Reduced Ventricular Ejection Phase

Reduced Ventricular Ejection Phase is the latter portion of ventricular systolic ejection during which blood continues to flow from the ventricles into the aorta and pulmonary artery, but at a progressively diminishing velocity compared to the preceding rapid ejection phase, occurring as active ventricular contraction begins to wane and the pressure gradient driving outflow correspondingly declines. It concludes ventricular systole, giving way to the onset of ventricular relaxation and the closure of the semilunar valves.

Position Within the Cardiac Cycle

Continuation from Rapid Ejection

The reduced ejection phase follows directly from rapid ejection, beginning at the point where the rate of ventricular volume decline starts to slow, reflecting a transition in the underlying balance between the ventricle's contractile force and the resistance offered by the arterial circulation.

Transition to Ventricular Relaxation

Reduced ejection continues until ventricular myocardial contraction has sufficiently waned that ventricular pressure falls below arterial pressure, at which point the semilunar valves close, marking the end of systolic ejection and the onset of isovolumetric relaxation.

Mechanism of Diminishing Outflow

Declining Pressure Gradient

As ventricular contraction passes its peak intensity, the rate of pressure generation by the myocardium slows and eventually reverses into decline, narrowing the pressure gradient between the ventricle and the arterial circulation that had driven the more vigorous outflow of the preceding rapid ejection phase.

Onset of Early Myocardial Relaxation

Toward the latter part of this phase, the ventricular myocardium begins the earliest stages of relaxation even while ejection is still occurring, reflecting the gradual decline in active cross-bridge cycling that will soon give way to full diastolic relaxation.

Pressure and Volume Behavior

Declining Ventricular Pressure

Ventricular pressure, having reached its peak during the transition from rapid to reduced ejection, begins a gradual decline throughout this phase, though it remains above arterial pressure for the majority of the period, sustaining continued, though slowing, forward flow.

Continued but Slower Volume Decline

Ventricular volume continues to fall during reduced ejection, but at a substantially slower rate than during rapid ejection, reflecting the diminished velocity of outflow as the driving pressure gradient narrows.

Pressure-Volume Loop Representation

Terminal Portion of the Ejection Curve

On the ventricular pressure-volume loop, the reduced ejection phase corresponds to the terminal segment of the upper curved portion, characterized by declining pressure accompanying a continued but flattening leftward shift in volume, concluding at the end systolic pressure-volume point.

Arrival at the End Systolic Point

The reduced ejection phase concludes at the end systolic volume and pressure, representing the smallest ventricular volume achieved during the cardiac cycle and the point from which the subsequent isovolumetric relaxation phase begins.

Flow and Pressure Correlates

Arterial Pulse Waveform Correlate

The declining velocity of outflow during reduced ejection corresponds to the descending limb of the arterial pressure pulse waveform, following the peak achieved near the transition from rapid to reduced ejection.

Transition Toward Valve Closure

As ventricular pressure continues to decline throughout reduced ejection, it approaches and eventually falls below arterial pressure, establishing the pressure crossover that will trigger closure of the semilunar valves and the momentary reversal of flow that produces the dicrotic notch in the arterial pressure tracing.

Proportional Contribution to Stroke Volume

Minority Share of Ejected Volume

The reduced ejection phase contributes a smaller proportion of total stroke volume than the preceding rapid ejection phase, reflecting the lower flow velocity sustained during this latter, decelerating portion of systolic outflow.

Functional Significance of the Representation

Completion of Systolic Ejection

The reduced ventricular ejection phase functions to complete the delivery of stroke volume initiated during rapid ejection, bringing ventricular volume to its systolic minimum before the onset of diastolic relaxation and refilling.

Marker of the Transition from Contraction to Relaxation

Because this phase reflects the waning of active ventricular contraction as the myocardium approaches the onset of relaxation, reduced ejection serves as a representation of the transitional mechanical state bridging peak systolic performance and the beginning of diastole.