Med/Surg 2: Pediatric Cardiac Dysfunction Lecture
Name the 4 classifications of congenital heart defects using hemodynamic characteristics
(1) increased pulmonary blood flow; (2) decreased pulmonary blood flow; (3) obstruction to blood flow out of the heart; and (4) mixed blood flow, in which saturated and desaturated blood mix within the heart or great arteries
Cardiovascular disorders in children are divided into two major groups:
1) congenital heart disease (CHD) 2) acquired heart disorders
The two major consequences of congenital heart disease (CHD)
1) heart failure 2) hypoxemia
Name the top 3 congenital heart defects with increased pulmonary blood flow
1. ASD: atrial septal defect (LA to RA) 2. VSD: ventricular septal defect (LV to RV) 3. PAD: patent ductus arteriosus (aorta to pulmonary artery)
Reflection question: What are the three principles to be considered for hemodynamics?
1. Pressure gradient: flow from high to low pressure 2. Resistance: take path of least resistance 3. Flow : high pressure is faster flow, high resistance is slower flow
Adaptations in fetal circulation
1. umbilical vein (placenta to ductus venosus & liver) 2. ductus venosus (umbilical vein to IVA) 3. foramen ovale (RA to LA) 4. ductus arteriosus (pulmonary truck to aorta) 5. umbilical arteries (internal illiac arteries to placenta)
Tetralogy of Fallot accounts for ___% of the cases of congenital heart disease.
10
Ventricular septal defects are the most common forms of congenital heart disease, accounting for ___% of all cases.
21
Describe the ventricular septal defect (VSD)
Abnormal opening between the right and left ventricles (could have one or multiple). May vary in size from a small pinhole to absence of the septum. A left-to-right shunt is caused by the flow of blood from the higher-pressure left ventricle to the lower-pressure right ventricle. The increased blood volume is pumped into the lungs, which may eventually result in increased pulmonary vascular resistance. Increased pressure in the right ventricle as a result of left-to-right shunting and pulmonary resistance causes the muscle to hypertrophy. If the right ventricle is unable to accommodate the increased workload, the right atrium may also enlarge as it attempts to overcome the resistance offered by incomplete right ventricular emptying.
Cyanosis definition
Blue discoloration results from presence of deoxygenated hemoglobin Cyanosis is usually apparent when arterial oxygen saturations are 80% to 85%.
When is the heart developmentally complete?
By the end of the embryonic stage, by weeks 4-5.
Cardiac output formula
CO = SV x HR
Congenital heart anomalies are often associated with chromosomal abnormalities. Name some.
Down syndrome (trisomy 21) Trisomy 13 Trisomy 18
The following three special characteristics enable the fetus to obtain sufficient oxygen from the maternal blood:
Fetal hemoglobin carries 20% to 30% more oxygen than maternal hemoglobin. •The hemoglobin concentration of the fetus is about 50% greater than that of the mother. •The fetal heart rate (FHR) is 110 to 160 beats/min, making the cardiac output per unit of body weight higher than that of an adult.
Clinical manifestations of ventricular septal defect (VSD)
Heart failure is common (seen 6-8 weeks old). There is a characteristic loud holosystolic murmur heart best at the left sternal border (turbulent blood flow crossing the hole--smaller hole, louder murmur). Can result in pulmonary hypertension.
What causes the ductus arteriosus to close?
Higher concentrations of O2 and decreased prostaglandin levels and decreased pulmonary vascular resistance
Describe the flow in TOF
In some infants and children, there can be profound narrowing of the right ventricular outflow tract. Because of the severe narrowing, it is easier for the blood to cross the VSD right-to-left and go out the aorta instead of going to the lungs. If this is the case, the infant or child can become quite blue (cyanotic).
Describe what is going on with defects with decreased pulmonary blood flow
In this group of defects, there is obstruction of pulmonary blood flow and an anatomic defect (ASD or VSD) between the right and left sides of the heart. Because blood has difficulty exiting the right side of the heart via the pulmonary artery, pressure on the right side increases, exceeding left-sided pressure. This allows desaturated blood to shunt right to left, causing desaturation in the left side of the heart and in the systemic circulation. Clinically, these patients have hypoxemia and usually appear cyanotic. Tetralogy of Fallot and tricuspid atresia are the most common defects in this group
How does the ductus arteriosus become a ligament?
