Congenital Heart Disease - Fung Flashcards
What is congenital heart disease?
- General term used to describe abnormalities of the heart and great vessels that are present from birth
- Arise due to faulty embryogenesis during week 3 and 8 of gestation
- 1% of births have a congential cardiovascular defect and are the most common form of cardiovascular disease among children
What are two general categories of causes of congenital heart diseases?
- sporadic genetic abnormalities
2. environmental factors
What are some sporadic genetic abnormalities that may cause congenital heart disease?
Single gene mutations Small chromosomal deletions Trisomies/ monosomies: Turner syndrome (XO) Trisomy 13 Trisomy 18 (Edward syndrome) Trisomy 21 (Down’s syndrome)
What are some environmental factors that can cause congenital heart disease?
Congenital rubella
Gestational diabetes
Teratogens
What is a shunt?
Abnormal communication between chambers or blood vessels.
What is atresia?
Complete obstruction to blood flow
What are the three primary categories of congenital heart diseases?
- left to right shunt
- right to left shunt
- obstruction
What is the main issue in right to left shunts?
Poorly oxygenated venous blood mixes with systemic arterial blood.
Patients with right to left shunts present with what?
Hypoxemia and cyanosis. Also with polycythemia and clubbing of fingers and toes (hypertrophic osteoarthropathy).
Name some conditions with right to left shunts.
Tetralogy of Fallot Transposition of the great vessels Persistent truncus arteriosus Tricuspid atresia Total anomalous pulmonary venous connection Paradoxical embolism
Tetrology of Fallot results from what?
Anteriosuperior displacement of the infundibular septum (which is supposed to form walls between atria).
What are the cardinal features of Tetralogy of Fallot?
- Ventricular septal defect – normally large
- Obstruction of the right ventricular outflow tract (subpulmonary stenosis)
- Overriding aorta – forms the superior border of the VSD and therefore overrides the defect of both ventricles
- Right ventricular hypertrophy
Describe the clinical features of Tetralogy of Fallot.
- Patients can survive into adulthood even untreated
- Clinical consequences are dependent on the degree of the subpulmonic stenosis
Mild: resembles an isolated VSD and more like a left to right shunt without cyanosis (pink TOF)
Severe:
Greater resistance to RV outflow and a right to left shunt (classic TOF) - Pulmonary arteries become hypoplastic and aortic dilation
- Most patients are cyanotic at birth
- Complete surgical repair is possible
What is Transposition of the great vessels (TOGV)?
- Aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle
Normally the aorta lies posterior to the pulmonary artery, but is reversed here - Defect develops due to abnormal formation of the truncal and aortopulmonary septa
Outcome of TOGV depends on what?
- Outcome depends on
Degree of mixing of blood (via a shunt)
Magnitude of tissue hypoxia
The ability of the RV to maintain the systemic circulation
Possible shunts
VSD (35%): stable
Patent foramen ovale, ductus arteriosus (65%): unstable - unstable shunts require balloon atrial septostomy
What are the clinical features of TOGV?
Right ventricular hypertrophy
Atrophic left ventricle
Without surgery most die within first months of life
With surgery can survive into adulthood
What is persistent truncus arteriosus (PTA)?
- Arises due to failure of separation of the embryological truncus arteriosus into the aorta and the pulmonary artery
- Single great vessel that receives blood from both ventricles and coronary circulation
- There is an associated VSD that produces systemic cyanosis and increased pulmonary blood flow (danger of irreversible pulmonary HTN)
Describe Tricuspid Atresia.
- Complete obstruction of the tricuspid valve orifice
Results from unequal division of the AV canal resulting in an:
Enlarged mitral valve
Underdeveloped right ventricle - Right to left shunt through the atria (ASD, patent foramen ovale) and a VSD allows communication between the left ventricle and pulmonary artery that arises from a hypoplastic right ventricle
- Cyanosis is present at birth and very high mortality rate
Describe total anomalous pulmonary venous circulation.
- Pulmonary veins fail to directly join the left atrium due to the failure of the development (atresia) of the common pulmonary vein
- During fetal life primitive systemic venous channels drain from the lung into the left innominate vein or coronary sinus
- A patent foramen ovale or ASD allows pulmonary venous blood to enter the atrium
What are the clinical features of total anomalous pulmonary venous circulation?
Volume and pressure overload leads to hypertrophy and dilation of the right heart
Dilation of the pulmonary trunk
Hypoplastic left atrium
Possible cyanosis due to the right to left shunt of the ASD
Describe left to right shunts.
- Increase pulmonary blood flow and volume
Pulmonary circuit is normally low flow, low resistance - The first response to the increased blood flow from the shunt is medial hypertrophy and vasoconstriction to maintain distal pressures and prevent pulmonary edema
- Prolonged increased pulmonary vasoconstriction induces obstructive intimal lesions (hyaline and hyperplastic arteriolosclerosis)
- Pulmonary vascular resistance reaches systemic levels and converts the left to right shunt to a right-to-left shunt
When pulmonary vascular resistance reaches systemic levels due to a left to right shunt and in response reverses to a right to left shunt what is this called?
This reversal is referred as late cyanotic congenital heart disease (Eisenmenger syndrome) and once irreversible pulmonary hypertension develops, structural defects are irreparable.
What are some examples of left to right shunts?
