1. Cardiac Anatomy & Physiology Flashcards
LV isovolumic contraction continues until…
Aortic valve opens
What causes aortic valve to open?
Lower pressure in the aorta compared to LV after a period of isovolumic contraction
What happens in the heart at end diastole?
MV closes (LV filling has completed)
What valve are Libman-Sacks lesions typically on?
Mitral (left sided valves)
Verrucous, non-bacterial valve lesion in a patient with SLE?
Libman-Sacks endocarditis
What % of patients newly diagnosed with SLE have Libman-Sacks lesion?
10%
Describe echo findings of a Libman-Sacks lesion?
Irregular vegetation <0.5cm in diameter on valve/chordal apparatus
Metabolic factor derived from breakdown of high energy phosphate?
Adenosine
True or False: ATP can’t be regenerated at times of low O2 tension
True
What happens to ATP in states of low O2 tension?
AMP made, breaks down to adenosine which causes coronary artery vasodilation
What does NO induce?
cGMP
What does NO induction of cGMP cause?
Muscle relaxation
What does Endothelin 1 cause?
Tonic vasoconstriction
What does prostaglandin cause?
Smooth muscle relaxation
Describe abdominal anatomy in polysplenia
- Multiple spleens on same side of vertebral column as stomach
- Gallbladder single (may have biliary atresia)
- Abdominal situs variable
- IVC commonly interrupted with azygous continuation to SVC
In a mature cardiac myocyte, where is the majority of calcium involved in the binding of troponin C/initation of myocyte contraction is stored where?
SR
What stores the most important source of Ca involved in initiatino of myocyte contraction?
SR
How does Ca enter the myocyte during an action potential?
L-type voltage gated Ca channel
What happens after Ca enters a myocyte during an action potential?
Ca activated Ca release via ryanodine receptor - Causes release of Ca from SR
What is different about Ca in a immature cardiac myocyte v. adult?
Function/organization of SR isn’t mature… activation more dependent on flow via L-type Ca channels v. Ca induced Ca release from SR
Most common form of bicuspid aortic valve?
R/L fusion (75%)
-Next:
R/N
L/N
What can fusion of 1+ cusp on an aortic valve result in?
Unicuspid valve
What hormone is released in response to decreased renal arterial pressure and induces cleaving of angiotensinogen to angiotensin 1?
Renin
What does the juxtaglomerular apparatus of the kidney secrete in response to low renal perfusion pressure?
Renin
What does renin do?
Cleaves angiotensinogen to angiotensin 1
What converts angiotensin 1 to angiotensin 2?
ACE
Where does ACE convert angiotensin 1 to angiotensin 2?
Lungs/vasculature
What does Angiotensin 2 do?
Induces vasoconstriction and stimulates ADH (vasopressin) secretion
What factor has the greatest impact on pressure change across 2 points in a vessel?
Radius
What equation describes the resistance between 2 points?
Poiseuille-Hagen relationship
-Resistance between 2 points is a function of pressure/flow
What is the Poiseuille-Hagen equation?
R = (8 x Length of vessel x viscosity) / (pi x radius2)
Normal left aortic arch is derived from what embryologic aortic arch?
Left 4th
Majority of the aortic arch arises from what embryologic structure?
Left 4th arch
What does the right 4th arch give rise to?
Proximal portion of right subclavian
Where do the pulmonary arteries and ductus arise from?
Left 6th arch
What does the 5th aortic arch give rise to?
Nothing… typically involutes
What other defect is most commonly seen in patients with ToF?
ASD/PFO
-80% of patients, “Pentalogy of Fallot”
True or False: Left heart abnormalities are common in patients with ToF?
Flase
A right aortic arch occurs in what % of patients with ToF?
25%
Most common coronary artery abnormality in TGA?
Left circumflex from the RCA (16%)
Most common coronary artery pattern in D-TGA?
Normal (67%)
After left circumflex from the RCA, what are the next most common coronary abnormalities in D-TGA?
- Single right
2. Inverted right and left circumflex with normal origin of LAD from anterior facing sinus
Echo-dark space around aortic sinus in PSSA view that extends anterior to SVC and posterior to ascending aorta and pulmonary trunk?
Transverse sinus
What is the transverse sinus?
