CARDIOVASCULAR- PHYSIOLOGY Flashcards
How are the phases of the cardiac cycle outlined?
Each is given a letter
How many phases are there of the cardiac cycle?
7
Where does the cardiac cycle begin?
Depolarization and contraction of the atria
What does A in the cardiac cycle stand for?
Atrial systole
Note that this is the final phase of ventricular filling
What happens prior to atrial systole?
P-wave of the ECG (i.e. atrial depolarization)
What happens to left atrial pressure with contraction of the left atrium?
Increase in pressure
How is atrial systole reflected in the venous pulse graph?
A-wave–increase in atrial pressure is reflected back into the veins
What does a S4 heart sound correspond with?
- Atrial contraction in ventricular hypertrophy
- Atrium is contracting/filling against a stiffened left ventricle
What is B in the cardiac cycle?
Isovolumetric ventricular contraction
What part of the ECG corresponds to isovolumetric ventricular contraction?
QRS Complex (prior)
What major events occur during isovolumetric ventricular contraction?
1) Ventricles contract
2) Ventricular pressure increases without a change in volume
When LV pressure is greater than LA pressure, mitral valve closes
What heart sound is produced in phase B of the cardiac cycle?
S1 i.e. closure of the AV valves
In S1 splitting, what’s happening?
Mitral valve is closing slightly before tricuspid valve
What is phase C of the cardiac cycle?
Rapid Ventricular Ejection
What events happen in phase C of the cardiac cycle?
1) Ventricles continue to contract, increasing pressure
2) Ventricular pressure exceeds aortic pressure (reaches maximum)
- Aortic valve opens
3) Blood is ejected into the aorta
- Ventricular volume decreases
4) Aortic pressure increases and reaches maximum value
What part of the ECG corresponds to phase C of the cardiac cycle?
ST segment
What is phase D of the cardiac cycle?
Reduced ventricular Ejection
What major events occur during phase D of the cardiac cycle?
1) Blood continues to eject into the aorta
2) Ventricular volume reach minimum
3) Aortic pressure starts to fall
*Note that at the same time, left atrial pressure increases are blood enters from the pulmonary vein
What part of the ECG corresponds to phase D of the cardiac cycle?
T-wave i.e. ventricular repolarization
What is phase E of the cardiac cycle?
Isovolumetric Ventricular Relaxation
What are the major events that occur during Isovolumetric Ventricular Relaxation?
1) Ventricles relax
2) Ventricular pressure decreases
3) Ventricular volume is constant
What happens in terms of the cardiac valves during phase E?
Isovolumetric relaxation, aortic (and pulmonic) valve closes
What heart sound corresponds with aortic and pulmonic valve closing?
S2
Why is there normally splitting of S2?
Inspiration causes a delay in the closing of the pulmonic valve
What happens to the aortic pressure curve when the aortic valve closes?
Blip or dicrotic notch/ incisura
What is phase F of the cardiac cycle?
Rapid Ventricular Filling
What major events occur during rapid ventricular filling?
1) Ventricles relaxed and pressure falls (AV valves open)
2) Ventricles fill with blood from the atria
3) Volume increases but pressure is constant
What heart sound can be produced in rapid ventricular filling?
S3, rapid filling of the ventricles
- Normal in kids
- Abnormal in adults
What does S3 in an adult indicate?
- Volume overload e.g. CHF
- AV valve regurgitation
What is the phase G of the cardiac cycle?
Reduced Ventricular Filling or “Diastasis”
What major events occur during reduced ventricular filling?
1) Ventricles are relaxed
2) Final phase of ventricular filling
What marks the end of diastole?
Atrial systole
What physiologic change can reduce diastasis? What are the implications?
Increased HR–>decreased SV
What is stroke volume?
The volume of blood ejected by the ventricles with each beat
What is the ejection fraction?
Fraction of the end diastolic volume ejected with each beat
What is cardiac output?
Total volume of blood ejected from the heart per unit of time
What is the equation for stroke volume?
EDV- ESV= SV
What is a normal SV?
70 mL
What is the equation for EF?
SV/EDV
What is a normal EF?
0.55 or 55%
What is the equation for CO?
CO= SV x HR
What is a normal CO?
5,000 mL/min
Describe the Frank-Starling Relationship.
1) Volume of blood ejected by the ventricle is dependent on the volume of blood in the ventricle at the end of diastole (EDV)
2) EDV is dependent on the volume of blood returned to the heart i.e. venous return
Thus, the volume ejected in systole equals the volume the heart receives in venous return
What happens to EDV, RAP, and SV with increased venous return?
EDV, RAP, and SV all increase
What happens to SV with a positive ionotrope?
SV and CO increase for a given EDV
A larger fraction of the EDV is ejected per beat
Draw the ventricular pressure volume loop. Label points 1, 2, 3, and 4.
N/A (p.147)
What happens between points 1 and 2 in the ventricular pressure volume loop?
Isovolumetric contraction
Describe what happens during isovolumetric contraction.
- Isovolumetric contraction starts at the end of diastole–the ventricle is relaxed but filled with blood
- It CONTRACTS
- PRESSURE INCREASES but VOLUME remains CONSTANT
What happens between points 2 and 3 on the ventricular pressure volume curve?
Ventricular ejection
Describe what happens during ventricular ejection.
- Point 2, ventricular pressure exceeds aortic pressure–AORTIC VALVE OPENS
- Ventricle continue to contract–increasing pressure–as blood volume is ejected (volume goes down)
- Point 3, contraction ends with some volume of blood remaining in the ventricle– the ESV
What is the width of the ventricular pressure-volume curve?
Volume ejected from the ventricle in one beat: the SV
What happens between points 3 and 4 in the ventricular pressure volume curve?
Isovolumetric relaxation
Describe what happens during isovolumetric relaxation.
- Ventricle relaxes, dropping its pressure rapidly
- Ventricular pressure drops below aortic pressure, closing the aortic valve
All valves are closed; thus, NO CHANGE IN VOLUME
What happens between points 4 and 1 on the ventricular pressure-volume curve?
Ventricular filling
Describe ventricular filling.
- Ventricular pressure falls to a point less than left atrial pressure, MITRAL VALVE OPENS
- Ventricle fills with blood