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Echo > Module 3 : Cardiac Hemodynamics > Flashcards

Module 3 : Cardiac Hemodynamics Flashcards

1
Q

Pressure - equation

A

Force/ unit area

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2
Q

Potential energy (static pressure)

A
  • ability to do work

- created by contraction of the ventricles AND vascular resistance from arteries

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3
Q

Kinetic energy

A
  • energy of motion

+ blood, walls

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4
Q

Gravitational energy

A
  • effect of gravity on static pressure

+ venous pressure in lower extremities

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5
Q

Normal blood pressure (BP)

A
  • 120/ 80 mmHg
    + top number = systolic = max pressure = 120 mmHg
    + bottom number = diastolic= min pressure = 80 mmHg
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6
Q

High BP

A
  • greater than 140/90 taken on 2 separate occasions
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7
Q

Borderline BP

A
  • 130/85 should be watch over time as it may increase
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8
Q

Mean Pressure

A
  • average pressure over the cardiac cycle
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9
Q

Resting heart rate - systole time

A
  • systole occupies 1/3 length of cardiac cycle time at resting heart rate
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10
Q

Resting heart rate - diastole time

A
  • diastole occupies 2/3 cardiac cycle time at resting heart rate
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11
Q

How would the length change if heart rate (HR) increases

A
  • systolic length would increase
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12
Q

Mean Pressure Equation ( mean arteriole pressure MAP)

A

MAP = diastolic P+ 1/3 pulse pressure

  • MAP= DBP + 1/3(systolic blood pressure - diastolic blood pressure)
    • SBP = systolic blood pressure
    • DBP = diastolic blood pressure
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13
Q

Pulse pressure

A
  • pulse pressure = SBP - DBP

Done with the cuff ( first sound - last sound)

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14
Q

Pressure gradient

A
  • difference in pressure between adjacent locations within the heart
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15
Q

Natural flow direction

A
  • higher to lower pressure until pressure equalize
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16
Q

Relationship between pressure and volume

A
  • as pressure gradient increases velocity increases
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17
Q

Bernoulli’s equation (simplified)

A
  • Pressure gradient = 4 x V^2
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18
Q

The cardiac cycle - phases

A 
1. IVCT = isovolumic contraction time 
      \+ heart about to contract 
      \+ END DIASTOLE 
2. systole 
3. IVRT - isovolumic relaxation time
      \+ heart about to relax 
      \+ END SYSTOLE
4. Diastole ( 3 phases)
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19
Q

IVCT - isovolumic contraction time

A
  • iso= same ; volumic = volume
    + no change in volume of the heart ALL VALVES CLOSED
  • period time between MV closer and AV valve opening
  • LV Pressure rising from 5 - 80 mmHg
  • ventricle starting to squeeze
  • 30 to 50ms
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20
Q

Threshold pressure for systole

A

Ventricle needs to reach 80 mmHg before the aortic valves open

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21
Q

Ventricular systole

A
  • period of time it takes for the ventricles to eject their contents
  • starts when LV/RV Pressure exceeds that of aorta and valves open
  • finishes when LV/ RV Pressure falls below aorta and valves
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22
Q

Valve movement

A
  • valves are passive and only move in response to a pressure change
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23
Q

Ventricular systole events

A
  • MUSCLE CONTRACTION BEGINS AT THE APEX AND MOVES TOWARD THE BASE OF THE HEART
  • rising pressure in the ventricles closes MV and TV and chordae prevent valve prolapse
  • pap muscles contract to pull chordae back in valves
  • 200-300ms
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24
Q

IVRT- Isovolumic Relaxation Time

A
  • period of time after the aortic valves closes that before the mitral valve open
    • END SYSTOLE
  • volume remains constant
  • PRESSURE FALLING IN THE VENTRICLES
  • 50 - 100ms
  • pressure in atria rising in prep to fill ventricles
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25
Q

Atria falling

A
  • ATRIA ALWAYS FILLING BECAUSE NO VALVES BETWEEN PULMONARY VEIN AND ATRIA
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26
Q

Diastole

A
  • period of time when the MV/TV are open and blood moves from atria to ventricles
  • STARTS WHEN LV PRESSURE FALLS BELOW ATRIA PRESSURE
  • FINISHES WHEN LV PRESSURE ABOVE ATRIA
  • 3 PHASES
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27
Q

3 phases of diastole

A
  • early filling = rapid filling , suction, first bump
  • diastasis = Pressure equalized, stopping
  • late filling = atria contraction , double bump
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28
Q

Early filling

A
  • pressure in LV falls below LA the MV opens
  • LV chamber expands rapidly dropping pressure in LV which sucks blood from LA (negative pressure)
  • 75% of filling done during this time
  • lasts 150-220ms
  • FIRST BUMB
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29
Q

Diastasis

A
  • period of time after early filling has slowed down
  • early filling stage pressure between LV and LA roughly equal causing the MV to “hang” in semi open position
  • near end atria polarizes
30
Q

Late filling

A
  • slow filling or atrial kick
  • atria depolarize and contract pressure in atria is higher than ventricle
  • pushes MV open again and adds last 30% of blood to LV
31
Q

Pressure changes within the heart - LV

A

100-140/ 3-12

32
Q

Pressure changes within the heart - LA

A

Average 2-12

33
Q

Pressure changes within the heart - RV

A

15-30/ 2-8

34
Q

Pressure changes within the heart - RA

A

Mean 2-8

35
Q

Volume changes in LV

A 
IVCT = END DIASTOLE = VERY FULL
systole = emptying
IVRT = END SYSTOLE = SMALLEST
diastole = filling again
36
Q

stroke volume

A

stroke volume is the volume of blood pushed in the heart

* NORMAL = 50 - 100 ml/beat AT REST

37
Q

stroke volume using chamber volume

A

we can use the LV chamber volume at end diastole and end systole to calculate the stroke volume

