Cardiac cycle and haemodynamics Flashcards
Name the 5 steps of the cardiac cycle
- Diastole
- Atrial systole/ventricular diastole
- Ventricular systole (isovolumic contraction)
- Ventricular systole (ejection)
- Ventricular diastole (isovolumic relaxation)
When do you hear the first heart sound?
During isovolumic contraction when the Av valves snap shut, but the SLs are still closed
When do you hear the second heart sound?
During isovolumic relaxation, when the SLs snap shut, and the AVs are still closed
On average, how long does a cardiac cycle take?
1-1.5 seconds
What is present on a Wigger’s diagram?
- AP (aortic pressure)
- LAP (left arterial pressure)
- LVP (left ventricular pressure)
- LVEDV
- LVESV
what is the max LVEDV?
120mL (100mL from passive filling, last 20mL comes from atrial contraction)
What are the four heart sounds?
S1: AV valves (two sounds, cannot be distinguished clinically)
S2: SL valves (two sounds)
S3: rush of blood during rapid diastolic filling (apparent in youth, exercise and pregnancy)
S4: forceful atrial contraction needed to overcome residual pressure in the ventricles (following ventricular hypertrophy)
What is mitral regurgitation?
A systolic heart murmur (as the mitral valve is only closed during systole)
The sound of blood rushing back into the left atria
What is Ohm’s law?
Flow = change in pressure/resistance
What is resistance related to?
- inversely proportional to the 4th power of the vessel radius
- directly proportional to the vessel length (l)
- directly proportional to blood viscosity (n)
What is poiseuille’s law?
R = 8nl/pi r^4
What does the flow through a tube equal?
pressure difference x radius ^4 / viscosity x tube length
How do you calculate resistance to blood flow in series?
R total = R1 + R2…
How do you calculate resistance to blood flow in parallel?
1/R total = 1/R1 + 1/R2….
What are some calculations of cardiac output?
CO = MAP-RAP/TPR
CO = SV x HR
