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It is caused by the failure to close the lower esophageal sphincter (LES) at the top of the stomach. This allows stomach contents, now mixed with gastric acid, to return into the esophagus. This return is also known as reflux, and may progress to gastroesophageal reflux disease (GERD) if it occurs frequently. Peristalsis, the rhythmic wave of muscular contraction in the esophagus, normally moves food down and past the LES.
If heartburn occurs when lying down, raising the head with pillows or sitting up frequently provides relief. Avoidance of certain foods shortly before bedtime is frequently advised to avoid future attacks.
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