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Circulation Flashcards

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1
Q

What defines the cardiac cycle?

A

Events that occur from the beginning of one heart beat to the beginning of the next heart beat.

Includes diastole (relaxation) and systole (contraction).

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2
Q

What is the formula for Mean Arterial Pressure (MAP)?

A

MAP = 1/3 SBP + 2/3 DBP

MAP is the arterial pressure integrated over one cardiac cycle.

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3
Q

What happens to the diastolic interval as heart rate increases?

A

The diastolic interval decreases more than the systolic interval.

This can impair ventricular filling.

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4
Q

What are the three contours in atrial pressure wave during the cardiac cycle? (ACV)

A
  • a wave = atrial contraction
  • c wave = initiation of ventricular contraction
  • v wave = flow of blood into atria while AV valve is closed
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5
Q

What is the duration of the cardiac cycle related to?

A

It is the reciprocal of heart rate.

Higher heart rate leads to shorter diastolic intervals.

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6
Q

What is the difference between mechanical and electrical systole?

A

Mechanical systole occurs during contraction, while electrical systole precedes it by 120-200 msec.

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7
Q

What characterizes the first third of diastole?

A

Rapid ventricular filling (passive) associated with S3 in the presence of ventricular dilation.

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8
Q

What constitutes isovolumetric contraction?

A

All valves are closed; interval between closure of AV valves and opening of aortic and pulmonic valves.

S1 is produced by closure of AV valves.

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9
Q

What is the ejection fraction (EF) in a normal heart?

A

EF = SV/EDV = 70/120 = 0.6 (60%).

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10
Q

What is the role of the papillary muscles?

A

To prevent prolapse of valve leaflets into atria during ventricular systole.

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11
Q

What occurs during isovolumetric relaxation?

A

All valves are closed; pressure in the ventricle decreases without a change in volume.

S2 occurs with closure of aortic and pulmonic valves.

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12
Q

What is the significance of the dicrotic notch?

A

It represents the closure of the aortic valve and occurs at the end of the systolic decline.

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13
Q

What is stroke volume (SV)?

A

SV = EDV - ESV = approximately 70 ml.

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14
Q

Fill in the blank: The first third of diastole is characterized by _______.

A

rapid ventricular filling.

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15
Q

True or False: The aortic valve closes slightly after the pulmonic valve.

A

False.

Aortic valve closure (A2) occurs before pulmonic valve closure (P2).

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16
Q

What happens during the fast ejection phase?

A

It corresponds to the first third of the ejection period, accounting for 2/3 of ejection fraction.

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17
Q

What are the components of the arterial waveform?

A
  • Systolic upstroke
  • Systolic peak pressure
  • Systolic decline
  • Dicrotic notch
  • Diastolic runoff
  • End-diastolic pressure
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18
Q

What causes the systolic decline in the arterial waveform?

A

Rapid decline in arterial pressure as ventricular contraction ends.

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19
Q

What does increased peripheral arterial compliance result in?

A

Higher peak systolic pressure and wider pulse pressure.

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20
Q

What is the relationship between stroke volume and pulse pressure?

A

Stroke volume and peripheral arterial compliance largely determine pulse pressure.

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21
Q

What is the significance of the incisura in the aortic waveform?

A

It is caused by the pressure increase from the closure of the aortic valve.

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22
Q

What is the primary function of the semilunar valves?

A

To prevent backflow of blood from the aorta and pulmonary arteries during ventricular diastole.

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23
Q

What causes the dicrotic notch in the arterial waveform?

A

The dicrotic notch results from the summation of several reflected waves, including a wave reflected from AoV closure.

It represents increased transit time from AoV to peripheral locations.

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24
Q

What is diastolic runoff?

A

Diastolic runoff is the drop in pressure after the Ao valve closes, influenced by the arterial pressure reservoir.

This reservoir contributes about 40% of delivered stroke volume.

