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cardiovascular mechanics > exam > Flashcards

exam Flashcards

1
Q

A patient with heart rate of 60 bpm and end systolic volume of 80ml and end-diastolic volume of 180 ml has cardiac output of?

A

6 l/m

100 ml/s

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2
Q

The patient has mean blood pressure of 100 mmHg and a diastolic blood pressure of 90mmHg. This corresponds to a systolic blood pressure of?

A

120 mmHg

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3
Q

What is the average flow in the left coronary artery if the patient has a cardiac output of 12 l/min?

A

600 ml/min

10 ml/s

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4
Q

When may a cardiologist use the simplified Bernoulli equation?

A

stenosis

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5
Q

Explain and draw the construction and function of an av-valve.

A

???

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6
Q
  1. Compute the total peripheral resistance in [Pa.s /cm³] for a cardiac output of 5l/min and a mean arterial pressure of 100 mmHg.
A

159,6 Pas/cm3

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7
Q

In an extracorporeal circuit (internal diameter 4.76 mm) flow 800 ml/min. is the flow laminar or turbulent?

A

laminar

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8
Q

Which leaflet is the most loaded?

A

mitral valve during systolic phase

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9
Q

The left atrium pumps blood into?

A

left ventricle

pulmonary veins

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10
Q

To solve an one dimensional flow problem one needs?

A

conservation of mass

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11
Q

Assuming a constant left ventricular wall stress in the myocardium means that if left ventricular pressure increases that…?

A

a reduction of volume over wall thickness ratio

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12
Q

Increasing arterial elastance leads to?

A

non correct

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13
Q

A pressure volume area shift to the right side in a PV-loop means?

A

increased preload

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14
Q

What is the influence of contractility and afterload on the stroke volume of the left ventricle?

A

preload + contrac. -> contrac. force + afterload -> stroke volume + heart rate -> cardiac output

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15
Q

laminar flow in a blood vessel is determined by?

A

viscosity of the fluid

geometry of the vessel

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16
Q

The Womersly parameter and Reynolds number are only valid for?

A

pulsatile flow

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17
Q

Wave separation of arterial waves is based on?

A

linear wave theory

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18
Q

Explain the vortex formation in the left ventricle.

A

concentric contraction of the ventricle with additional twisting -> no stop of blood flow

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19
Q

The characteristic impedance of an arterial circuit is?

A

pressure over flow

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20
Q

Arterial tonometry

A

needs a cuff blood pressure measurement for its calibration

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21
Q

The power of the right ventricle is…?

A

always lower than the left heart

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22
Q

Give the value of the “critical Reynolds number” for water in a straight tube! What is the meaning of a value smaller or higher than the “critical Reynolds number”?

A

crit: 2300 - 4000
above 4000: turbulent
below 2300: laminar
between: transitional

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23
Q

What is the relevance of preload of the left ventricle to cardiac output and coronary perfusion?

A

if preload goes up, cardiac output goes up and coronary perfusion is decreased

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24
Q

What is the critical Reynolds number for a vascular tube?

A

300

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25
Q

Explain the hemodynamic relevance of the “windkessel function” during the systolic phase.

A

reduced flow velocity and peak pressure because of the storage of energy/volume

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26
Q

Explain the hemodynamic relevance of the “windkessel function” during the diastolic phase.

A
  • perfusion of coronary system
  • ongoing perfusion of the systemic circulation
  • pressure and flow velocity are slowly decreasing
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27
Q

Explain the influence of arteriosclerosis (stenosis) on flow, resistance and pressure within the stenotic section of an artery and influence on Tissue supply?

A
  • increased flow velocity
  • increased resistance
  • decreased pressure
  • hardening/increase of stiffness of bloodvessel, therefore worse tissue supply
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28
Q

Where in the healthy arterial system the highest resistance is to be found under physiological conditions?

A

arterioles

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29
Q

List the advantages and disadvantages of bioprosthesis and mechanical prosthesis!

A 
mech:
\+ lifelong
\+ all sizes
- bad flow
- anticoagulants

bio:
+ antocoag only after surgery
- max 15 years (calcification etc)
- non human tissue

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30
Q

Describe the flow and pressure course during diastolic filling of left ventricle?

