Hemodynamics Flashcards
1
Q
Bernoulli’s principle says that energy can be changed but not ____
A
Destroyed
2
Q
Per Bernoulli’s principle, as ____ of fluid flow increases, there is a coexisting reduction in ____
A
velocity; pressure
3
Q
Bernoulli’s principle states there will be an ____ in kinetic energy with a ____ in pressure at the site of an obstruction to flow
A
increase; decrease
4
Q
Based on the conservation of energy principle: If ____ or ____ changes, there will be a change in the other energy to maintain the same level of total energy
A
pressure or kinetic energy
5
Q
According to Bernoulli’s equation, ____ and ____ are inversely related
A
Velocity and pressure
6
Q
If a vessel has plaque causing a narrowing, the flow velocity will ____ at the site of a stenosis so the pressure must ____
A
increase; decrease
7
Q
What do we use Bernoulli’s principle to predict?
A
- The pressure drop (gradient) between two chambers
8
Q
What does Bernoulli’s principle determine?
A
- Max and mean pressure gradients across stenotic valves
- Max pressure gradients across regurgitant valve lesions and abnormal shunt communications
9
Q
What does Bernoulli’s principle estimate?
A
Intracardiac pressure
10
Q
What is the modified Bernoulli’s equation?
A
∆P = 4 (v2^2 - V1^2)
11
Q
What is the simplified Bernoulli’s equation?
A
∆P = 4(V2^2)
12
Q
What does ‘P1’ stand for?
A
Pressure at location 1
13
Q
What does ‘P2’ stand for?
A
Pressure at location 2
14
Q
What does ‘ρ’ stand for?
A
Density of the blood (1.06 x 10^3 kg/m^3)
15
Q
What does ‘V1’ stand for?
A
Velocity of location 1
16
Q
What does ‘V2’ stand for?
A
Velocity of location 2
17
Q
When is modified Bernoulli’s equation used?
A
Typically used with aortic stenosis when V1 is > 1.2 m/s
18
Q
When is simplified Bernoulli’s equation used?
A
When V1 is </= 1.2 m/s
19
Q
What does P1 - P2 = ?
A
∆P; or Q
20
Q
What is the pressure in the left ventricle?
A
120 mmHg
21
Q
What is the pressure in the aorta?
A
100 mmHg
22
Q
What is the pressure in the arterioles?
A
45 mmHg
23
Q
What is the pressure in the capillaries?
A
10 mmHg
24
Q
What does ‘Q’ stand for?
A
Flow volume
25
Arterial Blood Pressure is determined by ____ and ____
Volume of blood and resistance
26
Equation for pressure
Pressure = flow (vol/min) x resistance
27
What is resistance?
The amount of pressure exerted against flow
28
What is distensibility?
Stretching of arteries or veins to accommodate more blood (systole)
29
What is elasticity?
The ability of a vessel to bounce back after being stretched
30
What is stroke volume (SV)? (definition)
The amount of blood pumped out of the heart per beat
31
What is the equation for stroke volume?
LVOTd^2 x .785 x LVOT⌄TVI
32
What is the normal range for stroke volume?
70-100 cc
33
What is cardiac output (CO)? (definition)
The amount of blood pumped by heart per minute
34
What is the equation for cardiac output?
SV (cc) x heart rate (HR) / 1000
35
What is the normal range for cardiac output?
4-8 L/min
36
What is cardiac index (CI)? (definition)
The cardiac output adjusted for Body Surface Area (BSA)
37
What is the equation for cardiac index?
Cardiac Output (CO) / BSA
38
What is the normal range for cardiac index?
2.4 - 4.2 L/m/m^2
39
What are the three resistance factors?
Viscosity, friction, and inertia (acceleration and deceleration)
40
What is viscosity?
The thickness of blood
41
What is friction?
Movement of blood against the vessels will change some pressure energy to heat
- there is some loss of the pressure energy to friction
42
longer, narrower vessels cause ____ friction
more
43
What is inertia?
property of all matter; an object at rest tends to stay at rest, an object in motion tends to stay in motion
- there is some loss of the energy pressure as inertial losses
44
What causes inertial losses
acceleration and deceleration
45
What is Poiseuille’s Law?
