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The BIG Test > Cardiac > Flashcards

Cardiac Flashcards

1
Q

Detail the conduction pathway starting with the SA node (normal pacemaker).

A
  1. SA node
  2. Internodal tracts - AV node + Bachmann’s bundle (to LA)
  3. AV node
  4. Bundle of His
  5. Bundle branches
  6. Purkinje fibers
  7. Ventricular muscle
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2
Q

Action potentials with plateau phases are found where?

A

Atrial and ventricular muscle cells

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3
Q

Action potentials that are biphasic (depolarization + repolarization withOUT plateau phase) are found where?

A

SA and AV node

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4
Q

Atrial + Ventricular Muscle Cell Action Potential

A

4: Resting -90 mV (leak K channels, K OUT)
0: Rapid depolarization + 30 mV (Na IN)
1: Brief repolarization (Cl IN, K OUT)
2: Plateau (Ca IN) - Na channel in the inactivated state
3: Repolarization (K OUT) - Na channel becomes activated
4: Diastole (Na/K pump)

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5
Q

SA + AV Node Action Potential

A

4: Resting -70 mV
0: Slow depolarization (Ca + Na IN)
3: Repolarization (K OUT)
4: Diastole — spontaneous depolarization to threshold = K OUT decreases progressively, Na IN increases progressively, last 1/3rd Ca IN

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6
Q

What is the resting potential of the ventricular cell?

A
  • 90 mV
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7
Q

How does the action potential of the AV node differ from the SA node?

A

The action potential of the AV node has a slower phase 4 depolarization

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8
Q

Changing the ______ of _______ depolarization causes heart rate to change.

A

Slope of phase 4

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9
Q

On what phase of the nodal action potential does digitalis /CCB work to slow heart rate?

A

Phase 4

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10
Q

On what phase of the nodal action potential does lidocaine/phenytoin work to control ventricular dysrhythmias?

A

Phase 4

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11
Q

On what phase of the cardiac ventricular action potential do CCB work?

A

Phase 2

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12
Q

What happens to the duration of the plateau with hypocalcemia?

A

Ca diffuses IN at a slower rate - plateau is prolonged

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13
Q

What happens to the duration of the plateau with hypercalcemia?

A

Ca diffuses IN at a faster rate - plateau is shortened

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14
Q

Ventricular depolarization proceeds from the ______ wall of the septum to the ____ wall.
Left or right?

A

Left to right

*Overall spread of depolarization is to the LEFT b/c the LV is normally electrically predominant

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15
Q

Right Bundle Branch Block

How do you make the diagnosis?

A

Look at V1 and V6
V1: rSR’ complex, broad R’ wave - “rabbit ears”
V6: qRs complex, broad S wave

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16
Q

Left Bundle Branch Block

How do you make the diagnosis?

A

Look at V1 and V6
V1: loss of normal septal r wave
V6: loss of normal septal q wave, wide + entirely positive R wave with a notch
Abnormally wide QRS complex

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17
Q

First Degree Heart Block

A

PR interval is > 0.2 sec

greater than one big box

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18
Q

Second Degree Heart Block
Mobitz Type I
Wenckebach

A

Progressive increase in the PR interval…until a DROP (missed QRS)

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19
Q

Second Degree Heart Block

Mobitz Type II

A

SUDDEN missed QRS

P waves are normal

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20
Q

Third Degree Heart Block

Complete Heart Block

A

Dissociated P waves and QRS

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21
Q

Sinus Arrhythmia
Inspiration - increase or decrease in HR? Why?
What is this reflex called?

A

Inspiration - INCREASE in HR
Intrathoracic press falls - IVC widens - VR increases - RA stretches - HR increases reflexively
*This is the Bainbridge reflex

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22
Q

Transmural ischemia is characterized by symmetrically inverted ____ waves.

A

T

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23
Q

Transmural injury demonstrates ST segment _______ greater than ____ mm.

A

Elevation

1

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24
Q

Calcium Disturbances and ECG
What happens with hypercalcemia?
What happens with hypocalcemia?