Intrapericardial space between the great arteries anterosuperiorly and atrial walls posterioinferiorly
What can be seen in post-operative patients as an echo-dark space around the aortic sinus in PSSA if fluid is present?
Transverse sinus
What can the transverse sinus be mistaken for in a neonate if there is a small amount of fluid in the sinus?
Take-off of LCA
What is the space between the posterior LA and reflections of great veins (SVC and pulmonary veins)?
Oblique sinus
How does ANP work on the kidney?
Decreases distal tubular resorption of sodium
What causes release of ANP?
Stretch from either atrium
What does ANP do to the kidney?
Dilates afferent arteriole, constricts efferent arteriole
Increases GFT
2 effects of ANP?
- Vasodilatory
2. Cardioinhibitory
Average ratio of ventricular septal thickness to LV free wall thickness in adolescent heart?
1.1
Average ratio of ventricular septal thickness to LV free wall thickness in heart in first 2 decards?
- 1 (range 0.8-1.4)
* Radio increases slowly into adulthood averaging >1.2 by 70
What diseases can affect the average ratio of ventricular septal thickness to LV free wall thickness?
HCM
*Diseases with asymmetric hypertrophy
What is the average ratio between LV/RV thickness?
3 (range 2-5)
Is the average ratio between LV/RV thickness higher or lower in fetuses and neonates as compared to adults?
Lower
*High right-sided pressure in utero
What causes a diastolic murmur in a VSD?
AI from herniation of aortic valve leaflet though defect
Which aortic cusp is most likely to herniate through a VSD?
Right
What types of VSDs can you see herniation of the right aortic cusp?
- Subarterial (supracristal/infundibular)
2. Perimembranous
What % of VSDs are subarterial (supracritsal/infundibular)?
5%
What ethnicity are subarterial VSDs more common in?
Asians
What is the definition of an overriding AV valve?
Empties into 2 ventricles
What is an overriding AV valve always assocaited with?
Malalignment VSD
What is it called if you have an AV valve that empties into 2 ventricles and has anomalous insertions of the chordae tendineae into the contralateral ventricle?
Overriding and straddling
Which chamber is most likely to rupture following chest wall trauma?
RV
*Thin walled and more anterior
True or False: Ventricular wall rupture is more common than atrial rupture
True
What is the most common site of an atrial rupture?
Appendage
- Descending aorta and IVC on same side of vertebral column
- High incidence of malrotation
- Variable position of stomach
- Typicall only 1 gallbladder
- Biliary atresia uncommon
- Liver most commonly midline with 2 mirror-image right lobes
Asplenia
4 changes with endurance training
- Increased blood volume/stroke volume
- Decreased HR
- Decreased resting arterial BP
- Decreased myocardial oxygen demand
Most reliable feature of normal AV valve that distinguishes mitral from tricuspid?
Level of attachment at cardiac crux
Which AV valve inserts higher into the cardiac crux?
Mitral (between 0-8mm/m2 higher than tricuspid)
In Ebstein’s the tricuspid valve is how much lower than the mitral?
> 8mm/m2
What 2 lesions have no difference between where the mitral and tricuspid valve inset?
- Partial AVSD
2. DILV
What shifts O2 dissociation curve left?
- Alkalosis
- Decreasing temp
- Decreasing 2,3-DPG
What shifts O2 dissociation curve right?
- Acidosis
- Increased temp
- Increased 2,3-DPG
Where is the sinus node in right juxtaposition of the atrial appendages?
Normal position
*Usually single SA node
Describe sinus node in right atrial isomerism
Bilateral
Describe sinus node in left atrial isomerism
Absent or malpositioned
Describe sinus node in left-sided juxtaposition of the atrial appendages
Displaced anteriorly or inferiorly
What type of lesions is left juxtaposition of the atrial appendages associated with?
Abnormal ventriculoarterial connections
What type of lesions is right juxtaposition of the atrial appendages associated with?
Simple (ASD, VSD)
A decrease in pO2 causes the systemic vasculature to do what?
Dilate- Local tissues trying to get more O2 through increased volume of flow
Name 3 things that cause local vasodilation
- Increased pCO2
- Acidosis
- Increased K
What does some tissue release as a vasodilator in response to increased oxygen demand?
Adenosine
What is the valvular remnant at the IVC/RA junction?
