The Cardiac Cycle 1 Flashcards
What’s a normal peak systolic pressure? What areas of the heart / vasculature experience this pressure?
Roughly 120 mmHg.
The left ventricle and aorta experience this pressure.
Should you confuse flow rate with flow velocity?
Nope.
Flow rate: L / min
Flow velocity: cm / s
What are the 4 phases of the cardiac cycle, from the perspective of the ventricles? How long does each last?
Isovolumetric relaxation (myocytes relax, but not enough to cause the tricuspid and mitral valves to open).
Diastolic filling.
Isovolumetric contraction (myocytes contract, but pressure doesn’t in ventricle doesn’t exceed that of PA or aorta).
Systolic ejection.
How long does isovolumetric relaxation usually last?
12-16ms
How long does diastolic filling of the ventricles usually last?
150-800ms depending on HR
How long does isovolumetric contraction usually last?
10ms
How long does systolic ejection usually last?
250-280ms
When do the atria fill?
During ventricular systole.
About how long before ventricular systole does atrial systole occur? During what phase of the ventricles’ cardiac cycle does it end?
120 - 160ms beforehand.
It should end during isovolumetric contraction (there’s some overlap of systoles).
Should diastolic relaxation be taken for granted?
Nope. It’s an active process, and optimum filling doesn’t occur when there’s reduced ventricular compliance.
4 components of the AV valves (mitral and tricuspid)?
Valve leaflets
Annuli fibrosa
Chordae tendineae
Papillary muscles
4 things that happen for AV valves to properly close?
Passive movement of valve leaflets driven by pressure.
Contraction of the annulus fibrosis.
Contraction of papillary muscles.
Proper contraction of ventricles such that valve leaflets line up.
What are 2 requirements for semilunar valve closure?
Passive movement of leaflets.
Contraction of annulus fibrosis.
(they’re simpler than AV valves)
What are 2 broad types of problems that occur with heart valves?
Regurgitation (backflow)
Stenosis (failure to fully open)
What is pulse pressure?
The difference between systolic and diastolic pressure.
What are the 3 phases of the arterial pressure waveform?
Rapid upstroke with early systole.
Rounded peak in mid to late systole (featuring the dichrotic notch due to semilunar valve closure).
Gradual decay of pressure in diastole.
4 parts of the atrial pressure waveform?
A wave: positive deflection due to atrial contraction
X descent: negative deflection due to atrial relaxation (diastole)
V wave: positive deflection due to atrial filling
Y descent: negative deflection due to atrial emptying
(I like to think of the Y descent as the ventricles’ relaxation “sucking” the blood out of the atria, then the A wave contraction gives a little extra kick)
What’s end diastolic pressure (LVEDP)? Significance?
Pressure in the LV at the end of diastole.
It reflects the extend of ventricular filling, aka. “preload.”
Do large arteries cushion the systemic circulation from the pressure changes of systole/diastole?
Yup.
Why is blood pressure in large arteries greater further from the heart?
Reflections from blood hitting small arteries.
the aortic valve seems to close just in time to be closed when the reflections hit
How does the effect of pressure wave reflections in arteries vary between young and old people?
In young people, compliant arteries cushion the reflections.
In older people, arteries stiffened by atherosclerosis can’t cushion the reflections, which can contribute to hypertension.
Say the systolic pressure is 120 mmHg in the LV. What’s the systolic pressure in the RV likely to be? Why?
Around 25 mmHg.
It’s lower because the top of the lungs aren’t as high up as the head (???… does that make sense?)
Why is diastolic pressure lower in the RV than in the LV?
Because the RV is more compliant.
What information does the right atrial pressure provide?
Blood volume and hydration state.
What region of circulation has the same pressure as the mean left atrial pressure?
The pulmonary capillaries.
