End Systolic Pressure Volume Point

End Systolic Pressure Volume Point is the specific coordinate within the ventricular pressure-volume relationship marking the ventricular pressure and volume present at the precise moment ejection ends and relaxation begins, representing the smallest volume and a characteristic pressure reached during that particular cardiac contraction.

Defining the Point Precisely

The Moment It Represents

This point corresponds to the instant the valve leading out of the ventricle closes, marking the conclusion of active ejection and the beginning of isovolumetric relaxation.

Marking the Transition Between Ejection and Relaxation

This point serves as the boundary between the preceding ejection segment of the cardiac cycle and the subsequent isovolumetric relaxation segment, representing the final state of active contraction and the starting state of relaxation.

The Two Coordinates Defining This Point

End Systolic Volume

The volume coordinate at this point reflects the amount of blood remaining in the ventricle once ejection has concluded, representing the portion of the ventricle's contents that was not ejected during that contraction.

End Systolic Pressure

The pressure coordinate at this point reflects the ventricular pressure present at the moment ejection ends, closely related to the arterial pressure the ventricle was working against during the final portion of ejection.

The Relationship to the Ventricle's Maximal Contractile Capability

Position Along a Boundary Reflecting Contractility

This point is understood to lie along a boundary describing the maximal pressure the ventricle is capable of generating at any given volume, with the steepness of this boundary reflecting the ventricle's underlying contractile state and the term representing a theoretical volume at which no pressure can be generated.

Sensitivity to Changes in Contractility

An increase in contractility shifts this boundary such that, for a given afterload, the ventricle is able to reach a smaller end systolic volume, while reduced contractility shifts the boundary in the opposite direction, resulting in a larger remaining end systolic volume for the same afterload.

Factors That Shift This Point

Changes in Afterload

An increase in the resistance faced during ejection tends to shift this point toward a larger end systolic volume, since higher afterload makes it more difficult for the ventricle to eject as completely before pressure falls below arterial pressure.

Changes in Contractility

An increase in contractility tends to shift this point toward a smaller end systolic volume at a given afterload, reflecting the ventricle's enhanced ability to continue ejecting blood against that same level of resistance.

Independence From Preload Under Ideal Conditions

Under idealized conditions, the position of this point along the contractility-defined boundary is considered relatively independent of preload, meaning that for a given afterload and contractility, the ventricle tends to reach a similar end systolic volume regardless of how much it was filled beforehand.

The Significance of This Point for Stroke Volume

Determining Stroke Volume Together With the End Diastolic Point

The volume coordinate of this point, combined with the volume coordinate of the end diastolic point, directly determines the stroke volume achieved during that cardiac cycle.

A Direct Reflection of Ejection Completeness

Because this point marks the smallest volume reached during the cycle, its position provides a direct indication of how completely the ventricle was able to empty during that particular contraction.

Locating This Point Within the Complete Pressure-Volume Relationship

The Endpoint of the Ejection Segment

This point marks the conclusion of the declining volume and changing pressure occurring during the ejection segment of the cardiac cycle, representing the final coordinate reached before relaxation begins.

The Starting Point of Isovolumetric Relaxation

Immediately following this point, the ventricle begins to relax with both valves closed, causing pressure to fall rapidly while volume remains temporarily fixed at the value established by this point.

Broader Physiological Relevance

A Direct Reflection of Contractile Performance

Because this point's position is closely tied to the ventricle's underlying contractile state, its location provides a meaningful representation of contractility 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 afterload or contractility, provides a precise way of illustrating how these factors specifically alter the ventricle's ability to empty during contraction.

Summary of Function

End Systolic Pressure Volume Point functions as the precise coordinate marking the transition from ventricular ejection to relaxation, capturing both the volume remaining after ejection and the pressure present at that moment, and serving as a direct, sensitive reflection of the ventricle's contractile state and its interaction with afterload during that particular cardiac cycle.