Phase 3 - Ventricular Ejection

Once the pressure in the left and right ventricles exceeds that in the aorta and pulmonary trunk, respectively,  then blood ejection can begin via the semilunar valves. The pressure peaks at 120mmHg in the left and 25mmHg in the right, to form an energy gradient. 

The blood flows out in two stages:

• Rapid ejection
• Reduced ejection

Ventricular ejection typically lasts for around 200-250 msec, and blood flow velocity and pressure reaches maximum early in this phase. Reduced ejection occurs due to ventricular repolarisation, shown by the T-wave on the ECG.

The ventricles do not completely empty. In the average ventricle there will be an EDV (end-diastolic-volume) of 130mL of blood, and with an average stroke volume of 70mL there will be 60mL left in the ventricle (end-systolic volume). With high levels of exercise the amount ejected will be higher, and conversely in a diseased heart the amount may be a lot lower.

 Heart Sounds:

This phase is normally silent. However, if there are sounds heard during ejection, known as murmurs, this can indicate disease or cardiovascular shunts.

Did you know?

Ejection fraction (Ef) is the amount of blood pumped out of the ventricles with each beat.

Ef = SV / EDV

It is an important measure of cardiac health.