End Diastolic Pressure Volume Point

End Diastolic Pressure Volume Point is the specific coordinate within the ventricular pressure-volume relationship marking the ventricular pressure and volume present at the precise moment filling ends and contraction begins, representing the immediate starting condition from which each cardiac contraction proceeds.

Defining the Point Precisely

The Moment It Represents

This point corresponds to the instant just before the ventricle begins to contract, capturing the final pressure and volume achieved after filling has completed but before any active tension development has begun.

Marking the Transition Between Filling and Contraction

This point serves as the boundary between the preceding filling segment of the cardiac cycle and the subsequent isovolumetric contraction segment, representing the final state of one phase and the starting state of the next.

The Two Coordinates Defining This Point

End Diastolic Volume

The volume coordinate at this point reflects the total amount of blood present in the ventricle after filling has concluded, directly representing the preload experienced by the ventricle for that particular contraction.

End Diastolic Pressure

The pressure coordinate at this point reflects the pressure within the ventricle required to have achieved that specific filling volume, shaped by both the volume itself and the compliance, or stiffness, of the ventricular wall at that volume.

The Relationship to the Passive Filling Curve

Position Along the Passive Pressure Volume Curve

This point lies along the passive filling relationship describing how ventricular pressure rises as volume increases during diastole, reflecting the mechanical properties of the relaxed ventricular wall at the specific volume reached.

Sensitivity to Ventricular Compliance

Because this passive relationship depends on the stiffness of the ventricular wall, a less compliant, stiffer ventricle will show a higher end diastolic pressure for the same end diastolic volume compared with a more compliant ventricle.

Factors That Shift This Point

Changes in Venous Return

An increase in venous return tends to shift this point toward a greater end diastolic volume, and correspondingly toward a higher position along the passive filling curve, reflecting the effect of greater filling on ventricular pressure.

Changes in Filling Time

A shortened diastolic filling time, such as occurs at elevated heart rates, can limit the volume reached by this point even when venous return itself remains adequate, since insufficient time may prevent complete filling from occurring.

Changes in Ventricular Compliance

Alterations in the stiffness of the ventricular wall shift the passive filling curve itself, meaning that a given end diastolic volume can correspond to a different end diastolic pressure depending on the underlying compliance of the ventricle at that time.

The Significance of This Point for Subsequent Contraction

Establishing the Starting Volume for Ejection

The volume present at this point directly determines the starting volume from which the subsequent contraction and ejection segment begins, making it a foundational reference for understanding the stroke volume ultimately achieved.

Reflecting the Degree of Fiber Stretch

Because greater ventricular volume corresponds to greater stretch of the muscle fibers within the ventricular wall, this point's volume coordinate reflects the degree of stretch that will influence the strength of the ensuing contraction through the underlying length-tension relationship.

Locating This Point Within the Complete Pressure-Volume Relationship

The Endpoint of the Filling Segment

This point marks the conclusion of the gradual pressure and volume increase occurring during the filling segment of the cardiac cycle, representing the final coordinate reached before the ventricle transitions into active contraction.

The Starting Point of Isovolumetric Contraction

Immediately following this point, the ventricle begins to contract with both inflow and outflow valves closed, causing pressure to rise rapidly while volume remains temporarily fixed at the value established by this point.

Broader Physiological Relevance

A Direct Reflection of Preload

Because this point's volume coordinate corresponds directly to preload, its position provides a clear, specific representation of one of the three key determinants of stroke volume within the overall pressure-volume framework.

A Reference for Comparing Different Physiological States

Comparing the position of this point across different conditions, such as varying venous return or ventricular compliance, provides a precise way of illustrating how these factors specifically alter the starting condition for each cardiac contraction.

Summary of Function

End Diastolic Pressure Volume Point functions as the precise coordinate marking the transition from ventricular filling to contraction, capturing both the volume achieved through diastolic filling and the corresponding pressure required to achieve that filling, and serving as the essential starting condition from which the subsequent phases of the cardiac cycle proceed.