38
Q

stroke volume equation - using chamber volume

A

SV = EDV - ESV

39
Q

cardiac output

A

amount of blood ejected from the heart

40
Q

cardiac output equation - using stroke volume

A 
CO = stroke volume x heart rate
CO = SV x HR
41
Q

cardiac index

A

amount of blood being ejected from the heart compared to body surface area

42
Q

cardiac index equation - using cardiac output

A 
CI = cardiac output / body surface area 
CI = CO / BSA
43
Q

stroke volume using doppler

A

individual flow velocities must be integrated over the time period of the ejection

44
Q

stroke volume equation - using VTI and CSA

A 
SV = cross sectional area x velocity time integral 
SV = CSA x VTI
45
Q

velocity time integral VTI

A

the amount of individual flow velocities calculated over the time period of ejections

46
Q

cross sectional area CSA

A

calculated at the LVOT diameter

CSA = pi x r^2

47
Q

stroke volume calculation

A

stroke volume through any valve in the heart can calculated by using the CSA of the valve annulus and the PW VTI

48
Q

oxygen saturation - pulmonary artery

A

75% = deoxygenated

49
Q

oxygen saturation - aorta

A

98% = oxygenated

50
Q

oxygen saturation - coronary sinus

A

50% saturated

51
Q

oxygen demand - Left Ventricle

A

comprises most of the hearts mass
uses aprox 50% of the oxygen supplied in the coronary arteries at rest
* hypertrophied LV the amount of oxygen needed by the LV would increase

52
Q

ischemia

A

feels line angina pectoris

not felt until affected coronary artery blocked about 75%

53
Q

angina pectoris

A

caused by not enough oxygen and nutrients getting to the heart muscle
or too much heart muscle
or high after load

54
Q

factors affecting stroke volume

A

preload, after load, inotropic force, chronotropic force

55
Q

preload

A

AMOUNT OF VOLUME OF BLOOD IN THE VENTRICLE AT END DIASTOLE
+ volume load delivered to the ventricle
in diseased heart increased preload or afterload the ventricle fails and they go into CHF

56
Q

End diastolic volume + Stroke volume

A

Frank - Starling law

57
Q

Frank - Starling law

A
  • the heart adapts to different preloads by pumping the volume of blood delivered to it
    + more blood enters the heart = greater force of contraction = due to greater stretch of the myocardial muscle fibers
58
Q

Frank - Starling principle (length-tension relationship)

A
  • degree of stretch of the cell in the ventricle wall
    + determined by the volume of blood within the chamber
  • the FORCE OF CONTRACTION is greater when the LV muscle is stretched prior to contraction by increased preload
    + more blood to the heart (preload) , greater tension, greater force generated during systole , greater stoke volume
59
Q

heart rate + preload + frank - starling

A

slow HR - more time for ventricular filling = more ventricular stretch
high HR - less time for filling, less time for ventricle to expand and stretch = less stretch

60
Q

factors affecting cardiac output

A

preload - degree of stretch on heart before contraction
after load - resistance heart must pump against
inotropic force - contractility of the heart
chronotropic heart - HR of rate of contraction

61
Q

inotropic force ( force - velocity relationship)

A
  • contractility of the heart muscle or force of contraction
62
Q

preload + inotropy

A
  • further you stretch a rubber band the faster it comes back together the stronger the force
  • increasing preload = increase inotropy
63
Q

after load

A
  • resistance to ventricular emptying (arterial hypertension or valvular stenosis)
64
Q

factors affecting after load

A
  • viscosity of blood ( little effect)
  • arterial resistance ( thickness of tunica intima)
  • vascular geometry (plaque, curves, bifurcation)
  • valvular stenosis
65
Q

factors effecting inotropic force

A
  • structural organisation = hypoxic, ischemic, infarcted, fibrosed, infiltrated muscle tissue
    • LEADS TO NEGATIVE INOTROPIC RESPONSE LV CANNOT CONTRACT ENOUGH
  • medication = digitalis / sympathetic nervous system
    • POSITIVE INOTROPIC RESPONSE MAKE IT EASIER FOR LV TO CONTRACT
66
Q

chronotropic force

A
  • heart rate / rate of contraction

- how fast and how much the walls move inward during systole

67
Q

chronotropic force - sympathetic nervous system

A
  • increases chronotropic force
    + times of stress
    + physical
    + emotional
68
Q

chronotropic force - parasympathetic nervous system

A 
- decreases chronotropic force
   \+ rest
   \+ beta blockers / calcium 
   \+ being fit
   \+ meditation and relaxation
69
Q

force - velocity relationship

A
  • AN INCREASE IN AFTERLOAD DECREASES THE VELOCITY OF FIBER SHORTENING
  • small amount of time for ejection so a decrease in fibre shortening velocity reduces rate of volume ejection so more blood left in ventricle after systole
  • INCREASE AFTERLOAD = DECREASED STROKE VOLUME AND CARDIAC OUTPUT
70
Q

relationship summary

A

length - tension relaionship
+ frank - starling principle / preload
force - velocity relationship
+ inotropic force / contractility / afterload
interval - strength relationship
+ chronotropic force / time for ventricles to fill / starlings P

71
Q

provocative maneuvers

A
  • inspiration increases venous return ( VR) to the right heart
  • expiration decreases VR to the right heart
  • valsalva reduces VR reducing preload and afterload
  • standing decreases VR = gravity pulls blood down into legs
  • squatting increases VR = squeezes blood in veins toward the heart

Echo (19 decks)

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