Impairment of pulmonary endothelium‐dependent relaxation in patients with Eisenmenger's syndrome

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Abstract
A comparison has been made between the endothelium-dependent relaxation of pulmonary arteries (PA) obtained at heart-lung transplantation from 4 patients with Eisenmenger's syndrome and secondary pulmonary hypertension, and PA obtained at lobectomy from 4 patients with lung carcinoma, the controls. All vascular rings were studied immediately after lung excision. PA rings from control patients dose-dependently relaxed to cumulative doses of acetylcholine (ACh, 10−10 to 10−5 m), achieving a maximal relaxation of 80 ± 5% (mean ± s.e.mean) from precontraction with phenylephrine. By contrast, PA rings from Eisenmenger's syndrome patients achieved a maximal relaxation of only 34 ± 12% (P < 0.05, unpaired t test), with even paradoxical contraction at high doses of ACh (10−6 to 10−5 m). Sodium nitroprusside (10−4 m) relaxed all PA rings, with and without endothelium (carefully removed before study), obtained from both control and Eisenmenger's syndrome patients. These results provide the first evidence that endothelium-dependent relaxation of PA mediated by endothelium-derived relaxing factors is impaired in Eisenmenger's syndrome patients with secondary pulmonary hypertension.