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8361 Exam I > Mod2: Review of Cardiac Anatomy > Flashcards

Mod2: Review of Cardiac Anatomy Flashcards

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1
Q

LOCATION

Where does the heart sits?

A

in the MEDIASTINUM

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2
Q

LOCATION

The heart sits in the mediastinum. Which structures is it boarded laterally by?

A

the lungs

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3
Q

LOCATION
Which structures sits anterior to the heart?

A

The Sternum

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4
Q

LOCATION

Which structures sit porterior to the heart?

A

Descending aorta

Esophagus

Major Bronchi

T5-8 vertebra

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5
Q

LOCATION

What’s the overall shape of the heart?

A

Blunt shaped cone

with 2/3 of its mass left of the midline

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6
Q

VALVES:AREA AUSCULTATED

Where is the Aortic valve auscultated? Why that location?

A

Aortic valve is auscultated at the second ICS right sternal border because the LV ejects towards the right

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7
Q

VALVES:AREA AUSCULTATED

Where is the Pulmonic valve auscultated? Why that location?

A

RV ejects towards the left, so the Pulmonic valve will be heart 2 ICS left sternal border

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8
Q

VALVES:AREA AUSCULTATED

Where is the Tricuspid valve auscultated? Why that location?

A

The tricupsid valve is ausculatated at the L (or R) lower sternum

Tricuspid is 5th ICS just to either the right or the left of the sternal line.

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9
Q

VALVES:AREA AUSCULTATED

Where is the Mitral valve auscultated? Why that location?

A

Apex

The mitral valve is located in the middle between the left atrium and ventricle at the apex of the heart. 5th ICS mid clavicular

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10
Q

HEART SOUNDS

S1 heart sound - What sound does it make? Where is auscultated? What events does is correspond to?

A

Makes “lupp” sound

Auscultated at the Apex

Corresponds to blood is being ejected form the LV

d/t closure of the AV valves

Marks the begining of Systole

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11
Q

HEART SOUNDS

S1 - EKG

A

Correlates with QRS

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12
Q

HEART SOUNDS

S2

A

S2 “dub”

Heard at the 2nd ICS

S2 is dub, so listen by the aortic valve because that’s where the blood is exiting the aortic valve

d/t closure of semilunar valves

Systole ends

Correlates with downstroke of T

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13
Q

HEART SOUNDS

S3

A

S3 (apex)

S3 listen for at the apex and its due to when the mitral valve opens

Beginning to mid third of diastole

d/t rush of blood from atria to ventricles

Correlates with isoelectric line

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14
Q

HEART SOUNDS

S4

A

S4 (apex)

Mid to end of diastole

d/t atrial contraction

Correlates with P wave

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15
Q

HEART SOUNDS

All heart sounds are heard at the apex except:

A

S2

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16
Q

BLOOD FLOW THROUGH HEART

Describe how blood flows through the heart

A

See picture

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17
Q

BLOOD FLOW THROUGH HEART

List structures through which blood flows through the heart

A

See picture

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18
Q

LAYERS OF THE HEART AND PERICARDIUM

Which two layers make up the pericardium?

A

Fibrous Pericardium

Serous Pericardium

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19
Q

LAYERS OF THE HEART AND PERICARDIUM

The skeleton that surrounds heart valves and separates atria and ventricular muscle masses is known as:

A

Fibrous pericardium

It’s also a protective tissue that prevents overdistension and anchors the heart to the mediastinum

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20
Q

LAYERS OF THE HEART AND PERICARDIUM

Serous Pericardium is double layered. What are the two layers called?

A
  1. Parietal layer
  2. Visceral layer (epicardium)
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21
Q

LAYERS OF THE HEART AND PERICARDIUM

Where is the Parietal layer of the Serous pericardium located?

A

Lies just under the fibrous pericardium

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22
Q

LAYERS OF THE HEART AND PERICARDIUM

Where is the Visceral layer of the Serous pericardium located? What’s its other name?

A

Visceral layer, which is the outermost layer of the wall of the heart also known as the epicardium

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23
Q

LAYERS OF THE HEART AND PERICARDIUM

What’s found between the parietal and visceral layers of the Serous pericardium?

