CARDIOVASCULAR SYSTEM CARDIAC CYCLE. LECTURE – 3 DR. ZAHOOR ALI SHAIKH. CARDIAC CYCLE. Cardiac events occurring during one beat (systole & diastole) are repeated during the next beat Cardiac cycle time : 0.8 second when heart rate is 75 beats per minute. CARDIAC CYCLE.
LECTURE – 3
DR. ZAHOOR ALI SHAIKH
We will discuss ECG in detail in coming lectures.
Atrial Cycle (0.8 Sec.)
Ventricular Cycle (0.8 Sec.)
During diastole, When ventricular pressure falls below the Aortic pressure, aortic valve closes, and AV valves are not open yet , ventricle is close cavity with all valves closed. This phase is called Isovolumetric Relaxation (means volume remains same but pressure is decreasing).
2. Filling phase
Last rapid filling phase is due to atrial systole and contributes to 20-30% of ventricular filling.
After atrial systole, cardiac cycle will re-start.
1 st Heart Sound
2 nd Heart Sound
3 rd Heart Sound
4 th Heart Sound
reduces the time for ventricular relaxation and filling.
Rt- Atrium = 0-7mm Hg.
Lt- Atrium = 2-10 mm Hg.
Rt – Ventricle = 25 / 6(2-8) mm Hg.
Lt – ventricle = 120 / 8(2-10) mm Hg.
Aorta = 120 / 80 mm Hg.
Pul. Artery = 25 / 10 mm Hg.
Events of cardiac cycle showing pressure changes in left ventricle, aortic pressure, atrial pressure, ECG & phonocardiogram
pressure curves for Rt. ventricle. & Pulmonary Artery ventricle, aortic pressure, atrial pressure, ECG & phonocardiogram
Stroke volume (SV) = EDV – ESV
It is about 120 – 130 ml.
Events of cardiac cycle showing left ventricular pressure, volume changes, & phonocardiogram
SV (EDV – ESV) volume changes, & phonocardiogram
X 100 = 62.5%
Normal ejection fraction is about 60 – 65 %.
Ejection fraction is good index of ventricular function.