In utero fetal PO2 is 20 to 30 mm Hg. After birth, when the PO2 level in the arterial blood approximates 50 mm Hg, the ductus arteriosus constricts in response to increased oxygenation. Circulating hormone prostaglandin E (PGE2) levels also have an important role in closure of the ductus arteriosus.
Incidence of congenital heart disease
Incidence: 5-8 per 1000 live births About 2 or 3 of these cases are symptomatic in first year of life
Assessments of note in an infant with coarctation of the aorta
Increase BP in upper extremity pressures Decreased BP in lower extremity pressures Will take all 4 extremity BP because of this Upper pulses: stronger, bounding Lower pulses: weak, thready, probably cooler skin *Can also have signs of heart failure
What causes a functional closure of the foramen ovale after birth?
Increased pulmonary blood flow from the left side of the heart increases pressure in the left atrium, which causes a functional closure of the foramen ovale.
Describe what happens with increased pulmonary blood flow in an infant heart
Increased volume on the right side of the heart, from abnormal connections between the two sides/increased volume on the right side/increased pulmonary flow or decreased systemic flow, causes more volume to go into the lungs and more pressure in the lungs. You will see signs and symptoms of heart failure.
Pediatric heart rate values
Infant 110-160 Toddler 100-150 (~120) Preschooler 95-140 (~100-110) School Age 80-120 (~90) Over 12: 60-100
Describe coarctation of the aorta
Localized narrowing near the insertion of the ductus arteriosus, which results in increased pressure proximal to the defect (head and upper extremities) and decreased pressure distal to the obstruction (body and lower extremities).
Reflection question: How do nurses measure adequate cardiac output?
Look at heart rate, pulses, capillary refill, weight, growth chart, feeding, urinary output
What is done if the VSD is small?
May not do anything for first year or two. May wait and see if VSD closes on its own.
Treatment for coarctation of the aorta
Mechanical ventilation and inotropic support are often necessary before surgery. Surgery repair to insert a graft of prosthetic material or portion of an artery (do this for less than 6 months). Balloon angioplasty also can be used (over 6 months). Stents can be placed (adolescents).
Describe pulmonic stenosis
Narrowing at the entrance to the pulmonary artery. Resistance to blood flow causes right ventricular hypertrophy and decreased pulmonary blood flow.
Describe aortic stenosis
Narrowing or stricture of the aortic valve, causing resistance to blood flow in the left ventricle, decreased cardiac output, left ventricular hypertrophy, and pulmonary vascular congestion.
Clinical manifestations of aortic stenosis
Newborns with critical AS demonstrate signs of decreased cardiac output with faint pulses, hypotension, tachycardia, and poor feeding. Children show signs of exercise intolerance, chest pain, and dizziness when standing for a long period. A systolic ejection murmur may or may not be present. Patients are at risk for BE, coronary insufficiency, and ventricular dysfunction.
What blood is mixed in the inferior vena cava?
Oxygenated blood from the ductus venosus and deoxygenated blood from the fetal legs and abdomen on the way to the right atrium.
Describe PA banding
PA banding stands for pulmonary artery banding. A band is placed around the pain pulmonary artery to decrease pulmonary blood flow in VSD. Increases pressure in the right ventricle, helping to equalize pressure on left and right sides.
Clinical manifestations of pulmonic stenosis
Patients may be asymptomatic; some have mild cyanosis or HF. Progressive narrowing causes increased symptoms. Newborns with severe narrowing are cyanotic. A loud systolic ejection murmur at the upper left sternal border may be present. However, in severely ill patients, the murmur may be much softer because of decreased cardiac output and shunting of blood. Cardiomegaly is evident on chest radiography. Patients are at risk for BE.
