1. Phases of the cardiac
cycle in correlation
with an ECG

3. Phases of the cardiac cycle in
correlation with an ECG (from
left upper):
Phase 1 (atrial systole): seen
as P wave on ECG; left atrium
contracts

4. Phase 2 (isovolumetric
contraction): left ventricular
(LV) pressure increases and
mitral valve closes; LV
depolarization is seen as a
QRS complex on ECG.

5. Phases 3 and 4: isovolumetric
contraction of the ventricle
continues until the aortic valve
opens in response to high LVP.
Ventricles contract and blood is
ejected. LV repolarization is seen as
a T wave on ECG.

6. Phase 5 (isovolumetric relaxation):
beginning of ventricular diastole. The
aortic valve closes due to decreasing left
intraventricular pressure. T wave
resolution is seen on ECG.
Phases 6 and 7 (ventricular filling): mitral
valve opens due to effects of decreased
left intraventricular pressure and left atrial
contraction, and ventricles fill with blood.