You've just eaten a big meal and feel a burning sensation in your chest. Heartburn, right? Probably, but there's a chance the chest pain is a warning sign of a heart attack.

Learning to tell the difference between heartburn and something more serious may be a matter of life and death. Here's what you need to know.

Heartburn isn't a disease. It's a symptom. You'll notice a burning sensation in your chest that may start in your upper abdomen and radiate all the way to your neck. Sometimes, stomach acid that backs up into the esophagus can leave a sour taste in your mouth — especially when you're lying down.

Normally, digestive acid is trapped in your stomach by the lower esophageal sphincter. This ring of muscle functions as a valve, which opens only as you swallow. But sometimes the valve relaxes or weakens, allowing stomach acid to flow back into your esophagus.

Pressure on the sphincter muscle from excess weight, overeating or lying down too soon after a meal may cause it to open slightly. Certain foods, as well as overindulgence in alcohol or caffeine, can relax the sphincter or increase production of stomach acid.

Frequent, persistent heartburn may indicate a more serious condition known as gastroesophageal reflux disease, or GERD — the chronic regurgitation of acid from your stomach into your lower esophagus. Long-term GERD can lead to Barrett's esophagus, a condition in which the color and composition of the cells lining the lower esophagus change because of repeated exposure to stomach acid. Barrett's esophagus is a risk factor for esophageal cancer.

Heartburn isn't the only digestive symptom that can cause chest pain. A muscle spasm in your esophagus may have the same effect. The pain of a gallbladder attack also can spread to your chest. You may notice nausea and an intense, steady ache in the upper middle or upper right abdomen — especially after a fatty meal. The pain may shift to your back or right shoulder.

It can be tough to tell what's causing chest pain. Be on the lookout for these heart-related warning signs:

• Sudden pressure, tightening, squeezing or crushing pain in the center of the chest that lasts more than a few minutes
• Pain spreading to the back, neck, jaw, shoulders or arms — especially the left arm
• Chest discomfort accompanied by shortness of breath, sweating, dizziness or nausea
• Pressure or tightness in the chest during physical activity or when you're under stress

Occasional bouts of heartburn are common. If you have persistent heartburn or take antacids daily, consult your doctor. Your heartburn may be a symptom of GERD.

If the heartburn seems worse or different from normal — especially if it occurs during physical activity or is accompanied by shortness of breath, sweating, dizziness, nausea or pain radiating into your shoulder and arm — seek emergency help. These signs and symptoms may indicate a heart attack. Proper diagnosis and prompt treatment may save your life.