Flashcards in Congenital Heart Disease Deck (65):
What is the definition of congenital heart disease?
It is a gross structural abnormality of the heart, great arteries or great veins present at birth that has actual or potential functional significance.
What are the most common causes of congenital heart disease?
They are most frequently multifactorial (genetic and environmental).
1. maternal rubella- PDA, PS, pulm artery stenosis
2. high altitude - PDA
3. FAS- VSD
4. maternal lithium
What is the live born prevalence of congenital heart disease?
Cases per year in US? World?
What is the recurrence risk for the defect in siblings or offspring?
4 to 9 per 1000 births (0.4-0.9%)
32,000 cases a year in the US
1.5 million cases worldwide
This does NOT include bicuspid aortic valve which is in 3%
Siblings or offspring: 2-10% so there is some genetic component, although it is usually a different defect
What percent of people with congenital heart defects survive to adulthood?
What is normal fetal circulation?
Gas exchange takes place in the placenta.
Blood flows from the umbilical vein to the IVC.
It goes to the RA and then RV.
Lungs are collapses and resistance is high so 90% of blood leaving the RV is directed away from the lungs.
RV-> pulmonary artery-> ductus arteriosus-> descending aorta -> placenta
Some blood from the RA goes to the LA via foramen ovale.
What changes happen to fetal circulation at birth?
The placenta is eliminated from circulation doubling systemic vascular resistance.
The lungs inflate decreasing pulmonary vascular resistance and pulmonary flow increases 8-10 fold
Flow across the ductus arteriosus reversed (because now the pulmonary arteries are less resistant than the descending aorta. DA starts to close at birth and should be gone by 24 hours.
Because more blood flowed to the lungs, more gets returned to the LA increasing the pressure, closing the flap (septum primum) of the foramen ovale.
What is a shunt?
What do they result from?
a congenitally abnormal connection between:
1. chambers of the heart (ASD, VSD)
2. a chamber and a great artery (TA)
3. between 2 great arteries (PDA)
They come from:
1. patency of normal fetal structure (patent FO, DA)
2. faulty embryogenesis (septal defects)
What determines the direction of blood flow through a shunt?
The relative distal resistance NOT the defect itself.
Resistance to flow is related to the presence of intracardiac obstructions and levels of pulmonary/systemic resistance.
Ex. VSD, ASD- left to right because pulmonary vascular resistance is less than systemic vascular resistance UNLESS there is severe hypertension that increases pulmonary vascular resistance. Then the shunt can reverse.
What is left-to-right shunting?
Is it cyanotic? Is there an O2 step up or step down?
What determines whether a shunt is hemodynamically significant?
It is when oxygenated blood from the left side of the heart moves to the right side and mixes.
This is called an "O2 step up" in the O2 content and saturation of blood. It is acyanotic.
Qp>Qs by 1.5 to 2x then the shunt is hemodynamically significant.
How can arterial saturation be measured to see if there is a step up?
cardiac cath can measure O2 saturation in the right chambers of the heart
What is right-to-left shunting?
Is it cyanotic? Is there an O2 step up or step down?
It is when desaturated blood moves from the right side of the heart to the left side.
It shows a "Step down" in oxygen saturation to the chamber it goes to.
The person will be cyanotic and will have a systemic O2 saturation of less than 95%
How can we tell a cardiac shunt vs. a pulmonary V/Q mismatch?
if desaturation is caused by hypoventilation of V/Q mismatch, the arterial saturation will rise with inhalation of 100% O2.
If it is a cardiac shunt, it will not correct.
What is the difference between central and peripheral cyanosis?
Central- decreased O2 saturation due to:
1. inadequate alveolar ventilation (V/Q mistmatch, hypoventilation)
2. intracardiac shunt (R-L)
3. intrapulmonary shunt
Peripheral is an increased O2 extraction in peripheral tissues due to:
1. circulatory shock
What determines the severity of central cyanosis?
hematocrit and the degree of Hb desaturation
What are the initial diagnostic steps in evaluating a patient suspected of congenital heart disease?
1. physical exam
2. measure O2 saturations
These should be sufficient to determine if they are acyanotic or cyanotic and can widdle down the possibilities for what defect is present.
Furthre evaluation requires:
6. cardiac cath in some cases to firmly est. diagnosis
If your patient is suspected to have a congenital heart defect but has normal arterial saturation, what are the possible diagnoses?
1. obstructive valve lesions
2. L to R shunts
3. regurgitant valve lesions
If your patient is a cyanotic child, what are the most commonly encountered defects?
