Flashcards in Twenty Three Deck (50)
Describe the embryological developmental timeline of the heart.
Week 3: Endocardial tube
Driven by metabolic needs exceeding diffusion alone
Bordered by aortic arches rostrally, venous system
Day 22-23: begins to beat
Day 23: tube bends to right
Constrictions form in tube
Separates truncus arteriosus, bulbus cordis,
ventricle, atrium, and sinus venosus
AV canal separates atrium and ventricle
Week 4: Ventricle begins to grow and septate (from apex)
Week 5: Spiraling of aorticopulmonary septum and formation of outlet ventricular septum
Weeks 4-6: Development of atrial septum
Describe the epidemiology of CHD?
Most common cause of heart disease in children
Most common organ malformed at birth
10% of early miscarriages
Spectrum of presentation and severity
Asymptomatic through childhood
Death in infancy without immediate treatment
Everything in between
Describe the etiology of CHD?
Genetic + environmental
~1/3 children with chromosomal abnormalities
Alcohol, lithium, etc.
Describe the pathway of oxygenated blood.
Umbilical vein to:
Ductus venosus to:
Inferior vena cava to:
Right atrium to:
Foramen ovale to:
Left atrium to:
Coronary arteries, brain
What are the ductus venosus, foramen ovale, and ductus arteriosus?
2. Ductus venosus-A way for oxygenated blood from the placenta to bypass the liver.
3. Foramen ovale-A way for blood to bypass pulmonary circulation (connects RA and LA)
4. Ductus arteriosus-Another way for blood to bypass pulmonary circulation (connects PA with Aorta)
Describe the resistance of both pulmonary and systemic vasculature in fetal circulation.
Placenta: very high vascular cross sectional area
= “low” systemic vascular resistance (SVR)
Lungs deflated (fluid-filled)
Low oxygen tension
= “high” pulmonary vascular resistance (PVR)
Describe the CO of the fetal heart? Where does it leave and where does it go?
Where does fetal blood go?
Right ventricle: ~2/3 of fetal
12% of flow to lungs
88% of flow to descending aorta
Left ventricle: ~1/3 of fetal
9% of flow to coronary arteries
62% of flow to carotid-
29% of flow to descending aorta
How and why does circulation change in a newborn?
Umbilical vessels constrict
Lungs inflate, pulling open pulmonary vasculature
Increased pulmonary flow increases LV stroke volume
LV cardiac output = RV cardiac output
What happens to the foramen ovale and ductus arteriosus after birth?
Decreasing PVR increases pulmonary blood flow
Increased left atrial filling
Foramen flap closes
Endogenous prostaglandin E1 (PGE1) decreases
Increased oxygen tension
Stimulates ductal closure
What happens to the individual ventricles after birth and why? How much time?
Higher SVR = thickeningof LV
Lower PVR = thinning of RV
LV:RV Weight Ratio
1 Month 1.5:1
6 Months 2:1
What is cyanosis? What are the two possible cardiac causes of it?
> 4 g/dL deoxygenated
Inadequate pulmonary blood flow (lack of
Mixing of systemic venous (blue) blood into systemic
arterial (red) blood
What are the three paired fetal veins? What do they do?
3 paired veins in embryo:
a) Vitelline veins (return from yolk sac)
b) Umbilical veins (return from placenta)
c) Cardinal veins (return from body of embryo)
Anterior and posterior
(subcardinal, supracardinal) cardinal veins
What fetal veins do the IVC and SVC come from? Why is this important to note?
Superior vena cava:
Right anterior cardinal vein
Bridging vein between anterior
cardinal veins becomes
Inferior vena cava:
1. Hepatic and subhepatic segments (vitelline vein)
2. Prerenal segment (right subcardinal vein)
3. Renal segment (subcardinal-
4. Postrenal segment (right supracardinal vein)
It's signinficant b/c the IVC comes from many different fetal veins which means that various factors can lead to a deformed IVC.
What is a persistent left SVC? What is the vasculature like? Is it cyanotic or acyanotic?
Persistent Left SVC: persistence of left anterior cardinal vein
Drains to coronary sinus
What is an interuppted IVC? What is the vasculature like? Is it acyanotic or cyanotic?
Interrupted IVC: absence of a contribution of IVC
development (most commonly hepatic segment)
IVC drains into azygous system
Describe the development of pulmonary veins.
Vascular plexus of foregut enmeshes lung buds (connections to
cardinal and vitelline systems)
Evagination in posterior wall of left atrium
“Common pulmonary vein” connects LA to foregut plexus
Systemic connections involute
What is TAPVR? What is the vasculature like? What are the three types? Is it acyanotic or cyanotic?
Venous Return (TAPVR)
Lack of connection to LA,
persistence of connections to
1. Supracardiac: Drain above
2. Cardiac: Drain back to
3. Infracardiac: Drain below
heart (often SVC)
heart (often coronary
heart (often IVC/hepatic
What occurs when TAPVR involves obstructed pulmonary veins? Clinical implications? Unobstructed? Clinical implications
“Obstructed” pulmonary veins (usually in infracardiac due to the diaphragm).
