Ischemic Heart Disease Flashcards
1
Q
What does the left coronary supply?
A
LV anterior wall
LV anteroseptal wall
The largest part of the LV
2
Q
What does the right coronary supply?
A
RV
SA, AV node
LV inferior wall
3
Q
What is another name for the LV inferior wall?
A
The diaphragmatic wall
4
Q
What are the main branches off of the left coronary artery?
A
Left anterior descending
Circumflex
5
Q
What is the main branch off of the right coronary artery?
A
Posterior descending
6
Q
What is the Sinus of valsalva?
A
A dilation about the aortic valve which allows the valve to open efficiently without occluding the coronary Ostia
7
Q
What is another name for the innominate artery?
A
Brachiocephalic artery
8
Q
What is another name for the innominate artery?
A
Brachiocephalic artery
9
Q
Which coronary dominance is more common?
A
Right dominant
10
Q
What does it mean to be right coronary dominant?
A
The RCA feeds the PDA
Taylor: More volume of blood flows through the right coronary than the left
11
Q
What is the second most common coronary dominance?
A
Equal right and left blood flow
12
Q
What is the least common coronary dominance?
A
Left coronary dominance
13
Q
A lesion in the LAD causes an infarct where?
A
Anterior LV
Anteroseptal LV
14
Q
In what leads will an anterior LV infarct be seen?
A
V3-V4
Co-existing: V3-V5
Barash: I, aVL, V1-V4
15
Q
In what leads will an anteroseptal infarct be seen?
A
Anterior V3-V4
Septal V1-V2
Co-existing: V3-V5
16
Q
A lesion in the RCA will cause an infarct where?
A
Inferior Wall LV
RV, RA
SA and AV node
17
Q
In what leads will an inferior wall infarct be seen?
A
II, III, aVF
18
Q
What else does the RCA supply that can cause dysrhythmias?
A
SA and AV nodes
19
Q
A lesion in the circumflex causes an infarct where?
A
Posterior LV
Lateral LV
20
Q
In what leads can a lateral infarct be seen?
A
I, aVL, V5-V6
21
Q
What structure receives most of the coronary venous drainage?
A
Coronary sinus
22
Q
Where is the coronary sinus located?
A
RA
23
Q
What veins drain venous blood into the heart chambers?
A
Thebesian veins
24
Q
Why does the blood that enters the aorta have just slightly lower PO2 than it did when it left the lungs?
A
Venous admixture from venous drainiage from heart and bronchial supply of the lungs
25
How much of CO goes to the coronaries?
4-5%
| -225 mL/min
26
Does metabolism affect the amount of CO that flows to the coronaries?
Yes
27
What predominently increases blood flow to the coronaries when metabolism increases?
Local factors
28
What is the predominant substance released by the heart itself inorder to cause vasodilation when metabolism is increased?
Adenosine
29
What is the Vasodilator theory?
Tissues release vasodilator substance as a result of increased metabolism
30
Where do the tissue released vasodilator subastance act?
Precapillary sphincter
31
When does blood flow through the coronaries?
During diastole
32
Why does blood flow to the coronaries during diastole?
Ventricular pressure during systole compresses the coronaries
33
What causes blood to flow
Pressure gradients
34
What opposes the movement of blood in the coronary arteries?
Tissue pressure within the myocardium (systole)
35
During systole, where in the myocardium is the highest pressure?
Subendocardium
36
What layer of the maycardium is at greatest risk of not receiveing adequate blood flow?
The subendocardium, because it is under the most pressure during systole
37
What layer needs the most blood flow/O2?
Subendocardium
38
What is the heart's main source of fuel for metabolism?
Fatty acids (stead of carbs)
39
Is the heart able to use anerobic metabolism?
Yes
40
What is released when tissues use anerobic metabolism?
Lactic Acid
41
How is lactic acid related to angina?
Lactic acid is a tissue irritant
42
How much oxygen does normal perfusion deliver to the heart?
8-10 mL/100g/min
| -g of tissue
43
How efficient is the heart in extracting oxygen?
