CVPR Week 2: Cardiac Cycle Flashcards
Objectives
The heart functions as?
Anatomy of heart chambers
Mitral valve resembles a?
Bishops miter
Heart valves
4 listed
Cardiac cycle key points
- Electrical events precede mechanical events
- Atria contract prior to ventricles
- Flow moves from high to low pressure (in general)
- All valves are unidirectional
Diastolic filling
- left atrium across left ventricle across mitral valve
- small pressure gradient drives blood from aorta to ventricle
- ventricle is in a relaxed state
- Tricuspid and mitral valves are open
- Semilunar valves are closed
Semilunar valves
pulmonary and aortic valves
Diastolic filling valve status
- Tricuspid and mitral valves are open
- semilunar valves are closed (pulmonary and aortic)
Atrial systole
- atria are contracting facilitating the ventricle filling
- immediately preceded by the P-wave of the ECG
- increasing pressure gradient in the atria driving to the ventricle
- This contributes to < 20% of total ventricular filling at rest
- Can increase to 40% with heavy exercise
P-wave
P-wave results from atrial depolarization
Ventricular systole
- the ventricles contract period of isovolumic contraction (short period of time when the ventricular pressure is still lower than aortic pressure so the aortic valve remains closed
- Mitral valve closes
- Aortic valve closes
- All valves closed
- The Same volume of blood as in the end of atrial systole = end diastolic volume
- corresponds to the QRS complex
typical end diastolic volume
Textbook ~ 120 mL
Isovolumic contraction description
- a short period of time when the ventricular pressure is still lower than the aorta
- all valves are closed
- the volume of blood is the same as it was at the very end of diastole (end-diastolic value)
Isovolumic contraction occurs when?
During ventricular systole
Isovolumic contraction AKA
Same volume contraction
corresponds to the QRS complex
immediately precedes Ventricular systole
corresponds to the P-wave
immediately precedes Atrial systole
Ventricular systole - ventricular ejection
- As soon as ventricular pressure exceeds aortic pressure the aortic valve opens
- The stroke volume is the volume of blood that is ejected from the ventricle at this time
The stroke volume
is the volume of blood that is ejected from the ventricle during ventricular ejection
End-diastolic volume (120 mL) - End-systolic volume (40 mL) = stroke volume (80 mL)
Typically 80 mL
Ejection fraction
Stroke Volume (80 mL) /End Diastolic Volume (120 mL) = Ejection fraction (67%)
typically 67% at rest
- can be up around 90% in elite athletes with heavy exercise
- can be down around 20% with congestive heart failure
Isovolumic relaxation
- follows the T-wave of ECG (reflects ventricular repolarization)
- no blood flow valves are closed because the left atrium has lower pressure and aortic pressure is higher than that of the left ventricle
- however, during this period, the left atrium is increasing in pressure due to blood returning from the pulmonary veins
Diastolic filling resumes
as soon as ventricular pressure is less than atrial pressure the mitral valve opens and blood rushes in the ventricle
~ 80% of ventricular filling from this phase
Complete cardiac cycle
Wigger’s Diagram
- Reduced ventricular filling
- Atrial systole
- ventricular isovolumic contraction
- ventricular ejection
- Isovolumic relaxation
- Diastolic filling resumes
Wigger’s Diagram: Atrial Systole: Venous pressure waveform
venous pressure waveform: a wave: atrial contraction
the only thing is that the atria do contribute to ventricular filling which is not represented on this diagram
Wigger’s Diagram: Atrial Systole: Heart sounds
S4: Atrial contraction (not normal, occurs with ventricular hypertrophy)
Wigger’s Diagram: Isovolumic contraction: venous pressure waveform
c wave: displacement of AV valve during isovolumic contraction of the ventricle
period of constant volume
Wigger’s Diagram: Isovolumic contraction: Heart sounds
S1: Closure of A-V valves (Lub heart sound)
Wigger’s Diagram: Ventricular ejection: features
- Aortic valve opens
- broken down into rapid ejection period and reduced ejection period
- big fall in ventricular volume
- In the reduced ejection period, the ventricles are beginning to relax
- associated with T-Wave of ECG
Wigger’s Diagram: Isovolumic contraction: diagram features
- ventricular volume remains constant
- ventricular pressure rapidly increasing
- short period of time with constant volume as ventricular pressure is still less than aortic pressure
Wigger’s Diagram: Isovolumic contraction: venous pressure waveform
C wave displacement of AV valve during isovolumic contraction of the ventricle
T wave is during this period and represents
- systole
- reduced ventricular ejection
- represent repolarization of ventricles
in reduced ventricular ejection ventricular pressure
- actually falls a little below aortic pressure but the aortic valve remains open due to the inertia created by the ventricular contraction and blood continues to be ejected for a short period of time despite the reversal of the pressure gradient
- Slight reversal but still have blood flow
Wigger’s Diagram: Isovolumic relaxation: features
- when ventricular pressure falls below aortic pressure the aortic valve closes but the mitral valve is also closed (ventricular volume is constant during this time because ventricular pressure is still greater than atrial pressure)
- Dicrotic notch- results from elastic recoil of the aorta and aortic valve closure
- S2 heart sound
- atrial pressure is increasing during this time since the mitral valve is closed
Dicrotic notch
results from elastic recoil of the aorta and aortic valve closure
Aorta essentially function s as a secondary pump even when the ventricles are relaxing driving blood (hydraulic filtering phenomenon)
Wigger’s Diagram: Isovolumic relaxation: Heart sounds
S2 closure of semilunar valves (dub heart sound)
Question
Question
Question
Question
Pressure in the right side of the heart
Blood volume in the left and right side of heart
very important that right and left cardiac outputs are equal
if not blood can pool in places like the lungs (pulmonary edema) happens to patients with heart failure
if pulmonary fails can have build up in lower extremities
Chronic pulmonary hypertension leads to?
Coronary flow during the cardiac cycle
Summary