Eustachian valve
What is the crescent-shaped valvular remnant at the os of the coronary sinus?
Thebesian valve
What is the fine, filamentous structure that represents the persistence of the valves of the sinus venosus?
Chiari network
Where does the Chiari network typically extend from?
Crista terminalis to Eustachian or Thebesian valves
What is the role of the Eustachian valve?
Directs blood flow from SVC/IVC through PFO to LA
What does the crista terminalis form from?
Resorption of the right valve of the sinus venosus
What is the crista terminalis?
Ridge in the RA that separates the sinus venosus portion of the RA from the muscular RA
Describe an intermediate AVSD
- Large atrial septal and ventricular septal defect
- Common atrioventricular valve
- Separate left and right orifices
*Rare subtype of a complete AVSD
What is a partial AVSD?
- Septum primum ASD
- Cleft left AV valve in anterior leaflet
- L/R AV valves are separate
What is a transitional AVSD?
Subtype of partial defect… primum ASD, cleft left AV valve, separate L/R AV valves + inlet VSD
What fetal venous structure has the lowest O2 saturation?
CS and SVC
Most reliable anatomic feature that distinguishes the normal RV from LV?
Level of insertion of AV valve at cardiac crux
Which valves are in fibrous continuity in the normal heart?
Aortic and mitral
The direction of blood flow through an ASD is primarily related to what?
Relative compliances of LV/RV
*Otherwise normal patient, RV is more compliant so get L-R shunting
Most common anatomic form of HLHS?
AA/MA
*AS/MS and AA/patent MV are similar in occurence
In the cardiac sarcomere, what includes the entirety of the myosin contractile elements?
A-band
What bisects the A-band in the cardiac sarcomere?
M-line
What contains purely actin elements of the cardiac sarcomere?
I-band
What bisects the I-band in the cardiac sarcomere?
Z-disk
What is the central subsection of the A-band that doesn’t include the areas of myosin-actin overlap?
H-zone
Most common truncal valve morphology in truncus arteriosus?
Tricuspid (70%)
*Next: Quadricuspid (20%) Bicuspid (10%) Pentacuspid (<1%) Unicommisural (<1%)
What valves is a truncal valve in fibrous continuity with?
Mitral in all patients
-Can rarely be in fibrous continuity with tricuspid
The resting potential of which ion is primarily responsible for the baseline (phase 4) resting conductance of cardiac myocytes?
K
What current is the dominant resting conductance of the myocyte keeping it negatively polarized around -85mV until an AP arrives to activate the cell into phase 0?
Ik1 K current
The rapid depolarization of cardiac myocytes (phase 0) is driven by the rapid influx of which ion into the myocytes?
Na
When an AP arrives to the cardiac myocyte, what channels open resulting in rapid depolarization?
Na
What provides the prolonged phase 1/2 depolarization required to achieve muscle contraction?
K and Ca conductance
Phase 2: Ca
Phase 3: K
SCN5A mutations involve which channel gene?
Na
SCN5A mutations can cause which 2 conditions?
- Type 3 Long QT
2. Brugada
Neonate with hypoxia + decreased vascular markings?
PS
Where is a sinus venosus ASD relative to the fossa ovalis?
Posterior/superior
What defect is typically secondary to absence of usual rim of tissue between the right pulmonary veins and the RA?
Sinus venosus
What commonly occurs with sinus venosus ASD?
Anomalous right upper pulmonary venous return
What is the most abundant non-myocyte cardiac cell in the mature heart?
Fibroblast
What type of cells are vital for structural integrity of the heart and play a large role in remodeling and development?
Fibroblasts
List 2 roles of cardiac fibroblasts
- Responsible for deposition of extracellular matrix and contribute to remodeling through secretion of metalloproteinases
- Also involved in secretion of cytokines and growth factors which influence neighboring cells
What are contractile cells that help regulate blood flow in capillaries?
Pericytes
What type of cells are mostly found in medium caliber blood vessels in the heart?
Vascular smooth muscle cells
Where are macrophages in the heart?
Scattered
What type of cells line the inner wall of the ventricles?
Endothelial cells
Most common additional abnormality seen in patients with Ebstein?