Very. It can extract 65-75% of the oxygen
44
What occurs when the heart needs more oxygen?
The only way to increase oxygen is to increase blood flow
| -the heart can not increase it's extraction
45
Besides the vasodilator theory, what else could be the cause of coronary dilation in times on increased demand?
Oxygen demand theory
46
What is the oxygen demand theory?
Vasocontriction requires constant oxygen, so when oxygen is inadequate vessels passively dilate
47
What does SNS stimulation cause in the heart?
Increased HR and contractility
48
What are the indirect effects of SNS stimulation on the heart?
Due to SNS induced increased contractility and HR, the metobolic rate of the heart is also increased, so the vessels dilate to get more blood flow
49
Which effect during SNS stimulation of the heart predominants?
The dilation effects
50
What vascular response do alpha receptors have to SNS stimulation?
Vasoconstriction
51
What vascular response do beta receptors have to SNS stimulation?
B1 increased HR and contractility
| B2 Vasodilation
52
What type of adrenergic receptors are present on the coronaries?
alpha and beta 2 receptors
53
What response does SNS stimulation have on beta 1 receptors?
Increase HR and contractility
54
How does SNS stimulation increase HR and contractility?
Through beta 1 receptors on the heart
55
Heart's response to SNS activity
```
Vasoconstriction due to alpha receptors
Increases HR and contractilty through B1
Increased metabolism and O2 demand
Local factors release Adenosine to cause vasodilation and increase blood flow
B2 stimulation causes vasodilation
```
56
What response does PSNS have on the heart?
Decreases HR > decreases metabolism, so the heart doesn't need as much blood flow
57
What is vagospastic disease?
A strong alpha response in coronary arteries
58
What is occuring with vagospastic disease?
With SNS stimulation alpha vasoconstriction predominates > angina and ischemia
59
How is vagospastic disease treated?
Calcium channel blockers
60
In the cath lab a person with vagospastic disease may have what result?
Clean coronaries
61
What factors affects coronary blood flow?
Vessel patency
Perfusion pressure
Heart rate
62
What can affect vessel patency?
CAD and spasm
63
What determines perfusion pressure?
DBP and LVEDP
64
What about HR affects coronary perfusion?
Time spent in diastole
65
CPP =
CPP = DBP-LVEDP
66
What affects arterial oxygenation?
Hemoglobin
| -quantity and quality
67
What affects saturation?
FiO2 and gas exchange
68
What supply factors affect myocardial oxygen balance?
```
Vessel patency
Perfusion pressure
HR
O2 extraction
-Hgb
-Saturation
```
69
What demand factors affect myocardial oxygen balance?
HR
Preload
Afterload
Contractility
70
What affects wall tension?
Preload and afterload
71
How does HR affect demand of O2?
Increased HR increases metabolism
72
How does contractility affect demand of O2?
Increased contractiity increases metabolism
73
How can contractility affect supply of O2?
If stronger contraction decreases LVEDV, this decreases wall tension and increases CPP
74
How does arterial hypertension affect O2 demand?
In order to overcome HTN metabolism is increased and so is demand
75
How can arterial hypertension affect O2 supply?
If the higher systemic BP also increases DBP, then CPP may improve
76
Does HR affect supply or demand? In what way?
Both
- HR decreases supply
- HR increases demand
77
What is the number 1 thing to control in a patient that has ichemia heart disease?
HR
| -do not allow tachycardia
78
What affect does an increase in BP have on the supply and demand of O2 in the heart?
BP increases demand, but it may help increase supply (not always)
79
What is more acceptable in a patient with ischemic heart disease hypotension or hypertension?
Hypertension
80
What demand factors affect myocardial oxygen balance?
Wall tension
HR
Contractility
Systemic HTN
81
High LVEDV increases risk of what?
Ischemia
| -D/T increase in preload and wall tension
82
What is tolerated better, hypertension or tachycardia
HTN
83
Low DBP is a risk for what?
Ischemia
| -because there is not enough driving perfusion
84
Causes of ischemia heart diease?
