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