ASD
- > 80% of patients
- Next most common is PS (even functional or true PA), then VSD
What has to be determined prior to designing treatment plans for a neonate with severe Ebstein?
Degree of RVOT obstruction
True or False: Left-sided lesions are common in Ebstein?
False
*LVNC reported in some genetic association studies, but otherwise uncommon
What 2 structures have the lowest O2 saturation in fetus?
SVC
CS
What structure passes under the transverse aortic arch in normal heart?
RPA and left bronchus
The PA at its bifurcation is to what side of the ascending aorta?
Left
Where does the LPA travel in relation to the left bronchus?
Over the left bronchus
What arterial vessel is partially formed by the remnants of the 3rd aortic arch?
Common carotid
What does 1st aortic arch form?
Part of maxillary artery
What does 2nd aortic arch form?
Part of stapedial artery
What does 3rd aortic arch form?
Common carotid artery
Proximal portion of the internal carotid artery
Which structures connect cardiac myocytes end to end and are responsible for structural integrity and synchronized contraction of cardiac tissue (transmission of electrical impulses)?
Intercalated discs
What are intercalated discs made of?
Adherens junctions
Desmosomes
Gap junction
Name 2 proteins that connect the myocytes to the extracellular matrix
Dystrophin
Costameres
What are invaginations of the sarcolemma which allows transmission of the action potential to the inner part of the cell?
T-tubules
What nerve is a branch of the vagus nerve that travels inferiorly around the aortic arch before traveling superiorly to innervate muscles in the larynx?
Left recurrent laryngeal nerve
What is a potential cause of post-op hoarseness and stridor?
Injury to the left recurrent laryngeal nerve
What types of surgery have risk to the left recurrent laryngeal nerve?
Anything with manipulation of the aortic arch
What structure does the right recurrent laryngeal nerve loop around?
Right subclavian artery
Most common aorto-pulmonary positions in patients with DORV?
Side-by-side with aorta to the right of the PA (2/3 of DORV)
Most common ASD?
Secundum (75%)
Where are secundum ASDs found?
Region of fossa ovalis
Second most common type of ASD?
Septum primum (20%)
2 least common types of ASD?
- Sinus venosus (5%)
2. Coronary sinus (<1%) - often associated with heterotaxy
Name 3 possible factors that can contribute to the formation of a secundum ASD
- Deficient growth of septum secundum
- Excessive resportion of septum primum
- Deficient valve tissue
Normal right SVC is derived from what embryologic structure?
Right anterior cardinal vein and right common cardinal vein
If the left anterior cardinal vein persists, what does it become?
Left SVC
*Left anterior cardinal vein typically regresses
What is the ductus venosus remnant termed?
Ligamentum venosus
The round ligament of the liver is part of what?
Umbilical vein remnants
What is the most common hemodynamically significant extracardiac AV malformation in neonates?
Vein of Galen
Which gender is more affected by Vein of Galen malformations?
Male
How does a Vein of Galen malformation present?
High-output cardiac failure soon after birth
What exam finding suggests a Vein of Galen malformation?
Bruit in the fontanelles
List morphologic features of the tricuspid valve
- Septal chordal attachments
- Triangular-shaped orifice at the mid-leaflet level
- Presence of 3 leaflets and commissures
- Emptying into a morphologic RV
List morphologic features of the mitral valve
- 2 leaflets
- Elliptical-shaped orifice
- 2 commissures
- Empties into morphologic LV
Which fetal remnant delivers blood from right/left hepatic veins to RA?
Ductus venosus
What does the ductus venosus do?
Receives blood flow from the hepatic veins and umbilical vein and delivers it to the RA
What happens to the ductus venosus after birth?
Becomes the ligamentum venosum
Where is the aortic isthmus located?
Between the origin of the left subclavian artery and the ligamentum arteriosum
What do the umbilical arteries do?
Bring deoxygenated blood from internal iliac arteries to placenta
What coronary abnormality needs to be identified in a ToF patient who will be undergoing a transannular patch?
LAD from RCA (5%)
*Coronary then takes a course anterior to the RVOT
Besides LAD from RCA, what is another potential coronary abnormality in ToF patients?
Accessory LAD (large conal branch), 10-15%
What is the association between the atrial and fossa ovalis?
