To clarify the factors controlling left ventricular inflow, hemodynamics and Doppler-derived indices were analyzed in six anesthetized open-chest dogs with intact pericardia. Low molecular dextran was intravenously infused at 1 L/hr. During rapid infusion, an electrocardiographic lead, left ventricular pressure curve, and a transmitral Doppler signal were recorded at various heart rates produced by right atrial pacing. In five of the six dogs, the relationship of the ratio of peak velocity during atrial contraction to that during rapid filling (A/R) and left ventricular end-diastolic pressure (LVEDP) showed a non-linear quadratic curve concave to the LVEDP axis. Data from the ascending and descending limbs of the A/R-LVEDP relationship were subjected to stepwise multiple linear regression analysis (criterion variables: A/R; explanatory variables: peak dP/dt, maximum left ventricular pressure, time constant T, minimum left ventricular pressure, LVEDP, and heart rate). In both limbs, the A/R correlated positively with maximum left ventricular pressure (left ventricular afterload) and negatively with LVEDP (left ventricular preload). The time constant T was selected as a positive correlate only in the ascending limb. The transmitral flow velocity profile is determined in a complex manner by multiple factors, including left ventricular loading conditions and heart rate, as well as the left ventricular diastolic property. It was suggested that the A/R is not altered unidirectionally by the changes in cardiac function and loading conditions, but that it returns to the initial value accompanied by systolic and diastolic cardiac dysfunction.