Impact of Atrioventricular Compliance on Pulmonary Artery Pressure in Mitral Stenosis

Abstract

Background —The decay of the pressure gradient across a stenotic mitral valve is determined by the size of the orifice and net AV compliance (C n ). We have observed a group of symptomatic patients, usually in sinus rhythm, characterized by pulmonary hypertension (particularly during exercise) despite a relatively large mitral valve area by pressure half-time. We speculated that this discrepancy was due to low atrial compliance causing both pulmonary hypertension and a steep decay of the transmitral pressure gradient despite significant stenosis. We therefore tested the hypothesis that C n is an important physiological determinant of pulmonary artery pressure at rest and during exercise in mitral stenosis. Methods and Results —Twenty patients with mitral stenosis were examined by Doppler echocardiography. C n , calculated from the ratio of effective mitral valve area (continuity equation) and the E-wave downslope, ranged from 1.7 to 8.1 mL/mm Hg. Systolic pulmonary artery pressure (PAP) increased from 43±12 mm Hg at rest to 71±23 mm Hg (range, 40 to 110 mm Hg) during exercise. There was a particularly close correlation between C n and exercise PAP ( r =−0.85). Patients with a low compliance were more symptomatic ( P <0.025). Catheter- and Doppler-derived values for C n , determined in 10 cases, correlated well ( r =0.79). Conclusions —C n , which can be noninvasively assessed, is an important physiological determinant of PAP in mitral stenosis. Patients with low C n represent an important clinical entity, with symptoms corresponding to severe increases in PAP during stress echocardiography.