States that flow volume (Q) varies directly with the pressure gradient (Pi-Po) and the fourth power of the radius of the tube (r). Flow (Q) varies inversely with the length (L) of the tube and the viscosity (n) of a fluid.
46
What does (Pi - Po) stand for?
Pressure gradient
47
What does 'n' stand for?
Viscosity
48
What is Poiseuille’s law equation?
Q = (Pi-Po) πr^4 / 8nL or
∆P = Q8nL / πr^4
49
What is Poiseuille’s Law simplified?
- As pressure gradient ↑ flow volume ↑
- As the tube diameter ↑, flow volume ↑
- As the length of the tube ↑, flow volume ↓
- As fluid viscosity ↑, flow volume ↓
50
Of all of the factors that effect blood flow, the ____ of the blood vessel is the most significant!
radius
51
What is velocity? (definition)
distance moved over a period of time
52
What is the equation for velocity?
velocity = distance x time (V=DxT)
53
What is the unit for velocity?
cm/min or M/min
54
What is flow? (definition)
amount of blood over time
55
What is the equation for flow?
flow = volume/time (F=V/T) or
flow = pressure ÷ resistance
56
What is the unit for flow?
mL/min or L/min
57
The less resistance blood meets, the ____ the flow
greater
58
Slow flow is important in ____ for the exchange of nutrients and wastes
Capillaries
59
Due to reduction in total cross-sectional area (diameter/radius), pressure ____ in the veins until blood reaches the right atrium
Decreases
60
Pressure in the venules is ____ than it is in the larger veins
Higher
61
____ of veins from capillary bed to IVC/SVC continues to become larger, helping create the energy gradient needed to move flow toward the heart
Diameter
62
What is the contraction of the heart during systole, causing blood to surge and strike the arterial walls called?
Pulsatile flow
63
The more dramatic the rise and fall of velocity during systole and diastole, the greater the ____
Pulsatility
64
This surge can be palpated at points where an artery is close to surface of the skin. As the surge of blood passes and diastole occurs, arteries contract and return to pre-systolic shape/area.
Pulsatile flow
65
____ flow occurs further from the heart, especially in the capillaries
Steady
66
Steady flow is essential for proper exchange of ____ and ____
Nutrients and waste
67
____ do not normally pulsate
Veins
68
____ flow (no change with respirations) in a vein may indicate deep vein thrombosis
Steady
69
How is blood flow affected by a stenosis?
Blood becomes turbulent which reduces the velocity
70
Conservation of energy theory
Energy can be changed, not destroyed
71
At stenotic lesion (decrease in diameter) what happens to velocity and pressure? What type of flow pattern is it?
- Velocity is increased
- Pressure is decreased
- Disturbed flow pattern
72
At the exit of a stenotic lesion (increase in diameter) what happens to velocity and pressure? What type of flow pattern is it?
- Velocity decreases
- Pressure increases
- Turbulent flow pattern
73
In order for a stenosis to be hemodynamically significant (patient has signs and symptoms) , it must be ___% reduced in diameter and ___% reduced in area.
50% reduced in diameter
75% reduced in area
74
What is energy?
The capacity to do work
75
What is potential?
The ability to do work
76
The faster blood moves, the more ____ energy (pressure) is turned into ____ energy
Potential; kinetic
77
As blood enters a stenosis (dramatically reducing size of vessel), two things occur:
- Blood changes direction to enter
- Blood changes direction to exit
78
Usually found at entrance of a great vessel (aorta)
Inlet/Plug flow
79
During what flow is the velocity of cells at wall similar to velocities in center of vessel
Inlet/Plug flow
80
As vessel size decreases and changes direction, cells at the wall slow in comparison to velocities in center of vessel
Parabolic flow
81
Exists when cells move in a forward direction but not in organized layers, as in movement over small amounts of wall plaque
Disturbed flow
82
Occurs when the fluid particles move in multiple directions at different velocities. Vortices (whirling blood flow) or Eddies (small circular currents) may develop at turbulent sites.
Turbulent flow
83
Reynold’s number (Re)
Predicts the onset of turbulence by using the following four factors
velocity (v), density (p), radius (r), and viscosity (n)
84
In cardiovascular imaging, ____ and ____ are constant
Fluid density and viscosity
85
What is the equation for Reynold’s number (Re)?
