Download Congenital Heart Defects, Fetal Circulation

Congenital Heart Defects,
Fetal Circulation, and
Extrauterine Transition
Developed by Lisa Fikac, MSN, RNC-NIC
Original Author Stacey Cashwell, MSN, RN
Expiration Date - 2/27/17
This continuing education activity is provided by Cape Fear Valley Health System,
Training and Development Department, which is an approved provider of Continuing
Nursing Education by the North Carolina Nurses Association, an accredited approver by
the American Nurses Credentialing Center’s Commission on Accreditation.
0.8 Contact hours will be awarded upon completion of the following criteria:
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Completion of the entire activity
Submission of a completed evaluation form
Completion a post-test with a grade of at least 85%.
The planning committee members and content experts have declared no financial
relationships which would influence the planning of this activity.
Microsoft Office Clip Art is the source for all graphics unless otherwise noted. These
graphics used with permission.
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Discuss risk factors associated with congenital heart defects (CHD).
Identify milestones in cardiac development.
Describe fetal circulation.
Discuss changes that occur during extrauterine transition.
Many times when parents are told that their baby has a
heart defect, they immediately assume the worst whether
the defect is simple or complex.
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They do not always hear or completely comprehend
all the information that the medical team has given
to them.
It is the nurse's role to reinforce the information
communicated by the medical team.
o In order to do that, the nurse needs to have a
basic understanding of  Cardiac development
 Fetal circulation
 Transition to extrauterine circulation after birth
Most of the time, the exact cause of congenital heart disease (CHD) is unknown.
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Many people assume that CHD is associated with a genetic defect.
However, about 8% of CHDs can be attributed to chromosomal abnormalities.
About 85-90% of CHD cases are found to be due to many factors.
CHD tends to occur most frequently in males.
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The ratio of male occurrence to female occurrence is 3-4:1.
However, atrial septal defects (ASDs) and patent ductus arteriosus (PDAs) tend
to occur more frequently in females.
CHD occurs in • 1-3% of all live births
• 20-25% of preterm infants
• 85% of preterm infants with a birthweight of < 800 grams are due to
the high incidence of patent ductus arteriosus (PDA) in this group
The risk of CHD increases by 1-3% if the mother has a •
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History of CHD
Previous child or children with CHD
CHD is associated with several genetic syndromes, which include •
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Trisomy 13 (Patau Syndrome)
o Infants with this syndrome frequently have  Ventricular septal defects (VSDs)
 PDA
Trisomy 18 (Edward's Syndrome)
o Infants with this syndrome frequently have  VSDs
 PDA
Trisomy 21 (Down Syndrome)
o Infants with this syndrome frequently have  ASDs
 Atrioventricular (AV) canal
 VSDs
 PDA
Turner's Syndrome (gonadal dysgenesis)
o Infants with this syndrome frequently have  Coarctation of the aorta
 Aortic stenosis
Chromosomal deletions
o Deletions usually involve chromosomes numbers 4, 5, 13, or 18.
o There are a wide variety of defects which may range in severity from
simple to complex.
CHD is also often seen in infants with VACTERL association.
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VACTERL is an acronym for a constellation of congenital, multi-system defects.
The acronym stands for •
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Vertebral defects, such as neural tube defects.
Anorectal defects, such as anal atresia with or without a fistula.
Cardiac defects, such as o VSD
o Dextrocardia
o Valve defects.
Tracheo-Esophageal fistula which often has an associated esophageal atresia.
Renal defects, such as o Polycystic kidney disease
o Hydronephrosis
o Agenesis of one kidney
o The presence of only one umbilical artery instead of two may indicate
renal defects.
Limb defects, such as o Thumb deformities
o Hypoplasia of the digits
o Syndactyly
o Polydactyly
About 2% of CHDs can be attributed to environmental factors.
Maternal alcohol use is associated with •
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VSDs, with or without subpulmonic and subaortic stenosis
Coarctation of the aorta
Aortic regurgitation
Atrial septal defects (ASDs)
Tetralogy of Fallot
CHD is associated with exposure to several different medications -
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Thalidomide - various defects
Anticonvulsants o VSD
o PDA
o Coarctation of the aorta
o Ventricular hypertrophy
Antineoplastics - dextrocardia
Lithium o Ebstein's anomaly
o ASD
o Tricuspid atresia
Exposure to toxins can cause a variety of defects with the severity ranging from simple
to complex. Some of toxins include •
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Asbestos
Paint
Chemicals in textiles
Several maternal health problems are linked to CHD.
