Cardiac Cycle Flashcards
The proper function of systole is ….., the proper function of diastole is …… .
Ejection
Filling
In each cycle, the ventricles act as ………., belong to ….. pressure system in systole & ….. pressure system during diastole.
Compession-suction pump
High
Low
Atria act as …. Pumps
Volume
Cardiac cycle duration is …… at HR 75 beats, ….. of cycle is diastole & ……of cycle is systole
0.8 sec
2/3 (0.53 sec)
1/3 (0.27 sec)
In accelerated HR, ….. is increased more than …….
Diastole, systole
Atrial systole time is ……. , it is responsible for ….. of v filling, its role is increased by …..
0.1 sec
20-30%
Increased heart rate
Mention events of atrial systole.
Atrial pressure is increased, “a” wave in JVP
Ventricular pressure is increased
Ventricular volume in increased
Aortic pressure is dec
A-V valves are open while semilunar are closed
Heart sounds, atrial systole given 4th heart sound which is not normally audible
ECG: P wave begins before atrial systole by 0.02 sec
GR: Aortic pressure is decreased during atrial systole & isometric contraction phase
As semilunar valves are still closed with no blood ejection, while there is continuous escape of blood to the periphery.
Ventricular wall tension is maximally increased during ….
Isometric contraction phase
Event during isometric contraction
Atrial pressure is increased, “c” wave in JVP
Ventricular pressure is unchanged
Ventricular volume in increased
Aortic pressure is dec
All valves are closed
Heart sounds, S1
ECG: Q wave begins before isometric contraction by 0.02 sec
EDV is ….
~130 ml
GR: Occurence of 1st heart sound
Closure of A-V valves (valvular component) as well as ventricular muscle contraction (ventricular component).
Mention events that take place during rapid ejection phase
Atrial pressure is increased, X descent in JVP
Ventricular pressure is increased
Ventricular volume in decreased
Aortic pressure is increased
A-V valves are closed while semilunar are opened
Heart sounds, S1
ECG: ST segment & beginning of T wave
GR: S1 continues during rapid ejection phase
Due to rush of blood in aorta & pulmonary artery
Mention events of reduced ejection phase
Atrial pressure is increased, due to return of venous blood
Ventricular pressure is decreased
Ventricular volume in decreased
Aortic pressure is dec
A-V valves are closed while semilunar are opened
No Heart sounds
ECG:first half and top of T wave
ESV is ….
~50 ml
GR: Aortic pressure decreases during reduced ejection phase.
Becausecthe nlood volume escaping to the periphery is larger than the blood volume ejected by the ventricle into the aorta.
When does S2 occur & why?
Protodiastole
Blood continues to enter aorta by momentum, then suddenly the momentum is overcome, blood in aorta starts to flow back & this causes closure of aortic valve producing S2.
Mention events of isovolumetric relaxation
Atrial pressure is increased, “v” wave in JVP
Ventricular volume is unchanged (=ESV)
Ventricular pressure decreases
Aortic pressure is decreasing
All valves are closed
Heart sounds, S2
ECG: End of T wave & start of T-P segment
Rapid filling phase is responsible for …… of ventricular filling.
60-70%
Events of rapid filling phase
Atrial pressure is decreased, X descent in JVP
Ventricular volume is increased
Ventricular pressure remains very low (near zero)
Aortic pressure is decreasing
A-V valves are open while semilunar valves are closed
Heart sounds, S3
ECG: Isolectric line of T-P segment
GR: Reduced filling phase is called diastasis
Because blood passes from big veins through atria to ventricles without staying in atria.
Mention the longest phase of cardiac cycle , its duration & factor prolonging it.
Reduced filling phase, 0.2 sec, decreases heart rate
Mention the most affected phase by tachycardia
Is that dangerous? Why?
Reduced filling phase
No, because most of the filling occurs in rapid filling phase.
GR: S3 occurence
Is caused by vibration set up by the rapid inflow of blood on the relaxed ventricular wall.
Mention events of reduced filling phase
Atrial pressure shows no change
Ventricular volume is increased
Ventricular pressure slightly increased less than 10 mmHg
Aortic pressure is decreased
A-V valves are open while semilunar valves are closed
No Heart sounds
ECG: Isolectric line of T-P segment is still recorded for 0.1 sec
What is the effect of heart rate on filling phases?
When heart rate is slow, filling is more dependent on slow filling phase with little contribution of atrial systole.
When the heart accelerates the contribution of atrial systole is very important while slow filling phase is abbreviated or vanished. In cases of more severe tachycardia, even the atrial systole cannot compensate for the inadequate v filling, because of encroachment upon filling phase, leading to marked decrease in the cardiac output.