LA: Valve of fossa ovalis
RA: Limbus of fossa ovalis
Name an anatomic hallmark of the morphologic RA
Ostium of the IVC
*Suprahepatic IVC nearly always connects to the RA
A finger-like appendage and smooth walled surfaces are characteristic of which atria?
Left
True or False: Pulmonary vein ostia are good predictors of atrial morphology?
False- High frequency of anomalous pulmonary venous return
Most common relationship of great arteries in tricuspid atresia?
Normal (70-80%)
Relationship between VSD size and PS in patients with tricuspid atresia?
- Bigger VSD with widely patent pulmonary outflow
- Smaller VSD with PS
During relaxation phase of cardiac muscle contraction, majority of Ca is removed from sarcoplasm by what?
Reuptake in the sarcoplasmic reticulum via SERCA pumps
- 80% of the Ca that is sequestered during the relaxation phase of the cardiac muscle contraction is via Ca-ATPase SERCA pumps located on the SR
- 20% is removed from the cell through Na-Ca and Ca-ATPase pumps located on the sarcolemma
Where is the AV node in tricuspid atresia?
Floor of RA
Where is the bundle of His in tricuspid atresia?
Courses from AV node on floor of RA to the crest of the intraventricular septum (muscular) and runs posterior to the VSD rim
*Any surgery involving VSD, worry about heart block
List features of the RV in the normal heart
- Tripartite (inlet, trabecular, outlet regions)
- Coarse septal surface
- Prominent apical trabeculations
- Tricuspid/pulmonary valves not in continuity
When can you see a tricuspid/pulmonary valve in continuity?
ToF with membranous VSD extension
Most common additional cardiac finding in TGA?
VSD (40-45%)
*Majority perimembranous, muscular, or malalignement
What are 3 less common additional cardiac findings in TGA?
- Isolated LVOTO (5%)
- CoA, arch hypoplasia or IAA (5%)
- Left juxtaposition of atrial appendages (2-5%)
What structure is often abnormal in TGA, but is rarely functionally significant?
Mitral valve (20%)
-Cleft MV most common
What causes cyanosis in a patient with severe Ebstein with severe TR?
R-L atrial shunting
*Often worsens with exercise in older patients
What is the most common associated finding in Ebstein?
ASD or PFO (80%)
Anatomic hallmark of morphologic LA?
Valve of fossa ovalis (septum primum)
Anatomic hallmark of morphologic PA?
Limbus of fossa ovalis and entrance of IVC
Which atria is more posterior?
LA
Describe the atrial appendages
LA: Fingerlike, trabeculated
RA: Broad-based
What is fetal Hgb composed of?
Alpha/Gamma subunits
Does fetal or adult Hgb have a higher affinity for O2?
Fetal
What is adult Hgb composed of?
Alpha/Beta subunits
Why does fetal Hgb have a higher affinity for O2 compared to adult?
Needed for transport of o2 across placenta
In a normal newborn, fetal Hgb is replaced by adult Hgb by what age?
3 months
Through what pathway does norepinephrine activate B1 adrenergic receptors?
Gs dependent activation of adenylate cyclase… increases cAMP
Norepinephrine activates B1 adrenergic receptors by doing what?
Activating the Gs subunit of the G-protein complex which activates adenylate cyclase
What does adenylate cyclase do?
Converts ATP to cAMP
What does cAMP do?
Activates protein kinase A
What does protein kinase A do?
Phosphorylates multiple proteins involved in muscle contraction and AP of heart
*Increases chronotropy and inotropy
What happens to pleural pressure and intra-abdominal pressure with inspiration?
- Fall in pleural pressure
- Rise in intra-abdominal pressure
What happens to right sided venous return and RV stroke volume with inspiration?
- Increased right sided venous return
- Increased RV stroke volume
What happens to the E’ velocity in the tricuspid and mitral valve with inspiration?
- E’ increases across tricuspid (5-10%)
- E’ decreases across mitral (5-10%)
What is characterized by absent or abnormal chordal insertions for the mitral valve?
Mitral arcade or hammock mitral valve
- Leaflet edges are often thickened and rolled
- Leaflets are relatively tethered with poor coaptation due to direct insertion of leaflets
- MR common, but functional MS can occur
What causes an ostium primum ASD?
Abnormal endocardial cushion development
Where is a primum ASD located?
