i might just be abnormally sensitive but when i feel like my blood is doing something weird i start moving the body part around, massaging it, changing its orientation, and so on.

the thing about a heart attack that can kill you is the pressure, so for sure laying down and breathing slowly will help.

honestly, it seems to me that you have to be half anaesthetised to have these things happen 'suddenly'. either that or a loose clod of something suddenly jams up a valve somewhere. having that kind of congestion would hurt like hell before even the chunk falls off and clogs something i would think.

by the way, main cause of it is cholesterols synthesised out of excess blood sugar.