Circulating big endothelin-1: an active role in pulmonary thromboendarterectomy?

BACKGROUND: Pulmonary thromboendarterectomy is an effective treatment for patients with chronic thromboembolic pulmonary hypertension. The early postoperative course may be associated with pulmonary vasoconstriction and profound systemic vasodilation. We investigated the potential involvement of endothelins in these hemodynamic alterations.
METHODS: Seventeen patients with chronic thromboembolic pulmonary hypertension (pulmonary vascular resistance, 1015 +/- 402 dyne x s x cm(-5) [mean +/- SD]) underwent pulmonary thromboendarterectomy with cardiopulmonary bypass and deep hypothermic circulatory arrest. Peripheral arterial blood samples were drawn before sternotomy, during cardiopulmonary bypass before and after deep hypothermic circulatory arrest, and 0, 8, 16, and 24 hours after surgery and were analyzed for big endothelin-1. The patients were divided into 2 groups according to whether their preoperative big endothelin-1 plasma level was above or below the cutoff point of 2.1 pg/mL, as determined by receiver operating characteristic curve analysis (group A, big endothelin-1 <2.1 pg/mL, n = 8; group B, big endothelin-1 > or =2.1 pg/mL, n = 9).
RESULTS: Patients in group B, with higher preoperative big endothelin-1 levels (3.2 +/- 1.0 pg/mL vs 1.5 +/- 0.4 pg/mL; P < .001), were poorer operative candidates (preoperative mean pulmonary artery pressure, 51.3 +/- 7.1 mm Hg vs 43.6 +/- 6.2 mm Hg; P = .006) and had a poorer outcome (mean pulmonary artery pressure 24 hours after surgery, 32.6 +/- 9.5 mm Hg vs 21.8 +/- 6.2 mm Hg; P < .001). Positive correlations were found between preoperative big endothelin-1 levels and preoperative mean pulmonary artery pressure (r = 0.56; P = .02) as well as postoperative mean pulmonary artery pressure at 0 hours (r = 0.70; P = .002) and 24 hours (r = 0.63; P = .006) after surgery. Preoperative big endothelin-1 levels predicted outcome (postoperative mean pulmonary artery pressure at 24 hours after surgery) after pulmonary thromboendarterectomy (area under the receiver operating characteristic curve, 0.85). Peak big endothelin-1 levels also correlated with maximal vasopressor dosage (r = 0.65; P = .004).
CONCLUSIONS: Preoperative big endothelin-1 levels seem to correlate with the hemodynamic alterations observed in pulmonary thromboendarterectomy and may be used to predict hemodynamic outcome after pulmonary thromboendarterectomy.