A

Pericardial cavity

Contains about 10-60 mL of fluid that allows the heart to move freely within the sac and prevents friction between the two layers

This is also where you would get Pericarditis and Cardiac Tamponade

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24
Q

HEART WALL

The outermost layer of the wall of the heart also known as:

A

The Epicardium

It is visceral layer of the Serous pericardium

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25
HEART WALL The three cardiac muscle which form the main muscle mass of the heart constitute which structure?
The **Myocardium**
26
HEART WALL There are three muscle masses of the heart:
Atria Ventricle Conduction system
27
HEART WALL Muscle of the atria and ventricle are completely separated by:
The ***fibrous skeleton*** of the heart
28
HEART WALL What's the only muscular connection between the atria and the ventricle?
The ***conduction system*** of the heart
29
HEART WALL The muscle of the atria is relatively thin and the myocardium of the LV is how many times thicker than the RV?
**Three times thicker** This is the case because the LV must eject to systemic circulation against afterload Whereas the RV ejects into the pulmonary circulation
30
HEART WALL Which structure lines internal surfaces of the heart and is continuous with tunica intimae of blood vessels?
**Endocardium**
31
HEART WALL Which layer of the heart is in direct contact with blood?
Endocardium
32
HEART WALL The endocardium is in direct contact with the blood in the heart and is divided into which layers?
Endothelial, and Subendothelial layers
33
HEART WALL Which layer of the heart wall is most susceptible to ischemia? and why?
**Endocardium** Because the arteries are smaller and the pressure is higher
34
HEART WALL T/F: Coronary arteries start off thick and then become thinner as the get deeper into heart muscle
True
35
DIVIDING THE CHAMBERS OF THE HEART What surrounds the heart valves?
Fibrous Skeleton
36
DIVIDING THE CHAMBERS OF THE HEART Where does the Fibrous Skeleton originate?
From connective tissue that separate the two heart muscle masses
37
DIVIDING THE CHAMBERS OF THE HEART There are two sulci called?
Coronary Sulcus Interventricular Sulcus
38
DIVIDING THE CHAMBERS OF THE HEART Which sulcus separates the atria from the ventricles and encircles the heart, houses the coronary sinus and RCA anteriorly and the circumflex of the LCA posteriorly?
Coronary sulcus
39
DIVIDING THE CHAMBERS OF THE HEART Which sulci separate the two ventricles anteriorly and posteriorly?
Anterior and posterior interventricular sulci Contain the LAD and PDA
40
DIVIDING THE CHAMBERS OF THE HEART The area where the coronary sulcus and the posterior interventricular sulcus meet on the back side of the heart is called?
The **Crux** of the heart
41
DIVIDING THE CHAMBERS OF THE HEART Why is the Crux of the heart important?
Because coronary artery that passes this point and descends as the PDA is the ***“dominant” coronary*** of the heart
42
RIGHT ATRIUM Which cavities are found in the RA?
Auricle (right atrial appendage) Main cavity
43
RIGHT ATRIUM What's the site of venous cannulation in the RA during bypass?
Auricle (right atrial appendage)
44
RIGHT ATRIUM The **RA Main cavity** has several openings. What are they?
**Superior Vena Cava** (has no valve; blood flows freely from the SVC to the RA) *SA node* at junction of SVC and RA **IVC**, which is covered by the *Eustachian valve* **Coronary sinus** (sits b/t IVC and TV); Coronary sinus which is the venous drainage of much of the heart; Drains venous blood from the heart back into the RA; also the area where *retrograde cardioplegia cannula* placed for CPB **Tricuspid Valve** **Fossa ovalis** which is located in the septal wall between both atria and is the corresponding site of the foramen ovale in the fetal heart; “probe-patent” in 10-20% of population; this is important because a “probe-patent” Fossa ovalis is a potential direct route for venous air to enter arterial circulation that goes back to the patient; must be assessed by cardiologist or surgeon prior to surgery to make sure it isn't wide open
45
RIGHT ATRIUM T/F: Superior Vena Cava has no valve
**True** Blood flows freely from the SVC to the RA
46
RIGHT ATRIUM Where is the SA node located?
At the junction of SVC and RA
47
RIGHT ATRIUM Which valve covers the IVC?
The Eustachian valve
