Pathophysiology of Congenital Heart Disease Flashcards
How does most of the blood proceed from the umbilical vein and why?
Umbilical vein -> ductus venosus -> IVC -> directly through foramen ovale -> LA -> LV -> aorta to oxygenate the head first
This is based on the direction of the jet stream hitting the right atrium, the most oxygenated blood will go through the patent foramen ovale
What blood reaches the pulmonary circulation and the lower extremities?
Venous blood from SVC coming back from the head will go into RV. A small amount will enter the pulmonary circulation, with the rest going through the PDA and mixing with the aortic blood for the head to give decently oxygenated blood to the lower extremities
When do symptoms of a congenital heart disease most often manifest?
When ductus arteriosus closes within first 10-15 hours of life, resulting in unfavorable conditions
Why is the fetal circulation described in terms of CVO (combined ventricular output)?
The amount of blood (stroke volume) pumped by the left and right ventricles is not equal - CVO is a better measure of cardiac output
- > RV generally pumps more blood and gives the extra through the PDA
- > in adults, SV is equal in left and right ventricle since circulations are in series
What provides the pressure surrounding the heart in fetal / adult circulation? Is this positive or negative?
Fetal - amniotic fluid - positive pressure
Adult - thoracic cavity - negative pressure
What factors maintain the aortic diastolic pressure?
Aortic valve
Elastic recoil of large arteries
What are the determinants of vascular resistance? What is it?
Resistance - the force opposing the movement of blood through the blood vessel
- Tube length
- Blood viscosity - determined by hemotocrit
- Radius of vessel - R^4!!
What chromosomal disorders are significant correlated with congenital heart disease (CHD)?
- Trisomy 21
- Trisomy 18
- Trisomy 13
- DiGeorge syndrome
- Turner syndrome
What is the definition of congestive heart failure and what types of things cause this in CHD?
Systemic CO is inadequate to meet metabolic needs of body.
- Poor ventricular function - severe obstructive lesions
- Abnormal distribution of cardiac output (VSDs)
What are some of the common symptoms of CHF in CHD?
Dyspnea on exertion
Frequent respiratory infections (esp. left-to-right shunts causing pulmonary edema)
Irritability / decreased feeding volumes, and growth failure
Tachypnea, tachycardia, and hepatomegaly (RAA activation)
What are some examples of CHDs with PDA dependent systemic circulation? Which way is the shunting of the blood in PDA? How will the patient present?
Hypoplastic left heart syndrome
Severe coarctation of aorta
Critical aortic stenosis
Shunting is right-to-left thru PDA (pump via RV)
Patient presents with cardiogenic shock upon PDA closure
What are some examples of CHDs with PDA dependent pulmonary circulation? Which way is the shunting of the blood in PDA? How will the patient present?
Pulmonary atresia
Critical pulmonic stenosis
Shunting is left-to-right thru PDA to get to lungs
Patient presents with severe cyanosis (blood not getting to lungs)
When does cyanosis become apparent? In what situation is this easy to detect?
When >5 gm/dL desaturated hemoglobin is present in blood
Normal blood is 2 gm/dL
Easy to detect with high hematocrit levels (polycythemia) -> less percentage O2 saturation decrease is needed to cause an absolute desaturation increase by 3 gm/dL
What is the general difference between central and peripheral cyanosis?
Central - Arterial O2 saturation is decreased
Peripheral - Blood flow to a local organ is decreased, causing cyanosis
How do central and peripheral cyanosis differ with respect to sites they will be seen, temperature of limb, clubbing / polycythemia, and improvement with local heat?
Central -> seen in mucous membranes of tongue / inside mouth, peripheral seen just on skin of distal extremities
Temperature of limb will be warm in central cyanosis (blood is able to reach, just deoxygenated), and cold in peripheral (decreased flow)
Clubbing / polycythemia will be present in central but not peripheral (transient in response to cold)
Local heat -> improves peripheral cyanosis with blood through and circulation, no effect on central
What is the hyperoxia test for cyanosis and how does it work?
Give patient 100% oxygen for 15 minutes. If arterial pO2 fails to increase more than 150 after 15 minutes, it suggests cyanotic heart disease (oxygen is sufficiency, but heart is not distributing blood adequately)
For mixing lesions, what is the optimal systemic arterial blood O2? What can be used to increase this number, and is this always better?
When pulmonary and systemic venous return are equal -> 80% (systemic = 60%, pulmonary = 100%)
Pulmonary blood flow can be increased via oxygen and PGE1 -> not always beneficial because it can cause hyaline membrane disease
Why does hypertrophic osteoarthropathy happen in cyanosis?
Same reason as polycythemia -> hypoxia causes growth factors to be released. In this case, capillaries are stimulated, and these growth factors cannot be inactivated in the lungs as well.
How does cyanosis predispose to strokes and cerebral abscesses?
- Lungs have a filtering function -> emboli from venous systemic circulation can be shunted directly to systemic circulation (paradoxical emboli)
- Increased blood viscosity due to polycythemia
What is the #1 risk factor for stroke in cyanotic heart disease? Why?
