Cardiac Flashcards
(169 cards)
1
Q
Detail the conduction pathway starting with the SA node (normal pacemaker).
A
- SA node
- Internodal tracts - AV node + Bachmann’s bundle (to LA)
- AV node
- Bundle of His
- Bundle branches
- Purkinje fibers
- Ventricular muscle
2
Q
Action potentials with plateau phases are found where?
A
Atrial and ventricular muscle cells
3
Q
Action potentials that are biphasic (depolarization + repolarization withOUT plateau phase) are found where?
A
SA and AV node
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)
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
6
Q
What is the resting potential of the ventricular cell?
A
- 90 mV
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
8
Q
Changing the ______ of _______ depolarization causes heart rate to change.
A
Slope of phase 4
9
Q
On what phase of the nodal action potential does digitalis /CCB work to slow heart rate?
A
Phase 4
10
Q
On what phase of the nodal action potential does lidocaine/phenytoin work to control ventricular dysrhythmias?
A
Phase 4
11
Q
On what phase of the cardiac ventricular action potential do CCB work?
A
Phase 2
12
Q
What happens to the duration of the plateau with hypocalcemia?
A
Ca diffuses IN at a slower rate - plateau is prolonged
13
Q
What happens to the duration of the plateau with hypercalcemia?
A
Ca diffuses IN at a faster rate - plateau is shortened
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
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
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
17
Q
First Degree Heart Block
A
PR interval is > 0.2 sec
greater than one big box
18
Q
Second Degree Heart Block
Mobitz Type I
Wenckebach
A
Progressive increase in the PR interval…until a DROP (missed QRS)
19
Q
Second Degree Heart Block
Mobitz Type II
A
SUDDEN missed QRS
P waves are normal
20
Q
Third Degree Heart Block
Complete Heart Block
A
Dissociated P waves and QRS
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
22
Q
Transmural ischemia is characterized by symmetrically inverted ____ waves.
A
T
23
Q
Transmural injury demonstrates ST segment _______ greater than ____ mm.
A
Elevation
1
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)
25
Potassium Disturbances and ECG
What happens with hyperkalemia?
What happens with hypokalemia?
Hyperkalemia - peaked T waves
Hypokalemia - prominent U waves
26
What 2 drugs should be avoided with Wolff-Parkinson-White Syndrome?
1. Digoxin
2. CCB - Verapamil
* B/c they increase conduction through the accessory bypass tract - bundle of Kent
27
What is the best overall lead for detecting an MI?
V5
28
Inferior MI
Leads?
Coronary artery supply?
II, III, aVF
| RCA
29
Anterior MI
Leads?
Coronary artery supply?
V1-V4
| LAD
30
Lateral MI
Leads?
Coronary artery supply?
I, aVL, V5, V6
| Circumflex
31
MAP is determined by what 2 factors?
1. CO
| 2. SVR
32
CO is determined by what 2 factors?
1. HR
2. SV
CO = HR x SV
33
SV is determined by what 3 factors?
1. Preload
2. Afterload
3. Contractility
34
Preload is determined by what 2 factors?
1. Intravascular volume
| 2. Venous tone
35
What is the major determinant of intravascular volume?
Amount of sodium
36
What hormone is the most important for controlling vascular volume?
Aldosterone
37
Frank-Starling Law of the Heart
Increased ventricular filling - Increased preload
| Increased preload - Increased SV
38
Contractility is determined by the _______ environment of the cardiac cell.
Chemical
39
Pressure Overload Hypertrophy
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)
40
Volume Overload Hypertrophy
LV eccentric hypertrophy
Chamber size dilates
Causes - mitral regurgitation, aortic regurgitation, morbid obesity
41
Ventricular hypertrophy in response to pressure or volume overload is an application of the ________.
Law of Laplace
42
LV Pressure-Volume Loops
```
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
```
43
When does systole begin and end on the P-V loop?
Begin - B
| End - D
44
When does diastole begin and end on the P-V loop?
