They can be much more subtle and sometimes begin with warning pains in the chest or other symptoms days or even weeks before the actual attack. Typically, however, if you're having a heart attack, the severe pain lasts for about 15-20 minutes and then can linger for some time after.

A heart attack does not always have obvious symptoms, such as pain in your chest, shortness of breath and cold sweats. In fact, a heart attack can actually happen without a person knowing it. It is called a silent heart attack, or medically referred to as silent ischemia or lack of oxygen to the heart muscle.

An electrocardiogram is an important test in suspected heart attacks. It should be done within 10 minutes of being admitted to hospital. An ECG measures the electrical activity of your heart. Every time your heart beats, it produces tiny electrical impulses.