48
RIGHT ATRIUM What's the function of the Coronary sinus?
It is the venous drainage of much of the heart Drains venous blood from the heart back into the RA
49
RIGHT ATRIUM Where is Coronary sinus located?
It sits between the IVC and the TV
50
RIGHT ATRIUM Where is retrograde cardioplegia cannula placed for CPB
Coronary sinus
51
RIGHT ATRIUM Which opening in the main cavity of the RA correspond to the site of foramen ovale?
Fossa ovalis
52
RIGHT ATRIUM What percentage of the population has a “probe-patent” Fossa ovalis?
10-20%
53
RIGHT ATRIUM Why is it important to assess the patency of the Fossa ovalis prior to bypass surgery?
Because Fossa ovalis is a potential direct route for venous air to enter arterial circulation that goes back to the patient Must be assessed by cardiologist or surgeon prior to surgery to make sure it isn't wide open
54
LEFT ATRIUM Similar to the right atrium, the left atrium is comprised of an auricle or appendage. What's the significance of the left auricle or Left atrial appendage?
Site where clots form during a-fib Site of atrial appendage ligation to reduce the chance of clot formation
55
LEFT ATRIUM What are Openings to the LA?
Four pulmonary veins: 2 from each lung in the posterior wall A-V orifice which is protected by the mitral valve And the possible Foramen Ovale/Fossa Ovalis
56
RIGHT VENTRICLE What is the structural appearance of the RV?
Crescent shaped, wrapped around 1/3 of the LV
57
RIGHT VENTRICLE What are openings to the RV?
**A-V opening** which is protected by the *tricuspid valve* **Pulmonary orifice** protected by the *pulmonic valve*
58
LEFT VENTRICLE Why is the muscle of the left ventricle three times thicker than the muscle in the RV?
because it must generate 4-5 times the pressure of the RV to eject blood into systemic circulation
59
LEFT VENTRICLE How does the LV eject blood into systemic circulation?
The **outer** layer ***pulls*** the apex toward the base, while The _inner_ layer *_constricts_* the inner lumen to eject blood
60
LEFT VENTRICLE T/F: Equal volume ejected by each ventricle
True
61
LEFT VENTRICLE T/F: blood ejected by both ventricles at the same pressure
False LV ejects at a pressure 4-5x \> RV
62
LEFT VENTRICLE What are openings to the LV?
**Atrioventricular orifice**, protected by the *mitral valve*, and **Aortic orifice** protected by the *aortic valve*
63
ATRIOVENTRICULAR VALVES TRICUSPID valve: location
Lies b/t RA & RV
64
ATRIOVENTRICULAR VALVES - TRICUSPID How many cups?
3 cusps: anterior, septal (medial), and posterior (inferior)
65
ATRIOVENTRICULAR VALVES - TRICUSPID has a valve area of:
7-10 cm
66
ATRIOVENTRICULAR VALVES - TRICUSPID T/F: Tricupsid valvular disease is much less common unless congenital
**True**
67
ATRIOVENTRICULAR VALVES - MITRAL/BISCUSPID Location:
Lies b/t LA & LV
68
ATRIOVENTRICULAR VALVES - MITRAL/BISCUSPID How many cups does it have?
2 large cusps: anterior and posterior 2 small cusps: come together to form the two main cusps of the valve Forms *anteromedial* (**always by aortic valve;** becomes important during systolic anterior motion of the Mitral valve) and *posterolateral* cusps
69
ATRIOVENTRICULAR VALVES - MITRAL/BISCUSPID Has an area of:
4-6 cm
70
ATRIOVENTRICULAR VALVES TV & MV What's the commonality between TV and MV in terms when they open or close?
They open when pressure in the atria is higher than that of the ventricle (ventricular diastole) and They close when pressure in the ventricle is higher than that of the atria (ventricular systole)
71
SEMILUNAR VALVES - PULMONARY Pulmonic valve sits
Between RV and pulmonary artery trunk
72
SEMILUNAR VALVES - PULMONARY VALVE of cups
3 cusps: right, left, anterior
73
SEMILUNAR VALVES - PULMONARY VALVE Area is
4 cm
74
SEMILUNAR VALVES - AORTIC VALVE The aortic sits
Between LV and aorta
75
SEMILUNAR VALVES - AORTIC VALVE of cups:
**3 cusps** right (coronary) left (coronary) and posterior (non-coronary)
76
SEMILUNAR VALVES - AORTIC VALVE Area
2-4 cm
77
SEMILUNAR VALVES When in the cardiac cycle do semilunar valves (pulmonary and aortic) close? When do they open?
Close during ventricular diastole and Open during ventricular systole This is a commonality between these valves
78
CORONARY CIRCULATION What's another name for the opening to the coronary arteries?
**Coronary ostium**
79
CORONARY CIRCULATION What's another name for the dilated pocket just outside of the aortic valve?
