Either arm can go numb during a heart attack, but it is more frequently the left arm. Numbness alone is not a sign of a heart attack and can be caused by a number of other conditions.
The most common signs of a heart attack are a painful or full feeling in the chest, shortness of breath, sweating, nausea, heart pain and pain in the jaw or teeth. Numbness in the arm can also manifest as pain. As many as a quarter of all heart attacks happen without any noticeable symptoms. If you experience the symptoms of a heart attack, contact emergency medical providers immediately.