SM 147a/148a - CHD Pathology, Pathophysiolgy (congenital) Flashcards
What is the equation that allows us to quantify the severity of a cardiac shunt?
Assume O2 uptaken by the lungs = O2 delivered to the tissues
If there is no shunt Qpulmonary/Qsystemic = 1
(Sat refers to O2 saturation)
List 3 indications for surgical closure of a cardiac shunt
- Failure to thrive in the context of increased respiratory rate
- The pressure drop through a VSD or PDA is low; this implies that RV pressure is as high as LV pressure, which increases the risk of pulmonary HTN. Repair must be completed before PVR rises/Eisnenmenger physiology manifests
- The flow through a VSD or PDA is high (QPulm/QSys >1.5); in this case, the LV must work to accomodate the extra flow through the pulmonary circuit. This can cause LV dilation, and increase the risk of dysfunction and failure
If a patient has a patent ductus arteriosus, which chamber will pump the extra blood?
LV
-> LV dilation due to volume overload
Risk of long-term failure
What size ventricular septal defects will close spontaneously in the first few years of life?
This increases the risk of which cardiac pathology?
Small to moderate VSDs (< 5mm) will close spontaneously
Valve closure increases risk of infective endocarditis
In a patent ductus arteriousus, which direction would you expect blood to flow?
What are the effects?
Left (Aorta) -> Right (Pulmonary Artery)
- This will cause volume hypertrophy of the LA and LV
- Increased flow through the pulmonary circulation
- Increased return to the LA -> LV
End-stage pulmonary hypertension due to a L->R shunt is characterized by __________ physiology.
End-stage pulmonary hypertension due to a L->R shunt is characterized by Eisenmenger physiology
Increased pressure causes thickening of the _________ of heart valves,
while increased flow causes thickening of the __________ of heart valves.
Increased pressure causes thickening of the edges and line of closure of a heart valve,
while increased flow causes thickening of the entirity of a heart valve.
If a patient has an aortopulmonary window, which chamber will pump the extra blood?
LV
-> LV dilation due to volume overload
Risk of long-term failure
(An aortopulmonary window has the same physiology as a patent ductus arteriosus with a larger communication)
What is the equation to calculate systemic flow using oxygen saturation?
How can a Tet spell be treated rapidly in a person with unrepaired Tetralogy of Fallot?
Squat
This increases systemic vascular resistance to counteract pulmonary resistance
- Decreases R->L shunting
- Increases flow through the pulmonary circuit
- Increases O2 saturation of systemic outflow
Describe the differences in cyanotic an acyanotic Tetralogy of Fallot
Tetralogy of Fallot
- Cyanotic
- When pulmonary stenosis causes increased pressure in the right heart, such that the VSD is R->L
- Acyanotic
- Less pulmonary obstruction
- VSD is L-> R
- Systemic outflow is more oxygenated
What are the 4 types of aortic steosis that can be caused by congenital defects?
- Valvular level
- Supravalvular
- Subarotic stenosis
- Muscular
- Asymmetrical septal hypertrophy of the IV septum due to hypertrophic cardiomyopathy
Coarctation of the Aorta causes __________ hypertrophy of the ___________, and sometimes the ____________.
Coarctation of the Aorta causes pressure** hypertrophy of the **left ventricle** , and sometimes the **left atrium.
What causes ostium primum type atrial shunts?
Which structures are abnormal?
Endocardial Cushion Defect
- Tricuspid and mitral valves may be abnormal
- The shunt is confluent with the atrioventricular valves
- Regurgitation is possible
- -> Volume enlargement of the LV
Describe the abnormality in blood flow in a PAPVR (Partial Anomalous Pulmonary Venous Return)
Pulmonary veins partially drain into the RA, SVC, or IVC.
This causes the RV to work harder -> RV dilation
How can we estimate the pressure drop across a VSD?
Why would we want to do this?
Use ultrasound with doppler to measure the velocity across the VSD; use this to estimate pressure change
We want to do this to assess the need for surgical repair
-
If the pressure drop is high, the VSD is restrictive; high LV pressure is not communicated to the right side. This is good!
- However, if flow is high, there is a risk of LV dilation due to increased pulmonary return; surgery is indicated
- If flow is low, surgery is not indicated
- If the pressure drop is low, the VSD is communicating the high LV pressures to the RV. This increases the risk of pulmonary HTN. Surgery is indicated to close the shunt before Eisenmenger physiology develops
Is pulmonary hypertension associated with all shunts?
Why or why not?
Not always!
- All L-> R shunts increase pulmonary flow
- However, the pulmonary vascular tree can usually dilate to accomodate these increases
- Pulmonary hypertension arises due to…
- Large VSD (usually)
- Patent ductus arteriosus
- ASD (least commonly)
What is the difference between enlargement and dilation of a heart chamber?
Enlargement = Increase in volume of the chamber, unrelated to myocardial failure
Dilation = When elargement is attributed to heart failure
If the pressure drop across a VSD is high, is surgical reapair indicated? Why or why not?
If the pressure drop is high, the VSD is restrictive; high LV pressure is not communicated to the right side. This is good!
- If flow through the VSD is low due to high resistance, surgery is not necessary
- However, if flow is high due to low resistance, there is a risk of LV dilation, dysfunction, and eventual failure due to increased pulmonary return; surgery is indicated
What congenital defect results in RV outflow to the aorta, and LV outflow to the pulmonary artery?
d-Transposition of the Great Arteries
What might cause increased flow to the pulmonary vessels?
How do they react?
Any L->R shunt (ASD, VSD, PDA, PAPVR) will cause flow through the pulmonary vessels to increase.
- Pulmonary vascular resistance (PVR) will increase
- This may prevent the PVR from falling after birth
-
If the PVR > SVR, shunting will be reversed, leading to Eisenmenger syndrome/physiology/complex
- End-stage pulmonary hypertension
- Leads to cyanosis, because blood skips the pulmonary circuit entirely
Pressurized shunts (VSD, PDA) are more likely to cause vascular disease; they increased PVR early in life
List the 4 types of atrial shunts
- Fossa ovalus or secundum (common)
- Ostium primum
- Sinus venosus, aka proximal
- Coronary sinus (rare)
What are the 3 basic mechanisms of cyanosis?
- Arterial connections are reversed (Ex: D-Transposition of the Great Arteries)
- Atresia or severe hypolasia that blocks flow through the right or left heart
- Shunt between L & R heart + something that elevates pressure or resistance in the right heart above left sided pressure
In a child born with Tetralogy of Fallot, what causes a “Tet spell”?
Anything that causes more vigorous contraction (ex crying)
This causes the RV outflow tract to get even smaller
- Increases R->L shunting
- Decreases oxygenation (due to decreased flow through the pulmonary circuit)
- Further agitation
- Loss of consciousness