B4.046 Cardiovascular Embryology

Question 1

CXR findings in ToF

Answer 1

right ventricular hypertrophy
boot shaped heart
decreased pulmonary vascular markings

Question 2

EKG findings in ToF

Answer 2

tall R waves in lead I- prominent RV forces
prominent P waves in lead V1- suggest right atrial enlargement
right axis deviation- suggests RVH

Question 3

echocardiogram findings in ToF

Answer 3

ventricular septal defect (vicinity of membranous portion of IV septum)
aortic valve situated over VSD
blood from both RV and LV can enter the overriding aorta across the VSD
may pick up pulmonary stenosis

Question 4

defining cardiovascular features and potential associated features with ToF

Answer 4

pulmonary stenosis
overriding aorta
ventricular septal defect
hypertrophy of right ventricle
sometimes with PDA

Question 5

noncardiac features of ToF

Answer 5

clubbed fingers and toes : bulbous uniform swelling of the soft tissue of the terminal phalanx of a digit

Question 6

underlying mechanism of clubbing

Answer 6

longstanding cyanosis and hypoxemia
distal digital vasodilation occurs, which results in increased blood flow to the distal portion of the digits
increased blood flow results in changes in the vascular connective tissue under the nail bed

Question 7

hemodynamic and physiological consequences of ToF

Answer 7

blood flows into aorta from both R and L ventricles due to VSD, thus mixing oxygenated and deoxygenated blood
pulmonary stenosis reduces blood flow to lungs, right to left shunt occurs (right chamber pressure higher than left chamber)
oxygen poor blood returns from the lung and is circulated to the body

Question 8

why does hypertrophy of right ventricle develop?

Answer 8

develops over time after birth

right side of heart has to work harder to pump blood into narrowed pulmonary arteries

Question 9

what is the effect of the PDA in ToF

Answer 9

helps provide some blood to the lungs

Question 10

how is DA kept open in newborns with ToF

Answer 10

prostaglandin E1 (alprostadil) infusion until surgical intervention

Question 11

what can cause fetal closure of DA?

Answer 11

prostaglandin antagonism

maternal used of NSAIDs

Question 12

acute management of tet spell

Answer 12

calm child
squatting w knees to chest
B blockers- reduce HR
vasopressors- increase SVR
morphine sulfate- reduce rate/depth of breathing, calming effect
administer high flow oxygen to decrease pulm vascular resistance
administer bicarb to correct acidosis

Question 13

why does squatting help tet spell?

Answer 13

increases systemic vascular resistance due to compression of lower extremity arteries
diminished R to L shunt across VSD and increases pulm blood flow

Question 14

surgical options

Answer 14

shunt between aorta and pulm arteries
VSD closure with patch
widening of narrowed pulm blood vessels with balloon dilation

Question 15

developmental events leading to ToF

Answer 15

• defective neural crest migration leads to abnormal conotruncal ridge development
• incomplete rotation and faulty partitioning of conotruncus leads to pulm stenosis
• aortic and pulm valves malaligned
• aorticopulmonary septum not aligned with IV septum, producing VSD
• malrotation of conotruncal ridges results in misalignment of the outlet and trabecular septum, straddling the aorta over the malaligned VSD

Question 16

ToF clinical features

Answer 16

loud murmur or cyanosis in first weeks (pulm stenosis)
PDA provides additional blood flow to lungs, so severe cyanosis is rare shortly after birth
after DA closure, cyanosis more severe
rapid breathing
tet spell

Question 17

what is a tet spell

Answer 17

sudden increase in constriction of the outflow tract to the lungs so pulm blood flow is further restricted
more severe cyanosis