Heart Failure in Infants and Children (26)

Four types of VSD:

1. Perimembranous 2. Muscular 3. Inlet 4. Juxtarterial/supracristal Muscular are the most common but spontaneously close more frequently, making perimembranous VSDs seem the most prevalent.

What are the causes of ductus arteriosus (DA) closure?

1. Pressure gradient reversal causes a reversal of flow. 2. Increases in O2 (a vasoconstrictor) in the DA. 3. Loss of PGE2 (a vasodilator) supply from the placenta. PGE2 seems to have little effect on peripheral resistance, however. 4. Loss of PGE2 by pulmonary circulation. 5. Eventually, hypertrophy of the LV and reduction in size of the RV wall helps to close it.

Umbilical arteries branch from:

Anterior division of the internal iliac arteries

Lesions which depend on flow via the ductus arteriosus to maintain pulmonary circulation

1. Pulmonary atresia 2. Critical pulmonary stenosis 3. Tricuspid atresia 4. Tetralogy of Fallot

General objectives of treatment of CHF in infancy

1. Reduce the preload with diuretics 2. Enhance cardiac contractility 3. Reduce afterload 4. Enhance nutrition

Preload reducing agents used in treatment of CHF

Furosemide, hydrochlorothiazide, spironolactone These are diuretics

How can you keep the DA open?

Give PGE1

TOF clinical signs

Harsh systolic ejection murmur at the left upper sternal border with radiation to both lung fields. Level of cyanosis varies Most common congenital heart disease beyond infancy Presents with a history of squatting, hyperpnea, irritability, and cyanosis. Heart is boot shaped on X-ray.

Ductus venosus

Shunts a portion of the umbilical vein blood flow to the IVC, bypassing the liver

Foramen ovale

Shunts blood from the RA to the LA

Ductus arteriosus

Shunts blood from the pulmonary trunk to the aorta, allowing it to bypass the lungs in the fetus

When is the administration of PGE1 indicated?

1. Right heart outflow obstruction (pulmonary atresia/stenosis, tricuspid atresia) 2. Left outflow obstruction (hypoplastic left heart syndrome, preductal coarctation of the aorta, interrupted aortic arch) 3. TGV

TOF 4 components

1. Right outflow tract obstruction 2. Overriding aorta 3. VSD 4. hypertrophic RV

Considerations in the *newborn nursery* w/ symptoms of CHF

1. Heart muscle dysfunction (same as in neonate) 2. Structural lesions (PDA, hypoplastic left heart, aortic/pulmonic stenosis) 3. Pulmonary, renal, and endocrine problems

When is the administration of PGE1 contraindicated?

1. Hyaline membrane disease 2. Persistent fetal circulation 3. Left-to-right shunt

Side effects of PGE1

1. Apnea 2. Systemic hypotension 3. Inhibition of platelet aggregation

Lesions which depend on flow via the DA to maintain systemic circulation

1. Coarctation of the aorta 2. Critical aortic stenosis 3. Hypoplastic left heart syndrome

Lesions most commonly not diagnosed prior to discharge

1. Coarctation of the aorta 2. Interrupted aortic arch 3. Critical aortic stenosis 4. Hypoplastic left heart syndrome 5. TGV 6. TOF 7.total anomalous pulmonary venous connection

When is surgical repair of VSDs indicated?

1. Congestive heart failure (CHF) 2. Failure to thrive 3. Left to right shunt > 2:1 4. Pulmonary hypertension

Differential diagnosis of neonatal cyanosis

1. Congestive heart failure w/ alveolar hypoventilation due to congenital heart disease 2. Mechanical impingement on lung function 3. Persistence of fetal circulation 4. Methemoglobinemia 5. Shock and sepsis 6. Neuromuscular conditions 7. Respiratory depression from maternal medications (meperidine, magnesium sulfate) 8. CNS depression 9. right-to-left shunt because of congenital heart disease 10. V/Q mismatch because of primary lung disease 11. Polycythemia

Maternal risk factors for congenital heart disease

1. Diabetes 2. Family history 3. Exposure to Lithium or indomethacin 4. First trimester rubella 5. Residence at high altitudes

Considerations in the *neonate* w/ symptoms of CHF

1. Heart muscle dysfunction (asphyxia, sepsis, hypoglycemia) 2. Structural lesions (tricuspid/pulmonary regurgitation, systemic AV fistula) 3. HR problems (supraventricular tachycardia, congenital heart block) 4. Hematologic conditions (anemia, hyperviscosity syndrome)

Considerations in *early infancy (1-6 weeks)* w/ symptoms of CHF

1. Heart muscle dysfunction (endocardial fibroelastosis, Pompe's disease, myocarditis) 2. Structural lesions (coarctation of the aorta, VSD, AV canal, ASD, PDA) 3. Renal and endocrine problems The same are true in *later infancy*

Eisenmenger syndrome

1. Systemic-to-pulmonary cardiovascular communication 2. Pulmonary arterial disease 3. Cyanosis Diagnosis implies that the development of pulmonary arterial disease is due to increased pulmonary blood flow leading to an increased pulmonary resistance. This causes a reversal of flow through the cardiac shunt (into the left heart), leading to cyanosis.

