Poor survival in pulmonary hypertension is known to be associated with unfavorable hemodynamic variables, including elevated right atrial pressure, elevated mean pulmonary artery pressure, and low cardiac index. However, the effect of plasma volume on outcome has not been evaluated. Our goal was to study the spectrum of plasma volume distribution in patients with pulmonary hypertension and to determine whether plasma volume could provide any prognostic insight in these patients. Our pilot study comprised 11 patients (aged 46 +/- 16 years; 7 women) who were undergoing pulmonary artery catheterization before vasodilator therapy. In all 11 patients, plasma volume was measured, with use of < 25 microCi 131I-radioiodinated serum albumin. Patient follow-up averaged 19 months. There were 2 deaths. The 2 patients who died had the highest right atrial pressures in the group: > or = 17 mmHg. Those 2 patients also had 2 of the 3 highest plasma volumes at > or = 8.4%. None of the patients underwent lung transplantation. The propensity for elevated plasma volume and right atrial pressure in patients who died in this pilot study is consistent with the advanced right-sided heart failure that occurs in the terminal stages of pulmonary hypertension. Elevated plasma volume may be a useful prognosticator; further studies are needed to assess whether manipulation of plasma volume affects prognosis.