Cardiac A&P Flashcards
The coronary veins empty into the ____ via the ___
Right atrium coronary sinus
This valve protects the coronary sinus
Thesbian valve
This valve protects the IVC
The Eustachian valve.
In fetal development, this valve helps to direct the flow of blood from the RA to LA. In adults, this mainly exists as a vestigial structure.
This muscle bundle of the trabeculae carneae carries the right branch of the AV bundle
The moderator band
Which is larger, the L or R atrium?
L
These vessels supply blood to the L atrium
The pulmonary veins
The upper third of the ventricular septum is ___, which the lower two thirds is ___
Upper third is smooth
Lower 2/3 thirds is muscular and covered with trabecular careener
These are the three leaflets of the tricuspid valve
Anterior, posterior, and septal
The valve area of the tricuspid valve is normally ___. Symptoms occur once the area is less than ____.
Normally 7 cm2
Symptoms once less than 1.5 cm2.
The valve area of the mitral valve is normally ___. Symptoms occur once the area is less than ____.
Normally 4-6 cm2
Symptomatic once 2-3 cm2 (less than 50% normal area)
These are the two leaflets of the mitral valve
Anteromedial and posterolateral.
The aortic valve has this may cusps
3
All of the valves have 3 cusps except the mitral, which has 2.
The valve area of the aortic valve is normally ___. Symptoms occur once the area is less than ____.
Normally 1-3 cm2
Symptomatic once less than 1/2 - 1/3 of normal area.
What are the aortic sinuses?
Sinuses that give rise to the two coronary arteries. They are also known as the sinuses of valsalva.
The valve area of the pulmonic valve is normally ___. Symptoms occur once the area is less than ____.
4 cm2
Symptomatic once less than 1/2 - 1/3 of normal area.
The LAD supplies this part of the heart muscle and can be evaluated by these leads
Supplies the anterior portion of the LV and the inter ventricular groove.
Leads V3-V5 look at the LAD
The circumflex coronary artery feeds this part of the heart muscle and is evaluated by this lead
Posterior LV and part of the RV.
Lead I
What artery feeds the RA and SA node?
The RCA.
A proximal branch of the RCA, called the right atrial branch feeds the RA. The right atrial branch gives rise to the SA nodal branch, which feeds the SA node.
This artery feeds the AV node.
The AV node artery, which is a distal branch off the posterior aspect of the RCA.
What vessels feed the RV?
The anterior branches of the RCA
What does the PDA supply?
The PDA is the posterior descending artery. It supplies the posterior 1/3 of the inter ventricular septum.
These leads can evaluate the integrity of the PDA
II, III, and AVF
How is the “dominance” of coronary circulation determined?
Dominance is determined by which major coronary artery feeds the posterior descending coronary artery (PDA).
80% of the population is RIGHT dominant, meaning that the RCA supplies the PDA.
20% of the population is LEFT dominant, meaning that the LCCA supplies the PDA.
The numbers above come from Brash. In Dr. E’s notes, she states that 50% are right dominant, 20% is left dominant, and a balanced pattern exists in the remaining 30%.
The LCA provides blood for these structures
LAD
The R&L bundle branches
The anterior and posterior papillary muscles of the mitral valve
The anterolateral left ventricle
The circumflex artery (LCCA) provides blood to
The lateral LV
The RCA provides blood to these structures
SA and AV nodes RA RV The posterior inter ventricular septum (in 80% of pts) The intertribal septum
The coronary arteries receive this % of the CO
5%, or about 250cc/min
What determines flow through the coronaries?
Duration of diastole
Coronary perfusion pressure
CPP = Diastolic BP - LVEDP
What is the formula for coronary perfusion pressure (CPP)?
CPP = DBP - LVEDP
Flow through the LCA occurs at this point during the cardiac cycle
Diastole
Flow through the RCA occurs at this point during the cardiac cycle
During both systole and diastole. This is because the pressures generated by the heart are much lower on the R than the L side of the heart.
Myocardial O2 consumption is low or high?
HIGH! So high in fact, that the venous sats in the heart are the lowest in the body (30%)
Coronary perfusion pressure (CPP) is usually auto regulated between ___-___ mmHg
50-120
What vessel supplies the anterior portion of the RV?
The LAD
The LA is mostly fed by this vessel
LCCA
When may there be an elevated LVEDP, thus resulting in decreased perfusion through coronary vessels?
CHF
This is the primary determinant of coronary vascular tone, and thus, myocardial perfusion
Metabolic factors (such as adenosine which is released under hypoxic conditions)
Which coronary artery is able to auto regulate more?
The LCA d/t it’s higher sympathetic innervation.
Where does the greatest dilation of vessels occur within the coronary circulation?
At the level of the smallest vessels
Where is the SA node located?
At the junction of the SVC and RA
These are the two cell types of the SA node
Pacemaker cells (p cells) Transitional/intermediate cells (these conduct impulses within and away from the node)
What is the internodal tract?