**Sinus of Valsalva** or **Aortic sinus**
80
CORONARY CIRCULATION What's another name for the posterior interventricular branch?
Posterior Descending Branch, or Posterior Descending Artery (**PDA**)
81
CORONARY CIRCULATION What's another name for the Anterior interventricular branch?
Left anterior descending branch, or Left Anterior Descending artery (**LAD**)
82
RIGHT CORONARY ARTERY The right coronary artery arises from
Right aortic sinus just outside of the aortic valve, and Runs through the coronary sulcus
83
RIGHT CORONARY ARTERY The right coronary artery has three branches:
Anterior branch Acute marginal, and Posterior descending branch (PDA)
84
RIGHT CORONARY ARTERY Which branch of the right coronary artery supplies blood to the RA?
**Anterior branch**
85
RIGHT CORONARY ARTERY Which branch of the right coronary artery supplies blood to the RV?
**Acute marginal branch**
86
RIGHT CORONARY ARTERY Which branch of the right coronary artery supplies blood to the inferior left ventricle?
Posterior descending branch (PDA) This is true in 85% of the population PDA connects with LAD in posterior interventricular sulcus
87
RIGHT CORONARY ARTERY Which branch of the right coronary artery supplies blood to AV node in 85%?
PDA
88
RIGHT CORONARY ARTERY Which coronary artery supplies blood to the SA node (55% of population)?
RCA How about the other 45%?
89
RIGHT CORONARY ARTERY Which branch of the right coronary artery supplies blood to the Posterior Fascicle LBB?
PDA
90
LEFT CORONARY ARTERY The left coronary artery arises from
The Left Aortic sinus
91
LEFT CORONARY ARTERY As the the Left Coronary artery enters the coronary sinus, it divides into
The **Circumflex** branch, and The anterior interventricular branch (**LAD**)
92
LEFT CORONARY ARTERY Important branches of the LAD include
***Diagonal arteries:*** supply the anterolateral aspect of the heart ***Septal branches:*** supply the interventricular septum, bundle branches (RBB and Anterior fascicle of LBB), and purkinje system
93
LEFT CORONARY ARTERY The LAD goes down the apex of the hart in the anterior intraventricular sulcus and passes the apex to anastomose with
the PDA on the posterior side of the heart
94
LEFT CORONARY ARTERY The Left circumflex courses along the atrioventricular groove and gives rise to
one of three obtuse marginal that supply the lateral wall of the left ventricle
95
LEFT CORONARY ARTERY While the RCA supplies blood to the SA node in 55% of the population, where do blood supply to the SA node comes from in the other 45%?
From the Left circumflex
96
LEFT CORONARY ARTERY In 15% of patients, the left circumflex gives rise to the PDA, which supplies the posterior inferior aspect of the left ventricle. What are these patients categorized in terms of LV coronary blood supply?
“**left-dominant**”
97
RIGHT VS. LEFT DOMINANT What does it mean to be Right vs. Left Dominant (Coronary Artery Dominance)?
Defined as the *vessel which gives rise* to the posterior descending artery (**PDA**), also known as the posterior interventricular branch This is the vessel that ultimately supplies the posterior inferior aspect of the left ventricle
98
RIGHT VS. LEFT DOMINANT According to Miller, what percentage of the population is "Right dominant"? Explain coronary supply in "Right dominance".
85% of patients are right dominant In "Right dominance", the RCA gives rise to the PDA (right dominant) PDA supplies posterior inferior aspect of the LV
99
RIGHT VS. LEFT DOMINANT According to Miller, what percentage of the population is "Left dominant"? Explain coronary supply in "Left dominance".
15% of patients are left dominant In "Left dominance", the PDA comes off of the left circumflex artery, thus the LCA (left dominant) PDA supplies posterior inferior aspect of the LV
100
RIGHT VS. LEFT DOMINANT T/F: The AV node blood supply will come from which ever artery is dominant
True
101
RIGHT VS. LEFT DOMINANT In the majority of the population, which vessel supplies blood to the AV node?
RCA
102
CORONARY VENOUS DRAINAGE Where do most of the venous blood from the heart wall drains?
From the ***Coronary sinus*** into the **RA**
103
CORONARY VENOUS DRAINAGE​ Where is the coronary sinus located? Where does it originate?
lies on the posterior side of the heart in the atrioventricular groove or coronary sulcus is a continuation of the great cardiac and middle cardiac veins that both drain into the coronary sinus and back into the right atrium
