AIRWAY STRUCTURE AND FUNCTION IN EISENMENGERS-SYNDROME

The responsiveness of airways from patients with Eisenmenger's syndrom e (n = 5) was compared with that in airways from organ donors (n = 10) . Enhanced contractile responses to cholinergic stimulation were found in airways from patients with Eisenmenger's syndrome. The maximal res ponses to acetylcholine, carbachol, and parasympathetic nel-ve stimula tion in airway tissue from these patients were 221%, 139%, and 152%, r espectively, of the maximal responses obtained in donor tissue. Furthe r, relaxation responses to isoproterenol and levocromakalim were absen t (n = 2) or markedly impaired (n = 3) in airways from patients with E isenmenger's syndrome. This attenuated relaxation response was nonspec ific in that it was also absent after vasoactive intestinal peptide, s odium nitroprusside, papaverine, and electrical field application. The se observations can most likely be explained by a decrease in intrinsi c smooth muscle tone, as precontraction of airways revealed relaxation responses that were equivalent to those obtained in donor tissues. Mo rphometric analysis of tissues used for the functional studies reveale d no differences in the airway dimensions (internal perimeter) or airw ay wall components (e.g., smooth muscle, cartilage) or total area to e xplain these observations. Although the mechanism for this observed de crease in intrinsic airway smooth muscle tone is not certain, it may b e due to alteration in the substructure of the airway wall or, alterna tively, may result from the continued release of depressant factors in the vicinity of the smooth muscle which permanently alters smooth mus cle responsiveness.