The conduction pathway between the SA and AV nodes.
The tract contains both P cells and transitional/intermediate cells.
Made of 3 tracts
1) The anterior internodal tract –> septum
2) Middle internal tract (Wenchebach’s tract) –> SVC
3) Posterior internodal tract (Thorel’s Tract)–> septum
Bachmann’s bundle is a branch off of this internal tract
The anterior internodal tract
Properties of the AV node
Causes a delay in transmission of the action potential. Accomplishes this by:
- Lower resting membrane potential (-60 vs. -50 for SA node)
- Fewer gap junctions
- Smaller cells
Supplied by vagal ganglionic cells
Intrinsic rate of about 50bpm
At rest, cardiomyocytes are more permeable to ____ and less permeable to __ and __
More to potassium
Less to sodium and calcium.
This means that the resting membrane potential is mostly dependent on potassium concentrations
5 phases of the cardiac action potential
Phase 0 - depolarization via fast Na+ channels
Phase 1 - depolarization as N+ influx ends
Phase 2 - Plateau as slow Ca++ channels open, allowing an influx of Ca++
Phase 3 - Terminal depolarization as slow Ca++ channels close, but mass efflux of K+ occurs
Phase 4 - Diastolic phase of the heart. Restoration of membrane potential via Na-K pump
The absolute refractory period lasts from ___-___
Phase 0 to the middle of phase 3
The relative refractory period lasts from ___-___
The middle of phase 3 to phase 4. During this period, a second stimulus will result in a weaker action potential than the first
Are the atria electrically isolated from the ventricles?
Yes. The atria are electrically isolated from the ventricles by the heart’s cartilaginous skeleton. As a result, atrial depolarization is directed to the ventricles solely through the AV node.
Pathway of sympathetic innervation of the heart
Sympathetic fibers to the hear originate from the stellate ganglion and caudal cervical fibers.
These turn into the dorsal, medial, and lateral cardiac nerves.
These nerves unite to form one large nerve that follows the course of the Left Main CA
It then branches along the anterior descending and circumflex arteries, providing cholinergic fibers to the ventricle.
Ach is released to post-synaptic NICOTINIC receptors.
Norepi will then activate B1 adrenergic receptors at the target site.
Pathway of parasympathetic innervation of the heart
PSNS fibers arise from the the medulla (more specifically, the vagal nucleus and the nucleus ambiguus).
These fibers enter the heart via the recurrent laryngeal nerve and thoracic vagal nerves, and form plexuses that give rise to the R and L coronary cardiac nerves, and the L lateral cardiac nerve.
Remember that in the PSNS, ganglia occur close to their target organ. This is true with the heart as well.
In the ganglion, Ach is released onto nicotinic receptors. At the target site, Ach is released onto muscarinic receptors within the heart.
Where are vagal receptors most prevalent in the heart?
Most are in the SA node.
The followed by the AV node, RA, LA, and the ventricles.
What five factors determine CO?
Cardiac output is determined by:
1) Preload
2) Afterload
3) Contractility
4) HR
5) Ventricular compliance
Which is easier for us as anesthesia providers to alter, O2 supply or demand of the heart?
It is easier for us to decrease O2 demand than it is for us to increase O2 supply.
How to treat intra-op ischemia
If the cause is low supply (as evidenced by low BP and low PCWP)
- Give vasoconstrictors
- Decrease anesthetic depth (to raise BP)
- Consider phenylephrine and NTG, inotropes, and CCBs
If the cause is high demand (as evidenced by high BP, high PCWP, and higher HR)
- Treat what’s causing the high BP and HR
- Increase anesthetic depth (to reduce HR and BP)
- NTG
- BBs
How the heart compensates in early AS
Basically, the heart is responding to the increased pressure needed to overcome the aortic valve by concentric hypertrophy. This hypertrophy leads to less ventricular compliance. As a result, there is less early (passive) diastolic filling, and it relies more on late (active) diastolic filling from the atrial kick. In early stages, SV remains normal.
Patho that occurs in late AS
In early AS, the ventricle has normal function, just decreased compliance d/t the hypertrophy.
In late AS, fibrosis occurs, resulting in less compliance, as well as decreased contractility and increased wall tension. This results in LV dilation and decreased stroke volume. The heart is no longer able to compensate.
Implications of low ventricular compliance
Pt will be very sensitive to volume depletion (need a lot of preload to stretch the ventricle!)
Pt will depend heavily on atrial kick for adequate filling (don’t want the patient too tacky or in an abnormal rhythm!)
Wide swings will occur in ventricular filling pressure (the patient will be labile)
PCWP will underestimate LVEDP
LVEDP will be higher, and this reduces CPP (remember that CPP = DBP - LVEDP)
What are the MAIN goals for a patient with AS?
1) Adequate filling time (prevent tachy)
2) Adequate perfusion pressure (prevent hypotension)
This valvular disease predisposes pts to a-fib
Mitral stenosis and mitral regurgitation
