Diastolic compliance of the left atrium in man: a determinant of preload of the left ventricle.

During the ventricular slow-filling period, both the left atrium and left ventricle fill passively, and their respective internal pressures equalize, becoming evenly elevated. If the diastolic chamber compliance of the left atrium is smaller than that of the left ventricle, we expect the inflowing blood to be distributed more to the left ventricle than to the left atrium during this period. We examined the magnitude of the diastolic compliance of the left atrium and the left ventricle at the end of the slow-filling period. We studied 10 patients, mostly with a mild degree of coronary artery disease, in whom hemodynamic variables were almost within normal limits. To estimate the compliance of the left atrium, we recorded the left atrial pressure directly (by the Brockenbrough technique) and determined the left atrial volume by biplane cineatriography. We determined the diastolic compliance of the left atrium from the pressure-volume relations between the nadir of the x trough and the peak of the v wave by fitting them to an exponential equation. P = b.eaV (P = pressure, V = volume, a, b = constants). The diastolic compliance of the left ventricle was determined from the pressure-volume relations during the ventricular slow-filling period. The compliances of the left atrium and the left ventricle at the pressure at the end of the ventricular slow-filling period were 1.60 +/- 0.41 (mean +/- SD) ml.mmHg-1.m-2 and 4.22 +/- 1.12, respectively. The ratio of compliance of the left ventricle to that of the left atrium was 2.60 +/- 0.71.(ABSTRACT TRUNCATED AT 250 WORDS)