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Flashcards in peds cardiology Deck (54):


Completion of the third week
Intraembryonic blood vessels noted at day 20
Days 21 – 23: the median heart tube is complete
Day 22: heart starts beating
Days 27 – 29: circulation begins


fetal circulation

For the fetus the placenta is the oxygenator so the lungs do no work
RV and LV contribute equally to the systemic circulation and pump against similar resistance (after born RV against less pressure)


Shunts are necessary for survival

ductus venosus (oxygenated blood bypasses the liver)
foramen ovale (R→L atrial level shunt)
ductus arteriosus (R→L arterial level shunt)


In a right to left shunt ??

Blood (that hasn’t traveled to lungs yet) is shunting across to the left side of the heart

The underlying goal of fetal circulation is to get oxygenated blood to the brain of the fetus


Fetal Normal Values

Umbilical vein PaO2 is 30-35 mmHg.
Fetus 70-80% saturated at this PaO2
Adult 50-60% saturated at same PaO2

Oxygen delivery must be achieved in a relatively hypoxic environment.


residue 143

Single amino acid change histidine to serine

Histidine positively charged. Serine neutral.

This change results in less binding of 2,3 BPG to fetal Hb which increase fetal oxygen affinity


transitional circulation

With first few breaths lungs expand and serve as the oxygenator
Placenta is removed from the circuit
Systemic pressure INCREASES (placenta WAS a low pressure circuit, now clamped/removed)
Pulmonary pressure DECREASES
Foramen ovale functionally closes
Ductus arteriosus usually closes within first 2-3 days, due to some residual flow (PGE1,2 KEEPS PDA open : placental makes PGs)
Indomethacin: ENDs PDA

if coarctations, take 7-10 days to close (hypoxic)


slide 13: after birth umbilical arteries close

systemic pressure increases-->inc. LA pressure greater than RA, no more right to left shunt

pulmonary pressure decreases, blood goes out to lungs instead of thru PDA

shunts essentially close first 30-45 seconds of life


Congenital Heart Disease:
Neonates with CHD often rely on a ?? and/or ?? to sustain life.

patent ductus arteriosus
foramen ovale


Unfortunately for these neonates, both of these passages begins to close following birth.
The ductus normally closes by ??
The foramen ovale normally closes by??

72hrs. (so small window to dx!)
3 months.


What function does the PDA provide after birth in a baby with cyanotic congential heart disease?
A. Provides a source of pulmonary blood flow
B. Provides a source of systemic blood flow
C. Prevents the PFO from closing
D. Supports blood pressure

Provides a source of pulmonary blood flow
(L side pressures are greater, L->R->lungs)


In the presence of hypoxia or acidosis (present in ductal-dependent lesions), ??

the ductus may remain open for a longer period of time

As a result, these patients can present to the ED as late as the first 2 weeks of life

*sepsis should be #1 on ddx* but keep ductus open and if find out infectious, close it back up


CHD s/s right side (more insidious)

Venous congestion
Pleural effusion


CHD s/s left side

Tachypnea (to breathe off CO2)
Pulmonary edema


CHD s/s low CO

Cool extremities
­ capillary refill

Feeding difficulty (sweating)
Poor growth

*present like adult CHF*


Neonatal Circulation

RV pumps to pulmonary circulation and LV pumps to systemic circulation
Pulmonary resistance (PVR) is high initially; so initially RV pressure ~ LV pressure
By 6 weeks pulmonary resistance drops and LV becomes dominant
(dramatic drop, then slow drop to adult levels)


baby comes in hx of ALTE (acute life threatening event)
EKG slide 19

acute life threatening event

LV typically has highest amplitudes (V5, V6)
if V1, V2 higher than V3, V4-6, RVH? right bigger than left? (i.e. Epstein's??)
no, normal finding: takes time for left side muscle mass to "bulk up"


Normal Infant Circulation

LV pressure is 4-5 x RV pressure (this is feasible since RV pumps against lower resistance than LV)
RV is more compliant chamber than LV
LV has stiffer, more muscular wall


Normal blood flow values:
No shunts
No pressure gradients
Normal AV valves
Normal semilunar valves

LA: 100%
LV: 90/60
aorta: 100%
RA: 75%
RV: 20/5
pulmonary artery: 75%


If you have a hole in the heart what affects shunt flow?

Pressure – blood takes the path of least resistance
Resistance – impedance to blood flow


Incidence of CHD

Occurs in 8–10/1000 live births (less than 1%)
Familial recurrence risk:
1 - 3% ⇨ sibling
2 - 4% ⇨ parent
25% ⇨ parent + sibling or 2 parents (Noonan's syndrome, Turner's (inseminated))
If the mother has a rare, left-sided defect ⇨ more likely to reoccur in offspring


Congenital causes

Multifactorial (70 - 85%) no single/specific cause

Chromosomal (18%)
Down Syndrome: up to 50% will have defects
VACTERL, CHARGE Association: 50 - 85% will have defects

Maternal or environmental (1-2%)


Maternal or environmental (1-2%) (is preventable!)

