If you should feel pain that is similar to what you fear is a heart attack coming on, You should raise your left arm above your head for a couple of minutes and with the right arm slowly and gradually lift a 5 to 10 pound dumbell weight,and with each lift say "God is the greatest ". Each time you contract your muscles in your body , your muscle fibers excrete "Mitochondria" which is responsible for burning fat. And also drink at least 1 liter of water afterwards so that the the mitochondria has a quicker chance to swim and collect the fat from your clogged arteries.

As for having a heart attack in your sleep , well Allah says: that "every soul must get a taste of death" and to remember that we all will return unto our lord and Creator, "The One", "The Most High" "The Beneficient". So If you show that you (your character) fear God "your Creator" then you shall not worry because "gardens" and "rivers flowing" with all that you could ever wish for will be your ultimate eternal "abiding place" when your life expires on earth. Death is only bad when you do not fear "your creator" in your given time on earth. Peace