RecruitingClinical trialPurinergic Signaling and the Postmenopausal HeartThere is an increased risk of diastolic heart failure in post menopausal women. Estrogen plays a positive role in regulating molecular pathways in heart remodeling. Such pathways may work through purinergic signaling and its downstream effects on the heart's mitochondrial metabolism and angiogenic response to stress. Loss of estrogen functionality in post menopausal women may account for the increased risk of diastolic heart failure. The investigators will explore said pathways using cardiac tissue obtained from patients undergoing cardiac surgery.