Purinergic Signaling and the Postmenopausal Heart

This study investigates how the heart's chemical communication system — called purinergic signaling, which involves molecules like ATP that help regulate heart rhythm and function — works differently in postmenopausal women compared to other patients during open-heart surgery. Menopause causes hormonal changes that may affect how the heart copes with the stress of surgery, and this study aims to understand those differences. **You may be eligible if...** - You are scheduled for open-heart surgery that requires a heart-lung bypass machine (cardiopulmonary bypass) **You may NOT be eligible if...** - You refuse to participate - Your surgery is an emergency - You have a pre-existing heart block or atrial fibrillation (irregular heart rhythm) - You are having redo heart surgery - You are currently taking estrogen or any hormone replacement therapy - You have a history of chronic heart failure or major kidney disease Talk to your doctor to see if this trial is right for you.