Begin - D
| End - B
45
```
What happens with an increase in preload (fluid bolus)?
EDV
ESV
SV
BP
HR/SVR
```
```
EDV: increases
ESV: stays the same
SV: increases
BP: increases
HR/SVR: decreases, reflex
*Pressure-volume loop widens withOUT a change in ESV
```
46
```
What happens with an increase in afterload (neo)?
EDV
ESV
SV
BP/SVR
HR
```
```
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)
```
47
```
What happens with an increase in contractility (calcium)?
EDV
ESV
SV
BP
HR/SVR
```
```
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)
```
48
P-V loop shift to the RIGHT means...
Greater volumes
49
P-V loop shift UP means...
Greater pressures
50
P-V loop shift to the LEFT means...
Smaller volumes
51
P-V loop shift DOWN means...
Smaller pressures
52
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.
Increase in afterload
| Decrease in contractility
53
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.
Increase in contractility
| Decrease in afterload
54
When preload increases, the P-V loop shifts...
P-V loop widens
| EDV increases
55
When preload decreases, the P-V loop shifts...
P-V loop narrows
| EDV decreases
56
When afterload increases, the P-V loop shifts...
UP and to the RIGHT
| Greater pressures, greater volumes
57
When afterload decreases, the P-V loop shifts...
DOWN and to the LEFT
| Lower pressures, smaller volumes
58
When contractility increases, the P-V loop shifts...
UP and to the LEFT
| Greater pressures, smaller volumes
59
When contractility decreases, the P-V loops shifts...
DOWN and to the RIGHT
| Lower pressures, greater volumes
60
The P-V loop in IHSS is unique. Describe the shift.
UP and to the LEFT
Greater pressures, smaller volumes
Narrow and very high!
61
Describe the P-V loop of aortic stenosis.
Increased afterload
UP
Greater pressures, volumes stay about the same
Concentric hypertrophy
62
Describe the P-V loop of mitral stenosis.
Decreased preload
Decreased EDV
Lower pressures, smaller volumes
63
Describe the P-V loop of aortic regurgitation.
| Acute vs. chronic
No isovolemic relaxation phase
Acute - P-V loop is small
Chronic - P-V loop is large (eccentric hypertrophy)
64
Describe the P-V loop of mitral regurgitation.
| Acute vs. chronic
No isovolemic contraction phase
Acute - P-V loop is small
Chronic - P-V loop is large (eccentric hypertrophy)
65
Ventricular Function Curves
Explain the shift with an increased preload.
Decreased preload?
Increased preload - point shifts to the RIGHT on the same curve
Decreased preload - point shifts to the LEFT on the same curve
66
Ventricular Function Curves
Y-axis?
X-Axis?
Y-axis: stroke volume
| X-axis: PCWP (EDV)
67
Ventricular Function Curves
Explain the shift with an increased afterload.
Decreased afterload?
Increased afterload - curve shifts DOWN and to the RIGHT
| Decreased afterload - curve shifts UP and to the LEFT
68
Ventricular Function Curves
Explain the shift with an increased contractility.
Decreased contractility?
Increased contractility - curve shifts UP and to the LEFT
| Decreased contractility - curve shifts DOWN and to the RIGHT
69
Formula for SV
| Normal SV
SV = CO/HR
(CO = HR x SV)
Normal SV = 60 mL
70
Formula for SI
| Normal SI
SI = SV/BSA
| Normal SI = 40 mL
71
Formula for SVR
SVR = (MAP - CVP)/CO x 80
72
Formula for PVR
PVR = (PAP - PCWP)/CO x 80
73
Baroreceptor Reflex
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
Where are the baroreceptors found?
1. Carotid sinus
| 2. Aortic arch
75
Afferent action potentials from the baroreceptors of the aortic arch are carried to the brainstem centers via what nerve?
Vagus
76
Afferent action potentials from the baroreceptors of the carotid sinus are carried to the brainstem centers via what nerve?
