Cardiac Cycle Flashcards
What is the cardiac cycle?
phases of cardiac function between each heart beat
What are the 7 steps of the cardiac cycle?
atrial systole
isovolumic contraction
rapid ejection
reduced ejection
isovolumic relaxation
rapid filling
reduced filling
Which side of the cardiac cycle generates more pressure?
the left
Define: atrial systole
contraction of atria
Define: Isovolumic Contraction
Contraction of ventricles but no change in volume
Define: Isovolumic Contraction
Contraction of ventricles but no change in volume
Define: rapid ejection
Ejecting blood
What occurs first, Electrical or Mechanical Events? Example?
Electrical events occur before mechanical events
(membrane depolarizes before muscle shortens)
What is pressure in the aorta dependent on?
How constricted the arterioles are
what is afterload somewhat equal to?
aortic pressure
If you have a patient with hypertension and BP of 150/110, how would that effect the pressures in the diagram?
Aortic Valve would open at 110 mmHG
for every heart beat, heart would have to generate 30 mmHG more of pressure before aortic valve would open
increases work of heart
can cause heart failure if untreated
What is the fundamental thing that causes pressure to change in the aorta?
the transfer of volume from one chamber to another (LV to aorta)
What would happen to the pressure change if you increases the SV?
it would increase
What is aortic pressure loosely dependent on?
SV
Why does left atrial pressure increase while the ventricle is contracting and relaxing?
while the ventricle is contracting, atria are accumulating volume, which increases pressure
Explain this Diagram
- Mitral Valve Closes → to stop blood from flowing back into atria
- LV pressure increases b/c muscle contracts
- atria contracts
- aortic valve open s→ blood flows from LV to aorta
- Aortic valve closes → pressure in aorta is higher then in LV
- LV pressure decreases → Ca flows back into SR and EC
- Mitral Valve opens (pressure is lower in LV)
What happens during atrial systole?
atria contracts
What happens during isovolumic contraction?
valves all closed
What happens during rapid ejection?
blood flows from LV to aorta
What happens during reduced ejection?
aortic valve closes at end
What happens during isovolumic relaxation?
pressure in LV drops
When is aortic pressure highest?
during rapid and reduced ejection
Preload is the same as…
EDV
Equation: SV
SV = EDV - ESV
What happens when atria contracts?
blood is forced into ventricle
volume increases slightly
Where is the LVEDV and the LVESV located on this diagram?
LVEDV → Top plateau
LVESV → bottom plateau
What are the normal heart sounds?
1&2
What are the abnormal (pathological) heart sounds?
they don’t always occur
3&4
When does the 1st heart sound occur?
at the beginning of isovolumic contraction and mitral valve closing
When does the 2nd heart sound occur?
when the aortic valve closes
When does the 3rd heart sound occur?
During rapid filling phase
often heard in patients with congestive heart failure
compliance of ventricle is reduced
When does the 4th heart sound occur?
During atrial systole
typically heard in patients that have long standing hypertension and hyperphery (thicker) ventricle
What is venous pressure pulse?
central venous pulse
follows atrial pressure low pressure
>5 mmHg
When does the P wave start?
before atria contracts
When does the QRS complex occur?
just before isovolumic contraction → ventricular depolarization/contraction
When does the T wave occur?
during reduced ejection
How would you use the Wiggers Diagram to calculate cardiac output?
CO = HR x SV
HR = 60/.8 (time from P wave to T wave) = 75 beats/min
SV = 40 (EDV) - 20 (ESV) = 20 (ventricular volume)
CO = 75 x 20 = 1,500 mL/min
Calculate the EF from the Wiggers Diagram.
EF = SV/EDV = 20/40 = 50%
Are the mitral and tricuspid valve opened or closed during diastole?
open
Are the mitral and tricuspid valve opened or closed during systole?
closed
What is the normal % oxygen saturation in the different chambers of the heart?
Aorta → 95%
Pulmonary Artery → 75%
L Atrium → 95%
LV → 95%
RV → 75%
R atrium → 75%
What is the average pressure of the right atrium?
3 mmHg
What is the average pressure of the right ventricle?
25 mmHg (peak systolic)
What is the average pressure of the pulmonary capillary wedge?
9 mm Hg
What is the average pressure of the left atrium?
8 mm Hg
What is the average pressure of the left ventricle?
130 mm Hg (peak systolic)
What is pulmonary capillary wedge?
an index of left arterial pressure
How is a pulmonary capillary wedge done?
through the right atrium → into the right ventricle through tricuspid valve → through pulmonic valve → into pulmonary artery → wedge position → inflate balloon
When is a pulmonary capillary wedge used? why?
used in patients with heart failure to see if left atrial pressure is increasing
When does the “a” wave occur?
during atrial systole when the atrium contracts during atrial systole → increasing atrial pressure
Atrial Systole: When does atrial pressure drop?
when the atria stops contracting
When does the P wave occur? What makes it occur?
It occurs during atrial systole due to atrial depolarization
Atrial Systole: When does the fourth heart sound occur
it is associated with the end of atrial emptying after atrial contraction
When does the AV valve close?
at the beginning of isovolumic contraction
when the pressure in the ventricles exceeds the pressure in the atria
Isovolumic contraction: What happens to ventricular volume as the ventricles contract isovolumetrically?
their volume does not change
When does the QRS complex of the ECG occur? Why?
during isovolumic contraction due to ventricular depolarization
When does the first heart sound occur?
during isovolumic contraction due to AV valves closing
When do the aortic and pulmonary valves open?
at the beginning of rapid ejection
Rapid Ejection: What happens when the aortic and pulmonary valves open?
blood exits the ventricles and the volume in the ventricles decreases rapidly
blood enters the arteries until it reaches a peak
atrial pressure increases due to RV contraction opening the tricuspid valve
When do the aortic and pulmonary valves close?
at the end of reduced ejection
Reduced Ejection: What happens after ventricular and arterial pressures peak?
blood flow out of the ventricles decreases and ventricular volume decreases more slowly
Reduced Ejection: What happens when the pressure in the ventricles falls below the pressure in the arteries?
blood in the arteries begins to flow back toward the ventricles and causes the aortic and pulmonary valves to close
marks the end of ventricular systole
When does the T wave occur?
during reduced ejection due to ventricular repolarization
In what phase does diastole begin?
isovolumic relaxation
What is causing the atrial pressure to rise during isovolumic relaxation?
atrium in diastole is filling with blood
Isovolumic Relaxation: What causes the “v” wave?
back flow of blood after it hits the closed AV valve
When is ventricular volume at its lowest?
during isovolumic relaxation
When does the second heart sound occur?
during isovolumic relaxation when the aortic and pulmonary valves are closed
Rapid Ventricular Filling: What occurs when the AV valves open?
blood accumulated in the atria flows rapidly into ventricles → ventricular volume increases rapidly
When does the third heart sound occur?
during rapid ventricular filling