Re = flow speed x tube radius x fluid density ÷ fluid viscosity
86
A Reynold’s (Re) value of ____ or greater indicates turbulence
2000
87
Resistance
Force that exists against layers of moving blood
88
Peripheral resistance
Walls of blood vessels offer the most resistance to blood flow
89
The ____ a blood vessel, the more resistance the blood flow meets
Smaller
90
Important function of the body is to control ____ blood pressure
Arterial
91
Reflexes in the body change the diameter of ____ to help regulate blood pressure
Arterioles
92
Arteriole diameter changes either increase or decrease ____ ____
Peripheral resistance
93
Arteriole diameter changes are controlled by the ____ ____ in the brain
Vasomotor center
94
Stimuli are transmitted to the smooth muscle of the vessel wall via the ____ nervous system
Sympathetic
95
Vasodilation
Increase in vessel diameter decreases peripheral resistance and lowers blood pressure
96
Vasoconstriction
Decrease in vessel diameter increases peripheral resistance and raises blood pressure
97
Lowers heart rate, controls digestion
Parasympathetic nerves
98
Increases heart rate, force of heart contraction, controls amount of contractions occurring in arteries and veins
Sympathetic nerves
99
What is collateral blood flow?
If an artery becomes blocked or occluded, other adjacent vessels may pick up the blood flow
100
Collateral routes are more ____ to flow
Resistant
101
What is resistance to flow?
The ratio of the pressure gradient across a vessel segment
102
What is the equation for resistance of flow?
Rseg = (P1 - P 2) / Q (flow)
103
The cardiac cycle includes all ____ and ____ events in one heartbeat
Electrical and mechanical
104
____ events precede ____ events.
Electrical; mechanical
105
____ events are graphed on the EKG
Electrical
106
P wave represents ____ ____
Atrial contraction/ atrial systole
107
QRS represents ____ ____
Ventricular depolarization
108
ST segment represents ____
Isoelectric period when the heart is refractory to electrical stimulation
109
T wave represents ____ ____
Ventricular repolarization (recovery phase of ventricle)
110
What is the definition of Isovolumic Relaxation (IVRT)
The time period between semilunar valve closure and MV and TV opening.
111
This time period represents early ventricular relaxation.
Isovolumic Relaxation (IVRT)
112
When does ventricular pressures drop below arterial pressures with no change in ventricular volume.
Isovolumic Relaxation (IVRT)
113
What are the three components of ventricular diastole?
- Rapid, early diastolic filling-blood enters ventricles passively, yet quickly due to swift ventricular relaxation (E wave)
- Reduced filling –flow is reduced, pressure begins to equalize (Deceleration of E wave)
- Diastasis (Time between E and A waves) Seen in slow heart rates
- Atrial systole
114
____% of ventricular filling occurs during the rapid, early diastolic filling phase
70%
115
The period when the ventricles are filling with blood. On the EKG begins with the end of the “T” wave and ends with the onset of the “QRS” complex.
Ventricular diastole
116
When are the MV and TV are open and the semilunar valves are closed?
Ventricular diastole
117
Occurs at the end of ventricular diastole with the onset of the “P” wave of the EKG.
Atrial Systole
118
When are the MV and TV open, and the semilunar valves are close?
Atrial Systole
119
Atrial systole contributes ____% of ventricular filling
30%
120
The time period between MV and TV closure and semilunar valve opening.
Isovolumic Contraction
121
When are all cardiac valves are closes as the ventricles begin to contract.
Isovolumic Contraction
122
During isovolumic contraction there is an increase in ____ pressure until ____ pressure is exceeded with no change in volume
Ventricular; arterial
123
When does ventricular systole begin?
Begins with the closure of the AV valves
124
What corresponds with the onset of the QRS to the T wave on EKG?
Ventricular systole
125
Events during ventricular systole occur as follows:
1. Isovolumic contraction (IVCT)
2. Rapid ejection
3. Reduced ejection
126
Rapid ejection
Semilunar valves open, rapid rise in pressure
127
Reduced ejection
Peak ventricular ejection, pressure begins to drop until it’s below great vessel pressure and then the semilunar valves close