Hering's --- a branch of the Glossopharyngeal
77
Which are physiologically more important: the carotid or aortic arch baroreceptors?
Carotid baroreceptors
78
Nitric Oxide
Pathway?
Produced by?
Regulated by?
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
How do sodium nitroprusside, nitroglycerine, and dinitrate work?
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
How does hydralazine work?
It is a membrane hyperpolarizing agent via activation of K channels
*Arterial dilator
81
Nitroprusside and nitroglycerine have __________ as well as vasodilatory actions.
Bronchodilator
82
What explains the following statement:
| Nitroglycerine works on venous capacitance vessels and nitroprusside works on arterial and venous capacitance vessels.
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
If 2 thermodilution curves are shown...how do you determine which curve has the highest CO?
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
Bainbridge Reflex
1. SVC dilates
2. Venous pressure falls
3. Pressure gradient increases
4. Venous return increases
5. HR increases d/t increased CVP
85
List determinants of myocardial oxygen supply.
1. O2 content (Hct, %sat)
2. DBP
3. CVR
4. HR
86
List determinants of myocardial oxygen demand.
1. HR
2. Afterload
3. Prelaod
4. Contractility
87
What hemodynamic change is most important to avoid in the patient with CAD?
Tachycardia
| *Double jeopardy - increases O2 consumption + decreases O2 supply
88
The pulse pressure _______ as the arterial pressure waveform passes into more peripheral arterial vessels.
Increases
| *Pulse pressure is greatest in the dorsalis pedis
89
What is the increase in pulse pressure as the pressure wave moves peripherally attributable to?
An increase in SBP + a decrease in DBP
| *Superimposition principle
90
MAP = the area under the arterial pressure curve divided by what?
Time
91
Are CCB venous or arterial dilators?
Arterial dilators
| Cause a decrease in HR
92
Which CCB causes a reflex increase in HR?
Nifedipine
93
Are ACE-I venous or arterial dilators?
Arterial dilators
94
How do Inamrinone and Milrinone increase myocardial contractility and decrease SVR/relax vascular smooth muscle?
By blocking the breakdown of cAMP
95
Name 3 indications for Adenosine.
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
Hypertrophic Cardiomyopathy w/ or w/o Ventricular Outflow Obstruction
IHSS
HOCM
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
Arterial waveform may be bifid (bisferiens pulse) in what condition?
IHSS
98
Aortic + Mitral Regurgitation
Systolic dysfunction - eccentric hypertrophy
| Fast, Full, Forward
99
Regurgitant volume depends on ______ and the _____ across the aortic valve.
HR
| Diastolic pressure gradient
100
Symptoms of regurgitation are minimal when volume remains under ___% of stroke volume, but is severe if it exceeds ___% of stroke volume.
40%
| 60%
101
What 4 factors determine degree of regurgitation?
1. Size of valve orifice
2. Pressure gradient
3. Systole time (time for regurge)
4. Aortic outflow impedance (SVR)
102
Symptomatic Progression of Regurgitant Factors
< 30% mild symptoms
30-60% mod symptoms
> 60% severe symptoms
103
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.
Inversely
| Directly
104
Aortic Stenosis
Diastolic dysfunction - concentric hypertrophy
Most common valvular disorder in the US
Triad - angina, syncope, DOE
SLOW, FULL, TIGHT
105
Critical aortic stenosis occurs with an aortic orifice of ___ cm2 and a transvalvular pressure gradient of ____ mmHg.
0.8
| 50
106
Mitral Stenosis
Diastolic dysfunction - RV concentric hypertrophy
90% will present with CHF + Afib
SLOW, FULL, TIGHT
107
In mitral stenosis, the enlarged left atrium may apply pressure to what structure and cause hoarseness?
Left recurrent laryngeal nerve
108
Mitral stenosis is usually due to...
| The most common cause of aortic stenosis is...
