ABSTRACT
BACKGROUND: A wide range of left atrial pressures exist in rheumatic mitral stenosis despite similar mitral valve area. Left atrial compliance may be an important determinant of left atrial pressure in mitral stenosis. Data regarding left atrial compliance in rheumatic mitral stenosis and changes following balloon mitral valvotomy are scarce. METHODS AND RESULTS: Left atrial compliance and predictors of left atrial pressure were analyzed in 85 patients with mitral stenosis undergoing balloon mitral valvotomy. The stroke volume was divided by systolic rise in left atrial pressure to calculate the left atrial compliance. Systolic rise in left atrial pressure was computed as difference between amplitudes of left atrial "v" wave and "x" descent. The mean left atrial compliance prior to balloon mitral valvotomy was 2.62+/-1.20 cm3/mmHg. Following successful balloon mitral valvotomy there was a significant fall in pulmonary artery pressure, mean left atrial pressure, transmitral gradient, and significant increase in cardiac output, stroke volume and mitral valve area. There was a marked increase in left atrial compliance from 2.62+/-1.20 to 6.1+/-3.16 cm3/mmHg. On univariate analysis pulmonary artery systolic pressure, pulmonary artery diastolic pressure, pulmonary artery mean pressure, mean transmitral gradient, mitral valve area and left atrial compliance were the only correlates of left atrial pressures, while no correlation was noted with age, gender, left atrial size, cardiac output and stroke volume. Those with higher pulmonary artery pressure, higher transmitral gradient, lower mitral valve area and lower left atrial compliance had higher left atrial mean pressure, and the strongest negative correlation was noted with left atrial compliance. On multivariate analysis the strongest predictors of left atrial mean pressure were transmitral gradient and left atrial compliance. CONCLUSIONS: Patients with rheumatic mitral stenosis have markedly depressed left atrial compliance and hence have "stiff" left atria. Left atrial compliance is an important determinant of left atrial pressure, and improves immediately after successful balloon mitral valvotomy, irrespective of pre-balloon mitral valvotomy left atrial pressures.