A

Hypercalcemia - shortened QT segment

Hypocalcemia - prolonged QT segment

*The QT interval reflects the duration of the plateau phase (phase 2)

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25
Q

Potassium Disturbances and ECG
What happens with hyperkalemia?
What happens with hypokalemia?

A

Hyperkalemia - peaked T waves

Hypokalemia - prominent U waves

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26
Q

What 2 drugs should be avoided with Wolff-Parkinson-White Syndrome?

A
  1. Digoxin
  2. CCB - Verapamil
    * B/c they increase conduction through the accessory bypass tract - bundle of Kent
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27
Q

What is the best overall lead for detecting an MI?

A

V5

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28
Q

Inferior MI
Leads?
Coronary artery supply?

A

II, III, aVF

RCA

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29
Q

Anterior MI
Leads?
Coronary artery supply?

A

V1-V4

LAD

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30
Q

Lateral MI
Leads?
Coronary artery supply?

A

I, aVL, V5, V6

Circumflex

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31
Q

MAP is determined by what 2 factors?

A
  1. CO

2. SVR

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32
Q

CO is determined by what 2 factors?

A
  1. HR
  2. SV
    CO = HR x SV
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33
Q

SV is determined by what 3 factors?

A
  1. Preload
  2. Afterload
  3. Contractility
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34
Q

Preload is determined by what 2 factors?

A
  1. Intravascular volume

2. Venous tone

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35
Q

What is the major determinant of intravascular volume?

A

Amount of sodium

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36
Q

What hormone is the most important for controlling vascular volume?

A

Aldosterone

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37
Q

Frank-Starling Law of the Heart

A

Increased ventricular filling - Increased preload

Increased preload - Increased SV

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38
Q

Contractility is determined by the _______ environment of the cardiac cell.

A

Chemical

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39
Q

Pressure Overload Hypertrophy

A

LV concentric hypertrophy
Chamber size remains unchanged
Causes - coarctation of aorta, aortic stenosis, untreated HTN
*IHSS does NOT apply to this situation (size of LV chamber decreases)

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40
Q

Volume Overload Hypertrophy

A

LV eccentric hypertrophy
Chamber size dilates
Causes - mitral regurgitation, aortic regurgitation, morbid obesity

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41
Q

Ventricular hypertrophy in response to pressure or volume overload is an application of the ________.

A

Law of Laplace

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42
Q

LV Pressure-Volume Loops

A 
Y-axis: LV pressure 
X-axis: LV volume 
A: ESV, mitral valve opens 
A-B: diastolic filling 
B: EDV, preload, mitral valve closes 
B-C: isovolumic contraction 
C: afterload, aortic valve opens 
C-D: ejection 
D: aortic valve closes 
D-A: isovolumic relaxation 
*SV is the width of the loop
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43
Q

When does systole begin and end on the P-V loop?

A

Begin - B

End - D

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44
Q

When does diastole begin and end on the P-V loop?

A

Begin - D

End - B

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45
Q 
What happens with an increase in preload (fluid bolus)? 
EDV 
ESV
SV
BP 
HR/SVR
A 
EDV: increases 
ESV: stays the same 
SV: increases 
BP: increases 
HR/SVR: decreases, reflex 
*Pressure-volume loop widens withOUT a change in ESV
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46
Q 
What happens with an increase in afterload (neo)? 
EDV
ESV
SV
BP/SVR
HR
A 
EDV: increases 
ESV: increases 
SV: decreases 
BP/SVR: increases
HR: decreases, reflex
*Pressure-volume loop shifts UP and to the RIGHT (greater pressures and volumes)
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47
Q 
What happens with an increase in contractility (calcium)?
EDV
ESV
SV
BP
HR/SVR
A 
EDV: decreases  
ESV: decreases
SV: increases 
BP: increases 
HR/SVR: decreases, reflex 
*Pressure-volume loop shifts UP and to the LEFT (greater pressures, smaller volumes)
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48
Q

P-V loop shift to the RIGHT means…

A

Greater volumes

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49
Q

P-V loop shift UP means…

A

Greater pressures

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50
Q

P-V loop shift to the LEFT means…

A

Smaller volumes

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51
Q

P-V loop shift DOWN means…

A

Smaller pressures

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52
Q

When stroke volume falls either as a result of an increase in ______ or a decrease in _______, the volume of blood in the LV chamber increases - chamber dilates.

