10. Cardiac Cycle and Heart Sounds Flashcards
2 basic causes of abnormal heart sounds (reflect changes in the valves)
- Regurgitation: valve unable to close or stay closed, blood flows in wrong direction
- Stenosis: narrowing, valve doesn’t open fully when its supposed to, making it hard for blood to get where it needs to be
what are the two ways a murmur can be classified
systolic vs diastolic
what happens to the SL valves and AV valves is a systolic murmur
- stenosis of SL valves; valves open but hard for blood to get out of ventricles
- regurgitation of AV valves; valves are closed allows blood to be squeezed back into atria
when and where can you hear a systolic murmur
- superimposed between lub and dub (during ventricular systole)
- heard at distinct listening points for AV and SL valves
what happens to the SL and AV valves in a diastolic murmur
- regurgitation of SL valves; valves closed but blood flows back into ventricles
- stenosis of AV valves; valves open but hard for blood to get out of atria
describe aortic pressure throughout cardiac cycle
- atrial systole
- IVC
- ejection
- IVR
- rapid inflow
- diastasis
Atrial systole: starts on a slow decline, ventricles are relaxed and no blood is moving into the aorta
- Peripheral run-off:
IVC: Pressure in ventricles increases enough to push open aortic valve at end of IVC
- Diastolic blood pressure
- Aortic pressure is very close to ventricular pressure (although ventricular is slightly higher)
Ejection: Blood rushes into aorta
- Systolic blood pressure
IVR: Aortic valve closes → Dicrotic notch
Rapid inflow, diastasis and atrial systole: Pressure gradually drops as blood moves into periphery
what is peripheral run off and when does it occur
- decline in pressure d/t movement of blood from aorta to periphery
- if TPR is high, blood moves slowly and pressure decreases slowly
- occurs in atrial systole, aortic pressure
describe diastolic vs systolic blood pressure in terms of aortic pressure
Diastolic blood pressure = aortic pressure when valve opens and blood begins to enter into aorta
Systolic blood pressure = peak of aortic pressure
Ventricles begin to relax, aortic pressure falls (from ~120 to 100)
what is the dicrotic notch
Slight increase in aortic pressure d/t closing of aortic valve as ventricle relaxes
describe ventricular pressure throughout cardiac cycle
- atrial systole
- IVC
- ejection
- IVR
- rapid inflow
- diastasis
Atrial systole: Ventricles at rest, blood from atria flows. Atrial contract causing a slight increase in pressure. Followed by a slight decrease in pressure caused by stretching of cardiac muscles. AV valve closes.
IVC: rapid increase in pressure b/c both valves are closed. SL valve opens at end of IVC when ventricular pressure > aortic pressure
Ejection: pressure continues to increase until it reaches peak ventricular pressure (systolic pressure), ventricles begin to relax and pressure begins to fall. SL valve closes at end of ejection
IVR: Pressure falls quickly after closing of SL valve. AV valve closes when ventricular pressure < atrial pressure
Rapid inflow, diastasis: pressure remains low until atrial systole
describe systolic vs diastolic pressure in terms of ventricular pressure
diastolic: when pressure in ventricle > aorta; opening of aortic valve
systolic: peak of ventricular pressure
describe atrial pressure throughout cardiac cycle
- atrial systole
- IVC
- ejection
- IVR
- rapid inflow
- diastasis
Atrial systole (A-wave): pressure increases shortly after P wave d/t atrial contraction pushing blood into the ventricle then falls to near 0 - AV valve closes
IVC (upstroke of C-wave): sharp increase in pressure d/t rapidly increasing ventricular pressure causing bulging of AV valve into atria
Ventricular ejection (downstroke C-wave): SL valve opens and relieves pressure on AV valve, atrial pressure drops again. Pressure gradually increases w/ venous return V-wave: atrial pressure gradually increases
IVR: AV valve opens at end, atrial pressure drops
Rapid inflow, diastasis: pressure remains low
***jugular pressure wave is basically the same
describe the a-wave, c-wave, and v-wave of ventricular pressure
a-wave: increase in atrial pressure d/t atrial contraction
c-wave: increase in atrial pressure d/t bulging of AV valve into the atria
v-wave: pressure created as blood returns back to heart but cant enter ventricle
describe ventricular volume throughout cardiac cycle
- atrial systole
- IVC
- ejection
- IVR
- rapid inflow
- diastasis
Atrial systole: ventricles relaxed but near max volume near max d/t returning blood is able to flow into ventricle.
