Cardiac Cycle Flashcards
Describe what happens at each part of a typical ECG wave
P, atrial depolarization Q, septal depolarization => atria R, ventricular depolarization=> apex S, ventricular depolarization => atria T, ventricular repolarisation => endocardiogram
Name the valves and describe how they are affected by changes in pressure
RA => tricuspid => RV
RV => pulmonary => pulmonary arteries
Pulmonary veins => LA => mitral/bicuspid => LV
LV => aortic semilunar => aorta
Healthy valves have v little resistance so small pressure resistance so small pressure gradient across is enough for them to open
How to interpret a 2D ECG
Black areas = heart chambers
Top of cone, probe
Blue, away from probe
Red, towards probe (color doppler)
How do the valves operate under changing pressures
Opening valves due to pressure differences
AV, anchored to ventricle walls by papillary muscles, chord tendinae to prevent inverting
Bulge back into atria in ventricular systole, causes increase in atrial pressure and pulse of blood into jugular vein
How are the anchoring structures damaged and what happens as a result
After MI, AV valve everts into atrium
Backflow, can be seen as mitral regurgitation in ECG
Describe the pressure and volume changes in the heart
Fractional increase in LA pressure > LV pressure => mitral valve opens
LA contracts but not very much
LV contracts, isovolumic contraction (increase in pressure, no change in volume)
LV pressure increases, aortic valves still closed
Aortic valve opens when V pressure > aortic pressure
V ejection
End systolic pressure falls
LV pressure falls below aortic pressure, shuts => dicrotic notch => isovolumic relaxation
LV pressure falls below atrial pressure => mitral opens, V fills
Describe the steps in the pressure volume loop
Mitral opens, empty ventricles Period of filling Mitral closes Isovolumic contraction Aortic opens Period of ejection Aortic closes Isovolumic relaxes
What information can you get from the pressure volume loop
Volume differences => ventricular volume/stroke volume
Diastolic function
Systolic function
Total area, stroke/work
Describe the peaks and troughs found in jugular venous pressure
A, atrial contraction (systole)
C, carotid pulse (carotid parallel to jugular, crushed jugular => P falls)
X, Atrial relaxation
V, R atrial filling in ventricular systole, closed tricuspid bulging, increasing RA pressure (pushes blood => venous system)
Y, Passive atrial emptying
What are the main characteristics of the jugular venous pulse
Biphasic, low pressure
Easily affected by other factors,
Describe the peaks and troughs found in the peripheral arterial pressures
Peak after ventricular systole
Smaller peak, wave of pressure bounces off peripheral vessels
What are the main characteristics found in the peripheral arterial pressure waves
What is it influenced by?
Monophonic and high pressure
Shape of peak and descending phase influenced by
- Reflected waves
- Resonance
- Compliance
- Interference
- Damping
Shape and magnitude of arterial pulse wave varies along arterial tree
How do hydrostatic influences affect the jugular vein
What is the pressure found here
Will collapse at 5cm above RA due to hydrostatic influences, blood can still flow here
4-8mmHg
How does arterial pressure change
Changes as you move away from heart
Generally high
Increased height, increased BP as gravity moves everything down
How to judge if CVP is normal
Support patient at 45
JVP is height of collapse of internal jugular above manubriosternal angle
Collapse point = 3cm above MBS angle
If above 3cm, something is not right
Why use the internal jugular and not the external one
Anatomically closer than external to RA Drains directly => SVC Valveless, pulse can be seen Vasoconstriction, 2ndary to hypotension can make external small, not visible External is superficial and kink prone
How does tricuspid stenosis affect the JVP wave
Atrial wave enhanced (RA pressure increases in atrial contraction due to increased tricuspid resistance)
Ventricular wave diminished (V pressure wave not transmitted well through stenotic tricuspid so less blood pushed out to periphery)
How does tricuspid regurgitation affect the JVP wave
Atrial wave diminished
Ventricular wave enhanced (V contraction ejects blood through incompetent tricuspid, increased RA and J pressure as blood pushed into atria)
How does the arterial pressure pulse change as you get further from the heart
Why
Greater time delay
Dicrotic notch gets looser
Changes due to dampening, reflection, interference, resonance
Affected by vasoconstriction, compliance, aging, hypertension, drugs
Reflected waves interfere w forward compression wave => altered pulse wave
Describe how reflected waves in phase and out of phase affect pressure
Summative => P increased
Out of phase => P falls
What are the normal heart sounds
S1, initiation of V systole, AV closer, low frequency
S2, closure of semilunar valves, high freq, shorter
What are the secondary heart sounds
S3, Opening of AV valves, rapid refilling
S4, Atrial systole, rarely heard except when EDP raised
What happens when EDP is raised
S3, S4 heard too
Gallop rhythm
What are heart murmurs caused by
Turbulence in blood
Not always pathological, occurs in young and exercise
Caused by
- Valve stenosis
- Valve regurgitation
Heard between valve sounds
Types of diastolic murmur
Mitral stenosis
-Diastolic murmur as ventricle fills
Aortic incompetence
-Early diastolic murmur with softening and prolongation of 2ndary sound
Types of systolic murmur
Aortic stenosis
-Systolic murmur (high pressure)
Mitral incompetence
-Pansystolic (lush)
