A possible role for systemic hypoxia in the reactive component of pulmonary hypertension in heart failure.

BACKGROUND: The mechanisms underlying the reactive component of pulmonary hypertension (PH) in heart failure (HF) are unclear. We examined whether resting systemic oxygen levels are related to pulmonary hemodynamics in HF. METHODS AND RESULTS: Thirty-nine HF patients underwent right heart catheterization. Subsequently, patients were classified as having: 1) no PH (n = 12); 2) passive PH (n = 10); or 3) reactive PH (n = 17). Blood was drawn from the radial and pulmonary arteries for the determination of PaO(2), SaO(2), PvO(2), SvO(2), and vasoactive neurohormones. PaO(2) and PvO(2) were lower in reactive PH versus no PH and passive PH patients (65.3 ± 8.6 vs 78.3 ± 11.4 mm Hg and 74.5 ± 14.0 mm Hg; 29.2 ± 4.1 vs 36.2 ± 2.8 mm Hg and 33.4 ± 2.3 mm Hg; P < .05). SaO(2) and SvO(2) were lower in reactive PH versus no PH patients (93 ± 3% vs 96 ± 3%; 51 ± 11% vs 68 ± 4%; P < .05), but not different versus passive PH patients. The transpulmonary pressure gradient (TPG) was inversely related to PaO(2), PvO(2), SaO(2), and SvO(2) in the reactive PH patients only (r ≤ -0.557; P < .05). Similarly, plasma endothelin-1 correlated with PaO(2), PvO(2), SvO(2) (r ≤ -0.495), and TPG (r = 0.662; P < .05) in reactive PH patients only. CONCLUSIONS: Systemic hypoxia may play a role in the reactive component of PH in HF, potentially via a hypoxia-induced increase in endothelial release of the vasoconstrictor endothelin-1.