The Role of Vessel Tone in Maintaining Pulmonary Vascular Resistance in Patients with Mitral Stenosis

Abstract
Changes in pulmonary vascular (arteriolar) resistance were estimated in 58 patients with mitral stenosis following mitral valvotomy and during exercise. Evidence is presented that changes in "resistance" reflect active changes in the caliber of the vessels due to alteration in their smooth muscle tone, valvotomy being followed by a decrease in tone and exercise by an increase.