There are two types of pain related to acid reflux:
1- The classical heartburn characteristic of acid reflux resulting from irritation of the esophageal surface lining.
2- The chest pain which is similar to that associated with coronary artery disease (coronary arteries are blood vessels supplying the heart with its essential requirements of oxygen and nutrients). This pain is due to spasm of the esophageal wall muscles.
It is evident that acid as a pain stimulus acts on surface receptors in case of heartburn. On the other hand it stimulates deeper receptors when causing chest pain and that suggests the pre-existence of breaks in the esophageal surface lining in the form of erosions or ulcers or an increase in the distance of spaces between cells lining the esophageal surface. Both of these mechanisms favor further acid diffusion deeper into the wall of the esophagus.
At times differentiation between esophageal and cardiac causes is very difficult.
In this situation the priority is for considering causes related to the heart first, simply because heart disease is serious and the chest pain may be a symptom of myocardial infarction which is an emergency condition following obstruction of coronary blood supply to the heart and resulting in impending death of a localized area of the musculture of the heart. That is why exclusion of heart disease is important to save life.
Needless to say that this rule applies especially to older patients with hypertension or diabetes or known heart disease.
Actually, both acid reflux and ischemic heart disease may co-exist as they are common health problems and that complicates the decision making process.
Out of all cases, having chest pain similar to typical heart attack, though their coronary arteries are normal, acid reflux contributes to 40-60% of the causes. This finding is documented by ambulatory esophageal acid monitoring.
To recall chest pain associated with heart disease (called angina) is a sense of fullness or tightness, dull aching or crushing in nature, in the middle of the chest. That pain may spread into the neck, shoulder or arm and is associated with difficulty in breathing and a cold sweat. On the other hand, chest pain of esophageal origin spreads more frequently to the back, is initiated by the same factors that trigger heartburn like fatty foods, lying down immediately after meals and is lasting for minutes or hours. Esophageal pain may also be associated with other symptoms of acid reflux such as heartburn, regurgitation and difficult swallowing. It is characteristically relieved with antacids. Diagnosis is confirmed with esophageal manometry which detects abnormalities in esophageal motility.
Chest pain of cardiac origin usually follows exertion and is relieved by rest. Nitrates and calcium channel blockers which are known to alleviate angina, aggravates pain of esophageal origin at the same time as they relaxes the lower esophageal sphincter.