Maternal illnesses that are related to CHD include •
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Diabetes mellitus
o Infants of diabetic mothers frequently have  VSDs
 PDA
 Coarctation of the aorta
 Transposition of the great vessels
Maternal infections, either bacterial or viral.
o Infants who have been exposed to maternal infection frequently have  PDA
 Pulmonary stenosis
Previous family history of CHD, particularly in the mother or a sibling.
Loss of perfusion and/or oxygenation to the mother or placenta can result in a
cardiac defect.
o The type of cardiac defect directly depends on the point during
development at which the insult occurs.
o Illnesses that can impair perfusion or oxygenation include lupus and
chronic respiratory problems.
Heart development is identifiable at 18-19 days post-conception.
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At this point, the heart is a single tube with an ebb and flow type of circulation.
The heart beat is uncoordinated.
Abnormal development during this time in gestation includes transposition of the
great vessels and dextrocardia.
At 3-4 weeks post-conceptional age, the single cardiac tube expands and begins to
coil to the right with the bottom portion moving to the top and the top portion moving
to the bottom.
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Primitive atria and ventricles are first identified.
A single great arterial vessel (truncus arteriosus) extends from the ventricle until
the fourth week of life.
Although there is a coordinated heart beat with a rate of 60-70 bpm, it is not
sufficient to sustain life.
At 5-6 weeks post-conceptional age, cardiac septation begins and is completed
during this time.
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All 4 chambers are clearly identifiable.
The primitive atrioventricular (AV) valves appear. These are o Tricuspid valve - located between the right atrium and right ventricle
o Mitral valve - located between the left atrium and left ventricle
There is still only one great vessel, the truncus arteriosus.
At 9-11 weeks post-conceptional age, the great vessel starts its rotation and
septation into two vessels, known as •
Pulmonary artery
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Aorta
All of the valves are developed and in place •
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Tricuspid - right side
Mitral - left side
Semi-lunar - valves to the pulmonary artery and aorta
At 10-12 weeks post-conceptional age, rotation and septation of the great vessel is
complete.
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The heart, which was initially located in the midline of the chest, completes its
migration to the LEFT side of the chest.
Click here to view 3-D view of fetal cardiac development
All organ development values are + 1-2 weeks
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Teratogenic events can occur at any time during organ
development.
o The particular defect is directly related to the specific
developmental sequence occurring at the time of the
insult.
 e.g.: maternal hypoxia at the time of AV development might result
in tricuspid atresia.
From Fetal circulation. (2014). In UpToDate 21.12-C22.20. Retrieved January 31, 2014.
In utero, the majority of the fetal blood volume bypasses pulmonary circulation.
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It does this by leaving the right side of the heart and using 2 of 3 fetal shunts.
Although the fetus does make respiratory-like movements, the placenta is the organ that
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Delivers nutrients for growth and development
Facilitates effective oxygen and carbon dioxide exchange
Meets all organ and tissue needs
There are three fetal shunts that allow fetal circulation to bypass the lungs and use the
placenta as the fetal organ of oxygenation and nutrition.
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Foramen ovale
Ductus arteriosus
Ductus venosus
The foramen ovale is the opening in the septum between the right and left atria.
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This allows the blood to bypass the lungs.
Approximately 50% of the blood volume passes through this shunt.
The ductus arteriosus is the passage located between the pulmonary artery (PA) and
aorta.
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In utero, blood leaves the PA and enters the aorta.
o This is what is referred to as a RIGHT-to-LEFT shunt.
Like the foramen ovale, the ductus arteriosus allows blood to by-pass the lungs.
Approximately 30% of blood volume passes through this shunt.
If the ductus arteriosus remains open, it becomes known as the patent ductus
arteriosus (PDA).
The ductus venosus is the opening located on the underside of the liver in the portal
system.
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This allows the umbilical vessels access to and from the placenta.
For some people, a picture is worth a thousand words, and everything is clear for them.
For others, those thousand words are needed.....another way of viewing fetal circulation.
Blood enters the inferior vena cava, joining with the blood returning from the upper
body and head via the superior vena cava, and then enters the right
atrium
Part of the blood in the right atrium passes through the foramen
ovale to the left atrium
The remainder of the blood in the right atrium crosses over the
tricuspid valve and enters the right ventricle
The right ventricle ejects the blood into the main pulmonary
artery, across the semi-lunar pulmonic valve
The main pulmonary artery carries blood to the lungs, BUT •
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The lungs are fluid filled and there is significantly lowered pulmonary oxygen
levels.
