Low Blood Sodium Predicts Mortality in PAH Patients

FRIDAY, June 20 (HealthDay News) -- New research shows that people with chronically high blood pressure in the blood vessels of the lungs and low serum sodium levels have a very high mortality rate.

Low blood sodium -- called hyponatremia, or HN -- is a known indicator of advanced left heart failure, but the new study from the University of Pennsylvania researchers now connects it with right heart failure in patients with pulmonary arterial hypertension (PAH).

PAH, a syndrome marked by narrowing of the arteries in the lungs, causes the right ventricle of the heart to work harder to pump blood into the lungs for reoxygenation.

"This is the first study to show the powerful prognostic significance of low blood sodium in these patients," lead author Dr. Paul R. Forfia, a medical director of the Pulmonary Hypertension Program at the Hospital of the University of Pennsylvania, said in a prepared statement.

The findings, published in a June issue of American Journal of Respiratory and Critical Care Medicine, are important, because serum sodium is a routine lab measurement that could now be a vital indicator in PAH patients.

In a study of PAH patients, 85 percent in the group with HN died during a two-year follow-up period, compared with just 19 percent of the group without HN. The median survival time was less than nine months. All the patients with sodium concentration levels right around the low-end of the minimum recommended level died, while all those at least slightly above the minimum lived.

The two groups in the study were similar in age, sex, ethnicity and body mass index, but those with HN had significantly poorer kidney function and three times the likelihood of lower extremity edema along with echocardiogram indications of significantly worse right heart function. During two years of follow up, hospitalization for HN patients occurred twice as often, mostly for right heart failure.

"Thus, serum sodium has important implications regarding right heart dysfunction, clinical right heart failure, and patient outcome, and should not be overlooked in the clinical assessment of patients with PAH," Forfia said.

More information

The National Heart, Lung, and Blood Institute has more about pulmonary arterial hypertension.