1.14.6 End Diastolic Pressure Volume Relation Definition

End Diastolic Pressure Volume Relation Definition is the curve describing how ventricular pressure rises as the relaxed ventricle is progressively filled with increasing volumes of blood, capturing the passive elastic, or compliance, properties of the ventricular wall independent of any active muscular contraction. This relationship is constructed by plotting the end-diastolic pressure achieved across a range of different end-diastolic volumes, tracing the lower boundary of the ventricular pressure–volume loop and providing a direct measure of how readily the ventricle accepts filling.

Physiological Basis

The end-diastolic pressure–volume relation reflects the passive mechanical behavior of the relaxed ventricular wall as it is stretched by incoming blood.

Passive Ventricular Compliance

As the ventricle fills during diastole, its wall is stretched by the increasing volume of contained blood; the relationship between this increasing volume and the resulting rise in pressure reflects the passive stiffness, or compliance, of the ventricular myocardium and surrounding structures.

Nonlinear, Curvilinear Shape

The end-diastolic pressure–volume relation is characteristically curvilinear rather than straight, remaining relatively flat at lower volumes, where the ventricle accommodates filling with little pressure rise, and becoming progressively steeper at higher volumes, where the chamber becomes increasingly resistant to further stretch.

Position Within the Pressure–Volume Loop

The end-diastolic pressure–volume relation forms the lower boundary that the pressure–volume loop cannot cross during filling.

Defining the Filling Segment

As the ventricle fills during diastole, the trajectory of the pressure–volume loop follows along this curve, terminating at the end-diastolic point where isovolumetric contraction begins.

Contrast with the End-Systolic Relation

Unlike the end-systolic pressure–volume relation, which reflects active contractile properties and shifts with changes in contractility, the end-diastolic relation reflects passive elastic properties and shifts primarily with changes in ventricular stiffness or wall structure.

Determinants of the Relation

Several structural and physiological factors influence the position and steepness of the end-diastolic pressure–volume relation.

Myocardial Stiffness

Increased myocardial stiffness, whether from hypertrophy, fibrosis, or infiltrative disease, shifts the curve upward and to the left, meaning that a given volume produces a higher filling pressure than in a normally compliant ventricle.

Chamber Size and Wall Structure

Ventricular dilation or structural remodeling can alter the compliance characteristics captured by this relationship, changing how the ventricle responds mechanically to increasing diastolic volume.

Diagrammatic Summary

Clinical Relevance

An upward-shifted, steeper end-diastolic pressure–volume relation is characteristic of reduced ventricular compliance and diastolic dysfunction, in which normal or even reduced filling volumes produce abnormally elevated filling pressures, contributing to symptoms of congestion despite preserved systolic contractile function.