A

due to the ventricular contraction in the left ventricle, the pressure in the left atrium is higher than the pressure of the left ventricle. the mitral valve will therefore open and blood will flow from the la to the lv. when the pressure difference is equalized the mitral valve will close. after this an atrial contraction causes the mitral valve to open again, late filling phase.

31
Q

Describe the mechanisms of venous blood backflow to right atrium?

A

venolen -> venen -> vci/vcs -> right atrium

32
Q

Give pressure values for heart.

A

vcs/vci: -4 -7
right atrium: -4 + 7
right ventricle: 25/0
pulmonary artery: 25/10

left atrium: 6
left ventricle: 110/0
aorta: 110/70

33
Q

Where is in our body circulation flow is slowest?

Where the pressure is lowest?

A

slowest: capillaries
lowest: right atrium/vc

34
Q

What is the physiological range of systolic and diastolic blood pressure?

A

systolic: 110-140
diastolic: 60-90

35
Q

Is blood a Newtonian fluid?

A

no it is non newtonian

36
Q

Describe flow and pressure at vascular stenosis

A

flow velocity is higher

pressure lower

37
Q

What is the risk of dead-water-areas in a blood circulation?

A

coagulation -> developement of thrombosis -> can narrow the blood vessel diameter. if thrombus dissolutes can cause stroke

38
Q

How can we obtain a family of PV loops? What kind of additional information can we get if we have normal PV loops?

A

increase the preload in physiological range,

gives EDPVR and ESPVR curves

39
Q

What is pulsed-wave ultrasound Doppler?

What is used for it?

A

transducer that sends as well as receives signals. Ultrasound is emitted in “pulses”
The same transducer element receives the reflected signal. As every emitted pulse is paired with a corresponding return signal, it is possible to determine where the reflection has occurred and calculate the distance of the “reflector”
- used to record flow velocities in certain locations/depths

40
Q

Explain (the mechanism behind) diastolic suction (sometime called diastolic recoil) in the left ventricle?

A

it is due to the low pressure on the left ventricle after the systolic ejection phase

41
Q

What is laminar flow?

A

fluid flows orderly in parallel layers (parallel to pipe wall), with no disruption between the layers and no lateral mixing. There are no cross-currents perpendicular to the direction of flow

42
Q

What is the Wormersley number?

A

It is a dimensionless expression of the pulsatile flow frequency in relation to viscous effects

43
Q

What is the meaning of “Kinematic Viscosity”?

A

viscosity of a fluid expresses its resistance to shearing flows. The kinematic viscosity is the ratio of the dynamic viscosity to the density of the fluid.

44
Q

What is the “Geometric Tapering” of arterial circulation?

A

describes the change in diameter of the aortic tree. causes a continuous increase in pressure wave velocity and aortic impedance distal to the heart.
relatively speaking, the aorta wall is much thinner than artery and arteriole walls and is made of 70% elastic muscle fibers to increase the windkessel function

45
Q

What is dynamic viscosity?

A

expresses a fluids resistance to shearing flows

46
Q

Explain the “Frank-Starling-Mechanism”

A

states that the stroke volume of the heart increases in response to an increase of the end diastolic volume when all other factors remain constant.
The increased volume of blood stretches the ventricular wall, causing cardiac muscle to contract more forcefully (the so-called Frank–Starling mechanisms).

47
Q

What is the relationship between mother and daugther vessel pressure drop for a biforcation?

A

dP1/dP2 = D^2/n

48
Q

Where at a biforcation can calcifications be observed and wy?

A

on the outside border of the vessel because the speed there is the lowest.

49
Q

What is “Preload”? Give an explanation and describe the importance in the cardiac cycle as well as factors which can influence the preload!

A

it is a passive force, not induced by ventricular contraction but by the filling of the ventricle. also end diastolic volume. together with the afterload it defines the stroke volume of the cardiac cycle.

can be influated by:
-heart rate
\+ venous pressure
- mitral inflow resistance
\+ atrial contractility
\+ vent. compliance
50
Q

Effect of preload in filament proteins myosin and actin?

A

increasing the the preload causes a reduced interaction of the filament proteins, because the heart cells are being stretched out to much and myosin and actin lose contact

51
Q

What is “Afterload”? Give an explanation and describe the importance in the cardiac cycle as well as factors which can influence the afterload!

