Heart Physiology

Question 1

What causes the 4th heart sound

Answer 1

when the left atrium contracts into a stiff, non compliant left ventricle we hear the 4th heart sound: a low pitched sound heard best with the bell of the stethoscope at the apex with patient lying on left side
In patients with longstanding high BP, the left ventricle hypertrophies because it has to overcome a higher pressure in the atrium
Double sound of S4 and S1 is referred to as a gallop rhythm

Question 2

What causes the 3rd heart sound

Answer 2

Can be normal in a healthy young person, caused by rapid filling of the right ventricle by the right atrium; occurs immediately after S2
Can be caused by congestive heart failure because block is backing up into the atrium

Question 3

Draw a Pressure-volume loop. Label points 1-4, identify end diastolic pressure/volume;

Answer 3

To be inserted

Question 4

How do you calculate stroke volume?

Answer 4

EDV - ESV

Question 5

Draw Wigger’s diagram. Include the two divisions and the four major phases of the cardiac cycle. Include heart sounds, ECG, left ventricular volume, left atrial pressure, left ventricular pressure and aortic pressure

Answer 5

insert image

Question 6

Define preload

Answer 6

Amount of blood in heart before left ventricle contraction

Question 7

Describe congestive heart failure/acute pulmonary edema and it’s two causes

Answer 7

Raised pressure in left ventricle leads to raised pressure in atrium (must overcome to begin filling). This leads to back up of blood in pulmonary circuit and increase hydrostatic pressure which causes leaking into lung alveoli
Causes are systolic dysfunction (reduced ejection fraction) and diastolic dysfunction (described above)

Question 8

What’s the formula for compliance?

Answer 8

Change in volume/change in pressure

Question 9

What’s the formula for stiffness?

Answer 9

Change in pressure/change in volume

Question 10

What is a reduced ejection fraction?

Answer 10

Pump is weak and blood ends up backing up into atrium/lungs

Question 11

What’s a positive inotrope and what does it do to the isovolumetric pressure/volume relation?

Answer 11

Causes increased heart contractility, shifts the curve to the left

Question 12

What are four factors that affect left ventricular performance?

Answer 12

Preload (the more blood in the LV the more it is stretched and the stronger the contraction–> larger stroke volume and higher velocity), LV afterload, HR and contractility

Question 13

What is the afterload?

Answer 13

The pressure in the aorta that must be overcome for the LV to eject its volume; decreasing afterload increases SV and increasing it decreases SV

Question 14

What is acute cardiogenic shock?

Answer 14

low BP, tachycardia, acute pulmonary edema. Danger! Because normally with low BP we give fluids, but here that will worsen the pulmonary edema (increasing preload). Treatment is intra-aortic balloon pump

Question 15

What is mean systemic pressure?

Answer 15

The pressure measured when there is no CO and no venous return. Affected by volume (proportional) and compliance in veins (inversely proportional)

Question 16

How does resistance affect venous return?

Answer 16

Most resistance in veins leads to less venous return; but it does not affect mean systemic pressure

Question 17

What is TPR?

Answer 17

Total peripheral resistance, calculated by Change in pressure/CO
Total Peripheral Resistance = (Mean Arterial Pressure - Venous Pressure) / Cardiac Output
and venous pressure often disregarded b/c very low

Question 18

How does exercise affect CO/VR?

Answer 18

Heart becomes hyper effective due to sympathetic stimulation, curve shifts up and to the left.
MSP increases, vein becomes less compliant, blood pushed back up to heart quicker (because effect of MSP is larger than the effect of vasoconstriction due to sympathetic activation); venous return curve shifts to the right and the slope increases

Question 19

What series of events happens in an MI in terms of CO, atrial pressure and venous return?

Answer 19

Immediately - CO drops
Higher right atrial pressure
Then the body starts to compensate - sympathetic system kicks in, increases the MSP which shifts venous return to the right; slightly higher CO, even higher right atrial pressure
Eventually the kidneys recognize the low incoming flow (low CO) and start to retain water and salt; this shifts VR even farther to the right… CO is the same as before, but with a much higher filling pressure

Question 20

What is decompensated heart failure?

Answer 20

Multiple MIs, not a lot of viable heart tissue remaining; chronic water retention for the kidneys. Drugs are administered to lower filling pressures, prognosis is poor.

Question 21

Where is best to hear S1?

Answer 21

Apex of the heart

Question 22

Where is best to hear S2?

Answer 22

Aorta - 2nd upper right sternal border