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25
What are the components that contribute to arterial pressure?
Arterial pressure is due to the summation of: * Forward traveling pressure wave * Reflected pressure wave * Reservoir pressure from elastic recoil of arteries.
26
How does arterial compliance affect the shape of the arterial waveform?
Very compliant arteries produce less reservoir pressure than stiff arteries, influencing the shape of the arterial waveform and diastolic runoff.
27
What is the relationship between end-diastolic pressure and vascular tree?
End-diastolic pressure is the pressure exerted on AoV by the vascular tree and is seen by the coronary arteries.
28
How does aortic regurgitation (AI) affect end-diastolic pressure?
In AI, end-diastolic pressure is lower due to AoV not being closed, exerting pressure against intra-ventricular cavity.
29
What is the formula for mean arterial pressure (MAP)?
Area under the curve!! MAP is approximately calculated as 1/3 SBP + 2/3 DBP.
30
What is the significance of narrow pulse pressure if arterial compliance is unchanged?
Narrow pulse pressure is defined as less than 25% of SBP and indicates potential issues like low stroke volume.
31
What is a wide pulse pressure?
Wide pulse pressure is defined as greater than 50% of SBP and may indicate increased stroke volume or decreased arterial compliance.
32
What is the relationship between pulse pressure and stroke volume?
Pulse pressure is largely determined by stroke volume and peripheral arterial compliance.
33
What are the phases of a normal pressure-volume loop?
The phases are: * Phase I: Filling * Phase II: Isovolumetric Contraction * Phase III: Ejection * Phase IV: Isovolumetric Relaxation.
34
What is preload in the context of cardiac function?
Preload is the left ventricular end-diastolic volume (LVEDV) related to the tension on cardiac muscle before contraction.
35
What does afterload refer to?
Afterload refers to the resistance against which the cardiac muscle exerts its contractile force during systole.
36
What is the Frank-Starling mechanism?
The Frank-Starling mechanism states that an increase in preload (LVEDV) leads to an increase in stroke volume due to increased myocardial stretch.
37
What is the effect of inotropy on the Frank-Starling curve?
Inotropy changes the length-tension relationship for cardiac muscle, shifting the Frank-Starling curve.
38
What factors can affect inotropy?
Factors affecting inotropy include: * Autonomic nervous system * Temperature * Drugs * Calcium levels * Disease states (e.g., ischemic heart disease).
39
What is the major determinant of pulse pressure?
The major determinants of pulse pressure are stroke volume (SV) and arterial compliance (C).
40
What happens to pulse pressure during hemorrhage?
During hemorrhage, preload decreases, leading to a narrowed pulse pressure.
41
What is aortic stenosis?
Aortic stenosis is a valvular obstruction to left ventricular output, leading to increased left ventricular systolic pressure and decreased stroke volume.
42
What characterizes chronic mitral regurgitation?
Chronic mitral regurgitation is characterized by volume overload of the left ventricle, leading to increased left ventricular end-diastolic volume.
43
What is the normal value for cardiac output (CO)?
The normal value for cardiac output is approximately 5 L/min.
44
What is the cardiac index (CI)?
Cardiac index is calculated as CO divided by body surface area (BSA), normal value is approximately 3.0 L/min.
45
What is the Frank-Starling Mechanism?
A mechanism where an increase in preload (LVEDV) leads to an increase in stroke volume (SV) ## Footnote It describes how the heart's output increases with the volume of blood filling the heart.
46
What factors affect inotropy?
* Autonomic Nervous System * Temperature * Drugs * [Ca+2] * Disease states (IHD; CMs) ## Footnote Inotropy refers to the force of heart muscle contraction.
47
What is the Bodwitch Effect?
An increase in heart rate leads to an increase in inotropy ## Footnote This effect illustrates the relationship between heart rate and contractility.
48
What is the Anrep Effect?
A sudden decrease in afterload leads to an increase in inotropy ## Footnote This effect highlights the heart's ability to increase contractility in response to changes in afterload.
49
What are the components of the Autonomic Nervous System's effect on the heart?
* Sympathetic Nervous System (SNS): affects contractility and heart rate * Parasympathetic Nervous System (PSNS): primarily affects heart rate ## Footnote The SNS and PSNS supply both atria and ventricles.
50
What determines Venous Return (VR)?
* Circulating blood volume * Venous capacitance (tone) * Respiratory pump * Musculo-venous pump * IVC compression ## Footnote These factors collectively influence the volume of blood returning to the heart.
51
How is flow calculated according to Ohm's Law?
Q = ΔP/R ## Footnote Where Q is flow, ΔP is the pressure difference, and R is vascular resistance.
52
What is the definition of Systemic Vascular Resistance (SVR)?
SVR = 80 (MAP - CVP)/CO ## Footnote SVR measures the resistance to blood flow in the systemic circulation.
53
What is the formula for Pulmonary Vascular Resistance (PVR)?
PVR = 80 (Mean PAP - LAP)/CO ## Footnote PVR assesses the resistance in the pulmonary circulation.
54
What characterizes Laminar Flow?
Flow in which layers of blood at equal distances from the wall flow at the same velocity ## Footnote This type of flow produces a parabolic profile.