- atrial septal defect - ASD
- ventricular septal defect - VSD
- patent ductus arteriosis - PDA
Describe atrial septal defect.
- Abnormal fixed opening in the atrial septum caused by incomplete tissue formation that allows communication of blood between the left and right atria
- Not the same as a patent foramen ovale
What are the three types of ASD?
- Secundum (90%): result from deficient or fenestrated oval fossa near the center of the atrial septum
- 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 the clinical features of ASD?
- Left to right shunt due to lower pulmonary vascular resistance and greater distensibility of the RV
- Increased pulmonary blood flow produces a murmur
- Do not become symptomatic before age 30 and irreversible pulmonary HTN is unusual
- surgical or catheter based repair is possible and prevents complications
What are some complications of ASD?
- heart failure
- paradoxical embolism
- irreversible pulmonary vascular disease
Describe a patent foramen ovale.
- During fetal life the foramen ovale (a small hole in the atrial septum at the oval fossa) allows oxygen rich blood from the placenta to bypass the underinflated lungs
- After birth is forced shut due to increased blood pressure on the left heart in 80% of people
- 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
- There is a small possibility of a paradoxical embolism
Describe a ventricular septal defect (VSD)?
- Most common form of congenital cardiac anomaly, also common with Trisomy 21
- Are associated with another congenital anomaly; only 20-30% occur in isolation
- Classified according to size and location
What are the classifications of VSD?
Classified according to size and location:
- Membranous interventricular septum: membranous VSD (90%)
- Below the pulmonary valve: infundibular VSD
- Within the muscular septum: may be multiple (swiss cheese septum)
What are the clinical features of VSD?
Clinical manifestation depends on the size and associated right-sided malformation:
1. Large VSD:
Difficulties from birth
Usually membranous or infundibular
Cause significant left to right shunting
Must have early correction
2. Small VSD: well tolerated and may close spontaneously
Describe a patent ductus arteriosus.
- In fetal circulation the ductus arteriosus shunts blood from the pulmonary artery to the aorta
- In PDA there is no spontaneous closure after birth
- Produces a harsh, machine like murmur
- 90% occur as an isolated anomaly
- 10% associated with VSD, coarctation of the aorta or pulmonic or aortic valve stenosis
Describe the clinical features of patent ductus areteriosus.
- Clinical features depends on the diameter and the cardiovascular status:
Asympotmatic at birth
Narrow PDA does not affect child’s growth and development
Larger PDA start out as a left to right shunt but can lead to Eisenmenger syndrome - Closure should happen in early life
- May keep open with prostaglandin E
Describe an atrioventricular septal defect.
- Also called atrioventricular canal defect
- 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
- surgical repair is possible
What are the forms of atrioventricular septal defect?
- Partial ASVD:
Primum ASVD and cleft anterior mitral leaflet leading to mitral insufficiency - Complete ASVD:
Large combined AV septal defect and a large common AV valve (hole in center of the heart)
Communication of the four chambers leads to volume hypertrophy
1/3 of patients have Down syndrome
Name the obstructive congenital heart diseases.
- coarctation (narrowing) of the aorta
- aortic valvular stenosis
- pulmonary valvular stenosis
Describe coarctation of the aorta.
Common structural anomaly (narrowing of aorta)
Associated with Turner syndrome (XO)
What are the forms of coarctation of the aorta?
Infantile:
Tubular hypoplasia of the aortic arch proximal to a patent ductus arteriosus
Symptomatic in early childhood
Adult:
Discrete ridgelike infolding of the aorta just opposite of the closed ductus arteriosus (ligamentum arteriosum) distal to the arch vessels
Clinical manifestation of coarctation of the aorta depends on what?
The severity of the narrowing of the lumen and the patency of the ductus arteriosus:
Infantile form leads to manifestations early in life (right after birth)
High mortality rate without surgical intervention
Delivery of unsaturated blood through the PDA produces lower extremity cyanosis
Adult form
Children may go unrecognized until adulthood unless severe
Symptoms include
Hypertension in the upper extremities
Weak pulses and hypotension in the lower extremities
Claudication and coldness of lower extremities
Development of collateral circulation between pre and post coarctation arteries via enlarged intercostal and internal mammary arteries (notching seen on radiograph)
Surgical repair possible
Describe pulmonary stenosis.
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
Describe pulmonary atresia.
No communication between the right ventricle and lungs
Hypoplastic RV and ASD
Blood reaches the lungs through a patent ductus arteriosus
Describe aortic stenosis/atresia.
Congential narrowing occurs at 3 places:
1. Valvular
Cusps may be hypoplastic, thickened/nodular or abnormal in number
2. Subvalvular
Caused by thickened ring or collar of dense endocardial fibrous tissue below the cusps
Associated with a prominent systolic murmur
Pressure hypertrophy of the LV
Mild stenosis managed conservatively & antibiotics (prevent endocarditis)
3. Suprvalvular
An inherited form of aortic dysplasia
Ascending aorta is thickened causing luminal constriction
What happens in severe aortic stenosis/atresia?
Severe stenosis/ atresia causes obstruction to LV outflow and leads to hypoplasia of the left ventricle and ascending aorta (hypoplastic left heart syndrome)
Patent ductus arteriosus is required for life
Nearly always fatal unless surgically repaired