Anterior to the fossa ovalis in the inlet portion of the ventricular septum
What 2 things result from failure of the endocardial cushions to develop?
- Primum ASD
2. AVCD
What happens when there is failure of the common pulmonary vein to connect to the LA?
Anomalous pulmonary venous return
What are 2 common etiologies behind secundum atrial septal defects?
- Excessive cell death/resorption of the septum primum
2. Insufficient growth of the septum secundum
A persistent L-SVC is a remnant of what?
Left horn of the sinus venosus
Where is a L-SVC seen on echo?
-TTE: Runs lateral and leftward to PA on high parasternal short-axis views with flow heading inferiorly. –TEE: Runs between left pulmonary veins and left atrial appendage (just posterior and superior to mitral valve)
What might an L-SVC be mistaken for?
Descending aorta
Where does a L-SVC run before joining the CS in the left AV groove?
Posteriorly along LA
How much deoxygenated blood is needed to visualize true cyanosis?
At least 5g/dL
In what patient would a relatively low O2 not result in expected clinical cyanosis?
Anemia- Not enough deoxygenated blood
What area is the best indicator of cyanosis and why?
Tongue- right vascular supply and minimal pigmented cells
Mutations in which protein may cause disassociation of the intracellular cytoskeleton and the extracellular matrix in cardiac myocytes in addition to causing muscular dystrophy?
Dystrophin
What does dystrophin do?
Protein that links extracellular matrix and cytoplasmic actin providing link between extracellular and intracellular structures of the myocyte
Mutations in the gene that encode for what protein can cause muscular dystrophy and DCM?
Dystrophin
Name 2 proteins that are involved in the linking of intracellular and extracellular structures and can cause long QT or SIDS if mutated
Caveolin
Syntrophin
Mutations in cytoplasmic actin or dystroglycan complex can cause what?
DCM
In the sarcomere, which protein binds to Ca and allows cross-bridges to form permitting contraction?
Troponin C
- Ca binds to troponin C, changing the tertiary structure of troponin C and other troponin subunits
- Allows tropomyosin to shift positions and allows myosin and actin binding leading to muscle cell contraction
Children living at high elevations have higher _ pressures as compared to those living at sea level?
Mean PA pressure
*More exacerbated with exercise
What might explain the relatively increased risk of persistence of the PDA in children living at high altitude?
Higher mean PA pressures
Where are baroreceptors located?
Carotid sinus
Aortic arch
Increased arterial pressure on the baroreceptors in the carotid sinus or aortic arch cause what?
Decreased BP via decreased HR and vasodilation
What is the primary mechanism that the myocardium uses to compensate for increased O2 demand?
Increased coronary blood flow
v. any change in O2 extraction
Why is coronary O2 tension low (20-25mmHg)?
High baseline O2 extraction levels by the myocardium
Relative to fossa ovalis, where is a coronary sinus ASD?
Anterior
Inferior
What is a coronary sinus ASD typically seen in association with?
Unroofing of CS and persistent L-SVC
Why is the 2nd heart sound often single and loud in d-TGA?
Anterior position of aorta
What causes a narrow mediastinum and “egg on a string” sign on CXR in d-TGA?
Aorta/PA are AP in position to each other
What is the most common associated cardiac lesion in DORV?
PS
*50% of patients with DORV
After PS what is the next most common associated cardiac lesion in DORV?
ASD: 25% secundum, 8% primum
*Can see subaortic stenosis and right aortic arch, but less common
A mitral valve in which all of the chordal attachments occur to a single papillary muscle is called what?
Parachute mitral valve
- There is a variant with attachments to 2 distinct papillary muscles, but most to just 1
- Chordae can be short and thick
What is it called if the mitral valve leaflets insert directly onto the papillary muscle?
Mitral arcade
True or False: The pulmonary veins contain cardiac myocytes instead of smooth muscle cells in the last 1-3cm before insertion to LA
True
*Allows them to minimize retrograde flow during atrial systole
What is a potential EP problem due to the pulmonary veins having cardiac myocytes instead of smooth muscle cells in the last 1-3cm before insertion to LA?
A-fib
*Why PV isolation procedures sometimes used in adults
What is the most common location of the PAs in truncus arteriosus?
