A new study shows pulmonary arterial hypertension when treated with bosentan (Tracleer) can change the course of the disease. PAH or pulmonary arterial hypertension is marked by the narrowing of the arteries in the lungs, causing the right ventricle of the heart to work harder to pump blood into the lungs.

Hyponatremia, or low blood sodium has been a known indication for advanced left heart failure, but a new study by researchers from the University of Pennsylvania, now connect it with right heart failure in patients who have PAH.  Also people with chronically high blood pressure in the blood vessels of the lungs and a low serum sodium level have a high mortality rate.

"This is the first study to show the powerful prognostic significance of low blood sodium in these patients," said lead author Dr. Paul R. Forfia, medical director of the Pulmonary Hypertension Program at the Hospital of the University of Pennsylvania. Published in American Journal of Respiratory and Critical Care Medicine, the findings claim that serum sodium, a routine lab measurement could now prove to be an important indicator in PAH patients.

The study showed that untreated patients showed deterioration in hemodynamic and other clinical features. This suggested that PAH progresses more rapidly than expected. Previous trials found benefits similar to bosentan but included few patients with early disease.

"If we wait to diagnose and treat patients until the later stages of the disease, at that point our chances of having successful responses to therapy and successful outcomes are markedly diminished," said Lewis J. Rubin, M.D. at the University of California San Diego, co-author on the paper.