There's another form in the lungs that's also very dangerous.
A longtime athlete and physical education teacher explains how it impacts his life and the new medication helping him get back to his old self.
"You were in really good shape, and now all of a sudden, you're not," John Smith of Ambler, Pa., notes.
After a lifetime of sports and teaching physical education, John was blindsided 16 years ago to learn he had Pulmonary Arterial Hypertension, or PAH.
It appeared suddenly after a heart defect was corrected.
"Both sides of my heart were enlarged. After they fixed the bridge, only one side went down," he remembers.
Dr. Paul Forfia, a Temple Health heart failure specialist, says in PAH, very small blood vessels in the lungs become narrowed.
"That puts a lot of resistance back onto the right side of the heart, and a lot of resistance for the passage of blood flow from the right heart through the lungs," Dr. Forfia says.
Normal lung blood pressures balloon over time.
"It could be 10 or 15 times higher than it should be, that will cause the right side of the heart to become dysfunctional," he says.
Dr. Forfia says PAH is three to four times more common in women, usually between the ages of 30 and 60, and more common in African American and Hispanic women.
Hallmark signs include increasing shortness of breath even with light activities; fatigue; edema, or swelling; and dizziness and fainting spells.
It gets worse over time, so aggressive treatment is a must.
"Seek out a Center of Comprehensive Care where there's a dedicated program," Dr. Forfia says.
Temple Health has that certification.
A combination of drugs has been used to control PAH.
But a new drug, Winrevair, could change the landscape.
"It's the first one that can actually fix the heart," John says, adding, "I actually went and ran, which is amazing. I haven't run in 10 years."
"The outlook for patients with PAH is very, very different and much more favorable now than it was two decades ago, or even one decade ago," Dr. Forfia says.
"I have twp young kids, and I want to be around for them. That's my goal," John says.