Again,
I cannot recall anything in all my years here in the USA that specifically called out cold weather as being a worry for patients with heart issues. Other than, "be careful shoveling snow off the sidewalk, you might get a heart attack. especially if you are older..."
Perhaps it's like everything else these days being called out to be worried about... I'd like to NOT believe it is because of something else, some conspiracy, some side effect of something else.
Oh, i just thought of something else that did get called out several times. Cold air hitting the lungs of people with lung conditions.., maybe regarding ashma ?