Iron deficiency anemia
- > microcytic RBCs are less deformable in microcirculation of CNS
- > greater stroke risk in presence of polycythemia
What is pulmonary vascular occlusive disease (PVOD) and when does it occur? How long does it take?
Increased resistance to pulmonary blood flow, occurs in left-right shunt conditions
Takes 1-2 years, possibly reversing the shunt to right to left and causing cyanosis
In the presence of a VSD -> Eisenmenger syndrome
What are the signs and symptoms of pulmonary vascular occlusive disease?
Exercise intolerance with cyanosis
Right heart failure
CNS events / strokes
Pulmonary hemorrhage w/ vascular changes (high pressure)
What is the result of non-cyanotic shunt lesions?
These are left-right shunts
Result is pulmonary congestion, as more blood enters pulmonary circulation than systemic circulation (regardless of shunt location)
What are the four main kinds of non-cyanotic shunt lesions?
- Atrial septal defect
- Ventricular septal defect
- Patent ductus arteriosus
- Common AV canal / AV septal defect
What murmur will ASD cause?
Asymptomatic pulmonary stenosis murmur due to relative increase of blood thru pulmonary artery (heart at LUSB)
How is ASD diagnosed and what is the prognosis? Main complication?
Diagnosed by Echo or TEE
Prognosis is good. Normal life expectancy w/o restriction.
Secundum ASD easily repaired by device
Main complication: Unoperated adults can have PVOD in 40+years
What congenital heart disease is especially more common among premature infants? When do symptoms develop? What happens to the left side of the heart?
Ventricular septal defect -> membranous portion is most common spot
Symptoms develop in first 6 months of life, as pulmonary vascular resistance drops in first 6 weeks
Left side of heart -> dilatation due to increased diastolic pressure from extra pulmonary flow
What are the physical exam findings of VSD? Include the heart sounds.
Holosystolic murmur which is larger with smaller hole
Diastolic murmur from increased flow across mitral valve
Loud S2 narrowly split (high pulmonary and systemic pressures (both will be 120 to make sure systemic circulation can be perfused))
Tachycardia, tachypnea, hepatomegaly from fluid overload and pulmonary edema
What will happen in terms of infections and growth in VSD patients?
Infections - recurrent, due to pulmonary edema
Growth - impaired, due to poor feeding since they don’t have the energy to do it (poor systemic blood flow)
What types of hypertrophy are seen in VSD?
LV hypertrophy - eccentric, due to volume overload
RV hypertrophy - concentric, due to pressure overload
When does Eisenmenger syndrome occur? Is it reversible?
Usually in the second decade
- > untreatable
- > pulmonary venous resistance exceeds systemic vascular resistance in the setting of a VSD
When should a VSD be repaired?
When CHF is not responsive to diuretics first, and does not spontaneous close
When pulmonary HTN persists >6 months
How does PDA present?
Same as VSD, symptoms depend on size of PDA
What syndrome is associated with common AV canal or atrioventricular septal defect? What is this condition basically?
Down syndrome (Trisomy 21)
Complete AVSD - primum ASD + inlet VSD (VSD at triscupid valve)
Some have just primum ASD with no VSD -> will not have pressure overload, just volume on right
What defect tends to exacerbate the situation in AVSD?
Volume overload is made worse by AV valve regurgitation (due to inlet VSD)
What are some examples of obstructive lesions in CHD?
- Coarctation of the aorta
- Aortic stenosis
- Pulmonic stenosis
- Hypoplastic left heart syndrome
Where does coarctation (CoA) tend to happen and what BP gradient is suggestive of this? What causes this / amount of significant stenosis?
50% or greater luminal narrowing opposite entry of PDA just distal to LSA, due to thickening of media
BP gradient of >20 from arm to leg is suggestive of this
What are the physical exam findings of coarctation?
Right arm hypertension with normal / low leg pressure
-> degree of hypertension dependent on amount of LV hypertrophy
Brachial-femoral pulse delay
Interscapular murmur of back due to collateral flow through intercostal arteries and ITA
How can CoA cause heart failure?
If severe enough -> LV cannot hypertrophy, and infants go into cardiogenic shock where left heart fails.
Causes LV volume overload and pulmonary congestion as a result
Also, in chronic coarctation, LV hypertrophies which can lead to ischemia and HF
What are the surgical and nonsurgical treatments of coarctation and what age groups are they used in?
Surgical - Left lateral thoracotomy - must be used in infants
Nonsurgical - Balloon catheterization or stenting - older children + adolescents only (will outgrow the stent in young children)
What is the general cause of cyanotic heart disease / what type of lesions are they? How does systemic flow relate to pulmonary?
Right-to-Left Shunt lesions
- > associated with a right heart obstruction
- > deoxygenated blood bypasses pulmonary circulation to reach systemic system
- > systemic flow GENERALLY exceeds pulmonary flow, causing cyanosis
What are the five T’s of cyanotic heart lesions? Give on more.
