A top American cardiologist has highlighted three important warning signs of a heart attack, saying that one of them may even go unnoticed and is more common in women. According to Dr Chris Kelly, chair of cardiology at UNC Rex Hospital in North Carolina, the signs are usually less common and more frequently associated with other illnesses.

Also known as a myocardial infarction, a heart attack occurs when blood flow to your heart gets severely reduced or blocked, leading to the heart muscle dying due to lack of oxygen. Doctors usually blame it on the buildup of plaque in the coronary arteries that rupture and form a blood clot, obstructing blood flow.

"The first sign of a possible heart attack is the most classic sign of them all, and that's chest pain. Sometimes it is described as chest pressure, tightness or fullness, or just aching,” Dr Kelly told his followers on Instagram. “If you're having anything in your chest that feels uncomfortable and it's not getting better after a few minutes, especially if it's also going into your shoulders, arms, or jaw, that's a really concerning sign, and you need to get to an emergency room right away,” he added.

According to Dr Kelly, if you have been facing frequent breathlessness, it could also be an indicator of an impending heart attack. “If you're not really doing anything but you feel like you've just run a mile, it could be a sign that your heart is struggling to function properly and fluid is backing up into your lungs.”

“So, if you get sudden-onset shortness of breath, get straight to an emergency room for further evaluation,” he said.

Dr Kelly says constant stomachache or abdominal pain followed by nausea can easily be a possible heart attack symptom which you may mistake for indigestion. He adds, “Now, a lot of things can cause that, but if you have risk factors for heart disease and you're over the age of 50, and you have sudden onset belly pain and nausea, and you just don't feel right, that actually could be a sign of a heart attack – and this is particularly common in women – so if you experience that and it doesn't get better within a few minutes, get straight to the emergency room."

For many people, apart from the pain in their chest, there are a few other symptoms that need immediate attention. It can cause discomfort, squeezing, or heaviness and may start in your chest and spread to other areas like your left arm (or both arms), shoulder, neck, jaw, back, or down toward your waist. A few symptoms include: