New research now indicates that women who have a mutated form of the BRCA 1 or BRCA 2 gene, who are already at risk for hereditary breast cancer, may also be at greater risk for heart disease. Details here: Breast Cancer and Heart Disease

I think because some types of breast cancer are rather common after menopause, they may be linked to heart disease as the decrease of female hormones that occurs after menopause increases the susceptibility to heart disease in most women.