"High blood pressure in the arteries that supply the lungs is called pulmonary hypertension (PHT). The blood pressure measured by cuff on your arm isn't directly related to the pressure in your lungs. The blood vessels that supply the lungs constrict and their walls thicken, so they can't carry as much blood. As in a kinked garden hose, pressure builds up and backs up. The heart works harder, trying to force the blood through. If the pressure is high enough, eventually the heart can't keep up, and less blood can circulate through the lungs to pick up oxygen. Patients then become tired, dizzy and short of breath.
If a pre-existing disease triggered the PHT, doctors call it secondary PHT. That's because it's secondary to another problem, such as a heart or lung disorder. Congenital heart disease can cause PHT.
It's important to repair congenital heart problems (when possible) before permanent pulmonary hypertensive changes develop. Intracardiac left-to-right shunts (such as a ventricular or atrial septal defect, a hole in the wall between the two ventricles or atria) can cause too much blood flow through the lungs. This situation is sometimes called Eisenmenger complex. Heart valve conditions, such as mitral stenosis (a narrowing of the mitral valve), can also cause PHT. Fixing the valve usually reverses the PHT."How do you treat PHT?
"Once PHT has been diagnosed, often more medical therapy is needed. You'll require regular follow-up with a cardiologist or pulmonologist trained in caring for patients with PHT.
As long as the underlying disease exists, it will keep causing PHT. Once you have PHT (especially if you've had it for some time), curing the disease that caused it may not make the PHT go away. In that case, the PHT will usually need separate treatment. It's not possible here to tell all you need to know about treating PHT. This is a serious illness, but treatment is available. You may be treated with oxygen, agents to help your heart pump better, diuretics, anticoagulants (blood thinners), and medications to lower your PHT. Sometimes lung transplants also are done".
Read more here where this article was lifted.
Why am I posting about PHT? For my own education only:-)