1. Head of Medical Department Tuanku Fawziah Hospital
Cardiac Cycle
Dr. SIA KOON KET
Head of Medical Department
Tuanku Fawziah Hospital

2. Cardiac cycle
There is a similar cycle on both sides of the heart, but the pressures in the right ventricle and pulmonary arteries are less than those in the left ventricle and aorta.
The cycle starts with depolarisation at the sinoatrial node leading to atrial contraction.
Until this time blood flow into the ventricles has been passive, but the atrial contraction increases filling by 20-30%.  

3. Cardiac cycle
A single cycle of cardiac activity can be divided into two basic stages. 
The first stage is diastole, which represents ventricular filling and a brief period just prior to filling at which time the ventricles are relaxing. 
The second stage is systole, which represents the time of contraction and ejection of blood from the ventricles.

4. Cardiac cycle To analyze these two stages in more detail,
it is convenient to divide the cardiac cycle into seven phases.
The first phase begins with the p-wave in the electrocardiogram, which represents atrial depolarization. 
The last phase of the cardiac cycle ends with the appearance of the next p-wave. 

5. Cardiac Cycle - Atrial Contraction (Phase 1) A-V Valves Open; Semilunar Valves Closed

6. Cardiac Cycle - Isovolumetric Contraction (Phase 2) All Valves Closed

7. Cardiac Cycle - Rapid Ejection (Phase 3) Aortic and Pulmonic Valves Open; AV Valves Remain Closed

8. Cardiac Cycle - Reduced Ejection (Phase 4) Aortic and Pulmonic Valves Open; AV Valves Remain Closed

9. Cardiac Cycle - Isovolumetric Relaxation (Phase 5) All Valves Closed

10. Cardiac Cycle - Rapid Filling (Phase 6) A-V Valves Open

11. Cardiac Cycle - Reduced Filling (Phase 7) A-V Valves Open