Treatment for hypercyanotic spells
Place infant in knee-chest position • Use a calm, comforting approach. • Administer 100% oxygen by blow-by. • Give morphine subcutaneously or through an existing IV line. (increases venous return) • Begin IV fluid replacement and volume expansion if needed. • Repeat morphine administration.
Describe where the ductus venosus is.
Placenta-->umbilical vein-->liver divides into two branches: 1) liver veins 2) ductus venosus. Ductus venosus-->inferior vena cava.
What is happening hemodynamically in obstruction defects in the heart?
Pressure load on the ventricles and decreased cardiac output.
A positive screening for congenital heart disease in infants
Pulse oximetry ≤90% in right hand or foot is considered a positive screening, and additional evaluation is warranted (e.g., echocardiogram).
Discuss blood flow to the lungs in fetal circulation
Right ventricle blood is squeezed into the pulmonary trunk. A small amount of blood circulates through the resistant lung tissue, but the majority follows the path with less resistance through the ductus arteriosus straight into the aorta, distal to the point of exit of the arteries supplying the head and arms with oxygenated blood.
Describe the surgical patch surgery for VSD
Small defects are repaired with sutures. Large defects usually require that a knitted Dacron patch be sewn over the opening. The approach for the repair is generally through the right atrium and the tricuspid valve.
Clinical manifestations of tetralogy of fallot
Some infants may be acutely cyanotic at birth; others have mild cyanosis that progresses over the first year of life as the PS worsens. There is a characteristic systolic murmur that is often moderate in intensity. There may be acute episodes of cyanosis and hypoxia, called blue spells or tet spells. Anoxic spells occur when the infant's oxygen requirements exceed the blood supply, usually during crying or after feeding. Patients are at risk for emboli, seizures, and loss of consciousness or sudden death after an anoxic spell.
Cardiac output definition
The amount of blood the heart pumps through the circulatory system in a minute. The amount of blood put out by the left ventricle of the heart in one contraction is called the stroke volume. The stroke volume and the heart rate determine the cardiac output.
Describe the overriding aorta
The aorta is enlarged and "overrides," or sits directly above, the ventricular septal defect (VSD). (#3)
Describe the tetralogy of fallot heart defect
The classic form includes four defects: (1) VSD, (2) PS, (3) overriding aorta, and (4) right ventricular hypertrophy.
Goal of PA banding
The goal of PAB is to reduce pulmonary artery pressure and excess pulmonary blood flow. Want to reduce blood flow to the lungs.
Discuss the path of deoxygenated blood going back to the placenta in fetal circulation
The oxygen-poor blood flows through the abdominal aorta into the internal iliac arteries, where the umbilical arteries direct most of it back through the umbilical cord to the placenta. There the blood gives up its wastes and carbon dioxide in exchange for nutrients and oxygen.
Clinical manifestations of coarctation of the aorta
The patient may have high blood pressure and bounding pulses in the arms, weak or absent femoral pulses, and cool lower extremities with lower blood pressure. There are signs of HF in infants. In infants with critical coarctation, the hemodynamic condition may deteriorate rapidly with severe acidosis and hypotension. Older children may experience dizziness, headaches, fainting, and epistaxis resulting from hypertension. Patients are at risk for hypertension, ruptured aorta, aortic aneurysm, and stroke.
Describe obstructive heart defects
Those in which blood exiting the heart meets an area of anatomic narrowing (stenosis), causing obstruction to blood flow. The pressure in the ventricle and in the great artery before the obstruction is increased, and the pressure in the area beyond the obstruction is decreased.
Discuss the BT shunt surgical treatment for TOF
To increase blood flow to the lungs, an operation known as a Modified B-T Shunt Procedure can be performed in which a "shunt", or tiny tube made of Gore-Tex® (yellow in the diagrams to left), is attached between the aorta (or one of its branches) and the pulmonary artery (or one of its two branches - the left pulmonary artery (LPA) or right Pulmonary Artery (RPA).
Where does the ductus venosus go?
To the inferior vena cava and then the right atrium.