A

Increase in afterload

Decrease in contractility

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53
Q

When stroke volume increases either as a result of an increase in _______ or a decrease in _______, the volume of the blood in the LV chamber decreases - chamber shrinks.

A

Increase in contractility

Decrease in afterload

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54
Q

When preload increases, the P-V loop shifts…

A

P-V loop widens

EDV increases

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55
Q

When preload decreases, the P-V loop shifts…

A

P-V loop narrows

EDV decreases

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56
Q

When afterload increases, the P-V loop shifts…

A

UP and to the RIGHT

Greater pressures, greater volumes

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57
Q

When afterload decreases, the P-V loop shifts…

A

DOWN and to the LEFT

Lower pressures, smaller volumes

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58
Q

When contractility increases, the P-V loop shifts…

A

UP and to the LEFT

Greater pressures, smaller volumes

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59
Q

When contractility decreases, the P-V loops shifts…

A

DOWN and to the RIGHT

Lower pressures, greater volumes

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60
Q

The P-V loop in IHSS is unique. Describe the shift.

A

UP and to the LEFT
Greater pressures, smaller volumes
Narrow and very high!

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61
Q

Describe the P-V loop of aortic stenosis.

A

Increased afterload
UP
Greater pressures, volumes stay about the same
Concentric hypertrophy

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62
Q

Describe the P-V loop of mitral stenosis.

A

Decreased preload
Decreased EDV
Lower pressures, smaller volumes

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63
Q

Describe the P-V loop of aortic regurgitation.

Acute vs. chronic

A

No isovolemic relaxation phase
Acute - P-V loop is small
Chronic - P-V loop is large (eccentric hypertrophy)

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64
Q

Describe the P-V loop of mitral regurgitation.

Acute vs. chronic

A

No isovolemic contraction phase
Acute - P-V loop is small
Chronic - P-V loop is large (eccentric hypertrophy)

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65
Q

Ventricular Function Curves
Explain the shift with an increased preload.
Decreased preload?

A

Increased preload - point shifts to the RIGHT on the same curve
Decreased preload - point shifts to the LEFT on the same curve

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66
Q

Ventricular Function Curves
Y-axis?
X-Axis?

A

Y-axis: stroke volume

X-axis: PCWP (EDV)

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67
Q

Ventricular Function Curves
Explain the shift with an increased afterload.
Decreased afterload?

A

Increased afterload - curve shifts DOWN and to the RIGHT

Decreased afterload - curve shifts UP and to the LEFT

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68
Q

Ventricular Function Curves
Explain the shift with an increased contractility.
Decreased contractility?

A

Increased contractility - curve shifts UP and to the LEFT

Decreased contractility - curve shifts DOWN and to the RIGHT

69
Q

Formula for SV

Normal SV

A

SV = CO/HR
(CO = HR x SV)
Normal SV = 60 mL

70
Q

Formula for SI

Normal SI

A

SI = SV/BSA

Normal SI = 40 mL

71
Q

Formula for SVR

A

SVR = (MAP - CVP)/CO x 80

72
Q

Formula for PVR

A

PVR = (PAP - PCWP)/CO x 80

73
Q

Baroreceptor Reflex

A
  1. Increase in BP
  2. Increase stretch of baroreceptors
  3. Increase in action potentials in afferents (sensory) of:
    Vagus nerve (aortic arch)
    Hering’s nerve (carotid sinus)
    to CV centers in medulla
  4. Increase in action potentials in Vagus nerve (efferent) + Decrease in action potentials to sympathetic nerves
  5. Decrease in BP
74
Q

Where are the baroreceptors found?

