Fung: Congenital Heart Disease Flashcards
General term used to describe abnormalities of the heart and great vessels that are present from birth
congenital heart disease
During what weeks of embryogenesis are congenital heart defects likely to occur?
during weeks 3 through 8 of gestation
(blank)% of births have a congential cardiovascular defect and are the most common form of cardiovascular disease among children
1
Explain fetal blood circulation
O2 rich blood from the placenta –> umbilical vein –> ductus venosus (bypasses liver) –> IVC –> right atrium –> foramen ovale (bypass right ventricle) –> left atrium –> left ventricle –> aorta –> umbilical arteries –> placenta
**ductus arteriosus from pulmonary trunk to aorta, shunts blood that did enter the right ventricle and out the pulmonary trunk
What are the two main causes of congenital heart disease?
sporadic genetic abnormalities - single gene mutations, small chromosome deletions, trisomies, monosomies
or
environmental factors - congenital rubella, gestational diabetes, teratogens
abnormal communication between chambers or blood vessels
shunt
a complete obstruction in blood flow
atresia
3 primary categories of congenital heart defects
left to right shunt
right to left shunt
obstruction
What happens to the blood flow in a right to left shunt?
poorly oxygenated blood returning from the veins mixes with systemic arterial blood; these patients will become hypoxic and cyanotic
What are some clinical features of right to left shunts?
clubbing of fingers and toes
polycythemia (increased RBCs)
What causes tetralogy of fallot? What are the four cardinal features of tetralogy of fallot?
tetralogy of fallot occurs when the infundibular septum is displaced anterosuperiorly
1) ventricular septal defect
2) overriding aorta (forms the superior border of the VSD and overrides the defect of both ventricles)
3) obstruction of right ventricular outflow tract (pulmonary stenosis)
4. right ventricular hypertrophy
Do patients with tetralogy of Fallot survive? How do these patients present at birth?
yes, patients can survive into adulthood and can undergo complete surgical repair; most patients are cyanotic at birth
What to the clinical consequences of tetralogy of Fallot depend upon?
the degree of the pulmonic stenosis
if mild: resembles an isolated ventricular septal defect and is more like an isolated left to right shunt without cyanosis
if severe: greater resistance RV outflow and a right to left shunt, pulmonary arteries become hypoplastic and aorta dilates
What is transposition of the great vessels?
when the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle
**normally the aorta is posterior to the pulmonary artery, but it is reversed here
How does transposition of the great vessels occur?
develops due to abnormal formation of the truncal and aortopulmonary septa
The outcome of transposition of the great vessels is dependent on what three things?
- degree of mixing of blood (if the patient has a ventricular septal defect, they can compensate…if they have an unstable shunt, like a patent foramen ovale, they need surgery)
- magnitude of tissue hypoxia
- ability of the right ventricle to supply to systemic circulation
If a patient has transposition of the great vessels and has an unstable shunt, what must they undergo?
they must undergo balloon atrial septostomy to open up and allow for mixing of bloos
Clinical features of transposition of the great vessels? Can these patients live to adulthood?
right ventricular hypertrophy; atrophy of left ventricle
**right ventricle must supply the systemic circulation
with surgery, can survive into adulthood; otherwise, die w/i first months of life
What is persistent truncus arteriosus?
this arises due to the failure of separation of the embryological truncus arteriosus into the aorta and pulmonary artery; results in a single great vessel that receives blood from both ventricles and the coronary circulation
Regarding persistent truncus arteriosus, There is an associated VSD that produces systemic cyanosis and increased pulmonary blood flow. Why is this a concern?
danger of irreversible pulmonary HTN
What is tricuspid atresia?
complete obstruction of the tricuspid valve orifice
How does tricuspid atresia occur?
when there is unequal division of the atrio-ventricular canal, you get a large mitral valve and an underdeveloped right ventricle
How do patients with tricuspid atresia present at birth? Do they survive into adulthood?
cyanotic at birth; very high mortality rate
What is total anomalous pulmonary venous circulation?
when the pulmonary veins (oxygenated blood) fail to develop into the common pulmonary vein and directly join to the left atrium
What can correct a total anomalous pulmonary venous circulation?
so if you have a patent foramen ovale (b/w the atria) or an atrial septal defect, then pulmonary venous blood can enter the atrium
What are the clinical features of total anomalous pulmonary venous circulation?
volume/pressure overload leads to hypertrophy and dilation of the right heart;
dilation of the pulmonary trunk; hypoplastic left atrium;
possible cyanosis due to right to left shunt of the ASD
Describe the blood flow and complications in a left to right shunt
increased pulmonary blood flow and volume (pulmonary circuit is usually low flow, low resistance); initially, body responds to increased blood flow with medial hypertrophy and vasoconstriction to maintain distal pressures and prevent pulmonary edema; over time, the pulmonary vasoconstriction can lead to obstructive intimal lesions; eventually, the pulmonary vascular resistance will reach systemic levels and will change the shunt to a right to left shunt (late cyanotic congenital heart disease)
So what is the first response to the increased blood flow to the pulmonary circulation in a left to right shunt?
vasoconstriction of pulmonary vasculature to maintain pressure and prevent edema in the lungs; also there will be medial hypertrophy to withstand the higher pressures
What happens to a left to right shunt over time?
the increased pulmonary vasoconstriction will cause obstructive lesions of the intima of the vessels (hyaline and hyperplastic arteriolosclerosis); eventually the resistance of the pulmonary vessels will reach systemic levels and convert the shunt to a right to left shunt (late cyanotic congenital heart disease)
In cases of left to right shunts, at what point are the structural defects of congenital heart disease irreparable?