```
Artherosclerotic plaque
Vascular disease
Coronary artery lesions
Coronary stenosis
CAD
```
85
What are the major risk factors for ischemic heart disease?
Male gender
| Age
86
What are the nother risk factors for ishemic heart disease?
```
Obesity
Sedentary life style
HLD
HTN
DM
Smoking
Family Hx
PVD
```
87
Where can angina be located?
```
Sternal
Left arm/shoulder
Face, neck, jaw
Right arm/shoulder
GI distress
```
88
What things distinguish angina from infarct?
Angina is transient ischemia that can be relieved
- rest
- NTG
89
What is the most common cause of an acute occlusion in a coronary artery?
Vessel with preexisting plaque is narrowed and a clot gets stuck
90
Coronary vessels with obstructive plaque are more prone to what?
Spasm
91
How does the body attest to compensate to ischemic heart disease, angina and transient ischemia?
Collateral circulation
92
What is the stimulus for collateral vessels to grow?
Long standing ischemia and hypoxia
93
How does infarct differ from angina?
Prolonged ischemia
Eventual necrosis
Persistent unrelieved pain
May be asymptomatic
94
Diagnostics for MI
```
12 lead
Pathologic Q wave
ST segment changes
PVCs are common
Elevated temperature from inflammatory response
Troponin
```
95
How much oxygen does myocardial tissue usually require?
8 mL/100g/min
96
Necrosis occurs when myocardial oxygen falls to less than what?
< 1.3 mL/100g/min
97
What is stunned myocardium?
Tissue that is ischemic without cell death
98
Is stunned myocardium reversible?
Yes
| -but there is contractile dysfunction
99
Where is stunned myocardium located?
In the area around the central necrosis (central part of the infarct)
100
What does MI extension mean?
The infarct has extended into the stunned myocardium
101
What is ischemic preconditioning?
Inhalation agents have a protective effect on stunned myocardium
102
Why is the subendocardial layer the most vulnerable to ischemia?
It is the area that receives the least supply from max compression and it has the most demand because it has the highest oxygen need
103
What is another name for a subendocardial MI?
Non Q wave MI
| -more minor since it has not gone all the way through the layers, but indicates something needs to occur
104
What is the formula for coronary perfusion pressure?
CPP = DBP-LVEDP
105
How does decreased DBP affect CPP?
decreases CPP
106
How does increased LVEDP affect CPP?
Decreases CPP
107
What is the risk with a decreased CPP?
Ischemia and infarct
108
What may an elevated DBP be needed/helpful?
In patients with CAD
109
How can LVEDP be measured?
PCWP
| PAD - pulmonary artery diastolic pressure
110
Why do MIs cause decreased CO?
Loss of muscle and contractility
111
Why is there risk of cariogenic shock with an MI?
Poor tissue perfusion due to decrease SV from loss of contractility
-Increased risk with larger infarcted areas
112
What happens with blood flow due to an MI?
Damming of blood occurs
- lack of forward flow
- accumulates in lungs and periphery
- renal fluid retention
113
What is systolic stretch?
Infarcted area bulges outward with each contraction (instead of the normal inward)
114
What is a possible consequence of systolic stretch?
Area may rupture
115
How does vasodilation cause coronary steal?
Vasodilation in health tissue pulls blood flow from ischemic area
116
What causes coronary steal?
Activity or vasodilating drugs
117
What is the treatment for chest pain in preop?
```
O2
Rest
NTG
BB
Thrombolytic
Surgical revascularization or angioplasty
```
118
Does NTG dilate veins or arteries more?
Veins
119
With NTG is preload or afterload decreased?
Preload
120
With NTG decreasing preload is O2 demand decreased or supply increased?
Demand is decreased
121
What affect do BB have on the O2 supply and demand?
BB decrease demand by decreasing HR and increases supply by decreasing HR
122
What affect does thrombolytics have on the O2 supply and demand?
They increase supply by restoring blood flow
123
What surgical sites increase risk of cardiac complications?