A
  1. Carotid sinus

2. Aortic arch

75
Q

Afferent action potentials from the baroreceptors of the aortic arch are carried to the brainstem centers via what nerve?

A

Vagus

76
Q

Afferent action potentials from the baroreceptors of the carotid sinus are carried to the brainstem centers via what nerve?

A

Hering’s — a branch of the Glossopharyngeal

77
Q

Which are physiologically more important: the carotid or aortic arch baroreceptors?

A

Carotid baroreceptors

78
Q

Nitric Oxide
Pathway?
Produced by?
Regulated by?

A

L -arginine - nitric oxide synthase - nitric oxide - activates guanyl cyclase - triggers the production of cGMP - smooth muscle relaxes
Produced by endothelial cells of the vascular wall
Regulated by calcium, bradykinin, Ach

79
Q

How do sodium nitroprusside, nitroglycerine, and dinitrate work?

A

They “donate” NO molecules at the vascular wall to promote vasodilation
Sodium nitroprusside has NO in its configuration
Nitroglycerine metabolism leads to the generation of a NO molecule

80
Q

How does hydralazine work?

A

It is a membrane hyperpolarizing agent via activation of K channels
*Arterial dilator

81
Q

Nitroprusside and nitroglycerine have __________ as well as vasodilatory actions.

A

Bronchodilator

82
Q

What explains the following statement:

Nitroglycerine works on venous capacitance vessels and nitroprusside works on arterial and venous capacitance vessels.

A

The nitric oxide generating system for nitroglycerin is found primarily in the VENOUS vasculature.
*Nitroglycerin = venodilator

The nitric oxide generating system for sodium nitroprusside is found in BOTH the arterial and venous vascular circuits.
*Nitroprusside = arterial and venous dilator

83
Q

If 2 thermodilution curves are shown…how do you determine which curve has the highest CO?

A

The smaller curve has the highest CO
CO is inversely proportional to the area under the thermodilution curve
Increased area under the thermodilution curve - Decreased CO

84
Q

Bainbridge Reflex

A
  1. SVC dilates
  2. Venous pressure falls
  3. Pressure gradient increases
  4. Venous return increases
  5. HR increases d/t increased CVP
85
Q

List determinants of myocardial oxygen supply.

A
  1. O2 content (Hct, %sat)
  2. DBP
  3. CVR
  4. HR
86
Q

List determinants of myocardial oxygen demand.

A
  1. HR
  2. Afterload
  3. Prelaod
  4. Contractility
87
Q

What hemodynamic change is most important to avoid in the patient with CAD?

A

Tachycardia

*Double jeopardy - increases O2 consumption + decreases O2 supply

88
Q

The pulse pressure _______ as the arterial pressure waveform passes into more peripheral arterial vessels.

A

Increases

*Pulse pressure is greatest in the dorsalis pedis

89
Q

What is the increase in pulse pressure as the pressure wave moves peripherally attributable to?

A

An increase in SBP + a decrease in DBP

*Superimposition principle

90
Q

MAP = the area under the arterial pressure curve divided by what?

A

Time

91
Q

Are CCB venous or arterial dilators?

A

Arterial dilators

Cause a decrease in HR

92
Q

Which CCB causes a reflex increase in HR?

A

Nifedipine

93
Q

Are ACE-I venous or arterial dilators?

A

Arterial dilators

94
Q

How do Inamrinone and Milrinone increase myocardial contractility and decrease SVR/relax vascular smooth muscle?

A

By blocking the breakdown of cAMP

95
Q

Name 3 indications for Adenosine.