2. tricuspid atresia
3. truncus arteriosus
4. transposition of great arteries
5. total anomalous pulmonary venous return
If your patient is a cyanotic adult, what are the differential diagnoses for congenital heart defects?
2. Eisenmenger's syndrome (R-L shunt due to severe pulmonary vascular disease and hypertension)
What is the most common congenital defect (not including biscuspid aortic valve)?
(then ASD, PDA)
What are 3 of the most common L to R shunts?
VSD. ASD, PDA
An ASD can occur in several different locations in the atrial septum, but the most common defect (75%) occurs where?
ostium secundum - middle portion of the septum (near fossa ovalis)
What are the pressure changes associated with an atrial septal defect in the:
3. main pulmonary artery
4. pulmonary vessels
5. left atrium
What are the 5 main areas where an ASD can occur?
1. superior sinus venosus defect
2. oval fossa defect (ostium secondum)
3. inferior sinus venosus defect
4. coronary sinus defect
5. AV septal defect (ostium primum)
What chambers are enlarged in an ASD?
3. pulmonary arteries
How do RA and LA pressures compare in an ASD?
there is no pressure gradient- they are equal
When do patients usually present to a physician for an ASD? What is their complaint?
They present at 40 or 50 complaining of problems associated with enlarged right heart:
1. palpitations (a fib)
2. CHF- JVD, edema, fatigue
What is the cardinal finding on the physical exam that is pathognomonic for ASD?
A widely fixed split second heart sound because P2 will be consistently delayed.
On inspiration, thoracic pressure drops and RV filling is increased which delays emptying and prolongs P2.
On expiration, more blood is shunted over to the right, so the P2 is still delayed.
Where and when is the murmur of ASD heard?
What is the sound contributed to?
It is heard over the pulmonary area in systole due to increased volume of flow out of the pulmonary artery.
(THE SOUND DOES NOT COME FROM THE BLOOD MOVING FROM LA TO RA)
What is seen on CXR and EKG for ASD?
CXR- increase RA, RV, pulmonary vasculature (lung markings = a sign of flow)
EKG- RAD (enlarged RV), RBBB (dilation causes delay in depolarization)
When should you do surgery on an ASD?
How is surgery performed?
If Qp is 1.5 to 2 times greater than Qs AND
as long as severe pulmonary vascular disease is not present.
There can be surgery or an occluder device inserted by catheter system. The choice depends on defect size and location.
Where do most VSD occur?
75% occur in the membranous portion of the septum (near A and T valves) and are called perimembranous defects
What are the pressure changes associated with VSD in:
3. main pulm artery
4. pulmonary vessels
2. n/a or slight increase
What drives blood from L to R in a VSD?
The pressure gradient between LV and RV (this is different from ASD where there is no pressure gradient btw LA and RA)
What is notable on auscultation of a heart with VSD?
There is a loud holosystolic murmur associated with the blood moving from LV to RV in systole.
It is accompanied by a thrill.
Murmur can be heard at 2-6wks of life and is detected early in childhood. It can close spontaneously.
What determines the significance of a VSD?
The size of the shunt.
Small shunts- loud murmur but no hemodynamic stress on the heart. (normal EKG, CXR)
Large shunts - LA and LV receive volume overload reflected by LV hypertrophy on EKG and cardiomegaly on CXR.
What secondary syndrome can arise from VSD?
Eisenmenger syndrome- severe pulmonary vascular disease reverses the shunt to R to L and the baby/child can become cyanotic
When is surgery recommended for a VSD?
If the L to R is significant (Qp is 2x Qs) and as long as pulmonary vascular disease is not present.
All patients with VSD need prophylaxis against bacterial endocarditis even with small shunts
Tricuspid, mitral regurgitation and VSD all have holosystolic murmurs. How do you differentiate them?
Tricuspid is heard at left lower sternal border and varies with respiration
Mitral is heard at apex
VSD is heard at LL sternal border but does NOT vary with respiration.
Normally the DA closes soon after birth and fibroses to form _________________. If this fails to occur, the PDA will permit blood to shunt from ___________ to _________.
If this fails to close, the PDA will permit blood to shunt from the aorta to the pulmonary artery.
The effects will be similar to VSD.
What are the pressure effects of PDA on:
3. main pulm artery
4. pulmonary vessels
If the PDA shunt is small, what do you see on EKG and CXR?
What if the shunt is large?
If it is small, there will not be any hemodynamic burden on the heart and CXR and EKG will be normal
If the shunt is large, there will be volume load on LV and LA
What are physical exam findings that can be found with a large PDA?
