Stay indoors when the heat index is higher than the low 90's. Beta blockers and other medications reduce your heat tolerance. Having a cardiovascular condition in itself reduces your tolerance for temperature extremes.

Exactly the same as ordinary folk...especially folk over 65:
Loose dark colored cloths to absorb uv including broad brim hats. Drink at least 2 quarts COOL water daily. Do not over exert ones self. Seak and find shade whenever possible ESPECIALLY if showing or feeling classic signs of too much heat LEARN SIGNS OF HEAT STROKE by searching reputable health web sites.
Avoid being alone outside...have friend or companion with you in risk likely situations.

Live life to the fullest bit responsibly

Praise God
Pray to the God of the Bible

Go swimming
Take a shower
Take a bath
Eat some watermelon
Go to a cooling center
Go to a business with AC
USE A FAN (or several)

Definitely hydrate and stay cool in AC.

I agree. Stay in a cool place with a good water supply. Chill out, Dudes!