Before genetic counseling related to cardiomyopathy, how can I express that I don't want all relatives to know my test information?

At the start of counseling, you can clearly state which information you are willing to share and which you prefer to keep confidential for now, and ask about the institution's privacy protections and family communication procedures. Ask the professional to distinguish between your personal test results and general information that may need to be explained to relatives, and discuss acceptable communication methods. Decisions about whether to undergo testing, whom to invite to counseling, and how to share materials should be made after fully understanding the situation.