Profoundly cyanotic, unstable
Cyanotic (mixed systemic
and pulmonary veins)
month of life
Describe atrial septal development. What happens at birth?
Goal: allow fetal shunt that
closes at birth
1. Septum primum: grows
Leaves ostium primum
Perforations in septum
Fuses with endocardial
from roof towards
between septum primum
and endocardial cushion
primum form ostium
cushion to close ostium
2. Septum secundum:
grows to right of septum
Leaves foramen ovale
“Flap” of foramen ovale
on LA side from septum
At birth: increased
increases LA flow, closes
What is a patent foramen ovale? How common is it? What is it like clinically?
Remnant of PFO flap:
“Patent” foramen ovale
present in 15-20% of the
significance unless. . .
Avenue for a clot to pass
from systemic veins to
• “Paradoxic” embolus
What is the pathology of an ASD? Cyanotic or acyanotic? What are the three distinct types? What symptoms are there? What will be found on exam? How are the distinct types treated?
Pathology: Atrial Septal Defect (ASD)
Due to deficiency of septal tissue
3 distinct types:
1. Sinus venosus (10%)
Often with RUPV PAPVR
2. Ostium secundum (60%)
Involves fossa ovalis
3. Ostium primum (30%)
Involves endocardial cushion
Symptoms: ~lower side of growth curve
Systolic ejection murmur at LUSB (pulmonary flow
Fixed split S2
No symptoms = no medications
~40% secundum ASD close by age 4 years
Surgery (primum, sinus
venosus, some secundum)
Describe the development of the AV valves.
Endocardial Cushions (EDC): Development
“Atrioventricular canal” = junction of atrium and ventricle
Endocardial cushions (EDC) form dorsal/ventral to
separate canal into 2 canals (right/left)
EDC also contributes to:
Atrial septum (fuses with septum primum to close
Ventricular septum (inlet portion)
Mitral and Tricuspid Valves: Development
Proliferation of tissue around AV canals
“Delamination:” valves “peel” off ventricular endocardial
surface (anchored at hinge point)
What is an AVC? What are the different names for it? What are the two different kinds? What is it commonly associated with?
Embryology: lack of fusion of endocardial cushions
Endocardial cushion defect (ECD) = atrioventricular
canal defect (AVC) = atrioventricular septal defect (AVSD)
“Complete” versus “partial” AV canal defect
Commonly associated with
Describe the pathology of complete AVC? Acyanotic or cyanotic? What are the symptoms? Physical exam findings? Treatment?
a) “Complete” Atrioventricular Canal Defect
Lack of fusion of entire endocardial cushion
1. Ostium primum atrial septal defect (ASD)
2. Common atrioventricular valve spanning both ventricles
3. Inlet ventricular septal defect (VSD)
Pitch/volume varies based on pressure difference
from LV to RV
Symptoms: pulmonary overcirculation (related to VSD)
Poor feeding = poor weight gain
Increased catechols = diaphoresis
Diuretics (dry out lungs)
Digoxin (augment contractility)?
ACE-inhibitor (afterload reduction)
Augment nutrition (increasing caloric density of formula)
Surgical closure (~4-6 months)
Describe partial AVC. Cyanotic? What are the syptoms? Exam Findings? Treatment?
b) “Partial” Atrioventricular Canal Defect
Incomplete fusion in a portion of endocardial cushion
1. Ostium primum ASD
2. Cleft in anterior leaflet of mitral valve
Symptoms: ~lower side of growth curve
Systolic ejection murmur at LUSB (pulmonary flow murmur)
Fixed split S2
+/- holosystolic murmur at apex (mitral regurgitation)
No symptoms = no medications
Surgical repair (ASD closure, cleft closure) ~2 years
Describe the vasculature and bloodflow in tricuspid atresia. Treatment?
2) Pathology: Tricuspid
Atresia = absence of a
Where does right atrial
ASD (right to left)
How does blood get to lungs?
VSD to right ventricle
Treatment: single ventricle palliation
What is the pathology of ebsteins anomaly? What is the resulting vasculature? What risk factor is it associated with? Cyanotic? Treatment?
3) Pathology: Ebstein’s Anomaly
Failure of delamination of
Results in leaflets “stuck”in body of RV
Significant tricuspid regurgitation
Varying degrees of
Association: maternal lithium (teratogen)
Clinical: May be acyanotic or cyanotic
Depends on severity of delamination failure
Treatment: tricuspid valve repair if significant
Describe ventricular septal development.
Ventricular Septum: Development
Week 4: muscular
ventricular septum grows
up from apex
“Excavation” of ventricles
forms inlet portion
Week 5: “Bulbar ridges”
grow from outflow tracts
Week 8: fusion of
What are the 4 regions of the ventricular septum?
composed of 4 regions:
1. Inlet (EDC)
2. Outlet (Bulbar)
3. Trabecular (Muscular)
4. Membranous (Fusion point)