Heartburn is usually associated with acid reflux. Yet, in a recently published study, researchers have discovered that in some people with frequent heartburn, the pain may also be caused by abnormalities in the esophagus.
"Acid is only one of the many causes of heartburn," said Dr. Ravi Mittal, Professor of Medicine at the University of California San Diego. "Acid does not explain heartburn in all patients."
Dr. Mittal and colleagues at the Veterans Affairs Medical Center in San Diego compared two diagnostic tests for heartburn in 93 patients. The first is called the Bernstein test, which involves the injection of acid into the esophagus to see if it produces heartburn symptoms. The other test is known as pH monitoring, where patients keep a diary of their heartburn symptoms—a symptoms index (SI)—over a 24-hour period while researchers monitor the acidity of their esophagus.
Because some patients had positive scores in one test and not the other, the researchers concluded that not all heartburn is caused by acid reflux.
"If acid was the major cause of spontaneous heartburn," the researchers write, "then all the patients with a positive SI should have a positive Bernstein test, which was not the case."
Instead, 58 of the 93 patients reported symptoms of heartburn over a 24-hour period, a positive SI. Of those 58 patients, only 35 had a positive Bernstein test score. In all 93 patients with chronic heartburn, only 49 had a positive Bernstein test during the study.
"For people with spontaneous heartburn who do not respond to a Bernstein test or acid infusion into the esophagus, the cause of heartburn is unlikely to be acid," said Dr. Mittal.
The researchers’ previous work on the causes of heartburn showed that distension of the esophagus—which they accomplished using a balloon in one study—produced symptoms of heartburn. The researchers explained that acid reflux might induce spontaneous heartburn through distention of the esophagus. They noted that the amount of distention is dependent on the volume of the reflux, which cannot be measured by pH monitoring.
"Some of these patients do not respond to acid infusion in the esophagus, suggesting that acid may be an innocent bystander and not the real cause of heartburn," said Dr. Mittal.
Another cause of heartburn may be what he termed "esophageal dysmotility," or a sustained esophageal contraction, which may or may not be triggered by the presence of acid in the esophagus.
The suggestion that something other than acid reflux causes heartburn is also supported by the fact that acid-suppressing medications, such as the proton pump inhibitors (PPI) and histamine receptor (H2) blockers, don’t work for everyone with heartburn. In fact, according to the study, only 65% of the patients who were on PPI’s reported dependable relief while taking the drugs.
"If a patient’s symptom of heartburn does not get better with proton pump inhibitors they should be carefully looked at for other abnormalities," concluded Dr. Mittal.
Dr. Mittal and his colleagues conducted their study at the Veteran’s Affairs Medical Center in San Diego. Their research is published in the March issue of the American Journal of Gastroenterology.