peds cardiology Flashcards
embryology
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 Hepatomegaly Ascitis Pleural effusion Edema
CHD s/s left side
Tachypnea (to breathe off CO2)
Retractions
Crepitations
Pulmonary edema
CHD s/s low CO
Acutely: Pallor Sweating Cool extremities capillary refill Tachycardia
Chronic:
Feeding difficulty (sweating)
Fatigue
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!)
-Illness:
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
Lungs: 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
remember..
pressure dictates flow, blood takes path of least resistance
L→R Shunts (“Acyanotic” CHD)
May not be apparent in neonate due to ??
Defects: VSD PDA ASD 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
ASD
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
CSR
Pulm vasc markings increased in upper and lower zones
cardiomegaly
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%
TGA 2
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.
