14. TOF- Exam 4 Flashcards
TOF is Classically understood to involve ___ anatomical abnormalities
4
–3 are congenital, 1 is acquired
TOF is what % of all cyanotic heart defects
10%
TOF is the most common cause of what syndrome
blue baby syndrome
TOF has a very high association with what syndrome
Down’s Syndrome
what are the 4 defects of a TOF
A large VSD
Pulmonary stenosis (RVOT obstruction)
An overriding aorta
Right ventricular hypertrophy (RVH)
TOF, simply put is a …
anterior-lateral displacement of the infundibular septum
describe TOF embryology
Aorta and PA start as a single tube (truncus arterosis) divided by the spiral septum. The spiral septum grows down and attaches to the ventricular septum which:
◦Isolates the ventricles
◦Isolates the aorta and the pulmonary artery
the Truncus Arteriosus becomes the
Aorta
the Conus Cordis becomes the
Pulmonary Artery
if the spiral septum is not midline, but shifted towards the RIGHT side of the heart… this would cause what?
◦The aorta opening to be large
◦pulmonary opening to be small
◦Spiral septum would miss the septum
if the spiral septum is not midline, but shifted towards the LEFT side of the heart… this would cause what?
◦The aorta opening to be small
◦pulmonary opening to be large
◦Spiral septum would miss the septum
with an aortico-pulmonary septum defect- is it better to have aortic or pulmonary stenosis
better to have pulmonary stenosis
–aortic stenosis can be fatal
Factors that increase the risk for this condition during pregnancy include what 5 things
- Alcoholism in the mother
- Diabetes
- Mother > 40 years old
- Poor nutrition during pregnancy
- Rubella or other viral illnesses during pregnancy
TOF w/Pulmonary Atresia=
TOF with PA (pseudotruncus arteriosus) is a severe variant in which there is complete obstruction (atresia) of the RVOT, causing an absence of the pulmonary trunk during embryonic development
describe shunting and flow of a TOF w/ PA
blood shunts completely from the right ventricle to the left where it is pumped only through the aorta. The lungs are perfused via extensive collaterals from the systemic arteries, and sometimes also via the ductus arteriosus
Pentalogy of Fallot=
TOF with the addition of an ASD
why does a TOF result in cyanosis
TOF results in low O2 of blood due to the mixing of blood in the LV via the VSD and preferential flow of the mixed blood through the aorta (because of the obstruction to flow through the pulmonary valve)
-In TOF w/PA this R→L shunt is significantly worse
how does a Classic TOF look on an X-ray
boot shaped heart
What might be the bodies response to the low saturations and decreased pulmonary blood flow?
Elevate the hematocrit, it is not uncommon for these children to have hematocrits >50 %
what is the primary symptom of TOF
low blood oxygen saturation with or without cyanosis
If the baby is not cyanotic then what is it sometimes referred to as a
pink tet
Periods of severe hypoxic spells are called what
tet spells
Clubbing of fingers=
skin or bone enlargement around the fingernails
what do children do during episodes of cyanosis
squat
Children having a TET spell may have what 4 symptoms:
- Rapid, deep breathing.
- Fainting/loss of consciousness.
- Increasing cyanosis of the lips, tongue and nailbeds
- Irritability or uncontrolled crying
what are the 6 steps of the TET spell cycle
- acute decrease in SVR
- Increased R–> L shunt across VSD
- Deceased PaO2 + pH and Increased PaCO2
- Increased hyperpnea (deep/rapid breathing)
- Increased negative intrathoracic pressure
- Increased VR to the RA — then repeats starting at #2
why do children either Squat or go to the knee chest position during a TET spell
will increase aortic wave reflection=
-increasing pressure on the left side of the heart, decreasing the right to left shunt (think clamping distal to outflow)
◦thus decreasing the amount of deoxygenated blood entering the systemic circulation.
