Study Overview: This trial is exploring how carvedilol, a medication used to treat heart problems, can help prevent heart issues in patients with HER-2-positive breast cancer that has spread. HER-2 is a protein that can promote the growth of cancer cells. Carvedilol is a type of drug called a "beta-blocker," which is commonly used to manage heart conditions.

Study Design: Patients are divided into three groups. In one group, patients take carvedilol twice daily for 108 weeks. Another group does not take the drug and receives no other treatment intervention for the same period. The third group consists of patients already on certain heart medications, who are simply observed during this time. The study will last up to 108 weeks, with follow-up visits after completion.

• Participants will be taking part in the study for approximately 2 years.
• There may be side effects from carvedilol, such as dizziness or fatigue.
• Participants will be monitored and have regular check-ups during the study.

It is important to note that participants must meet specific health criteria to join the study, and they should not be taking certain medications. They will also need to agree to provide blood samples for further research.