A
  1. Slow conduction through the AV node
  2. Interrupt reentry pathways through the AV node
  3. Restore NSR in SVT patients (WPW syndrome too!)
    * 6-12 mg IV RAPID, no hemodynamic effects, elimination half-time < 10 sec
96
Q

Hypertrophic Cardiomyopathy w/ or w/o Ventricular Outflow Obstruction
IHSS
HOCM

A

Diastolic dysfunction - concentric hypertrophy
Represents a dynamic stenosis of the aortic outflow tract
Venturi effect draws leaflet out as blood rushes by (Bernoulli’s Law)
Conditions normally impairing LV function will actually improve function in this disease
SLOW (keep sinus), FULL, TIGHT, DECREASE contractility
Volume is the 1st line of defense for hypotension
Tx - BB, CCB
NO spinal or epidural

97
Q

Arterial waveform may be bifid (bisferiens pulse) in what condition?

A

IHSS

98
Q

Aortic + Mitral Regurgitation

A

Systolic dysfunction - eccentric hypertrophy

Fast, Full, Forward

99
Q

Regurgitant volume depends on ______ and the _____ across the aortic valve.

A

HR

Diastolic pressure gradient

100
Q

Symptoms of regurgitation are minimal when volume remains under ___% of stroke volume, but is severe if it exceeds ___% of stroke volume.

A

40%

60%

101
Q

What 4 factors determine degree of regurgitation?

A
  1. Size of valve orifice
  2. Pressure gradient
  3. Systole time (time for regurge)
  4. Aortic outflow impedance (SVR)
102
Q

Symptomatic Progression of Regurgitant Factors

A

< 30% mild symptoms
30-60% mod symptoms
> 60% severe symptoms

103
Q

The height of V-waves is _____ related to atrial and pulmonary vascular compliance.
The height of V-waves is _____ proportional to pulmonary blood flow and regurgitant volume.

A

Inversely

Directly

104
Q

Aortic Stenosis

A

Diastolic dysfunction - concentric hypertrophy
Most common valvular disorder in the US
Triad - angina, syncope, DOE
SLOW, FULL, TIGHT

105
Q

Critical aortic stenosis occurs with an aortic orifice of ___ cm2 and a transvalvular pressure gradient of ____ mmHg.

A

0.8

50

106
Q

Mitral Stenosis

A

Diastolic dysfunction - RV concentric hypertrophy
90% will present with CHF + Afib
SLOW, FULL, TIGHT

107
Q

In mitral stenosis, the enlarged left atrium may apply pressure to what structure and cause hoarseness?

A

Left recurrent laryngeal nerve

108
Q

Mitral stenosis is usually due to…

The most common cause of aortic stenosis is…

A

Rheumatic fever

109
Q

Symptoms of mitral stenosis occur when the mitral valve orifice is < than how many cm2?

A

< 2

110
Q

Acute aortic regurgitation presents with a sudden onset of ________ and _________.

A

Pulmonary edema

Hypotension

111
Q

The patient has WPW syndrome. Afib develops. How should the Afib be treated?

A

RVR then cardioversion
Procainamide
AVOID verapamil or digitalis

112
Q

Concentric hypertrophy may be one of the best ways to decrease _________.

A

Wall tension

Law of LaPlace: T = Pr/2h (h=wall thickness)

113
Q

What is the best indicator of diastolic dysfunction?

A

Decrease in LV compliance

114
Q

What valve problem is associated with both a systolic and diastolic murmur?

A

Aortic stenosis

Or a combo of mitral and aortic regurge

115
Q

A very low diastolic pressure and wide pulse pressure suggest…

A

Aortic regurgitation

116
Q

Why is it important to maintain afterload in the patient with aortic stenosis?

A

To maintain coronary perfusion pressure

117
Q

What reflects the severity of the outflow tract obstruction in IHSS?

A

LV-aortic systolic pressure gradient

118
Q

What is the normal ACT? What ACT indicates adequate heparinization for cardiopulmonary bypass?

A

70-110 seconds

ACT > 400

119
Q

Give 2 possible reasons for decreased effectiveness of heparin.

A
  1. Nitroglycerine

2. AT III deficiency - 2 units of FFP

120
Q

To what temp can you cool a patient before V.Fib?