Surgical Treatment for TOF: Palliative surgery or Corrective Surgery for what conditions
◦TOF
◦TOF w/PA or absent pulmonary valve
The condition was initially thought untreatable until what happened?
surgeon Alfred Blalock, cardiologist Helen B. Taussig, and lab assistant Vivien Thomas at Johns Hopkins University –formed an anastomosis between the subclavian artery and the pulmonary artery
Palliation Shunts used:
BT or Central shunt
Currently, Blalock-Thomas-Taussig shunts are NOT normally performed on infants with TOF except for what cases?
severe variants such as TOF with pulmonary atresia (pseudotruncus arteriosus).
Central Shunt=
ascending aorta to main pulmonary artery
Central Shunt advantages= (6)
- Applicability to small children with small peripheral vessels
- Prevention of distortion of pulmonary arteries
- Provision of equal pulmonary blood flow to both lungs
- Lower occlusion rate (compared with the CBTS or MBTS techniques)
- Avoidance of subclavian artery steal
- Ease of closure during corrective repair
when is Corrective Surgery performed?
first few months of life
why is Corrective Surgery preferred over palliation
Less RV hypertrophy
Total repair of TOF initially carried a ____ mortality risk. This risk has gone ____ steadily over the years. Surgery is now often carried out in infants
high
down
1 yr
5%
how is the surgery of total repair of TOF designed
(1) Relieve the RVOT stenosis by careful resection of muscle
(2) Repair the VSD with a Gore-Tex patch or a homograft patch.
- -Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy.
how is the surgery of total repair of TOF designed
(1) Relieve the RVOT stenosis by careful resection of muscle
(2) Repair the VSD with a Gore-Tex patch or a homograft patch.
- -Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy.
after surgery for a TOF, what is needed due to large VSD patch
Pacing wires
where is the Intracardiac incision for a TOF repair? whats the disadvantage to this
right atriotomy or right ventriculotomy-(depending on the severity RVOT obstruction)
◦This will disrupt the conduction system
CPB Considerations for TOF: Incision
Median sternotomy
CPB Considerations for TOF: Arterial + Venous Cannula
Arterial: Aortic
Venous: Bicaval
CPB Considerations for TOF: Temperatures
Hypothermia: Mild to Moderate
CPB Considerations for TOF: Cardioplegia
Antegrade
multiple doses due to Ao-pulmonary collateral circulation
CPB case notes for TOF: The heart warms quickly so be prepared for …
LOTS of CP
CPB case notes for TOF: Your __ was stressed pre-op be careful with it
RV
CPB case notes for TOF: Be careful of ________ post-op since low BP can worsen RV dysfunction
vasodilators
CPB case notes for TOF: May need ____ to keep BP ↑
ionotropes
CPB case notes for TOF: _____ and _____ pressures may stay high post-op for a while
CVP and RV
CPB case notes for TOF: Due to RV dysfunction _____ is a possibility
ECMO
CPB case notes for TOF: Make sure you know how you are going to deal with high hematocrits before going on CPB (_________)
pull off volume
CPB case notes for TOF: Be careful with MUF since it will be easy to get the hct at _____ (most likely will add volume pulled off when your warming)
50%+
Double Outlet Right Ventricle (DORV)=
- -The Aorta and PA both originate from the RV and blood from the LV passes across a VSD into the RV to reach the great arteries.
- -Pulmonary circulation is very high pressure with increased blood flow (as with a large VSD).
CT=
conal tissue
The anatomic dysmorphology of DORV can vary from that of ___ on one end of the spectrum to ___ on the other end
TOF
TGA
The majority of DORV cases occur with what other defect? how does this make it behave?
pulmonary stenosis and VSD
–behaving as a severely cyanotic TOF
how are DORV classified/diagnosed?
Classified according to the VSD location
-One of the ways that DORV is diagnosed is by the location of the VSD
DORV symptoms (6)
- Baby tires easily, especially when feeding
- Bluish skin color (the lips may also be blue)
- Clubbing on toes and fingers
- Failure to gain weight and grow
- Peripheral edema
- Dyspnea
Complications from DORV may include what 3 things
- Congestive heart failure (CHF)
- Pulmonary hypertension
- Irreversible damage to the lungs due to untreated high blood pressure in the lungs
what are the 4 types of DORV
Sub-aortic VSD
Sub-pulmonary VSD (Tausigg-Bing)
Doubly committed VSD
Non-committed VSD
what type of DORV is most common
Sub-aortic VSD
Sub-aortic VSD pathophysiology depends on what
the degree of PS.
