Lightheadedness or fainting during a heart attack can be due to a drop in blood pressure as the heart struggles to pump blood efficiently. A sudden decrease in blood pressure can cause a temporary reduction in blood flow to the brain, resulting in feelings of dizziness, weakness, or even fainting.
Fainting or near-fainting episodes should always be taken seriously and warrant immediate medical attention. If you experience lightheadedness or fainting, particularly when accompanied by other heart attack symptoms, seek help right away.