Rheumatic fever
109
Symptoms of mitral stenosis occur when the mitral valve orifice is < than how many cm2?
< 2
110
Acute aortic regurgitation presents with a sudden onset of ________ and _________.
Pulmonary edema
| Hypotension
111
The patient has WPW syndrome. Afib develops. How should the Afib be treated?
RVR then cardioversion
Procainamide
AVOID verapamil or digitalis
112
Concentric hypertrophy may be one of the best ways to decrease _________.
Wall tension
| Law of LaPlace: T = Pr/2h (h=wall thickness)
113
What is the best indicator of diastolic dysfunction?
Decrease in LV compliance
114
What valve problem is associated with both a systolic and diastolic murmur?
Aortic stenosis
| Or a combo of mitral and aortic regurge
115
A very low diastolic pressure and wide pulse pressure suggest...
Aortic regurgitation
116
Why is it important to maintain afterload in the patient with aortic stenosis?
To maintain coronary perfusion pressure
117
What reflects the severity of the outflow tract obstruction in IHSS?
LV-aortic systolic pressure gradient
118
What is the normal ACT? What ACT indicates adequate heparinization for cardiopulmonary bypass?
70-110 seconds
| ACT > 400
119
Give 2 possible reasons for decreased effectiveness of heparin.
1. Nitroglycerine
| 2. AT III deficiency - 2 units of FFP
120
To what temp can you cool a patient before V.Fib?
V.Fib begins b/t 25-30 deg C
121
Blood draining from what cardiac vessels explains why the LV will fill during cardiopulmonary bypass for aortocoronary bypass graft surgery?
Thebesian and bronchial veins
122
What is the normal CVP during cardiopulmonary bypass? What does an increased CVP indicate?
Normally CVP = 0
| An increased CVP indicates there is an obstruction to venous drainage
123
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.
Increased volatile agent
| Unless, poor ventricular function (myocardial depression) - vasodilator
124
What % of coronary bypass patient return to surgery? When?
4-10% in the 1st 24 hrs
125
What is the characteristic EKG change with digitalis?
Down sloping of the ST segment
126
Which is the best standard limb lead for detecting arrhythmias?
Lead II
127
The patient is hypokalemic. What change in HR may be seen?
Increased
128
What are 3 characteristic changes seen on the ECG with hypercalcemia?
1. Short QT
2. Prolongation of QRS complex
3. Widening of T wave
129
Flat T-waves are seen with what 2 electrolyte imbalances?
1. Hypokalemia
2. Hypocalcemia
* Both of these also have prolongation of QT interval
130
Prolongation of PR interval is seen with what 2 electrolyte imbalances
1. Hypokalemia
| 2. Hyperkalemia
131
What are 2 causes of ST segment depression?
1. Subendocardial ischemia
| 2. Subendocardial infarction
132
What are 2 causes of ST segment elevation?
1. Transmural ischemia (Prinzmetal's angina)
| 2. Transmural infarction
133
Where are the leads placed for Lead I? Lead II? Lead III?
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
The upstroke of the arterial pressure waveform is determined by what 2 factors?
1. Contractility
2. SVR
*Steep upstroke with increased contractility or decreased SVR
135
What determines the position of the dicrotic notch in relation to the peak of the arterial blood pressure waveform?
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
Which diagnostic test is best for determining CAD: resting ECG, Holter monitor ECG, stress ECG, stress thallium testing?
Stress ECG has a high specificity of 90%
137
What are the 2 most significant risk factors identified by the Goldman Cardiac Risk Index for non-cardiac surgery?
1. Myocardial infarction
| 2. S3 gallop
138
Elective surgery is best not performed until how much time has elapsed after a MI?
Six months
139
Which types of surgery cause the biggest risk of perioperative reinfarction?
Intrathoracic
Intraabdominal
Lasting longer than 3 hours
140
What is the likelihood that a patient will experience an infarction in the perioperative period?
< 10%
141
How is LV compliance assessed?
