Heart Physiology Flashcards
(22 cards)
What causes the 4th heart sound
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
What causes the 3rd heart sound
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
Draw a Pressure-volume loop. Label points 1-4, identify end diastolic pressure/volume;
To be inserted
How do you calculate stroke volume?
EDV - ESV
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
insert image
Define preload
Amount of blood in heart before left ventricle contraction
Describe congestive heart failure/acute pulmonary edema and it’s two causes
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)
What’s the formula for compliance?
Change in volume/change in pressure
What’s the formula for stiffness?
Change in pressure/change in volume
What is a reduced ejection fraction?
Pump is weak and blood ends up backing up into atrium/lungs
What’s a positive inotrope and what does it do to the isovolumetric pressure/volume relation?
Causes increased heart contractility, shifts the curve to the left
What are four factors that affect left ventricular performance?
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
What is the afterload?
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
What is acute cardiogenic shock?
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
What is mean systemic pressure?
The pressure measured when there is no CO and no venous return. Affected by volume (proportional) and compliance in veins (inversely proportional)
How does resistance affect venous return?
Most resistance in veins leads to less venous return; but it does not affect mean systemic pressure
What is TPR?
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
How does exercise affect CO/VR?
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
What series of events happens in an MI in terms of CO, atrial pressure and venous return?
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
What is decompensated heart failure?
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.
Where is best to hear S1?
Apex of the heart
Where is best to hear S2?
Aorta - 2nd upper right sternal border