55
What characterizes Turbulent Flow?
Disorderly flow with crosswise whorls called eddy currents ## Footnote It occurs with increased blood velocity or interference with flow.
56
What does Reynolds Number (Re) predict?
It predicts whether blood flow is laminar or turbulent ## Footnote Re = v(d)(p)/N, where v is velocity, d is diameter, p is density, and N is viscosity.
57
What does Poiseuille’s Law state about resistance (R) during laminar flow?
R = 8L(N)/π (r^4) ## Footnote This law highlights that the radius of the vessel has the greatest impact on resistance.
58
What is Compliance in vascular terms?
Compliance = ΔV/ΔP ## Footnote It measures the change in volume per change in pressure.
59
What is the relationship between arteries and veins regarding compliance?
A vein is approximately 24 times more compliant than its corresponding artery ## Footnote This is due to differences in distensibility and volume.
60
What is the immediate response to hemorrhage?
SNS stimulation increases arterial and venous pressures for any given volume ## Footnote This mechanism helps maintain blood pressure despite volume loss.
61
What is the function of the Baroreceptor Reflex?
Maintains blood pressure with changes in body posture and provides a buffer function ## Footnote It involves stretch receptors in the carotid sinus and aortic arch.
62
What triggers the Chemoreceptor Reflex?
Low PaO2, elevated PaCO2, and increased [H+] ## Footnote These conditions stimulate the vasomotor center to raise blood pressure when SBP falls below 80 Torr.
63
What is the Bainbridge Reflex?
Atrial stretch leads to an increase in heart rate ## Footnote It modulates vagal tone to increase heart rate and contractility.
64
What is the Cushing Reflex?
An increase in BP associated with decreased MAP or increased ICP ## Footnote It occurs only with systolic BP < 60 mm Hg.
65
What is the role of the Vasomotor Center in the brain?
It regulates vasomotor tone and transmits signals for sympathetic and parasympathetic impulses ## Footnote It plays a crucial role in controlling blood pressure.
66
What is the Baroreceptor Reflex responsible for?
BP Homeostasis
67
Which cranial nerves are involved in the Baroreceptor Reflex?
X (Vagus) and IX (Glossopharyngeal)
68
What do sensors in carotid and aortic bodies detect in the Chemoreceptor Reflex?
Low PaO2, elevated PaCO2, and increased [H+]
69
What is the primary function of Atrial and Pulmonary Artery Reflexes?
Minimizing arterial pressure changes associated with changes in blood volume
70
What is the Atrial-Renal Reflex?
Increased atrial stretch leads to vasodilation of renal arterioles and decreased ADH from posterior pituitary
71
What does the Bainbridge Reflex respond to?
Increased atrial stretch leading to an increase in heart rate Spinal anesthesia --> acute decrease stretch --> asystole
72
What is the CNS Ischemic Reflex associated with?
Elevation in BP associated with CNS ischemia (decreased CPP)
73
What does the term 'Pressure Diuresis' refer to?
The ability of kidneys to control ECF volume in response to elevated BP
74
What is the role of the Renin-Angiotensin-Aldosterone System (RAAS)?
Hormonal mechanism utilized by kidney for long-term BP control Pro-renin --> renin] w release of renin into circulation in response to any of 3 stimuli: ● Decrease in renal perfusion pressure (major pathway) ● Decrease in Na+ [Cl-] load of distal tubule ● Stimulation of the SNS via beta-1 adrenergic receptors
75
What triggers the release of renin in the RAAS?
Decrease in renal perfusion pressure, decrease in Na+ load, or stimulation of the SNS
76
How long does the RAAS system take to respond?
Approximately 20 minutes
77
What happens when the RAAS system functions normally regarding salt intake?
No significant change in BP despite 100x fold increase in salt intake
78
Fill in the blank: Elevated BP leads to increased GFR, which results in increased urine output and increased _______.
naturesis
79
True or False: The renal control of BP is a fast mechanism providing immediate responses.
False
80
What is the time course for pressure diuresis?
Days to weeks response time
81
What are the components of the Reflex Mechanisms for BP homeostasis?
Baroreceptor Reflex, Chemoreceptor Reflex, Atrial and Pulmonary Artery Reflexes
82
S4
Produced at atrial contraction by vibration of stiff ventricle (LVH)
83
Trouble shooting pressure lines
Is there a trend? Bubbles/clots/loose connections Concomitant AEs
84
Describe PV loop of aortic stenosis
85
Three areas of the vasomotor center?
(1) Vasoconstrictor Area (2) Vasodilator Area: inhibits vasoconstrictor area (3) Sensory Area: receive afferent signals from circulation and transmit to (1) and (2); involved in baroreceptor reflex
86
Function of the chemoreceptor reflex
Stimulate vasomotor center of brain to raise BP ONLY when SBP falls below 80 Torr.
87
Relate chemoreceptor reflex to hypotension
Detect low PaO2, elevated PaCO2 and increased [H+] which are indirect measures of low perfusion pressure in small arteries to these receptors -if you aren’t perfusing you aren’t transporting
88
CPP
MAP-ICP
89
Why does hypotension cause hypoxemia?
Shunt Can’t perfused the lung apices when upright- so v/q mismatch and shunting through the bases of the lungs
90
MAP
COxSVR
91
CO
SVxHR
92
What is organ auto regulation?
Maintaining constant flow over a range of MAPs

780 (7 decks)

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