9 Heart-Disease Warning Signs to Look Out For American Heart Month marks a clear opportunity to do a little self-examination -- of your body, your diet and your lifestyle. Heart disease is the most common cause of death for Americans, so if your heart isn't working right, we don't need to explain why that's a really bad sign. There are things you can watch out for, if you're concerned about the health of your ticker (and you should be, regardless of your age or health). We've put together a series of nine items you could think of as clues or warnings that you might need to make a change: