Although the fourth heart sound (S4) is thought to be associated with a stiff left ventricle, this association has never been proven.

Recently, single-beat estimation of the end-diastolic pressure volume relationship (EDPVR) has been characterized (P = αVβ), allowing the estimation of EDPVR in larger groups of patients.

We hypothesized that the S4 is associated with an upward- and leftward-shifted EDPVR, indicative of elevated end-diastolic stiffness.