Atrial contraction causes an increase in ventricular volume as it “tops off” off the ventricle
- End diastolic volume (EDV): volume of blood in ventricle before systole start
IVC: volume doesn’t change at the beginning of systole because in early phase of contraction both the AV and SL valves are closed (isovolumetric contraction: pressure increases, volume stays same).
- SL valve opens when ventricular pressure > SL pressure
Ejection: SL valves open and volume rapidly decreases, line flattens out
IVR: ventricles relaxed, volume does not change (isovolumetric relaxation). SL valves close before AV valve open (nothing in or out). AV valve opens at end of IVR.
Rapid inflow: rapid ventricular filling, filling slows mid way through and flattens out
- Can be associated with turbulent blood flow into ventricles
Diastasis: volume relatively constant
what is the lowest ventricular volume for a healthy heart
50 mL aka ESV
what is happening during atrial systole
- preceded by p-wave (end of p-wave, QR)
- purpose is to “top off” the ventricular volume; atrial contraction forces blood into ventricle (4th heart sound)
- increase in atrial pressure = a-wave
- end of systole: atria begin to relax; A and V pressure decrease a little; AV valves close
what is happening during IVC
- begins after onset of QRS
- AV valve closes at beginning of IVC when ventricular pressure > atrial pressure (1st heart sound)
- ventricular pressure increases rapidly w/ contraction
- AV valves bulge into atrial, causing increased atrial pressure. Valves prevented from everting by papillary muscles.
- SL valve opens at the end of IVC when ventricular pressure > aortic pressure
what is happening during ventricular ejection
- SL valve opens, blood pushed into aorta; most of SV is ejected
- atrial filling begins
- onset of T wave in the middle of ejection marks end of ventricular contraction and beginning of relaxation
- ejection of blood continues but is slowed, ventricular pressure begins to decrease
- aortic pressure also increases and decreases w/ ventricular pressure
- SL valve closes at end
what is happening during IVR
- ventricle repolarization is complete (T wave ended)
- SL valve closes (2nd heart sound), causes dicrotic notch
- ventricular pressure decreases rapidly, volume is constant because all valves are closed
- at the end, atrial pressure > ventricular pressure and AV valve opens
what is happening during rapid ventricular filling
- AV valve is open and ventricles begin to fill rapidly (3rd heart sound)
- aortic pressure continues to decrease d/t peripheral run off
what is happening during diastasis
- ventricular filling continues but at a slower rate
- ventricular pressure is almost equal to atrial pressure
which phase of the cardiac cycle does the heart spend the most time in
diastole
how does HR affect diastole
High HR: diastole can be shortened
- ventricular filling time sacrificed, blood pressure decreases because CO cant keep up
- most likley to occur at >200 bpm
Low HR: diastole can be prolonged
- ventricular filling is normal, blood pressure drops d/t slow HR
what events occur to cause the 1st heart sound and when
- Closing of AV valves at beginning of IVC
- Blood entering atria hits closed valves
- RST
what events occur to cause the 2nd heart sound
- Closing of SL valves; occurs when dicrotic notch occurs in atrial pressure curve
- Blood in the aortic/ pulmonary arteries moving backwards when pressure from ventricle is cut off
- end of T wave
what events occur to cause the 3rd heart sound
- Period of rapid ventricular filling in early diastole
- Not normally heard in adults
what events occur to cause the 4th heart sound
- Blood forced into ventricle during atrial contraction
- Occurs just before S1
- Not normal to hear in adult, can hear with gallop rhythm (HR high enough that S3 merges with S1)
what is normal aortic pressure?
pulmonary artery?
aortic: 120/70
pulmonary: 25/15
