Pulmonary arterial pressure after priscoline in mitral stenosis.

It has been observed that in certain cases of mitral stenosis the increase in pulmonary arterial pressure is out of proportion to the pressures on the venous side of the pulmonary circulation. This increase is due to narrowing of the pulmonary arterioles (Dexter et al., 1950; Baker et al., 1952; Ferrer et al., 1952), which may result either from organic changes in the pulmonary arterioles (intimal proliferation and medial hypertrophy) (Parker and Weiss, 1936; Larabee et al., 1949) or from increased pulmonary vascular tone due to over-activity of the autonomic nervous system (Holling, 1952; Curti et al., 1953) or both. Various drugs have been used to determine the influence of the autonomic nervous system on pulmonary hypertension in cases of mitral stenosis. Thus, large decreases in right ventricular pressure (Wilson and Keeley, 1953) and in pulmonary arterial pressure-without decrease in cardiac output-have been observed following the administration of hexamethonium (Davies et al., 1954). Using priscoline Gardiner (1954) observed a fall in the pulmonary arterial pressure in two cases of mitral stenosis. In the present study priscoline was used to analyse the role played by increased vascular tone in the pulmonary hypertension of mitral stenosis. Priscoline t (2-benzyl 1-4-5 imidazoline hydrochloride) is a sympathicolytic and adrenolytic agent (Chess and Yonkman, 1940) and is thought to cause vaso-dilatation by blocking the sympathetic end-organs in the vessel walls.