Hyponatremia predicts right heart failure and poor survival in pulmonary arterial hypertension.

RATIONALE Hyponatremia is associated with decompensated heart failure and poor prognosis in patients with left ventricular systolic dysfunction. OBJECTIVES We sought to determine if hyponatremia is associated with right heart failure and worse prognosis in patients with pulmonary arterial hypertension (PAH). METHODS We prospectively followed 40 patients with PAH and examined the relationship between serum sodium and right heart function as well as survival. MEASUREMENTS AND MAIN RESULTS Subjects with hyponatremia (Na < or = 136 mEq/L) were more symptomatic (11/13 World Health Organization [WHO] class III/IV vs. 12/27 WHO class III/IV; P = 0.02), had more peripheral edema (69 vs. 26%; P = 0.009), and had higher hospitalization rates (85 vs. 41%; P = 0.009) than normonatremic subjects. Hyponatremic subjects had higher right atrial pressure (14 +/- 6 vs. 9 +/- 3 mm Hg; P < 0.001), lower stroke volume index (21 +/- 7 vs. 32 +/- 10 ml/m(2); P < 0.01), larger right ventricular:left ventricular area ratio (1.8 +/- 0.4 vs. 1.3 +/- 0.4; P < 0.001), and lower tricuspid annular plane systolic excursion (1.4 +/- 0.3 vs. 2.0 +/- 0.6 cm; P = 0.001), despite similar mean pulmonary artery pressure (49 +/- 10 vs. 47 +/- 12 mm Hg; P = 0.60). The 1- and 2-year survival estimates were 93% (95% confidence interval [CI], 73-98%) and 85% (95% CI, 65-94%), and 38% (95% CI, 14-63%) and 15% (95% CI, 2-39%) for normonatremic and hyponatremic subjects, respectively (log-rank chi(2) = 25.19, P < 0.001). The unadjusted risk of death (hazard ratio) in hyponatremic compared with normonatremic subjects was 10.16 (95% CI, 3.42-30.10, P < 0.001). Hyponatremia predicted outcome after adjusting for WHO class, diuretic use, as well as right atrial pressure and cardiac index. CONCLUSIONS Hyponatremia is strongly associated with right heart failure and poor survival in PAH.