- Cardiac cycle is the sequence of electrical and mechanical events occurring in the heart during a single beat, precisely repeated in each beat.
- Duration is 0.8 s at a heart rate of 75/min: systole about 0.3 s, diastole about 0.5 s.
Phases of Cardiac Cycle
- Atrial systole → Isovolumic contraction → Rapid ejection → Reduced ejection → Isovolumic relaxation → Rapid filling → Diastasis
- Atrial systole contributes less than 20% of ventricular filling at rest, since more than 80% of ventricular filling is passive.
Valve, pressure and volume events across the phases of the cardiac cycle