This results in vasoconstriction of the pulmonary arterial bed and increased
pulmonary vascular resistance (PVR)l
Blood looks for the path of least resistance instead of pumping against such a
high PVR
It finds the ductus arteriosus (DA)
A large volume of blood passes through the DA into the aorta
The remainder of the blood continues along the PA to the pulmonary
circulation
Blood nourishes the pulmonary arterial bed to foster its health and
growth
Blood returns to the heart via the four pulmonary veins.....
Blood enters the left atrium where it mixes with the blood that previously passed
through the foramen ovale
Blood crosses over the mitral valve and enters the left ventricle
For the second time, blood exits the heart
The left ventricle ejects the blood into the aorta, across the semi-lunar aortic valve
At the aortic arch, the blood mixes with blood coming across the DA
The total blood volume of the fetus is together again
The blood proceeds down the descending aorta, ultimately entering the systemic
circulation
Following circulation systemically, the blood makes its way to the placenta via the
umbilical vessels and the ductus venosus
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Systemic vascular resistance (SVR) is decreased, allowing ready access to and
from the placenta, a large lobular organ with very little vascular resistance
After giving up waste products and picking up nutrients and oxygen from the
placenta, the blood starts the trip again
This process works well for the fetus while in utero, even when pulmonary and/or
cardiac defects are present.
In utero, the placenta is the organ of oxygenation, not the lungs.
When birth occurs, three major events must take place in order
for the neonate to make the transition from placenta-based
oxygenation to pulmonary-based oxygenation......to survive.
1. Pulmonary vascular resistance (PVR) must decrease.
2. Systemic vascular resistance (SVR) must increase.
3. The fetal shunts must close.
AT BIRTH...
When the neonate is delivered, the chest mechanically expands, and the infant takes
his first breath.
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Oxygen rushes in, and the alveoli expand.
EFFECTIVE respirations are established.
When gas exchange begins, the pulmonary arterial bed dilates, and PVR decreases.
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This process increases pulmonary blood flow.
Once the umbilical cord is clamped, SVR increases, and cardiac return from the
body increases.
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Cardiac output to the lungs and body also increases.
When all of these events take place -
Normal, adult, pulmonary-based circulation is established, and fetal shunts close.
The heart begins the transition from a fetal right-sided heart dominance to an adult leftsided heart dominance.
After extrauterine transition, blood flows in the customary adult, pulmonary-based
circulatory pattern.
The inferior vena cava (IVC) and superior vena cava (SVC) return blood to the
Right atrium and then, ejects over the
Tricuspid valve to the
Right ventricle and then, ejects over the
Pulmonary semi-lunar valve to the
Main pulmonary artery to the
Right and left pulmonary arteries that carry blood to the
Lungs where gas exchange occurs, then
Blood returns via the four pulmonary veins to the
Left atrium and ejects over the
Mitral valve to the
Left ventricle and ejects over the
Aortic semi-lunar valve to the
Aorta where blood is carried to the
System circulation
The transition from placenta-based oxygenation to pulmonarybased oxygenation is complete!
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Askin, D.F. (2009). Fetal-to-neonatal transition – what is normal and what is not?
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Federspiel, M.C. (2010). Cardiac assessment in the neonatal population. Neonatal
Network, 29(3), 135-142.
Fernandes, C.J., Weisman, L.E., & Kim, M.S. (2014). Physiologic transition from
intrauterine to extrauterine life. In UpToDate Online 21.12-C22.20.
http://www.uptodate.com/contents/physiologic-transition-from-intrauterine-toextrauterinelife?source=search_result&search=fetal+circulation&selectedTitle=1%7E79 (Retrieved
January 31, 2014).
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Merenstein & Gardner's Handbook of Neonatal Intensive Care, 7th Edition. St. Louis:
Mosby-Elsevier.
Verklan, M.T. & Walden, M. (Eds.) (2010). Core Curriculum for Neonatal
Intensive Care Nursing, 4th Edition. St. Louis: Saunders-Elsevier.
Yeung, F. (2007). Heart embryology. In Cardiac Embryology. Retrieved January
31, 2014, from http://pie.med.utoronto.ca/HTBG/index.htm
The authors would like to thank Creative Memories™ for their kind permission for our
use of their graphics in Mother-Baby University learning activities.