Mod2: Review of Cardiac Anatomy Flashcards
LOCATION
Where does the heart sits?
in the MEDIASTINUM
LOCATION
The heart sits in the mediastinum. Which structures is it boarded laterally by?
the lungs
LOCATION
Which structures sits anterior to the heart?
The Sternum
LOCATION
Which structures sit porterior to the heart?
Descending aorta
Esophagus
Major Bronchi
T5-8 vertebra
LOCATION
What’s the overall shape of the heart?
Blunt shaped cone
with 2/3 of its mass left of the midline
VALVES:AREA AUSCULTATED
Where is the Aortic valve auscultated? Why that location?
Aortic valve is auscultated at the second ICS right sternal border because the LV ejects towards the right
VALVES:AREA AUSCULTATED
Where is the Pulmonic valve auscultated? Why that location?
RV ejects towards the left, so the Pulmonic valve will be heart 2 ICS left sternal border
VALVES:AREA AUSCULTATED
Where is the Tricuspid valve auscultated? Why that location?
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.
VALVES:AREA AUSCULTATED
Where is the Mitral valve auscultated? Why that location?
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
HEART SOUNDS
S1 heart sound - What sound does it make? Where is auscultated? What events does is correspond to?
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
HEART SOUNDS
S1 - EKG
Correlates with QRS
HEART SOUNDS
S2
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
HEART SOUNDS
S3
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
HEART SOUNDS
S4
S4 (apex)
Mid to end of diastole
d/t atrial contraction
Correlates with P wave
HEART SOUNDS
All heart sounds are heard at the apex except:
S2
BLOOD FLOW THROUGH HEART
Describe how blood flows through the heart
See picture
BLOOD FLOW THROUGH HEART
List structures through which blood flows through the heart
See picture
LAYERS OF THE HEART AND PERICARDIUM
Which two layers make up the pericardium?
Fibrous Pericardium
Serous Pericardium
LAYERS OF THE HEART AND PERICARDIUM
The skeleton that surrounds heart valves and separates atria and ventricular muscle masses is known as:
Fibrous pericardium
It’s also a protective tissue that prevents overdistension and anchors the heart to the mediastinum
LAYERS OF THE HEART AND PERICARDIUM
Serous Pericardium is double layered. What are the two layers called?
- Parietal layer
- Visceral layer (epicardium)
LAYERS OF THE HEART AND PERICARDIUM
Where is the Parietal layer of the Serous pericardium located?
Lies just under the fibrous pericardium
LAYERS OF THE HEART AND PERICARDIUM
Where is the Visceral layer of the Serous pericardium located? What’s its other name?
Visceral layer, which is the outermost layer of the wall of the heart also known as the epicardium
LAYERS OF THE HEART AND PERICARDIUM
What’s found between the parietal and visceral layers of the Serous pericardium?
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
HEART WALL
The outermost layer of the wall of the heart also known as:
The Epicardium
It is visceral layer of the Serous pericardium
HEART WALL
The three cardiac muscle which form the main muscle mass of the heart constitute which structure?
The Myocardium
HEART WALL
There are three muscle masses of the heart:
Atria
Ventricle
Conduction system
HEART WALL
Muscle of the atria and ventricle are completely separated by:
The fibrous skeleton of the heart
HEART WALL
What’s the only muscular connection between the atria and the ventricle?
The conduction system of the heart
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
HEART WALL
Which structure lines internal surfaces of the heart and is continuous with tunica intimae of blood vessels?
Endocardium
HEART WALL
Which layer of the heart is in direct contact with blood?
Endocardium
HEART WALL
The endocardium is in direct contact with the blood in the heart and is divided into which layers?
Endothelial, and
Subendothelial layers
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
HEART WALL
T/F: Coronary arteries start off thick and then become thinner as the get deeper into heart muscle
True
DIVIDING THE CHAMBERS OF THE HEART
What surrounds the heart valves?
Fibrous Skeleton
DIVIDING THE CHAMBERS OF THE HEART
Where does the Fibrous Skeleton originate?
From connective tissue that separate the two heart muscle masses
DIVIDING THE CHAMBERS OF THE HEART
There are two sulci called?
Coronary Sulcus
Interventricular Sulcus
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
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
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
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
RIGHT ATRIUM
Which cavities are found in the RA?
Auricle (right atrial appendage)
Main cavity
RIGHT ATRIUM
What’s the site of venous cannulation in the RA during bypass?