- Tetralogy of Fallot
- Transposition of the Great Arteries (TGA)
- Truncus Arteriosus
- Total Anomalous Pulmonary Venous Return (TAPVR)
- Tricuspid Atresia
- Hypoplastic Left Heart Syndrome
Does cyanotic congenital heart disease always decrease blood flow to the pulmonary bed?
No -> it is increased in HLHS, TGA with VSD, truncus arteriosus, and TAPVR
What is the most common cyanotic heart defect and what conditions is it associated with?
Tetralogy of Fallot
Associated with:
DiGeorge
All three trisomies
Alagille syndrome
How do infants vs adults typically present with Tetralogy of Fallot?
Infants - heart murmur due to VSD & pulmonary stenosis
Adults - shortness of breath due to cyanosis
Other than the holosystolic murmurs from VSD and pulmonic stenosis, what will be characteristic of the S2 heart sound in Tetralogy of Fallot?
S2 is loud and not split
-> VSD equalizes ventricular pressures so semilunar valves close at the same time
What are TET spells? What causes them?
Hypercyanotic spells in Tetrology, where there is a sudden increase in right-to-left shunting, causing hypernea and even unconsciousness
Caused by an increase in pulmonary vascular resistance (crying) or decrease in systemic vascular resistance (fever, exercise)
What will happen to the heart murmurs during a Tet spell?
Pulmonary Stenosis murmur disappears -> due to decreased blood blow through pulmonary circulation (increased resistance, or decreased resistance thru systemic system shunts blood flow)
How do you manage Tet spells?
- Put knees to chest, increasing vascular return
- Oxygen to decrease lung resistance, and morphine to calm the patient.
- Volume expansion with IV fluids
- Use of vasoconstrictors (i.e. epinephrine) to increase systemic vascular resistance, putting more flow thru the pulmonary vasculature
What is the most common cyanotic congenital heart lesion that actually presents as a neonate? What infants is it seen most commonly in?
Transposition of the great arteries
Seen most commonly in diabetic mothers
What is the most common associated anomaly with TGA and why?
VSD -> shunting of blood allowing mixing is required for life, as pulmonary trunk is attached to the left ventricle, and aorta to right. In order for life to occur, need VSD, ASD, or PDA.
What heart sound does a PDA present with?
A mechanical, washing-machine like sound best heart between aortic and pulmonic areas
How are the vessels seen in relation to eachother in TGA? How will the patient be on physical exam?
Pulmonary artery leaves the LV, will be posterior
Aorta leaves the RV, will be anterior
Physical exam: central cyanosis with tachypnea
Who is Truncus arteriosus associated with? how many valves will there be and what arteries come from it?
Associations: Maternal diabetes and DiGeorge syndrome
Valves: One semilunar valve with trunk supplying systemic, pulmonic, and coronary circulations
What will EKG show for Truncus arteriosus? What determines the O2 saturation?
EKG: Biventricular hypertrophy (has to push against both circulations with equal pressure)
O2 saturation determined by pulmonary blood flow
What lesion is always present with Truncus arteriosus? What valvular abnormalities exist?
VSD - since it is a failure of aorticopulmonary septum, which also forms membranous IV septum
Truncal valve is often regurgitant / stenotic
What condition will develop overtime if Truncus arteriosus is untreated?
Eisenmenger syndrome -> due to increased pulmonary arterial pressure to match systemic pressure
-> cyanosis and HF symptoms will develop overtime
How is a Truncus arteriosus typically repaired?
Close the VSD to the truncus, use truncus as new aorta.
Disconnect the Pulmonary artery from the trunk, use a conduit to run from PA to RV.
What happens in tricuspid atresia? What defects are required for viability?
Systemic venous return comes to RA, but cannot get to RV due to atresia of tricuspid valve.
Requires an ASD (PFO) and VSD so that blood can reach pulmonary trunk to get circulated. Mixing of blood occurs in LA / LV.
What are the EKG chamber size findings in tricuspid atresia?
Left axis deviation:
- Right atrial enlargement
- Left atrial enlargement
- LV hypertrophy
- Hypoplastic RV
What are the defects in hypoplastic left heart syndrome (HLHS)? What does the pumping of the blood?
LA / LV do not form properly, causing:
Stenotic or atretic aortic / mitral valves, and hypoplastic ascending aorta from lack of blood flow
Pumping of the blood is done entirely by RV (combined ventricular output)
How is the systemic circulation supplied in HLHS if aortic valve is stenotic + ascending aorta is hypoplastic?
PDA is required for life
If closed -> cardiogenic shock, multi organ failure
Other than PDA, what other defect is required for life in HLHS? What occurs if there is too much resistance to this?
Atrial septal defect, to allow pulmonary venous return to LA to make it back to the RA / RV for mixing and expulsion
If too much resistance thru this hole, it’s more resistance for RV to push against to send blood thru (increases pulmonary vascular resistance)
-> may cause right heart failure