A

active effect due to the contraction on the left ventricle during the systolic ejection phase. has to overcome a peripheral resistance after the heart

influences:
stenosis
heart valve deseases

52
Q

Which factor can influence the cardiac output?

A

directly: stroke volume and heart rate
indirectly: smoking, high blood pressure, other genetic deseases (kidney failure)

53
Q

Give a definition of “Compliance”?

A

The term compliance is used to describe how easily a chamber of the heart or the lumen of a blood vessel expands when it is filled with a volume of blood.
(C) = (ΔV) / (ΔP).

54
Q

Describe the effect of high preload on coronary perfusion.

A

a higher preload can reduce the flow of the inner layers of the heart due to volume expansion of the left ventricle. therefore the coronary arteries are less perfused

55
Q

Describe coronary perfusion during the systolic phase.

A

during the systolic phase, the left ventricle contracts, causing the aortic valve to open and therefore closing the opening to the left and right coronary artery, resulting in the corr. arr. not being perfused during the systolic phase. the vent. contr. causes the blood in the corr. arr. to move in direction of the coronary sinus

56
Q

What is the “Diastases” during diastolic function of the left ventricle?

A

after the early filling phase of the left ventricle, the mitral valve closes. the pressure of atrium and ventricle are the same and there is no blood flow. this is called the diastasis. a atrial contraction will cause the mitral valve to open again after the diastasis, the so called late filling phase.

57
Q

What is the dynamic pressure?

A

is the kinetic energy per unit volume of a fluid particle,
can be measured with pitot tube

P(dyn) = 1/2 * p * v^2

58
Q

Define Contractility.

A

contractility represents the natural ability of the myocardium to contract.

c+ -> SV+ -> Preload+
Afterload+ or HR+ -> c+

59
Q

Define elastance.

A

elastance is a measure of the tendency of a hollow organ to recoil toward its original dimensions upon removal of a distending or compressing force

(E) = (ΔP) / (ΔV)

60
Q

Describe the flow from the mitral valve to the aortic valve.

A

??

61
Q

Where in the systemic circulation can we find real laminar flow?

A

in the capillaries

62
Q

Explain shear stress.

A

stress parallel to the surface of a material. for example the motion of a fluid on a surface results in shear stress.
T = F/A (Pa)

63
Q

Explain shear rate.

A

the rate at which a progressive shearing deformation is applied to a material. typical for fluids, layers sliding onto each other

y = v/h

64
Q

Is there backflow to the lung during left ventricular contraction?

A

no, because the mitral valve is closed

65
Q

Function of the bulbi of aortic valve?

A

after the ejection phase, the bulbi create a backflow which causes the cusp to close fast and efficient. has a nice wash out effect and no dead-water areas exist.

66
Q

Which wave or period in the ECG indicates the contraction of the atria?

A

the P-wave

67
Q

How can a decreased compliance be seen in a PV loop?

A

ventricle is stiffer -> higher EDP with for any given EDV and vice versa. slope EDPVR curve is higher.

68
Q

How do you calculate the ejection fraction?

A

EF = Stroke Volume / EDV

69
Q

PV loop for dilatated left ventricle.

A

ESV and EDV increase, pressure relatively unchanged, ESPVR and EDPVR shift to the right

70
Q

Explain LaPlace law in means of wall mechanics.

A

sigma = Pd / 4t

wall tension shld be kept constant. if P+ -> t+ -> hypertrophia of the muscle

71
Q

Effect of spiral course of ventricle muscle layer?

A

concentric contraction with twisting -> no stop of blood flow

72
Q

What is the dicrotic notch?

A

the sudden drop in pressure after systolic contraction, caused by the flow back of blood in the arteries when the valve is still in closing up phase.

73
Q

Wedge pressure?

A

Because of the large compliance of the pulmonary circulation, it provides an indirect measure of the left atrial pressure.
how? by wedging a pulmonary catheter with an inflated balloon into a small pulmonary arterial branch

74
Q

How can you measure preload and afterload in the PV loop?

A 
pre = enddiastolic volume
after = endsystolic volume

cardiovascular mechanics (1 decks)

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