Why am I getting chest pain?
Chest pain is a non-specific symptom; this means that many different kinds of medical problems can cause you to have pain in your chest. People have been taught to think that chest pain indicates a heart attack (meaning a sudden decrease in blood flow through the coronary arteries supplying the heart). While this is an important cause of chest pain and should not be overlooked, it is not the only one. Chest pain in people with pulmonary arterial hypertension is more often than not due to causes other than a heart attack. Another heart-related cause of chest pain, angina, may resemble a heart attack but usually resolves on its own. Angina is due to a temporary or incomplete blockage of a coronary artery, whereas a heart attack occurs when the blockage is complete and there has been permanent damage to the heart muscle. Chest pain is not necessarily heart-related it can be due to gastrointestinal causes, such as reflux disease (so-called "heartburn"), or pulmonary (lung) causes, including pneumonia, asthma, pulmonary emboli (blood clots in the lung), and pulmonary arterial hypertension.
The way chest pain feels may depend on its cause. For example, the pain that people feel from angina and heart attacks is typically described as a pressure sensation ("it feels like there is an elephant sitting on my chest"). In contrast, asthma, a problem of muscle spasms around the airways in the lungs, usually causes people to feel a sensation of "tightness" in their chest. Patients who describe their chest pain as more of a "burning" sensation would probably make their doctor think about acid reflux or heartburn.
In trying to determine the cause of your chest pain, you may want to think about how you would best describe what you are feeling, what seems to bring the pain on or make it better, how long it seems to last, and whether the sensation moves around at all or just stays in one place. This sort of information may help your doctor narrow down the list of possible causes and figure out why you are having pain.
What are the causes of chest pain that are more specific to PAH? One potential cause is that the increased pulmonary arterial pressures result in a "strain" on the muscle tissue of the right ventricle. To understand why this strain may cause discomfort, let's walk through the steps involved. PAH leads to narrower, stiffer pulmonary arteries, similar to blocked pipes in a plumbing system. The right ventricle pumps blood through the pulmonary arteries (see the relationship between the lungs and heart), and it has to work harder to squeeze a normal level of blood flow through narrowed "pipes". This is similar to the way it takes more effort to blow air through a partially blocked straw than through an open straw.
The muscle of the right ventricle, as it works harder, needs more oxygen and nutrients (supplied via the blood) to do its work. If the blood flow through the small arteries that supply the right ventricle ("coronary arteries") isn't sufficient to meet the ventricle's demands, the muscle tissue can begin to starve for oxygen and a painful sensation may result. With exertion, such as walking, climbing stairs, running, or even daily tasks such as making a bed, there is even greater oxygen demand and this may make existing pain worse or bring on new pain (if there was none at rest). This type of pain, related to the right ventricle, is usually felt in the middle or on the right side of the chest even though the heart is on the left.
The second mechanism that may result in chest pain in patients with pulmonary hypertension involves the fact that as pulmonary pressures rise, the blood vessels themselves actually expand or stretch. This is similar to the way in which a car or bicycle tire expands as you use a pump to raise the pressure inside. Stretching the walls of the pulmonary arteries causes signals to be sent to the brain, and you end up feeling this as pain. With exertion, the heart has to pump more blood and this leads to greater stretch of the pulmonary arteries, causing increased pain (or new pain if there was none at rest). Since you have pulmonary vessels on both sides of your chest, this pain is not restricted to left or right, and may occur anywhere across the chest.