104
CORONARY VENOUS DRAINAGE​ Where are retrograde cardioplegia cannula placed during bypass?
In the ***coronary sinus***
105
CORONARY VENOUS DRAINAGE​ Small veins that drain directly into any chamber of the heart are also known as:
**Thebesian veins**
106
CORONARY VENOUS DRAINAGE​ What's created when Thebesian veins drain into the left side of the heart?
Small ***arteriovenous** **shunts***
107
CORONARY VENOUS DRAINAGE​ What percentage of arteriovenous shunts is normally present?
**1-3%**
108
CORONARY VENOUS DRAINAGE​ Which coronary vein drains the anterior cardiac wall, and empties into the coronary sinus?
**Great cardiac vein** (anterior)
109
CORONARY VENOUS DRAINAGE​ Which coronary vein drains posterior wall, empties into coronary sinus?
Middle cardiac vein (posterior)
110
CORONARY VENOUS DRAINAGE​ Which coronary vein drains RA and RV, empties into RA?
Small cardiac vein (inferior)
111
CORONARY BLOOD FLOW What's the range of Coronary blood flow?
225-250 ml/min which is 4-7% of cardiac output
112
CORONARY BLOOD FLOW Normally coronary blood flow is autoregulated to which MAP range? What happens above or below the limits of this range?
Between 50-120 mmHg This is why its important to maintain MAP in these patients because their autoregulation is dependent on MAP Above or below the MAP limits, coronary blood flow is pressure dependent
113
CORONARY BLOOD FLOW Why is it important to maintain MAP in cardiac surgery patients?
Because **autoregulation** is dependent on MAP
114
CORONARY BLOOD FLOW What happens to autoregulation when there is an obstruction? How does it affect coronary blood flow or coronary perfusion pressure (CPP)?
you lose the ability to autoregulate and coronary blood flow becomes pressure dependent so THEN coronary blood flow or coronary perfusion pressure (CPP) = diastolic blood pressure (DBP) - LVEDP so, anything that decreases your DBP or increases your LVEDP will decrease your coronary blood flow (CPP)
115
CORONARY BLOOD FLOW T/F: Coronary blood flow directly proportional to CPP and inversely proportional to coronary vascular resistance
True
116
CORONARY BLOOD FLOW Why does someone who is in heart failure has a decraesed coronary blood flow?
Because their LVEDP is elevated This is also why we do adequate chest compression during cardiac arrest to increase coronary blood flow
117
CORONARY BLOOD FLOW Which heart chamber receives most of the coronary blood flow?
80% to the left ventricle
118
CORONARY BLOOD FLOW When, in the cardiac cycle do most LV coronary perfusion occur?
**80-90%** of LV coronary perfusion occurs during **diastole**
119
CORONARY BLOOD FLOW What makes the RV more difficult to protect during CPB?
The right coronary receives blood flow during both systole and diastole
120
CORONARY BLOOD FLOW What's the value of myocardial O2 consumption?
**8-10 mL** O2/100 g per min
121
CORONARY BLOOD FLOW What's the value of myocardial O2 extraction?
**65-70%**
122
FACTORS INFLUENCING CORONARY BLOOD FLOW How does Coronary artery disease affect autoregulation?
Coronary artery disease causes a ***loss in autoregulation*** Flow beyond the obstruction becomes pressure dependent
123
FACTORS INFLUENCING CORONARY BLOOD FLOW So when coronary perfusion pressure is inadequate, which part of the heart the first to become ischemic? Why?
The **_Subendocardial layer_** When coronary perfusion pressure is inadequate, the ***inner ¼-1/3 of the left ventricular wall*** is the first to become ischemic Because as the ***vessels*** descend into that layers of the heart, they become ***smaller*** Blood flow is much more dependent on higher pressure in that layer You can see why it’s important to keep MAP up
124
FACTORS INFLUENCING CORONARY BLOOD FLOW SNS stimulation causes: A. Vasoconstriction B. Vasodilation
**A. Vasoconstriction** B. Vasodilation
125
FACTORS INFLUENCING CORONARY BLOOD FLOW PSNS stimulation causes: A. Vasoconstriction B. Vasodilation
A. Vasoconstriction ## Footnote **B. Vasodilation**
126
FACTORS INFLUENCING CORONARY BLOOD FLOW How do Ischemic tissue cause the coronaries to vasodilate?
Ischemic tissue causes the release of ***local metabolic byproducts***, which cause the coronaries to vasodilate
127
FACTORS INFLUENCING CORONARY BLOOD FLOW Why would a person who is chronically ischemic have their coronaries maximally dilated all the time?