Auricle (right atrial appendage)
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
RIGHT ATRIUM
T/F: Superior Vena Cava has no valve
True
Blood flows freely from the SVC to the RA
RIGHT ATRIUM
Where is the SA node located?
At the junction of SVC and RA
RIGHT ATRIUM
Which valve covers the IVC?
The Eustachian valve
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
RIGHT ATRIUM
Where is Coronary sinus located?
It sits between the IVC and the TV
RIGHT ATRIUM
Where is retrograde cardioplegia cannula placed for CPB
Coronary sinus
RIGHT ATRIUM
Which opening in the main cavity of the RA correspond to the site of foramen ovale?
Fossa ovalis
RIGHT ATRIUM
What percentage of the population has a “probe-patent” Fossa ovalis?
10-20%
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
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
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
RIGHT VENTRICLE
What is the structural appearance of the RV?
Crescent shaped, wrapped around 1/3 of the LV
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
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
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
LEFT VENTRICLE
T/F: Equal volume ejected by each ventricle
True
LEFT VENTRICLE
T/F: blood ejected by both ventricles at the same pressure
False
LV ejects at a pressure 4-5x > RV
LEFT VENTRICLE
What are openings to the LV?
Atrioventricular orifice, protected by the mitral valve, and
Aortic orifice protected by the aortic valve
ATRIOVENTRICULAR VALVES
TRICUSPID valve: location
Lies b/t RA & RV
ATRIOVENTRICULAR VALVES - TRICUSPID
How many cups?
3 cusps: anterior, septal (medial), and posterior (inferior)
ATRIOVENTRICULAR VALVES - TRICUSPID
has a valve area of:
7-10 cm
ATRIOVENTRICULAR VALVES - TRICUSPID
T/F: Tricupsid valvular disease is much less common unless congenital
True
ATRIOVENTRICULAR VALVES - MITRAL/BISCUSPID
Location:
Lies b/t LA & LV
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
ATRIOVENTRICULAR VALVES - MITRAL/BISCUSPID
Has an area of:
4-6 cm
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)
SEMILUNAR VALVES - PULMONARY
Pulmonic valve sits
Between RV and pulmonary artery trunk
SEMILUNAR VALVES - PULMONARY VALVE
of cups
3 cusps: right, left, anterior
SEMILUNAR VALVES - PULMONARY VALVE
Area is
4 cm
SEMILUNAR VALVES - AORTIC VALVE
The aortic sits
Between LV and aorta
SEMILUNAR VALVES - AORTIC VALVE
of cups:
3 cusps
right (coronary)
left (coronary) and
posterior (non-coronary)
SEMILUNAR VALVES - AORTIC VALVE
Area
2-4 cm
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
CORONARY CIRCULATION
What’s another name for the opening to the coronary arteries?
Coronary ostium
CORONARY CIRCULATION
What’s another name for the dilated pocket just outside of the aortic valve?
Sinus of Valsalva or Aortic sinus
CORONARY CIRCULATION
What’s another name for the posterior interventricular branch?
Posterior Descending Branch, or
Posterior Descending Artery (PDA)
CORONARY CIRCULATION
What’s another name for the Anterior interventricular branch?
Left anterior descending branch, or
Left Anterior Descending artery (LAD)
RIGHT CORONARY ARTERY
The right coronary artery arises from
Right aortic sinus just outside of the aortic valve, and
Runs through the coronary sulcus
RIGHT CORONARY ARTERY
The right coronary artery has three branches:
Anterior branch
Acute marginal, and
Posterior descending branch (PDA)
RIGHT CORONARY ARTERY
Which branch of the right coronary artery supplies blood to the RA?
Anterior branch
RIGHT CORONARY ARTERY
Which branch of the right coronary artery supplies blood to the RV?
Acute marginal branch
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
RIGHT CORONARY ARTERY
Which branch of the right coronary artery supplies blood to AV node in 85%?
PDA
RIGHT CORONARY ARTERY
Which coronary artery supplies blood to the SA node (55% of population)?
RCA
How about the other 45%?
RIGHT CORONARY ARTERY
Which branch of the right coronary artery supplies blood to the Posterior Fascicle LBB?
PDA
LEFT CORONARY ARTERY
The left coronary artery arises from
The Left Aortic sinus
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)
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
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
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
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
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”
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
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
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
RIGHT VS. LEFT DOMINANT
T/F: The AV node blood supply will come from which ever artery is dominant
True
RIGHT VS. LEFT DOMINANT
In the majority of the population, which vessel supplies blood to the AV node?