A

V.Fib begins b/t 25-30 deg C

121
Q

Blood draining from what cardiac vessels explains why the LV will fill during cardiopulmonary bypass for aortocoronary bypass graft surgery?

A

Thebesian and bronchial veins

122
Q

What is the normal CVP during cardiopulmonary bypass? What does an increased CVP indicate?

A

Normally CVP = 0

An increased CVP indicates there is an obstruction to venous drainage

123
Q

How should you treat elevated blood pressure during the rewarming phase of cardiopulmonary bypass? The pump flow is 50-70 mL/kg/min, which is normal.

A

Increased volatile agent

Unless, poor ventricular function (myocardial depression) - vasodilator

124
Q

What % of coronary bypass patient return to surgery? When?

A

4-10% in the 1st 24 hrs

125
Q

What is the characteristic EKG change with digitalis?

A

Down sloping of the ST segment

126
Q

Which is the best standard limb lead for detecting arrhythmias?

A

Lead II

127
Q

The patient is hypokalemic. What change in HR may be seen?

A

Increased

128
Q

What are 3 characteristic changes seen on the ECG with hypercalcemia?

A
  1. Short QT
  2. Prolongation of QRS complex
  3. Widening of T wave
129
Q

Flat T-waves are seen with what 2 electrolyte imbalances?

A
  1. Hypokalemia
  2. Hypocalcemia
    * Both of these also have prolongation of QT interval
130
Q

Prolongation of PR interval is seen with what 2 electrolyte imbalances

A
  1. Hypokalemia

2. Hyperkalemia

131
Q

What are 2 causes of ST segment depression?

A
  1. Subendocardial ischemia

2. Subendocardial infarction

132
Q

What are 2 causes of ST segment elevation?

A
  1. Transmural ischemia (Prinzmetal’s angina)

2. Transmural infarction

133
Q

Where are the leads placed for Lead I? Lead II? Lead III?

A

Lead I: L.arm = pos, R.arm = neg
Lead II: R.arm = neg, L.leg = pos
Lead III: L.arm = neg, L.leg = pos

134
Q

The upstroke of the arterial pressure waveform is determined by what 2 factors?

A
  1. Contractility
  2. SVR

*Steep upstroke with increased contractility or decreased SVR

135
Q

What determines the position of the dicrotic notch in relation to the peak of the arterial blood pressure waveform?

A

CO

  • Dicrotic notch will be high on the descending limb if SV is high
  • The position of the dicrotic notch is probably most determined by preload
136
Q

Which diagnostic test is best for determining CAD: resting ECG, Holter monitor ECG, stress ECG, stress thallium testing?

A

Stress ECG has a high specificity of 90%

137
Q

What are the 2 most significant risk factors identified by the Goldman Cardiac Risk Index for non-cardiac surgery?

A
  1. Myocardial infarction

2. S3 gallop

138
Q

Elective surgery is best not performed until how much time has elapsed after a MI?

A

Six months

139
Q

Which types of surgery cause the biggest risk of perioperative reinfarction?

A

Intrathoracic
Intraabdominal
Lasting longer than 3 hours

140
Q

What is the likelihood that a patient will experience an infarction in the perioperative period?

A

< 10%

141
Q

How is LV compliance assessed?

A

Doppler electrocardiography

*LV compliance is the best indicator of diastolic function

142
Q

What Swan-Ganz catheter data suggest LV failure?

A

Decreased CO/CI

Increased preload/PCWP

143
Q

What is the hallmark of decreased cardiac reserve and low CO?

A

Fatigue at rest with minimal reserve

4 METs: flight of stairs without fatigue, walking at 4 mph, run a short distance, recreational sports

144
Q

Is the hypotension that accompanies cardiac tamponade due to a change in preload, afterload, or contractility?

A

Preload

*The principle hemodynamic feature is a decrease in CO

145
Q

What is Beck’s triad?

A
  1. Hypotension
  2. JVD
  3. Muffled heart sounds
146
Q

Explain pulsus paradoxus in cardiac tamponade.