- -With PS the pulmonary blood flow is decreased with variable cyanosis like a TOF
- -In the absence of PS, the pulmonary blood flow is increased, resulting in heart failure like a VSD
Sub-pulmonary VSD (Tausigg-Bing)=
- The PA preferentially receives LV oxygenated blood
- Desaturated blood from the RV streams to the aorta
Sub-pulmonary VSD (Tausigg-Bing) is similar to what
TGA
Doubly Committed VSD=
The infundibular septum is absent leaving both aortic and pulmonary valves related to the VSD.
–Clinical features depend on the presence or absence of pulmonary stenosis
Non-committed VSD=
remote from the aortic and pulmonary valves.
–Most patients with non-committed VSD undergo single ventricular w/palliative strategies.
Non-committed VSD=
remote from the aortic and pulmonary valves.
–Most patients with non-committed VSD undergo single ventricular w/palliative strategies.
Non-committed VSD has what kind of appearance
univentricular
Two basic types of repair for DORV=
ANATOMIC repair
UNIVENTRICULAR repair
ANATOMIC repair=
restores a circulation with two ventricles
UNIVENTRICULAR repair=
only one ventricle is functional
Surgery: DORV with Sub-aortic VSD=
Intra-ventricular tunnel (LV→VSD→ Ao)
Low risk
Age 6 months
Rastelli procedure for PS
Intra-ventricular Tunnel=
- -Channels (tunnel/patch )LV blood through the VSD to the aorta (LV→VSD→Aorta)
- -Uses of a patch (polytetrafluoroethylene [PTFE]) that corresponds to the circumference of the aorta
Rastelli Procedure=
extra cardiac conduit btwn RV and PA
Native pulmonary trunk is over sewn
Surgery: DORV with Sub-pulmonary VSD (Taussig-Bing Heart)=
Complex intra-ventricular tunnel to Ao or PA
With infundibular resection
Close VSD to PA plus
arterial switch procedure
Surgery: DORV with Doubly Committed VSD=
- Intra-ventricular tunnel (LV→VSD→Aorta)
- PS or obstruction of the RVOT due to the tunnel may necessitate the creation of a RV outflow patch or even a Rastelli.
- The VSD, which is typically large, usually does not create difficulty in channeling LV blood to the aorta with an intra-ventricular tunnel
what type of DORV is the most difficult to repair
DORV with non-committed VSD
Surgery: DORV with non-committed VSD=
- univentricular repair
- Complex intra-ventricular tunnel to Ao or PA patch/baffle
- May use of combined atrial and ventricular approaches
- Fontan procedure ultimately
CPB considerations for DORV: incision
Median sternotomy
CPB considerations for DORV: Arterial+Venous Cannula
Arterial: Aortic
Venous: Bicaval (except with univentricular repair)
CPB considerations for DORV: Temperatures
Mild to Moderate
CPB considerations for DORV: Cardioplegia
Antegrade
multiple doses due to Ao-pulmonary collateral circulation
CPB considerations for DORV: Cardioplegia
Antegrade
multiple doses due to Ao-pulmonary collateral circulation
CPB case notes for DORV: These cases are amazingly variable in length, severity, and can be difficult post-op in ___________
pressure regulation
CPB case notes for DORV: Will resemble pump runs for ___
TOF
CPB case notes for DORV: Univentricular repairs will be of the ________ nature
Fontan procedure
CPB case notes for DORV: Depending on pre-op lung damage and pulmonary hypertension – _____ again may be warranted
ECMO
CPB case notes for DORV: Make sure you know how you are going to deal with high hematocrits in severe cyanotic conditions (_______)
pull off volume
CPB case notes for DORV: Be careful with MUF since it will be easy to get the hct at ___% (most likely will add volume pulled off when your warming)
50%+