Doppler electrocardiography
| *LV compliance is the best indicator of diastolic function
142
What Swan-Ganz catheter data suggest LV failure?
Decreased CO/CI
| Increased preload/PCWP
143
What is the hallmark of decreased cardiac reserve and low CO?
Fatigue at rest with minimal reserve
| 4 METs: flight of stairs without fatigue, walking at 4 mph, run a short distance, recreational sports
144
Is the hypotension that accompanies cardiac tamponade due to a change in preload, afterload, or contractility?
Preload
*The principle hemodynamic feature is a decrease in CO
145
What is Beck's triad?
1. Hypotension
2. JVD
3. Muffled heart sounds
146
Explain pulsus paradoxus in cardiac tamponade.
Normally, SBP decreases 6 mmHg or less during inspiration
| Tamponade, SBP decreases > 10 mmHg during inspiration = pulsus paradoxus
147
What should be the goals for the patient with pericardial tamponade?
Avoid vasodilation
Avoid cardiac depression
Fast and Full!
Induction agent of choice - Ketamine
148
Takayasu's Arteritis
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
What does an S3 heart sound during mid-diastole indicate?
CHF
150
List the VRG. What % of CO goes to each of these organs?
```
Lungs 100%
Liver 25%
Kidney 20%
Brain 15%
Heart 5%
```
75% of CO, 10% of total body mass
151
What causes a change in BP when changing the patient's position?
Altered preload
152
The resistance to BF is greatest in the...
Arterioles
| *Greatest decrease in pressure in the arterial tree occurs in the arterioles
153
What are the 2 determinants of pulse pressure ?
1. SV
2. Arterial compliance
*PP increase when either CO increases or arterial compliance decreases
154
The arterial system contains what % of the total blood volume?
Venous - 64%
Arterial - 13%
Capillaries - 7%
155
Albumin is responsible for ___% of the total colloid osmotic pressure in the plasma.
80%
156
How does hypercapnia/acidosis affect systemic vasculature? Pulmonary vasculature?
Systemic - decrease SVR
Pulmonary - increase PVR
*Both HTN and hypotension may occur with hypercapnia
157
What is unusual about the flow pattern in the left and right coronary arteries during systole and diastole?
Flow through the R ventricle is sustained during both systole and diastole
158
What is the venous saturation of coronary blood?
30% (PO2 = 18-20 mmHg)
* O2 extraction level of coronary blood is 70%
* O2 consumption rate 8-10 mL O2/100g/min
159
Is coronary BF autoregulated?
| What is the formula for coronary perfusion pressure?
YES, b/t 60-160 mmHg
CPP = aortic DBP - LVEDP(PCWP)
160
What most determines coronary BF?
Myocardial metabolism
| Coronary dilation in response to increased metabolic demand
161
What is the most potent local vasodilator substance released by cardiac cells?
Adenosine
162
Arrange the following in order that shows greatest to least effect on myocardial O2 consumption: afterload, preload, and HR
HR > afterload > preload
163
Where is the density of capillaries the greatest in the LV?
Subendocardium
Higher blood flow, greater O2 requirements
Most vulnerable to ischemia
164
What anesthetic agents can trigger or modulate the myocardial preconditioning response? What anesthetic agents can antagonize the effect?
Good - volatile agents, adenosine, opioids
| Bad - Ketamine
165
In what segment of the cardiac conduction system is the action potential conducted slowest? Fastest?
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
Is the heart equally innervated by the SNS and PNS?
NO!
SNS - both atria and ventricle + both nodes
PNS - atria + both nodes
167
What cardiac electrical event is represented by the PR interval?
Action potentials passing through the AV node
168
What cardiac electrical event is represented by the QT segment?
Ventricular action potential is in phase 2, the plateau phase
Ventricular contraction
169
What 2 electrolytes are membrane potential stabilizers (decrease the excitability of the cell)?
1. HYPERcalcium
| 2. HYPERmag