Thoracic
| Upper abdominal
124
What type of procedures increase risk of cardiac complications?
Vascular procedures
125
What clinically can be used to assess LV function?
```
Activity tolerance
-SOB
Breath sounds
Peripheral edema
Neck vein distention
```
126
What diagnostic tests can be used to assess LV function?
Echocardiogram
Ejection fraction
Cardiac cath
-Wall motility
127
What is the number 1 predictor of cardiac complications in surgery?
Symptomatic CHF
128
Is current, symptoms CHF a contraindication to elective surgery?
Yes
129
What is the goal during anesthesia for a patient with poor LV function, but no acute CHF?
Optimal LV function
- fluid balance
- optimal filling pressure
- +/- invasive monitoring
- avoid drug induced myocardial depression
130
What questions do you ask about chest pain?
```
Duration
Frequency
Precipitating factors
At rest - non cardiac vs vasospastic
Relief measures
```
131
History of MI increases risk of complications, especially with what surgical location?
Thoracic or upper abdominal
132
What is the importance of timing of an MI and an elective procedure?
If less than 30 days since MI, postpone elective procedures
133
What constitutes stable angina?
No change in 60 days
134
What is the anesthetic goal in a patient with angina?
Maintain myocardial oxygen supply and demand
135
If angina is unstable or accelerating what should be obtained?
Cardiac consult
- stress test
- cardiac cath
136
What is unstable coronary syndrome?
Acute MI
Recent MI
Unstable angina
137
Is the risk of recent subendocardial MI different from the risk of recent transmural MI?
No, risk is the same
138
What are the postop cardiac complications associated with risk of unstable coronary syndrome?
```
MI
Pulmonary edema
CHF
Arrhythmias
Thromboembolism
```
139
What is THE most common cause of myocardial ischemia?
| M&M
Atherosclerosis of coronary arteries
140
Major preop risk factors for CAD?
```
Hyperlipidemia
Hypertension
Diabetes
Smoking
Increasing age
Male
Family Hx
```
141
Other preop risk factors for CAD
Hx of cerebrovascular or peripheral vascular disease
Menopause
High-estrogen oral contraceptives by smokers
Sedentary lifestyle
142
What is unstable angina?
An abrupt increase in servity, frequency or duration
Angina at rest
New onset with severe or frequent episodes
143
What is Chronic Stable Angina?
Relieved by NTG or rest
144
What patients are at increased risk for silent ischemia?
Diabetics
145
Before what percentage of occlusion of coronaries are patients generally asymptomatic?
50-75%
146
At what percentage of occlusion is maximum compensatory dilation usually present distally in the coronaries?
70%
147
What factors may precipitate vasospastic episodes?
Emotional stress or upset
| Hyperventilation > hypocapnia > coronary artery vasoconstriction
148
How do beta blockers help ischemic heart disease?
They decrease O2 demand by decreasing HR and contractility, and in some cases afterload
149
What affects can occur with B2 blockade?
Mask hypoglycemic symptoms
Delay metabolic recovery from hypoglycemia
Impair the handling of large K+ loads
150
How do calcium channel blockers help ischemic heart disease?
They reduce myocardial oxygen demand by decreasing cardiac afterload and augment myocardial oxygen supply via coronary vasodilation
151
What CCBs also reduce demand by decreasing HR?
Verapamil and diltiazem
152
What class and specific drug is used primarily in preventing cerebral vasospasm following subarachnoid hemorrhage?
Nimodipine - CCB
153
What affect if any do CCB have on NMB?
All CCB potentiate depolarizing and nondepolarizing NMB agents
154
What affect is potentiaed by CCB with inhalation agents?
Circulatory effects
155
Verapamil and diltiazem can potentiate what affects of VAs?
Depression of cardiac contractility and conduction in the AV node
156
Nifedipeine and similar agents can potentiate what affects of volatile and IV agents?
Systemic vasodilation
157
How do nitrates help with ischemic heart disease?
