Determinants of Decreased Early Ventricular Filling in Man: A Role for External Forces

Abstract

The determinants of reduced early left ventricular filling and their relative importance were examined in 14 subjects with an ejection fraction > 40%. Simultaneous high-fidelity left ventricular pressure, mitral annular Doppler velocity recordings, and two-dimensional echocardiographic data were used. Pressure-volume curves were created from pressure/echocardiographic/Doppler data and the chamber stiffness constant calculated. The influence of changing filling pressure was examined by studying subjects before and after ventriculography. The ventricular relaxation time constant, chamber stiffness constant, mean right atrial pressure (an index of pericardial restraint and/or ventricular interaction), pulmonary wedge pressure, and heart rate were analyzed for their influence on Doppler filling parameters: isovolumic relaxation time, peak early (E) and atrial (A) filling velocities, and the E/A ratio. The relaxation time constant was the primary determinant of isovolumic relaxation time (r = 0.82, P<0.001). Prolonged relaxation also caused a decrease in the E/A ratio (r=0.73, P<0.001) and early filling. Peak atrial filling velocity and its integral decreased as chamber stiffness rose (P<0.005). Pulmonary wedge pressure had only a modest influence on early filling (r=0.46, P<0.05). Ventriculography did not eliminate the influence of stiffness and relaxation on filling, although it caused early filling and the E/A ratio to rise and isovolumic relaxation time to shorten. Filling became earlier with increasing right atrial pressure and upward pressure-volume curve shifts. In multivariate regression the E/A ratio was influenced independently by relaxation, filling pressure, right atrial pressure, and chamber stiffness. We conclude that isovolumic relaxation time is a useful measure of ventricular relaxation. However, the E/A ratio is too complex to allow characterization of diastolic function when used alone. Finally, pericardial restraint and/or ventricular interaction during a volume load may confound the relationship between filling pattern and intrinsic ventricular diastolic properties.