Patients with signs and symptoms of heart failure and a normal left ventricular ejection fraction are said to have diastolic heart failure. It has traditionally been thought that the pathophysiological cause of heart failure in these patients is an abnormality in the diastolic properties of the left ventricle; however, this hypothesis remains largely unproven.

We prospectively identified 47 patients who met the diagnostic criteria for definite diastolic heart failure; all the patients had signs and symptoms of heart failure, a normal ejection fraction, and an increased left ventricular end-diastolic pressure. Ten patients who had no evidence of cardiovascular disease served as controls. Left ventricular diastolic function was assessed by means of cardiac catheterization and echocardiography.

The patients with diastolic heart failure had abnormal left ventricular relaxation and increased left ventricular chamber stiffness. The mean (±SD) time constant for the isovolumic-pressure decline (τ) was longer in the group with diastolic heart failure than in the control group (59±14 msec vs. 35±10 msec, P=0.01). The diastolic pressure–volume relation was shifted up and to the left in the patients with diastolic heart failure as compared with the controls. The corrected left ventricular passive-stiffness constant was significantly higher in the group with diastolic heart failure than in the control group (0.03±0.01 vs. 0.01±0.01, P<0.001).

Patients with heart failure and a normal ejection fraction have significant abnormalities in active relaxation and passive stiffness. In these patients, the pathophysiological cause of elevated diastolic pressures and heart failure is abnormal diastolic function.