Hemodynamic Variables Affecting the Relation Between Mean Left Atrial and Left Ventricular End-Diastolic Pressures

The observations reported in this paper support the view that a vigorous and properly timed atrial contraction, by transporting blood into the ventricle and by approximating the atrioventricular valve prior to ventricular systole, provides a mechanism by which mean atrial pressure is maintained at a substantially lower level for any ventricular end-diastolic pressure than would be the case if these functions of the atrium were not operative. The central nervous system, by way of efferent sympathetic pathways, can regulate appropriately the vigor and timing of atrial systole as well as the duration of the diastolic filling period. The net effect of such regulation is to decrease mean atrial pressure at any given heart rate and cardiac output, and to permit rapid heart rates which could not otherwise be tolerated without elevations of atrial pressure. The fact that MLAP-LVEDP is independent of aortic pressure and stroke volume, and of heart rate over certain ranges suggests that this hemodynamic measurement is uniquely dependent on, and therefore useful in the analysis of, atrial performance.