How common is the prevalence of some form of congenital cardiac malformation? During which weeks of development does the heart form? How is this significant?
Around 1% have some type of cardiac malformation (fairly common) Heart develops between 3-8 weeks. Significant because mother may not know she is pregnant yet. May be drinking, smoking, etc.
In what % of cases is the pathogenesis of heart defects known? What are some known environmental causes of heart defects?
Only 10% have a clear etiology, 90% are unknown.
Some known causes: maternal diabetes, congenital rubella infection, teratogen exposure
What are some genetic / chromosomal abnormalities that often result in congenital heart defects? (4 examples are listed)
Trisomy 13 (Patau), 18 (Edwards), 21 (Down)
Turner Syndrome (45, X0)
Although surgery has been effective in correcting congenital heart defects, why is the repaired heart never quite the same as a normal heart? What are some risks later in life?
The surgery may cause scarring, and the defect itself may have caused irreversible myocardial hypertrophy and cardiac remodeling
May result in arrhythmias, ischemia, hyperviscosity, and other myocardial dysfunction later in life
What are the 5 most common congenital defects? (don't worry about it too much, from book not lecture)
- Ventricular Septal Defect (42%) - however, most close spontaneously and they are more rare in adults than ASD
- Atrial Septal Defect (10%) - less common but rarely close spontaneously
- Pulmonary Stenosis (8%)
- Patent Ductus Arteriosus (7%)
- Tetralogy of Falot (5%)
What are the 3 groups of Congenital Heart Defects?
Right-to-Left Shunts: "Blue Baby Syndromes" - deoxygenated blood in systemic circulation
Left-to-Right Shunts: "Non-Blue Baby Syndromes" - some pre-oxygenated blood in pulmonary circulation (may still be cyanotic as it gets more severe)
Obstruction: there's a narrowing somewhere
Left-to-Right Shunts: Which side of the heart hypertrophizes, why? What is its "point of no return"?
Right side hypertrophizes because it receives too much blood, has to compensate for it. May have pulmonary edema because of the high pressure in lung circulation.
- Point of no return: Eisenmenger Syndrome "shunt reversal" where it now goes right-to-left. Due to chronic pulmonary hypertension, pulmonary circuit endothelium thickens, resistance increases and blood flows backwards through the shunt, and it's irreversible. Baby then becomes cyanotic. Should do surgery before it happens.
What are 3 examples of left-to-right shunts? (will detail them in other cards)
Atrial Septal Defect (Patent Foramen Ovale)
- Ventricular Septal Defect
Patent Ductus Arteriosus (Botelli duct)
Note all of them are just foramen where blood flows from the high pressure left system to the low pressure right (simple mechanism compared to the right-to-left shunts). The severity of all of them depends on the size of the hole, and most complications are related to pulmonary hypertension and R side hypertrophy.
What are the 2 main kinds of atrial septal defects (from lecture + Robbins)?
Which part is defective?
Ostium secundum: 90% of cases, have patent foramen ovale because second septum does not fully form (insufficient)
Ostium primum: remaining 10% of cases. This is a fixed opening in septa because spetum primum doesn't develop. Occurs more inferiorly.
What are the 2 types of ventricular septal defect?
Absence of Membranous Part: often part of complex cardiac malformation (only 20-30% of VSDs occur in isolation). If it is an isolated defect, it's called a Roger defect
Underdevelopment or Holes in Muscular Part. Causes high-pressure bloodstream from left to right, and the blood hits the endocardium causing damaging "jet lesions" which are prone to infective endocarditis
How does the Botelli duct normally close?
What happens if it doesn't?
Permits blood to flow from pulmonary trunk to aorta during fetal stage, but after birth it closes due to:
- Increased arterial oxygenation
- Decreased pulmonary vascular resistance
- Declining local levels of PGE2 (I think Matolcsy said "released" but it's decreased in Robbins/elsewhere)
If it doesn't close -> aorta to pulmonary artery shunting, pulmonary hypertension, eventually Eisenmenger syndrome.
Can make ligature to close it or administer prostaglandins inhibitors like NSAIDS
3 examples of Right-to-Left Shunts:
(only from lecture; but there are others)
- Tetralogy of Falot
- Transposition of the Great Arteries
- Truncus Arteriosus
What are the clinical consequences of right-to-left shunts?
Cause cyanosis from hypoxia which also leads to
- Clubbing of tips of fingers/toes
- Compensatory overproduction/hyperplasia of RBCs (polycythemia) causing hyperviscosity, which increases risk for venous thrombosis
- Pardoxical embolism risk
What are the 4 Defects of Tetralogy of Falot:
Upper ventricular septal defect (membranous part)
Dextra (right-side) position of aorta - (with "overriding of the VSD by the aorta")
Pulmonary trunk stenosis (narrowing)
Hypertrophy of the right ventricle (compensatory) - sometimes thicker than the left ventricle
Tetralogy of Falot can cause shunting in various directions (right to left or left to right), what does this depend on?
Depends on Degree of Pulmonary Stenosis
- Severe stenosis -> right to left shunt (cyanotic baby)
- Moderate/Medium stenosis -> bidirectional shunt
- Weak stenosis -> left to right shunt
What occurs in Transposition of the Great Arteries?
What is required for them to be compatible with life?
As the name says, the aorta is coming from the right ventricle, and the pulmonary trunk is coming from the left ventricle
If some sort of shunting still exists (like VSD), they may be compatible with life for a long enough time (a few days) to perform surgery. May try to keep the ductus arteriosus open by giving prostaglandins to maintain a shunt.
Surgery involves catheter placement to help direct blood flow
What is (Persistent) Truncus Arteriosus?
Missing separation between pulmonary trunk and aorta
(remember they grow together, then are separated by aorticopulmonary septum)
Causes right sided hypertrophy to compensate for higher pressure, cyanosis due to hypoxia, heart failure
May be associated with other defects like DiGeorge syndrome
What are the 2 kinds of obstructive congenital heart defects?
- Ones inside the heart: tricuspidal stenosis is the most common, but also mitral stenosis or complete closure (atresia)
Outside the heart: Aortic Coarctation - most important one
What are the two kinds of Aortic Coarctation?