What is pulmonary hypertension?

Pulmonary hypertension is defined as a high average blood pressure in the pulmonary artery that connects the right and left sides of the heart. The pulmonary artery starts in the right heart, interfaces with the lungs, and connects to the left heart.

If the average blood pressure is > 25 in the pulmonary artery at rest, this defines pulmonary hypertension. The diagnosis can only be made cardiac catheterization. Other tests such as an echocardiogram can suggest elevated pressures, but only a cardiac catheterization can confirm the diagnosis.

Only three things contribute to the pressure in the pulmonary artery:

1. Blood flow (cardiac output)
2. Resistance to flow (pulmonary vascular resistance)
3. Left sided pressure (left atrial pressure)

Although pulmonary artery pressures are measured on the right side of the heart and pulmonary hypertension is defined by high pressures on the right side, because the heart is a circuit, high left sided pressures can "back up" into the right side causing the pressures to increase.

The vast majority of cases in the United States are because the left sided pressures are high from left heart disease. For example, narrow heart valves, leaky heart valves, stiff heart muscles, heart attacks; decreased left heart pump function can all make the left sided pressures increase.

Although pulmonary hypertension makes one think that the primary problem is a lung problem, in fact the majority of cases turn out that the predominant contributor to high pressures in the pulmonary artery is really heart dysfunction. The description of pulmonary hypertension is merely geographical, i.e. the pulmonary artery is located in the chest between the right and left side of the heart.

Similar confusing terms exist in medicine: superficial femoral vein and diabetes insipidus. The superficial femoral vein is really a DEEP vein. Likewise, diabetes insipidus has nothing to do with diabetes, but rather the kidney's ability to handle salt and water.

Pulmonary hypertension is a serious disease. The right diagnosis needs to be made by the right test. 

While general hypertension is a concept most people are well aware of, pulmonary hypertension is less familiar. Armin Meyer, M.D., a physician with GHS’ Pulmonary Hypertension Program, offers this explanation: “Wherever there’s blood flow, there has to be pressure to make it flow. Hypertension is when that pressure is elevated because of resistance in the body’s arteries.” He continued, “After blood goes through the body, the heart pushes it through the lungs to pick up more oxygen. When those arteries in the lungs are constricted and the pressure builds, it’s called pulmonary hypertension.”

Although pulmonary hypertension was first identified more than 100 years ago, only with the rise of echocardiography -- a non-invasive technology that provides information regarding heart function and lung pressures -- has diagnosis become more feasible. “In the body, we can measure pressure with a blood pressure cuff,” Dr. Meyer said. “But we can’t put a blood pressure cuff around our chest.”

While the condition is not common, the infrequency of diagnosis also stems from the difficulty – even with new technology – of pinpointing pulmonary hypertension as the cause of the patient’s problems. “The symptoms are quite nonspecific,” Dr. Meyer commented. “Shortness of breath, a bit of a cough, a bit of chest pressure, and then when you start having fainting spells and get a lot of swelling around the ankles and feet, that’s when you’re really in the late stages.”

Although it can be related to other conditions such as lupus, scleroderma, congenital heart disease, HIV and liver problems, the development of PAH is not always restricted to patients with those conditions.

Treatments now range from pills to nebulized medicines to IV treatments and may soon include gene therapy and drugs related to cancer therapy.

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