Can compress the laryngeal nerve and cause hoareness (similar to thoracic AA)
What is the cardinal finding in children and adults that is pathognomonic for PDA?
continuous murmur because Aortic pressure > Pulmonary Artery pressure in systole and diastole, so blood will be continuously shunting.
The murmur begins at 2-6 wks in systole and by 6 months, it will be continuous.
When is surgery recommended for PDA?
All patients regardless of size of PDA because they are at a risk for endocarditis or endarteritis.
What is coarctation of the aorta?
an area of narrowing within the aorta that results in a pressure gradient across the area of narrowing.
BP will be elevated in vessels proximal to the coarctation and decreased (maybe even absent) distal to the coarctation.
What are the pressure changes caused by coarctation in the:
3. Pulm artery
4. pulm vessels
None of them change except the LV and aorta
What is though to be the cause of coarctation?
As the ductus arteriousus retracts and fibroses, it constricts the aorta a little bit
What are the notable findings on physical exam that point toward coarctation?
1. elevated BP in upper extremities and hypotension in lower extremities
2. delayed timing btw radial and femoral pulses
3. systolic murmur heard in the back over the area of the coarctation
4. murmurs associated with bicuspid aortic valves
What do the EKG and CXR show for coarctation?
EKG- can be normal or show LVH
CXR- enlarged LV, 3-sign (curve in aorta), rib-notching in adults from collaterals
What 3 techniques are used to detail anatomy and decide if an intervention should proceed?
What are options for intervention?
3. cardiac cath- gradient over 30-40mmHg across the coarctation requires intervention
Surgery to correct coarctation or balloon aortoplasty and stenting
What are the 4 things that make up the tetralogy of Fallot?
Is it considered a Shunt or obstructive defect?
1. ventricular septal defect
2. overriding aorta (communicates with R and LV)
3. pulmonic stenosis (obstruction to outflow path)
4. RV hypertrophy
It is both a shunt and obstructive defect
How does LV and RV pressure gradients differ btw:
1. LV >> RV which is what causes the shunting
2. LV = RV
Describe the shunting in TOF.
LV and RV have equal pressure. The RV has an obstructed outflow tract, so blood will flow from the RV to the aorta (which connects to both RV and LV ).
This causes cyanosis
What are the TOF associated pressure changes in:
3. pulm artery
4. pulm vessels
1. n/a or slight increase
What is the "natural history" of TOF?
1. cyanosis in first year of life with clubbing
2. squatting child to increase systemic pressure to shunt blood to pulmonary
3. spells of worsening cyanosis, decreased intensity of murmur, and loss of consciousness
What is heard on auscultation of someone with TOF?
1. harsh systolic murmur with ejection click over the pulmonary region due to the obstructed pulmonary artery
2. single second heart sound (aorta overwhelms pulmonary)
How do you differentiate the harsh systolic murmur of TOF from that of pulmonary stenosis?
TOF person will be blue.
other than that the murmurs are very similar.
What is seen on EKG and CXR for someone with TOF?
CXR- enlarged RV, small pulmonary arteries, decreased lung markings due to decreased flow
"boot shaped heart"
What is performed in infancy on babies with TOF?
palliative shunts to increase pulmonary flow and decrease degree of cyanosis
Describe Eisenmenger Reaction.
What is the impetus?
What are the morphological changes?
With L to R shunts (mostly VSD and PDA) the sustained exposure of the pulmonary vessels:
1. systemic arterial pressures
2. increased flow
over years will lead to morphological changes in the pulmonary vasculature such as:
1. arteriolar medial hypertrophy
2. intimal thickening/fibrosis
3. capillary occlusion and obliteration
This increases pulmonary vascular resistance that is IRREVERSIBLE
When PVR = SVR the shunt reverses to R to L and the person becomes cyanotic
Why must surgery be performed in a person with L to R shunt before the onset of Eisenmengers?
Eisenmengers is irreversible and permanent.
Surgery after its onset has an unacceptably high mortality rate and does not reverse the pulmonary artery vascular disease
What are the 5 major complications someone with Eisenmengers is prone to?
1. renal dysfunction
4. bleeding disorders
5. paradoxical embolism due to R to L shunt
What do patients with chronic cyanosis develop?
compensatory rise in hematocrit and RBC mass to increase O2 carrying capacity.
This results in improved delivery of O2 to tissues despite arterial desaturation
What are the 3 types of Echo used in assessment of congenital heart defects? What does each focus on?
1. TEE/TTE- visualize anatomy, function of chambers, intracardiac communications
2. Contrast echo- IV injection of saline to detect small R to L shunts by observing appearance of microbubbles in left heart chambers
3. Doppler Echo- estimates velocity of blood flow and evaluates obstructive lesions, pressure gradients