Describe acyanotic vs cyanotic heart defects
Traditionally cyanosis, a physical characteristic has been used as the distinguishing feature between the two. However, this is problematic because children with acyanotic defects may develop cyanosis. Also those with cyanotic defects may appear pink.
How can we tell that an infant's cardiac output is adequate?
Will actually look at EXPENSE ORGANS to see that they are well oxygenated (heart, brain and lungs get priority with oxygen). GI system: feeding, weight, growth chart, vomiting? Kidneys: urinary output (1ml/kg, 1/2 ml/kg newborn) Pulses to extremities: strength, rate, capillary refill
What is done if baby with VSD has signs and symptoms of increased pulmonary flow?
Will do PA banding if younger or a surgical closure if older.
Why would PA banding be a surgery of choice for an infant?
Young, less invasive, patient not stable, let your heart grow and become more stable if want to do the patch
Heart failure signs and symptoms
activity intolerance crackles cough decreased urinary output short of breath GI issues increased HR and RR pallor sweating takes long time to feed signs of dehydration (not many wet diapers)
Name the 2 classes of congenital heart defects (keep it mind this is traditionally classification and should not be used as much anymore)
acyanotic & cyanotic
Hypoxemia definition
an abnormally low concentration of oxygen in the blood, specifically the arteries (low PaO2, <80 mm Hg)
Why might the prisons of cyanosis may not accurately reflect arterial hypoxemia?
because both oxygen saturation and the amount of circulating hemoglobin are involved. Children with severe anemia may not be cyanotic despite severe hypoxemia because the hemoglobin level may be too low to produce the characteristic blue color. Conversely, patients with polycythemia may appear cyanotic despite a near-normal PaO2.
Maternal risk factors for the infant developing a congenital heart defect
chronic illnesses such as diabetes or poorly controlled phenylketonuria, alcohol consumption, and exposure to environmental toxins and infections. Family history of a cardiac defect in a parent or sibling increases the likelihood of a cardiac anomaly.
Discuss repairs for TOF
closure of VSD pulmonary valvotomy (open valve if obstructed) transannular patch resection of obstructive muscle in right ventricle hypertrophy
Name the top 3 defects in the obstruction group
coarctation of the aorta (narrowing of the aortic arch) aortic stenosis pulmonic stenosis
Major cause of death in the first year of life (after prematurity) is:
congenital heart disease
Defects that cause decreased pulmonary blood flow result in _______
cyanosis
Pressure changes with the firth breath at birth
decrease pulmonary vascular resistance decrease pulmonary artery pressure decrease right atrium pressure increase in left sided pressure=closes foramen ovale
Primary nursing diagnosis for VSD
decreased cardiac output
Hypoxia definition
deficiency in the amount of oxygen reaching the tissues resulting in impaired cellular processes and can lead to organ damage
Babies with heart failure due to VSD may be treated with:
diuretics (lasix or aldactone) digoxin (increases contraction of heart) nutritional additives to baby's milk (NG tube if necessary) surgery may be required: closed by patching or suturing during open heart surgery
The opening that bipasses the lungs in fetal development
ductus arteriosis
The fetal lungs do not function for respiratory gas exchange, so a special circulatory pathway, the __________ _______, bypasses the lungs.
ductus arteriosus
Right ventricle blood goes to the pulmonary arteries but a majority is shunted through the ________ ________ to the _______ ______ and back to the umbilical artery.
ductus arteriosus to the descending aorta
Tet spells
episodes of cyanosis and hypoxia that happen in TOF. Spells, rarely seen before 2 months of age, occur most frequently in the first year of life. They occur more often in the morning and may be preceded by feeding, crying, defecation, or stressful procedures. Because profound hypoxemia causes cerebral hypoxia, hypercyanotic spells require prompt assessment and treatment to prevent brain damage or possibly death.
Air sacs are full of _____ in a fetus
fluid, not air
Most of the mixed blood from the inferior vena cava passes straight through the right atrium and through the _______ ______, an opening into the left atrium.
foramen ovale
Cyanosis in the newborn could be caused by:
foramen ovale not closing
Lungs in a fetus
full of fluid, not air. Increased resistance. Low oxygen. Pressure in pulmonary arteries are high. Not much blood comes back through the pulmonary veins.
