- The cardiac cycle represents the evens during 1 heart beat. It consists of periods of atrial and ventrical systole (contractions) and diastole (relaxation).
- Systole = contraciton
- Diastole = relaxation
- The L and R atria contract at the same time and then the L and R ventricles contract at the same time - blood always flows from high pressure to low pressure
- Atrial systole = atria contract, ventricles relax - atrial contraction forces blood throgh open AV valves into ventricels. Atrial kick = blood pushed into ventricels is about 25 cc - added to the 105 cc already there
Atrial diastole = atria relax, ventricles contract - AV valves forced closed by ventricel systole
Ventrical systole = ventricles contract - atria relax - AV valves forced closed by ventrical contraction - short period where all 4 valves are closed - then SL valves open and the ventricles eject 70 cc of blood
Ventrical diastole = ventricels relax - backflow of blood causes the SL valves to close - after a short period the AV valves open and ventricular filling begins.
Atrial kick is not present in A-fib and as a result stagnant blood in the atria can clot and cause a stroke.
End-diastolic volume - EDV- the volume of blood each ventricle at the end of diastole - about 130 cc (105 in vent + 25 from atrial kick)
End-systolic volume - ESV - volume of blood remaining in ventricel at the end of systole ( about 60 cc)
- Stroke volume - the volume ejected from each ventricle per beat
- EDV- ESV = SV
- 130 - 60 = 70 cc