Heart and the Breast

Although heart disease has been considered to be a disease that mainly affects men, data from the American Heart Association shows that  women generally have worse outcomes with heart artery disease. In particular women who are not considered high risk for heart disease , based on current risk assessment tools, will not be advised to take drug cholesterol medications ( statins) .  However, a large proportion of these women do develop heart attacks . How then can one identify those in this cohort of women who will be at risk of heart disease ?

Calcium and the heart

There is a large body of evidence that the presence of calcium deposits in the heart arteries  (coronary artery calcium or CAC) is a powerful indicator of increased risk for heart disease. The use of a computed tomogram (CT)  scan of the heart to detect the presence of calcium deposits in heart arteries has been validated as a useful tool to identify high risk individuals .  However, it is not routinely done in many countries as it is not usually covered by insurance.  The latest 2015 Dietary Guidelines Advisory Committee scientific report commissioned by the US government advises against the routine consumption of calcium supplements, as there is evidence that the consumption of calcium supplements is associated with an increased risk of heart attacks.

Mammograms and calcification

Most women who are of the age at which they are at risk of getting heart disease are also at the age where they undergo mammograms ( X-ray examinations of the breasts ).  As almost every post-menopausal woman will undergo a mammogram at some point in time, researchers are using the presence of breast arterial calcification (BAC) to determine whether it correlates with a higher likelihood of finding heart artery disease.

When the BAC is severe, it appears as a tram-track appearance along the breast arterial circulation. The presence of  BAC can be as high as  60% to 70% in women more than 70 years of age or in women with chronic kidney disease. In a study on women with chronic kidney disease by Duhn published in 2011 in the Clinical Journal of the American Society of  Nephrology Studies , 63% of the women with kidney failure had BAC compared to only  17% of the women without kidney failure.

Although risk factors for heart disease such as age, high blood pressure and diabetes mellitus are also risk factors for BAC, unlike heart disease smoking has an inverse relationship  with smoking. Observational studies on BAC have shown a correlation between the presence of BAC with an increased incidence of heart artery disease, increased death from heart artery disease and heart failure. The exact mechanism for the correlation between BAC and increased adverse heart events is not clearly understood. However, it has been demonstrated that the presence of BAC is associated with the presence of calcification in other arteries as well. This calcification in other arteries may provide an explanation  why the presence of BAC is associated with heart artery disease, heart failure and stroke.

Breast calcification and heart disease

A 2016 Journal of the American College of Cardiology Cardiovascular Imaging publication by  Margolies on mammography and screening for heart artery disease has provided evidence of the association between BAC and CAC.  In middle aged women ( 39 to 59 years of age)  with BAC, 52% had CAC (13% being moderate to severe) .  For those who were older  (60 to 69 years of age)  with BAC, 67% had CAC (31% being moderate to severe) .

Based on the  10-year estimated risk of developing heart artery disease, among lower-risk women  (risk of <5%)  , the prevalence of BAC was 23%. For those at higher risk (risk > 7.5%)  ,  60% had BAC. After statistical adjustment for variables, the study found that only the presence of moderate to severe BAC , age and high blood pressure remained significant predictors of the presence of CAC. The authors surmised that the presence of moderate or  severe BAC may increase the risk of heart artery disease beyond traditional risk factors for heart disease.   The study showed a positive predictive value of BAC for CAC of 53%, among women aged 39 to 59 years, 67% among women aged 60 to 69 years and 86% among women aged ≥70 years. In other words, the presence of BAC in older women ,who are likely to go for routine breast screening , was associated with a high likelihood of CAC.

Breast and heart screening

While screening the breast together with heart assessment may provide information beyond conventional risk factors, there is no standard format or guideline on the reporting format for BAC. Usually, it is not reported as the focus of the mammogram report  has always been on the detection of cancer of the breast.

Hence for women going for mammograms , the following tips may be helpful. First,  request that the absence or presence of calcification of the breast arteries to be included in the report . As BAC is not routinely reported in the mammogram report, patients may want to ask specifically for the inclusion of the presence of BAC if present .  Second,  presence of BAC denotes increased risk. Hence, if BAC is present, the patient should have a proper assessment of risk factors for heart disease and start on medication where deemed appropriate based on guidelines. Third,  assessment of CAC may be considered in moderate to severe BAC to determine the necessity of starting cholesterol lowering medication ( statin). Based on the American College of Cardiology/American Heart Association Guideline on the Assessment of Cardiovascular Risk if the CAC score is >300 or >75th percentile , the use of statin can be considered.  Fourth,  scanning of heart arteries may be considered in centres with the latest generation of CT scanners. The radiation dose of a conventional mammogram is about 0.4 millisieverts (msV – unit used to measure biological effect of radiation absorbed by body) . Newer types of mammograms of the heart such as tomosynthesis result in higher radiation doses. The latest CT scanners can produce 3 dimensional images of heart arteries including detailed visualisation of the calcium distribution in the heart arteries with radiation doses comparable to a standard mammogram and lower than a breast tomosynthesis.  Hence, where a centre has the newest scanners which are able to perform sub- milli-sievert CT scans of the heart arteries, you may wish to consider doing a full CT scan of the heart arteries  instead of a CAC study using older CT scanners , where the radiation dose may vary from 0.8-10.5 mSv ( based on publication in Archives of Internal Medicine  in 2009 by Kim ).  The reality is that women are more likely to die from heart disease than from breast cancer. Finally, breast cancer and heart disease share many common risk factors such as diabetes mellitus, smoking, physical inactivity, poor diet, and obesity. As such , active management of these risk factors can not only reduce the risk of heart disease but also the risk of breast cancer.  So the next time one goes for a mammogram, remember to get the maximum information as the breast can be a window for the heart.