The blood flows into the left ventricle and is squeezed out into the aorta, where the arteries supply the following places that receive most of the oxygen-rich blood:
heart, head, neck, and arms (think cephalo-caudal development)
A more useful classification of congenital heart defects is based on:
hemodynamic characteristics (blood flow patterns within the heart)
Defects that allow blood flow from the higher-pressure left side of the heart to the lower-pressure right side (left-to-right shunt) result in:
increased pulmonary blood flow and cause heart failure (HF).
Obstructive defects impede blood flow out of the ventricles; whereas obstruction on the left side of the heart results in _____, severe obstruction on the right side causes ______.
left side results in heart failure right side results in cyanosis
Oxygen-rich blood goes from the placenta to the fetal abdomen. When the umbilical vein reaches the _____, it divides into two branches. One goes to the liver, one goes through the ductus venosus to the inferior vena cava.
liver
Placenta has a _______ resistance
low (makes blood divert towards it)
___________ are not functional in a fetus
lungs
What is the minimal normal urinary output for a newborn and for a pediatric patient?
newborn: 1/2ml per kg pediatrics: 1ml per kg
PDA
patent ductus arteriosis. This is a condition when the ductus arteriosus fails to close after birth.
Reflection question: What is the route of blood circulation of the fetus?
placenta-->umbilical vein-->1)liver 2) ductus venosus 3) inferior vena cava + deoxygenated blood from legs-->right atrium-->1)foramen ovale-->left atrium OR 2) right ventricle-->pulmonary trunk-->1) pulmonary arteries to lungs to pulmonary veins OR 2) ductus arteriosus to aorta OR left atrium to left ventricle to aorta-->aorta to abdominal aorta --> illiac arteries -->umbilical artieres --> placenta
Over time, two physiologic changes occur in the body in response to chronic hypoxemia
polycythemia and clubbing. Polycythemia, an increased number of red blood cells, increases the oxygen-carrying capacity of the blood. However, anemia may result if iron is not readily available for the formation of hemoglobin. Polycythemia increases the viscosity of the blood and increases the risk for blood clot formation. Clubbing, a thickening and flattening of the tips of the fingers and toes, is thought to occur because of chronic tissue hypoxemia and polycythemia
Where is the pressure highest in a fetal heart?
pressure actually higher on the right side. This causes blood to go into the left atrium from the right side.
How does hemodynamics affect blood flow?
pressure and resistance affects flow by making the flow faster or slower. It can also effect where the blood flow is moving. The blood may take a different path than normal due to pressure and resistance. Blood may shunt right to left or left to right. Alterations in flow can be fatal if not corrected, such as causing heart failure.
PS
pulmonic stenosis. a condition in which a deformity on or near your pulmonary valve, the valve that influences the blood flow from your heart to your lungs, slows the blood flow.
Inferior vena cava in fetal circulation gets blood from:
right leg, left leg, ductus venosus. This blood is mixed.
For VSD, why get an EKG?
see heart rhythm and rate
For VSD, why get a doppler/echo?
see structures, defects, and size of the heart
For VSD, why get a chest x-ray?
see the size of the heart, see if pulmonary congestion, may see right sided hypertrophy
Deoxygenated blood returning from the head and arms enters the right atrium through the ___________ ________ _____.
superior vena cava
The heart defect we need to know that causes decreased pulmonary blood flow
tetralogy of fallot
With the clamping and severing of the cord, what 3 vessels are functionally closed? They are converted into ligaments within 2 to 3 months.
the umbilical arteries, the umbilical vein, and the ductus venosus
Oxygen-rich blood from the placenta flows rapidly through the ______ ______ into the fetal abdomen.
umbilical vein
Oxygenated blood from the placenta enters via the umbilical _____
vein
Most common congenital heart defect
ventricular septal defect (VSD)
A negative screening for congenital heart disease in infants
≥95% in the right hand or foot and ≤3% difference between the two extremities is a negative screen (no further testing is required).
