Breast arterial calcium (BAC) has been suggested as a marker and predictor of cardiovascular risk and coronary artery disease (CAD). However, an association between BAC and these cardiovascular end points has not been fully elucidated in patients undergoing cardiac catheterization. Consecutive patients undergoing mammography and cardiac catheterization within a 36-month period were retrospectively evaluated through chart review. Cardiac catheterization films and mammograms from 94 patients were independently reviewed for the presence of CAD and BAC, respectively. Cardiovascular risk factors, history of revascularization, and history of myocardial infarction were compared between women with and without BAC. BAC was more prevalent in older women (mean age 69 ± 10 vs 63 ± 11 years, p = 0.02). Aside from an inverse correlation with smoking, there was no difference in the presence of CAD or cardiovascular risk factors between patients with and without BAC. Patients with BAC had a lesser history of acute myocardial infarction (21% vs 41%, p <0.05) and were less likely to undergo revascularization (23% vs 43%, p <0.05). In conclusion, BAC was not positively associated with cardiovascular risk factors, documented CAD, or acute cardiovascular events, suggesting that the presence of BAC as determined by mammography is not a useful predictor of CAD in intermediate- to high-risk patients.
Previous studies have attempted to document a relation between breast arterial calcium (BAC) and coronary artery disease (CAD) using the presence of coronary calcium as a marker of CAD, or alternatively have explored the potential association between BAC and cardiovascular events and disease through questionnaires assessing patient history of abnormal angiographic findings, coronary heart disease, previous myocardial infarction (MI), and angina pectoris. Few previous studies have examined the utility of BAC for prediction of CAD in conjunction with independent review of catheterization films, with 1 finding no correlation between BAC and documented CAD, whereas others have reported a significant association. To further elucidate the usefulness of BAC to predict CAD and cardiovascular events, we undertook a study in women who had undergone mammography and cardiac catheterization by performing independent chart review and review of catheterization films to characterize associations between BAC and CAD, MI, and/or coronary revascularization events.
Methods
Patient charts from consecutive women having undergone mammography and cardiac catheterization within a 36-month period were identified from the cardiology database at our institution and reviewed retrospectively for baseline characteristics (age, cardiovascular risk factors, co-morbidities) and clinical events of MI, coronary angioplasty, stent placement, or coronary artery bypass grafting. Patients were referred for cardiac catheterization based on positive stress test results and/or anginal symptoms. Selective coronary angiography was performed for evaluation of known or suspected CAD in all cases. Cardiac catheterization films were retrospectively reviewed in blinded fashion by an experienced interventional cardiologist and evaluated for CAD, which was defined as ≥50% luminal narrowing of a major epicardial and/or branch coronary artery, or any degree of coronary stenosis. A separate analysis was performed for coronary calcium from angiographic films. Mammograms from 1998 to 2003 were digitized (R2 Technology, Hologic, Co., Sunnyvale, California) and reanalyzed for breast arterial microcalcification on state-of-the-art equipment (Senographe 2000D, GE Healthcare, United Kingdom) with high sensitivity for any degree of calcium by an experienced board-certified radiologist who was blinded to the results of patients’ cardiac catheterization results and history. Ethical approval was obtained from William Beaumont Hospital’s (Royal Oak, Michigan) ethics committee (Human Investigational Committee Number 2004-066). The conduct of this study was consistent with the principles of the Declaration of Helsinki.
Patient charts were reviewed for a history of the following atherosclerotic risk factors: hypercholesterolemia (defined as patient history of hypercholesterolemia and/or use of cholesterol-lowering medication), current or previous (≥6 months) smoking, hypertension (defined as patient history of hypertension and/or use of antihypertensive medication), and diabetes mellitus (defined as patient history of diabetes and/or use of oral hypoglycemic medication or insulin). A history of hormone replacement therapy, chronic kidney disease (estimated glomerular filtration rate <30 ml/min by the Cockcroft-Gault method ), and a patient’s body mass index were recorded, along with a history of MI (defined as positive cardiac enzyme levels or typical electrocardiographic changes in the setting of symptoms consistent with cardiac ischemia) and revascularization events including angioplasty, stenting, or coronary artery bypass grafting.
We compared data from patients with and without BAC for baseline demographics, cardiac risk factors, CAD, MI, and revascularization events. Categorical variables were reported as counts and percent frequencies and were examined using Pearson chi-square test where appropriate (expected frequency >5) or alternatively using Fisher’s exact test. Continuous variables were examined using Wilcoxon rank-sum tests. All continuous variables are presented as means ± SDs. All analyses used SAS 9.2 for Windows (SAS Institute, Cary, North Carolina).
Results
Complete datasets were available from 94 patients; the mean time between mammography and catheterization was 15.7 ± 10.5 months. Fifty-seven patients had positive results for BAC and 37 had negative results ( Table 1 ). BAC was more prevalent in older women (p = 0.02). There was no difference in the history of hypertension, diabetes, or hypercholesterolemia between BAC-positive and BAC-negative groups. Furthermore, there was no significant difference in angiographic evidence of coronary artery stenosis, defined as ≥50% (clinically significant CAD) or >0% stenosis, in patients with BAC compared to those without. Presence of coronary calcium was no greater in patients with BAC compared to those without. Patients with BAC were not more likely to use hormone replacement therapy or to have chronic kidney disease compared to those without BAC. Similar to findings in previous studies, there was a negative association between BAC and current or previous smoking (p = 0.015). With regard to cardiovascular events and revascularization, patients with BAC had a lesser incidence of MI (p <0.05; Figure 1 ) and were less likely to undergo revascularization procedures including coronary angioplasty, stenting, or coronary artery bypass grafting (p <0.05).
| Parameter | Total (n = 94) | BAC | p Value | |
|---|---|---|---|---|
| Yes | No | |||
| (n = 57) | (n = 37) | |||
| Age (years) | 66.7 ± 10.5 | 68.9 ± 9.7 | 63.2 ± 10.9 | 0.021 |
| Body mass index (kg/m 2 ) | 28.0 ± 5.9 | 28.1 ± 5.5 | 27.9 ± 6.6 | 0.71 |
| History of | ||||
| Hypertension | 68 (72%) | 41 (72%) | 27 (73%) | 0.91 |
| Hypercholesterolemia | 50 (53%) | 30 (53%) | 20 (54%) | 0.89 |
| Current or previous smoking | 23 (24%) | 9 (16%) | 14 (38%) | 0.015 |
| Diabetes mellitus | 20 (21%) | 13 (23%) | 7 (19%) | 0.65 |
| Chronic kidney disease | 9 (10%) | 5 (9%) | 4 (11%) | 0.73 |
| Hormone replacement therapy | 36 (38%) | 19 (33%) | 17 (46%) | 0.22 |
| Coronary artery stenosis ≥50% | 53 (56%) | 32 (56%) | 21 (57%) | 0.95 |
| Coronary artery stenosis >0% | 63 (67%) | 39 (68%) | 24 (65%) | 0.72 |
| Coronary calcium | 47 (51%) | 28 (50%) | 19 (53%) | 0.79 |
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