RCA
CORONARY VENOUS DRAINAGE
Where do most of the venous blood from the heart wall drains?
From the Coronary sinus into the RA
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
CORONARY VENOUS DRAINAGE
Where are retrograde cardioplegia cannula placed during bypass?
In the coronary sinus
CORONARY VENOUS DRAINAGE
Small veins that drain directly into any chamber of the heart are also known as:
Thebesian veins
CORONARY VENOUS DRAINAGE
What’s created when Thebesian veins drain into the left side of the heart?
Small arteriovenous** **shunts
CORONARY VENOUS DRAINAGE
What percentage of arteriovenous shunts is normally present?
1-3%
CORONARY VENOUS DRAINAGE
Which coronary vein drains the anterior cardiac wall, and empties into the coronary sinus?
Great cardiac vein (anterior)
CORONARY VENOUS DRAINAGE
Which coronary vein drains posterior wall, empties into coronary sinus?
Middle cardiac vein (posterior)
CORONARY VENOUS DRAINAGE
Which coronary vein drains RA and RV, empties into RA?
Small cardiac vein (inferior)
CORONARY BLOOD FLOW
What’s the range of Coronary blood flow?
225-250 ml/min
which is 4-7% of cardiac output
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
CORONARY BLOOD FLOW
Why is it important to maintain MAP in cardiac surgery patients?
Because autoregulation is dependent on MAP
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)
CORONARY BLOOD FLOW
T/F: Coronary blood flow directly proportional to CPP and inversely proportional to coronary vascular resistance
True
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
CORONARY BLOOD FLOW
Which heart chamber receives most of the coronary blood flow?
80% to the left ventricle
CORONARY BLOOD FLOW
When, in the cardiac cycle do most LV coronary perfusion occur?
80-90% of LV coronary perfusion occurs during diastole
CORONARY BLOOD FLOW
What makes the RV more difficult to protect during CPB?
The right coronary receives blood flow during both systole and diastole
CORONARY BLOOD FLOW
What’s the value of myocardial O2 consumption?
8-10 mL O2/100 g per min
CORONARY BLOOD FLOW
What’s the value of myocardial O2 extraction?
65-70%
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
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
FACTORS INFLUENCING CORONARY BLOOD FLOW
SNS stimulation causes:
A. Vasoconstriction
B. Vasodilation
A. Vasoconstriction
B. Vasodilation
FACTORS INFLUENCING CORONARY BLOOD FLOW
PSNS stimulation causes:
A. Vasoconstriction
B. Vasodilation
A. Vasoconstriction
B. Vasodilation
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
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
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
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
FACTORS INFLUENCING CORONARY BLOOD FLOW
Which inhalation agent was suspected to cause Coronary steal?
Isoflurane
But now we know that inhalation anesthetics are cardioprotective
FACTORS INFLUENCING CORONARY BLOOD FLOW
What’s responsible for the cardioprotective effect of inhalation agents?
Preconditionning
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
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”
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
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
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND
Myocardial O2 determinants are:
Maintained diastolic BP
Reduced LVEDP
Increased coronary blood flow
Increasedd arterial O2 content
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND
What determines arterial O2 content
Amount of hemoglobin-bound O2
Supplemental O2
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
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)
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND
When does perfusion of the LV occur?
during diastole
MYOCARDIAL ISCHEMIA= SUPPLY< DEMAND
When does perfusion of the RV occur?
primarily during systole
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
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
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
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
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
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
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
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.
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
CARDIAC CONDUCTION SYSTEM
Where is the SA node located?
It sits in the right atrium just at the junction of the SVC
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
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
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 40-60bpm
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
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
CARDIAC CONDUCTION SYSTEM
What percentage of Cardiac Output comes from Atrial kick?
20%
CARDIAC CONDUCTION SYSTEM
In Aortic stenosis, what percentage of cardiac output could come from atrial kick?
40%
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
CARDIAC CONDUCTION SYSTEM
What is the conduction pathways for the ventricles?
The purkinje fibers
CARDIAC CONDUCTION SYSTEM
Where are the Purkinje fibers located?
They sit just below the endocardium
CARDIAC CONDUCTION SYSTEM
The Purkinje fibers have the slowest depolarization. At what rate do they depolarize?
at a rate of 20-40 bpm
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
CARDIAC CONDUCTION SYSTEM
What’s the difference between “Automaticity” and “Conduction”?
“Automaticity” = spontaneous depolarization
“Conduction” = transmission of electrical impulse