-MPA from left postero-lateral aspect of truncus right above valve (48-68%, Type I)
- 29-48% type II, Branch PAs from posterior surface
- 6-10% type III, Branch PAs from lateral sides of truncus
- Type IV, Branch PAs from descending aorta
In truncus, when there is a single PA, what one is likely to absent?
PA on side of the aortic arch
*Same outflow, same side
In ToF, when there is a single PA, what one is likely to absent?
PA on opposite side of arch
What happens to the embryonic 5th arch?
- Typically rudimentary and doesn’t develop into any known vessels in a normal neonate
- Rare cases of persistence, can be asymptomatic or associated with other cardiac findings
What is the clinical scenario of a persistent 5th arch, but interruption of normal 4th arch?
CoA
What is seen in around 80% of patients with CoA?
Bicuspid AoV
*Combo is considered to be indication of a true aortopathy
What proportion of CoA patients have “simple” CoA with normal intracardiac anatomy other than a bicuspid AoV?
1/2
-Then 1/2 with CoA + Associated anomalies
Besides a bicuspid AoV, what is the most common associated anomaly with CoA?
VSD
LV isovolumic relaxation continues until what event?
MV opens
- End systole, LV ejection is complete and AoV closes
- This begins isovolumic relaxation with drop in LV pressure
- Next, MV opens allowing filling of ventricle due to lower pressures in the ventricle
Where is AV node located?
Triangle of Koch
What are the borders of the triangle of Koch?
Tendon of Todaro
Attachment of septal leaflet of tricuspid valve
Ostium of CS
What is the most common type of TAPVR?
Supracardiac (46%)
- Pulmonary veins form a confluence posterior to LA and blood is directed through a venous channel to left cardinal system
- Most common anatomical site is left innominate vein
What are frequencies of the different types of TAPVR?
- Supracardiac (46%)
- Infracardiac (23%)
- Cardiac (20%)
- Mixed (11%)
Elevated pH
Normal pCO2
High bicarbonate
Acute metabolic alkalosis
What are causes of acute metabolic alkalosis?
Vomiting
Hypokalemia
Use of alkalotic meds (bicarbonate, hyperaldosteronism, Bartter syndrome)
What coronary artery typically supplies the inferior LV wall and posteromedial papillary muscle of the mitral valve?
Right
What supplies the anterolateral papillary muscle of the mitral valve?
Dual: LAD and cicumflex
What supplies the posteromedial papillary muscle of the mitral valve?
RCA
What supplies the inferior wall of the LV?
RCA
In fetal circulation, which structure has the highest O2 content?
Umbilical vein
*Brings blood from placenta to the fetus (UV - DV/L Hepatic Vein- Atria)
What 2 structures typically have the lowest O2 concentration in the fetus??
SVC
CS
What drains deoxygenated blood into the CS?
Great cardiac vein
What is the name of the valve at the ostium of the cardiac vein?
Veiussens valve
What is Vieussens valve?
Bicuspid valve at the site of the cardiac vein that merges with the CS
Where is the Eustachian valve?
Entrance to IVC
Where is the Thebesian valve?
Where CS drains to RA
The AV nodal artery arises from which coronary artery?
Right
- 90%: AV nodal artery from RCA
- 10%: AV nodal artery from left circumflex
- Comes from the dominant coronary artery
What is the most common coronary artery abnormality seen in patients with otherwise normal heart?
Anomalous origin of the left circumflex from right main coronary artery
*1/3 of major coronary artery anomalies
After anomalous origin of the left circumflex from the right main, what is the next most common coronary artery anomly?
Anomalous origin of the RCA from the left sinus of Valsalva
*Just <30%
What % of coronary artery anomalies are single coronary arteries?
5-20%
True or False: Anomalous origin of the left or right coronary from the posterior sinus of Valsalva is a rare finding
True
What is the most common abnormality of the aortic arch?
Anomalous right subclavian from the left
- Occurs in 0.5% of the general population, usually asymptomatic
- Often found at autopsy or imaging for something else
What population is it common to see an anomalous right subclavian artery from the left?
Trisomy 21 with CHD (>30%)
What is Uhl anomaly?
-Partial or complete absence of the RV myocardium (epicardium and pericardium opposed to each other)
- Rare
- Valvular morphology often normal
What is characterized by fatty infiltration and replacement of the RV myocardium and arrhythmias or SCD?