A

Normally, SBP decreases 6 mmHg or less during inspiration

Tamponade, SBP decreases > 10 mmHg during inspiration = pulsus paradoxus

147
Q

What should be the goals for the patient with pericardial tamponade?

A

Avoid vasodilation
Avoid cardiac depression
Fast and Full!
Induction agent of choice - Ketamine

148
Q

Takayasu’s Arteritis

A

Pulseless disease
Absence of palpable peripheral pulses
Chronic inflammation of the aorta and its major branches
Primarily affects young Asian females
S/S reflect decreased perfusion
Tx - corticosteroids
Anesthesia goal - maintain perfusion pressure

149
Q

What does an S3 heart sound during mid-diastole indicate?

A

CHF

150
Q

List the VRG. What % of CO goes to each of these organs?

A 
Lungs 100% 
Liver 25%
Kidney 20% 
Brain 15% 
Heart 5%

75% of CO, 10% of total body mass

151
Q

What causes a change in BP when changing the patient’s position?

A

Altered preload

152
Q

The resistance to BF is greatest in the…

A

Arterioles

*Greatest decrease in pressure in the arterial tree occurs in the arterioles

153
Q

What are the 2 determinants of pulse pressure ?

A
  1. SV
  2. Arterial compliance

*PP increase when either CO increases or arterial compliance decreases

154
Q

The arterial system contains what % of the total blood volume?

A

Venous - 64%
Arterial - 13%
Capillaries - 7%

155
Q

Albumin is responsible for ___% of the total colloid osmotic pressure in the plasma.

A

80%

156
Q

How does hypercapnia/acidosis affect systemic vasculature? Pulmonary vasculature?

A

Systemic - decrease SVR
Pulmonary - increase PVR

*Both HTN and hypotension may occur with hypercapnia

157
Q

What is unusual about the flow pattern in the left and right coronary arteries during systole and diastole?

A

Flow through the R ventricle is sustained during both systole and diastole

158
Q

What is the venous saturation of coronary blood?

A

30% (PO2 = 18-20 mmHg)

  • O2 extraction level of coronary blood is 70%
  • O2 consumption rate 8-10 mL O2/100g/min
159
Q

Is coronary BF autoregulated?

What is the formula for coronary perfusion pressure?

A

YES, b/t 60-160 mmHg

CPP = aortic DBP - LVEDP(PCWP)

160
Q

What most determines coronary BF?

A

Myocardial metabolism

Coronary dilation in response to increased metabolic demand

161
Q

What is the most potent local vasodilator substance released by cardiac cells?

A

Adenosine

162
Q

Arrange the following in order that shows greatest to least effect on myocardial O2 consumption: afterload, preload, and HR

A

HR > afterload > preload

163
Q

Where is the density of capillaries the greatest in the LV?

A

Subendocardium
Higher blood flow, greater O2 requirements
Most vulnerable to ischemia

164
Q

What anesthetic agents can trigger or modulate the myocardial preconditioning response? What anesthetic agents can antagonize the effect?

A

Good - volatile agents, adenosine, opioids

Bad - Ketamine

165
Q

In what segment of the cardiac conduction system is the action potential conducted slowest? Fastest?

A

Slowest - AV node

Fastest - Purkinje fibers

*Phase 4 depolarization is fastest in the SA node and slowest in the Purkinje fibers (SA node - 60-100, AV node - 40-60, Purkinje - 15-40)

166
Q

Is the heart equally innervated by the SNS and PNS?

A

NO!
SNS - both atria and ventricle + both nodes
PNS - atria + both nodes

167
Q

What cardiac electrical event is represented by the PR interval?

A

Action potentials passing through the AV node

168
Q

What cardiac electrical event is represented by the QT segment?

A

Ventricular action potential is in phase 2, the plateau phase
Ventricular contraction

169
Q

What 2 electrolytes are membrane potential stabilizers (decrease the excitability of the cell)?

A
  1. HYPERcalcium

2. HYPERmag

The BIG Test (21 decks)

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