['The restrictive filling pattern seen with severe heart failure (HF) may be due to diastolic dysfunction with elevated left ventricular (LV) diastolic pressure or may be merely a manifestation of an overfilled LV as a result of increased left atrial (LA) pressure. We investigated whether the LV restrictive filling pattern is due to elevated LA pressure alone.', "We studied conscious dogs instrumented to measure LA pressure, LV pressure, and 3 LV diameters. LV filling dynamics were evaluated in 2 situations with similar elevations of LA pressure: in normal animals after rapid volume loading with dextran 500 mL and in animals with pacing-induced HF with restrictive filling. With HF, there was increased LV chamber stiffness and slow relaxation. Volume loading and HF had similar heart rates (129+/-19 versus 131+/-15 bpm) and LA pressure (22.1+/-5.8 versus 22.6+/-3.3 mm Hg). The peak early filling rate (E) was increased with both HF and volume loading. However, in HF, the peak mitral annular velocity (E') was decreased and delayed, and the E deceleration time was shorter. In contrast, with volume loading, E' was increased and not delayed."] Does restrictive left ventricular filling pattern result from increased left atrial pressure alone?