Arrhythmogenic RV dysplasia
What is the definition of a straddling AV valve?
Involves anomalous insertion of chordae tendineae
- Have to have VSD
- May limit repair options
What is most responsible for high PVR in a fetus?
Low blood and alveolar O2 tension
*Fetus also produces vasoconstrictive substances such as thromboxane and leukotrienes (but doesn’t have as significant an effect)
What is the initial connection between the pulmonary venous plexus and the heart?
Common pulmonary vein
*Typically has 4+ feeding veins which become the left and right upper/lower pulmonary veins
What eventually happens to the common pulmonary vein?
Incorporated into the back wall of the LA and individual pulmonary veins connect independent to the atrium
What phase of the cardiac AP is characterized by influx of Ca2+ into cell through L-type voltage gated Ca2+ channels?
Phase 2 (plateau)
Which phase of the cardiac AP is characterized by rapid depolarization due to Na+ entry?
Phase 0
Which phase of the cardiac AP is characterized by early repolarization with K+ efflux from the cell?
Phase 1
Which phase of the cardiac AP is characterized by K+ efflux from the cell?
Phase 3 (repolarization phase)
Which phase of the cardiac AP is characterized by return of resting membrane potential and is maintained by Na/K ATPase channels?
Phase 4
Describe a tet spell
- Abrupt onset of cyanosis, hypoxemia, dyspnea, agitation
- Usually starts after 2 months
- Crying/agitation increase PVR which increases R-L shunting and reduces PBF
- Infundibular spasm may also be involved
What is an indication to proceed with surgical repir of ToF?
Presence of hypercyanotic spells
What structure is a continuation of the sarcolemma?
T-tubule
What is an enveloping myofibril at the level of the Z-disks?
T-tubule
What are T-tubules important for?
Rapid activation of the entire myocyte after the arrival of AP (excitation-contraction coupling)
What type of channels are present in T-tubules?
L-type Ca channels: Provide the initial Ca flow into the cell during excitation
What are intercalated disks?
Junctions between adjacent myocytes
What structure links myofibrils to costameres (intracellular protein complexes) and transmit force from the sarcomere to the extracellular matrix and adjacent myocytes and functions to link the cytoplasmic actin filament to the cytoskeleton and connect intermediate filaments between adjacent cells?
Intercelated disks
What does decreasing end diastolic volume do to myocardial O2 consumption?
Decreases it
Myocardial O2 consumption is determined by what?
Wall tension- Related to intraventricular pressure and radius
*Decreasing EDV decreases pressure and radius of ventricle
What effect does cardiac contractility have on wall tension and thus myocardial O2 consumption?
-Increased work so increased wall tension and myocardial O2 consumption
What does increased HR do to O2 consumption over time?
Increases it- Increased frequency of generating pressure during LV contraction
What are the normal branching patterns of the RPA and LPA?
RPA: Anterior to the RUL bronchus
LPA: Posterior to the LUL bronchus
In situs inversus, what is the branching pattern of the RPA and LPA?
RPA: Posterior to RUL bronchus
LPA: Anterior to LUL bronchus
With bilateral morphologic right lungs, what is the branching pattern of the PAs?
Both anterior to the upper lobe bronchus
With bilateral morphologic left lungs, what is the branching pattern of the PAs?
Both posterior to the upper lobe bronchus
What is the power stroke in cardiac muscle contraction?
Interaction of myosin head and actin that allows myosin to pull actin filament inward
What powers the power stroke in cardiac muscle contraction?
ATP hydrolysis and conversion to ADP
What is troponin made up of?
Troponin T, C, I
In diastole, what prevents cross-bridging between actin and myosin?
Tropomyosin and troponin I
In systole, what binds troponin C, which then binds troponin I and moves it from the ATP-reactive site on actin?
Ca
What happens when troponin T binds to tropomyosin?
Causes a conformation change what allows cross-bridging of actin and myosin
What structure has intrinsic ATPase activity?
Myosin head
If the myosin head is uninhibited, what happens?
ATP becomes hydrolyzed which allows the myosin head to interact with actin and pull the filament inward … Power stroke
What happens after the power stroke?
ADP released which allows myosin and actin to detach