demonstrated that the presence of BAC provides important prognostic information related to cardiovascular risk. In a systematic review of the data related to BAC and CVD, Hendricks et al2 cited studies that used either hospital admission data or municipal death records to examine the association of BAC and CVD events. The authors reported a hazard ratio of 1.32 (95% confidence interval [CI], 1.08–1.60) for incident coronary heart disease, 1.44 (95% CI, 1.02–2.05) for coronary heart disease mortality, 1.29 (95% CI, 1.01–1.66) for CVD mortality, and 1.52 (95% CI, 1.18–1.98) for heart failure.2 Exactly why BAC signifies an increased cardiovascular risk is not well understood. It may simply represent long-term exposure to known cardiovascular risk factors. BAC has also been shown to be indicative of medial calcification in other vascular beds. Medial calcification is known to increase vascular stiffness and likely explains the association of BAC with heart failure, in addition to coronary heart disease and stroke. Studies of women with chronic kidney disease are particularly helpful, given Breast Arterial Calcification