Once irreversible pulmonary hypertension develops the structural defects of CHD are irreparable
List 3 examples of left to right shunts
atrial septal defect
ventricular septal defect
patent ductus arteriosus
What is an atrial septal defect?
an abnormal fixed opening in the atrial septum caused by incomplete tissue formation that allows for communication of blood b/w the left and right atria **not the same as a patent foramen ovale
What is the most common type of atrial septal defect?
secundum
**result from deficient or fenestrated oval fossa near the center of the atrial septum
What are two other types of atrial septal defects?
Primum (5%): occur adjacent to the AV valves Sinus venosus (5%) occur near the entrance of the SVC and may be associated with anomalous pulmonary venous return to the RA
What are some clinical features of an atrial septal defect?
left to right shunt b/c lower pulmonary vascular resistance and greater distensibility of RV
increased pulmonary blood flow –> murmur
asymptomatic before age 30 and irreversible pulmonary HTN is abnormal
What can you do to prevent complications of an atrial septal defect, like heart failure, paradoxical embolization, or pulmonary vascular disease?
surgical or catheter based repair!
What is the formamen ovale used for in the fetus? What happens to this hole after birth?
the foramen ovale is a small hole in the atrial septum at the oval fossa - it allows oxygen rich blood from the placenta to bypass the lungs; after birth it is forced shut due to increased systemic pressure in 80% of people
What is a patent foramen ovale?
Occurs in 20% of people; during times of increased pressure on the right side (bowel movement, coughing, sneezing), the flap can open and can create a right to left shunt
This is the most common congenital cardiac defect
ventricular septal defect (VSD)
T/F: Most VSDs occur in isolation
False; only 20-30% occur in isolation, while most VSDs are associated with another congenital anomaly
3 types of VSDs
with the membranous interventricular septum
below the pulmonary valve (infundibular)
within the muscular septum (may be multiple - swiss cheese septum)
What are the clinical features of a large VSD? Can these patients survive?
difficulties from birth
usually membranous or infundibular
significant left to right shunting
**must be corrected
Can patients with a small VSD survive?
yes, small VSDs are well tolerated and may close spontaneously
What is the ductus arteriosus used for in the fetus?
shunts blood from the pulmonary artery to the aorta
**close should happen shortly after birth
What is a patent ductus arteriosus? Does it usu occur isolated or associated with another anomaly (VSD, coarctation of the aorta or pulmonic or aortic valve stenosis)?
when the PDA does not spontaneously close after birth; 90% occur as an isolated anomaly
what are the clinical features of a patent ductus arteriosus?
usu asymptomatic at birth
small PDAs no big deal
larger PDAs start as a left to right shunt but can progress to Eisenmenger syndrome
What can be used to keep a PDA open?
prostaglandin E
Results from the embryologic failure of the superior and inferior endocardial cushions of the AV canal to fuse adequately
Patients have incomplete closure of the AV septum and malformation of the tricuspid and mitral valves
atrioventricular septal defect
Primum ASVD and cleft anterior mitral leaflet; mitral insufficiency
partial atrioventricular septal defect
Large combined AV septal defect and a large common AV valve (hole in center of the heart)
Communication of the four chambers –> volume hypertrophy;
1/3 of patients have Down syndrome
complete atrioventricular septal defect
List three forms of obstructive congenital heart disease
- coarctation of the aorta
- aortic valvular stenosis
- pulmonary valvular stenosis
What is coarctation of the aorta? What genetic syndrome is it associated with?
common structural anomaly in which the aorta narrows in the area where the ductus arteriosus/ligamentum arteriosum enters; associated with Turner’s syndrome
Compare the infantile and adult forms of coarctation of the aorta. How are the symptoms different?
infantile: narrowing of the aortic arch proximal to the patent ductus arteriosus; symptomatic early on, high mortality rate if not surgically corrected; unsaturated blood through the PDA produces lower extremity cyanosis
adult: discrete infolding of the aorta just opposite the ligamentum arterosum; distal to the arch vessels; symptoms include hypertension in upper extremities, weak pulses in lower extremities, claudication and coldness of lower extremities, development of collateral circulation in the are
Common malformation May be isolated or be a part of a syndrome ( TOF, TGA) Resultant RVH Mild cases may be asymptomatic Severe cases require surgical repair
pulmonary stenosis
No communication between the right ventricle and lungs
Hypoplastic RV and ASD
Blood reaches the lungs through a patent ductus arteriosus
pulmonary atresia
Where is the aorta most likely to undergo stenosis?
- valvular: cusps of aortic valve become hypoplastic, thickened or abnormal in number
- subvalvular: thickened ring or collar of tissue below the valve, associated with a prominent systolic murmur, causes pressure hypertrophy of LV
- supravalvular: thickening of ascending aorta causing luminal constriction
What does severe aortic stenosis or atresia cause?
obstruction to LV outflow –> hypoplasia of the left ventricle and ascending aorta
How do you correct severe aortic stenosis/atresia?
patent ductus arteriosus for life
**nearly always fatal unless surgically repaired