Because the stenotic lesions decrease perfusion distal to the obstruction So the vasculature will maximally dilate to maintain adequate blood supply
128
FACTORS INFLUENCING CORONARY BLOOD FLOW What would happen if a vasodilator like Nipride was added to a patient with chronic coronary ischemia?
It would cause normal coronaries to vasodilate With blood going preferentially down the path with no obstruction, this could cause more ischemia This is called **Coronary steal**
129
FACTORS INFLUENCING CORONARY BLOOD FLOW Although it has never been shown to be clinically significant, which phenomenom causes some providers to still believe atemently that the use of Nipride in CAD pts will cause ischemia?
**Coronary steal**
130
FACTORS INFLUENCING CORONARY BLOOD FLOW Which inhalation agent was suspected to cause Coronary steal?
**Isoflurane** But now we know that inhalation anesthetics are cardioprotective
131
FACTORS INFLUENCING CORONARY BLOOD FLOW What's responsible for the cardioprotective effect of inhalation agents?
**Preconditionning**
132
FACTORS INFLUENCING CORONARY BLOOD FLOW Once the lesion has been repaired with bypass surgery and the flow has been restored, what causes left ventricular function to be impaired after bypass surgery?
***Reactive hyperemia***, also known as ***Reperfusion injury*** or a ***Stunned myocardium***, can occur
133
FACTORS INFLUENCING CORONARY BLOOD FLOW How would Reactive hyperemia, also known as Reperfusion injury or Stunned myocardium be interpreted on TEE?
as "Regional wall abnormality"
134
FACTORS INFLUENCING CORONARY BLOOD FLOW Explain the phenomenom of Reactive hyperemia, also known as Reperfusion injury or Stunned myocardium
Once flow is restored following a period of ischemia, coronary blood flow increases by 5-6x through the coronaries This causes edema of the tissue
135
FACTORS INFLUENCING CORONARY BLOOD FLOW What is a treatment option for Reactive hyperemia, also known as Reperfusion injury or Stunned myocardium?
Epinephrine infusion for 24 hrs
136
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Myocardial O2 determinants are:
Maintained diastolic BP Reduced LVEDP Increased coronary blood flow Increasedd arterial O2 content
137
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND What determines arterial O2 content
Amount of hemoglobin-bound O2 Supplemental O2
138
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Why is it more important to reduce the demand on the heart rather than trying to increase supply?
Eventhough a high hemoglubin level will give the blood a higher O2 carrying abilities, the minimum levels of O2 supply needed to reduce incidence of ischemia are known It becomes important to reduce the O2 demand on the heart
139
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Controlling for which variables reduce the O2 demand on the heart?
Heart rate Contractility Myocardial wall tension These are the determinants of Myocardial O2 demand (MVO2)
140
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND When does perfusion of the LV occur?
during diastole
141
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND When does perfusion of the RV occur?
primarily during systole
142
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND T/F: the duration of diastole becomes extremely important when considering blood flow, especially to the LV
**True** Because perfusion of the LV occurs during diastole
143
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND How does tachycardia decrease myocardial delivery?
Perfusion of the LV occurs during diastole Time for diastole decreases with increased tachycardia Tachycardia decreases myocardial delivery by increasing demand especially during low O2 states
144
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Why are beta-blockers good to use in patients with myocardial ischemia?
Increased contractility can also impair LV function Beta-blockers decrease contractility
145
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Which law states that "wall stress is directly proportional to pressure 1x the radius, and inversly proportional to 2x the wall thickness"
LaPlace’s Law
146
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND Why is it important to reduce preload and afterload in patients with myocardial ischemia?