Pre-Gestational Diabetes: 50 % inc. risk (poorly controlled, not gestational DM): risk for VSD, Transposition (TGA), Coarctation (COA)

-Lupus: complete heart block (may do C-section, watch moms w. SLE)
-Infection (Viral): rubella in 1st 7 wks = Patent Ductus Arteriosus
-Substance Abuse: Severe FAS (EtOH) = 50 % have CHD


Syndrome Associations

*Down – AV canal* and VSD
*Turner – CoA*
Trisomy 13 and 18 – VSD, PDA
Fetal alcohol – L→R shunts, ToF
CHARGE – conotruncal lesions (ToF, truncus arteriousus)


Physical Exam

Inspection and palpation
Cardiac cyanosis is central
Differential cyanosis = USMLE
PDA with R-->L shunt
CoA with PDA after constriction

(can't always see cyanosis, check pulse ox)

Increased precordial activity
Displaced PMI


Differential cyanosis

pulse ox on RUE (higher, preductal) and LE, 10% difference in sat
before and after coarctation (PDA or coarct. with constricted PDA)


pulmonary HTN and PDA causes

"blue blood" (deox) from RV to shunt thru PDA (avoiding lungs) to aorta to systemic circulation


if coarctation after PDA constricts

less blood to system, more to pulmonary circulation


Physical exam 2

Respiratory rate and work of breathing
Oxygen saturations
Abdominal exam: Hepatomegaly
Extremities: Perfusion, Edema

if blue baby and no breathing problems, heart problem


slide 31

diff btw cardiac and pulmonary cyanosis


PE: pulses

Differential pulses (strong UE, weak LE) = CoA (radial ok, femoral v. weak)
Bounding pulse = run-off lesions (L→R PDA shunt, AI, BT shunt)
Weak pulse = cardiogenic shock or CoA
Any ductal dependent lesion once the PDA is closing


PE: Heart sounds

Ejection click = AS or PS
Loud S2 = Pulmonary HTN
Single S2 = one semilunar valve (truncus), anterior aorta (TGA), pulmonary HTN
*Fixed split S2 = ASD*
Muffled heart sounds and/or a rub = pericardial effusion ± tamponade


PE: Types of Murmurs

Systolic Ejection Murmur = turbulence across a semilunar valve (Ao, Pulm)
Holosystolic murmur = turbulence begins with systole (VSD, MR)
Continuous murmur = pressure difference in systole and diastole (PDA, BT shunt)


Simplest way to classify CHD:

L→R shunts – Acyanotic HD
R→L shunts – Cyanotic HD
-The baby appears cyanotic due to deoxygenated blood entering the systemic circulation
Obstructive lesions



pressure dictates flow, blood takes path of least resistance


L→R Shunts (“Acyanotic” CHD)

May not be apparent in neonate due to ??

AV canal (combined ASD/VSD)
- Endocardial cushion defect

high Pulmonary Vascular Resistance (PVR) not much pressure difference, not much flow until pulmonary pressures drop


PDA and VSD present when ??
with what??

Presents in infancy w/ heart failure, murmur, and poor growth
Left heart enlargement (LHE): Transmits flow and pressure



Presents in childhood w/ murmur or exercise intolerance
Right heart enlargement (RHE): Transmits flow only


AV Canal can present as either depending on ?

size of ASD and VSD component


both ASD and VSD

increase pulmonary blood flow


ASD ?? overload

right heart
extra blood from LA
LV contracting does NOT transmits pressure to pulmonary circuit, just extra volume
-takes longer to present


VSD: ?? overload

left heart
LV contracting transmits pressure and volume to pulmonary circuit-->comes back to LV



Pulm vasc markings increased in upper and lower zones


Is a L--> R shunt a cyanotic lesion?

No but can become one: pulmonary pressures become to great (R-->L) Eisenmenger's syndrome


Eisenmenger’s Syndrome

A long standing L→R shunt will eventually cause irreversible pulmonary vascular disease
-This occurs sooner in unrepaired VSDs and PDAs (vs an ASD) because of the high pressure transmitted with the VSD/PDA
-Once the PVR gets very high the shunt reverses (ie- now R→L) and the patient becomes cyanotic


R→L Shunts (cyanotic CHD)

Degree of cyanosis varies depending on the lesion
-Classify based on pulmonary blood flow (PBF)


R→L Shunts ↑ PBF
(still may be blue)

Truncus arteriosus
Total anomalous pulm. venous return (TAPVR)
Transposition of the great arteries (TGA)

Presents more often with heart failure (except TGA)
Pulmonary congestion worsens as neonatal PVR lowers (CHF findings)
Sats can be 93-94% (high!) when there is high PBF; fetal Hgb, may be pink


R→L Shunts ↓ PBF

Tetralogy of Fallot
Tricuspid atresia
Ebstein’s anomaly

Presents more often with cyanosis
See oligemic lung fields
Closure of PDA may worsen cyanosis (may be PGE dependent)


Truncus arteriousus

common trunk, mixing of blue and red blood before entering aorta

too much PBF (path of least resistance)
may sat 90% (cyanosis: mixed blood reaching system)


Tetralogy of Fallot

pulmonary stenosis causes too little PBF-->less oxygenated blood to LV
more blue blood from RV and a little red blood from LV to aorta-->system

inc. pressure in RV prevents VSD from closing, causes overriding aorta

causes RVH
may sat 70% (variable)
monitor until PDA starts to close, determine if ductal dependent: if yes: PDE then sx


truncus on CXR

hazy pulmonary edema lung fields
generalized confluence
too much PBF


ToF on CXR

dark lung fields, decreased vasculature, too little PBF
boot-shaped heart


Transposition of the Great Arteries (TGA)

*Most common cyanotic congenital heart defect in newborns*
5% of all CHD, Male to female 3:1
Dextroposition, Parallel circuits
Incompatible with life unless communication between the two circuits

PDA helps
if have restrictive ASD: femoral catheter-->put catheter across ASD, blow up balloon, widens ASD: allows more oxygenated blood flow
may sat 75-80%



Mixing may occur at a number of levels, most commonly at the atrial level through an ASD or a PFO.
-Two levels of mixing are necessary to maintain adequate systemic oxygen delivery with a VSD or PDA serving as an additional site for cardiac mixing. (need equal mixing)
In TGA, there can be no fixed shunt in one direction without an equal amount of blood passing in the other direction; otherwise, one circulation would eventually empty into the other.