Should a person with cardiomyopathy avoid the sun and heat?

Probably: Especially with excessive heat and direct sun, as your body chemistries can be affected if your fluid balance is not just right. Also, the heat can add stress to your heart, which you would also want ot avoid. Best to stick with your outdoor activity to cooler times of the day.

Sometimes: Exposure to the sun and heat are not necessarily harmful to a person with cardiomyopathy. But performing strenuous activities in the sun/heat can be dangerous as this will increase the stress on the heart and potentially cause serious symptoms. Taking a casual walk is probably ok.