Because based on LaPlace’s Law, any increase in chamber size (preload), or any pressure increase in the ventricle during contraction (afterload) could lead to increase wall stress
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THE CONDUCTION SYSTEM Why are cells the atria and ventricles considered "working myocardial muscle cells" which are cells normally found in muscle mass of atria and ventricles?
Because they contain the property of “contractility”, or the ability to shorten and return to original length during depolarization
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THE CONDUCTION SYSTEM What's required in order for atria and ventricles to contract?
They must be electrically stimulated, or depolarized This is a capability they do not carry themselves
149
THE CONDUCTION SYSTEM Where are pacemaker cells that have the property of “automaticity” because they can spontaneously depolarize found? What's their main role?
In the SA, AV, Bundle of His, and Purkinje System They are the electrical system of the heart They are responsible for the formation of the electrical current that spreads to the working myocardial muscle cells, causing them to depolarize.
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CARDIAC CONDUCTION SYSTEM What is the pacemaker of the heart? and why is it so considered?
The **SA node** is the pacemaker for the heart It is so considered because it has the fastest automaticity, or spontaneous depolarization at a rate of 60-100 bpm
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CARDIAC CONDUCTION SYSTEM Where is the SA node located?
It sits in the **right atrium** just at the junction of the SVC
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CARDIAC CONDUCTION SYSTEM Down which three pathways does the SA node send its depolarization?
one to the **left atrium** via ***Bachman’s bundle*** the other two to the **AV node**
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CARDIAC CONDUCTION SYSTEM Where is the AV node lacated?
Just outside the fibrous skeleton of the heart anterior to the coronary sinus This is the floor of RA
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CARDIAC CONDUCTION SYSTEM T/F: While the **AV node** receives its depolarization from the SA node (depolarizes after SA node), it also has the ability to spontaneously depolarize
True But at a slower rate of **40-60**bpm
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CARDIAC CONDUCTION SYSTEM Why is conduction (not to be confused with depolarization or automaticity), why is conduction through the AV node is slow?
To allow for both atria to completely empty into the ventricles This process is known as ***Atrial kick***
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CARDIAC CONDUCTION SYSTEM What's another name for the process that allows for both atria to completely empty into the ventricles before ventricular contraction?
**Atrial kick**
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CARDIAC CONDUCTION SYSTEM What percentage of Cardiac Output comes from Atrial kick?
20%
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CARDIAC CONDUCTION SYSTEM In Aortic stenosis, what percentage of cardiac output could come from atrial kick?
40%
159
CARDIAC CONDUCTION SYSTEM What is the only connection between atria and ventricle?
The Bundle of His/AV bundle Splits into left and right bundle branches
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CARDIAC CONDUCTION SYSTEM What is the conduction pathways for the ventricles?
The purkinje fibers
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CARDIAC CONDUCTION SYSTEM Where are the Purkinje fibers located?
They sit just below the endocardium
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CARDIAC CONDUCTION SYSTEM The Purkinje fibers have the slowest depolarization. At what rate do they depolarize?
at a rate of 20-40 bpm
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CARDIAC CONDUCTION SYSTEM Why do the the purkinjes fibers have the fastest speed of conduction?
Because the impulse must travel to both ventricles and contract them at the same time
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CARDIAC CONDUCTION SYSTEM What's the difference between "Automaticity" and "Conduction"?
"Automaticity" = spontaneous depolarization "Conduction" = transmission of electrical impulse

8361 Exam I (18 decks)

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