Reduce myocardial O2 demand by:
- decrease venous and arteriolar tone
- increase vascular capacitance
- reduce ventricular wall tension
158
Where does nitrite-induced coronary vasodilation preferentially increase blood flow?
In the subendocardial ischemic areas
159
Where in epicardial vessels do obstructions most commonly occur and why?
Nagelhout
Areas of bifurcation, because flow is turbulent
160
Coronary artery dominance %
RCA 50%
LCA 10-15%
Mixed R and L 35-40%
161
What factors determine myocardial oxygen supply?
```
Arterial blood content
DBP
Diastolic time as determined by HR
Oxygen extraction
Coronary artery blood flow
```
162
What determines myocardial oxygen demand?
Preload
Afterload
Contractility
HR
163
What is the most important factor that negatively affects MVO2?
HR, doubling HR doubles MVO2
164
How can oxygen delivery to the myocardium increase?
Only by increasing blood flow
165
What vasodilator substances have been identified and are released from the myocardium?
```
Adenosine
Adenosine phosphate compound
Potassium ions
Hydrogen ions
Carbon dioxide
Bradykinin
Prostaglandins
```
166
How is oxygen extraction in the coronaries determined?
By measurement of the difference between the oxygen tension in the pulmonary arterial blood and that in the coronary sinus
167
What is the equation for arterial oxygen content?
CaO2 = (SaO2 x Hgb x 1.34) + (0.003 x PaO2)
168
Coronary blood flow is autoregulated through what range?
MAP range of 60 to 140 mmHg
169
What determines coronary blood flow if MAP is outside of autoregulated range?
Coronary blood flow becomes pressure dependent
170
During hypotension, coronary arteries are maximally dilated, what equation determines blood flow?
MAP - RAP
171
CPP =
DBP - LVEDP
172
What is the major determinant of CPP?
DBP, because under normal conditions it is significantly higher than LVEDP
- N: DBP 80
- N: LVEDP 10
173
What is coronary vascular reserve?
The difference between the maximal flow and the autoregulated flow
-closer the two values, the lower the reserve
174
What decreases coronary reserve flow?
Factors that increase myocardial oxygen demand and limit supply
175
What is coronary steal?
If a patient has a stenotic coronary vessel with collateral flow and a vasodilator is given, only the autoregulated vessel dilates and receives preferential flow over the stenotic area
176
What is at coronary steal-prone anatomy?
Completely occlusion of one artery and at least 50% of a second artery that supplies collateral blood flow to the occluded area
177
How are volatile anesthetics myocardial preconditioners?
Decrease the formation of free radials, preserving myocardial ATP stores and inhibiting intracellular calcium
178
What is the most useful measure of CPP in the clinical setting?
MAP
179
In patients with CAD, what happens to coronary autoregulation just after the partial obstruction?
It becomes pressure dependent, especially with MAP below 70
180
What is the most significant cause of peri operative ischemia?
Increased HR
181
Ideally what is the best HR for patients with CAD or elevated LVEDP?
It’s determined on an individual basis, but less than 70 is a good guide
182
With myocardial ischemia, what occurs first systolic or diastolic dysfunction?
Diastolic
183
What is the most sensitive intraoperative monitor for detecting myocardial ischemia?
TEE
184
What is experienced with brief periods of myocardial ischemia (< 20 minutes)?
Necrosis does not occur, but reversible contractile dysfunction (stunning) can
185
What is stunning? How long can it last? Treatment?
Stunning is reversible contractile dysfunction
- 12-24 hours
- inotropic support
186
What is ischemic preconditioning?
Phenomenon whereby a short period of ischemia improves the heart’s ability to tolerate subsequently longer periods of ischemic insult
187
What causes/is hibernation?
A state of left ventricular dysfunction at rest caused by reduced coronary blood flow, which can be reversed by restoring myocardial oxygen supply or reducing demand
188
Besides patient’s with CAD, who else will benefit from high perfusion pressure and low HR?
Chronic HTN
Aortic stenosis
Obstructive cardiomyopathy
189
What determines coronary dominance?
Which main coronary artery supplies the PDA