Possible physical exam findings suggesting CHF?

1. Tachycardia (>150/min) 2. Increased respiratory rate (>50/min) 3. Extremities cool to the touch 4. Hepatomegaly and facial edema in right heart failure 5. Rales 6. Cardiomegaly on chest X-ray 7. Hyperexpansion of lungs w/ flattened diaphragm on X-ray

Closure of umbilical arteries (UA) is due to:

1. Trauma to the vessels 2. Increased levels of NE and Epi from stress during birth 3. Change in O2 tension These lead to increased resistance and increased BP (afterload) Umbilical veins (UV) close for the same reasons

What percentage of congenital heart defects can be detected prenatally by echocardiography?

30-60% Many cases present days to months after birth.

Chance of closure of a 3-8 mm ASD

75%

Incidence of congenital heart disease

8.1 cases per 1000 births

Normal O2 saturations for pre-term neonates

84-90%

Normal O2 saturations for full term neonates

95-100% If 24 hour value is less than 95%, the possibility of a cyanotic defect should be investigated.

Why does the foramen ovale close shortly after birth?

An increase in circulating catecholamines from sympathetic nerves and the adrenal medulla causes an increase in arterial pressure (increased afterload to LV). Inspiration creates negative pressure and, therefore, decreased pulmonary vascular resistance. This increases VR to the LA, increasing LA pressure. RA pressure is decreased due to negative thoracic pressure and a reduction of flow due to closure of the umbilical vein. *This change in pressure in the atria closes the Foramen Ovale*

TGV

Aorta arises from RV, pulmonary artery arises from LV. Only auscultory finding is a single 2nd heart sound from the aorta (now positioned anteriorly) "Egg on a string" appearance on X-ray Secondary lesion (ASD or PDA) is required for survival.

What stimulates breathing to begin?

Asphyxia due to closure of the placental circulation and cooling of the body

Inlet VSDs

Associated with AV canal and Down syndrome. Do not close spontaneously.

Afterload reducing agents used in treatment of CHF

Captopril, Enalapril, Lorsatan, Nitroprusside, Nitroglycerine Beta blocks (like carvedilol) can also be used to reverse the long-term effects of increased sympathetic activity.

Cardiomegaly on X-ray

Cardiothoracic ratio greater than 0.55 in an infant less than one year old is defined as cardiomegaly

Presentation of ASDs

Commonly are asymptomatic until adulthood, presenting with exercise intolerance. Fixed split 2nd heart sound. Diastolic flow rumble across the tricuspid valve and/or a pulmonic systolic murmur may also be heard (with increased right-to-left shunting).

Complete AV canal

Consists of a primum ASD, common AV canal, and an inlet-type VSD. Both types of AV canal defects are common w/ trisomy 21.

Partial AV canal

Consists of a primum atrial septal defect and a cleft mitral valve

Common ways for a child to present with congenital heart disease

Cyanosis Heart murmur Congestive heart failure

Inotropic agents used in treatment of CHF

Digoxin, dobutamine, epinephrine, milrinone, dopamine

Why does aortic pressure increase after birth?

Increases in NE and decreased TPR.

What drug can help close the DA?

Indomethacin - A prostaglandin inhibitor

Umbilical vein connects to:

Liver and IVC (via ductus venosus)

Supracristal VSDs

Most frequently seen in Asian populations.

Typical presentation of VSD

Murmur with or without signs of congestive heart failure. The murmur is harsh and holosystolic, located along the mid to lower sternal border. A diastolic flow rumble may also be present in significant left to right shunting occurs. This can act as a functional mitral stenosis.

Why is infant feeding important for diagnosing CHF?

Normally, an infant is finished feeding in 10-20 minutes. If they take 30-45 minutes with increased repiratory effort, fatigue, and sweating, it could suggest CHF. Other indications of CHF are slow weight gain and frequent lower respiratory tract infections.

Ostium primum ASD

Often associated with cleft mitral valve and AV canal Unlike secundum ASD, these do not close spontaneously.

Chance of closure of a >8 mm ASD

Probably just need to do surgery.

Changes to the lungs leading to Eisenmanger's syndrome

Prolonged increase in blood flow to the pulmonary vasculature leads to hypertrophy and hyperplasia of the pulmonary arterioles. This decreases lumen size and gradually increases pulmonary vascular resistance. Initially, the lungs are responsive to pulmonary vasodilators but eventually, surgery is required.

Why might some congenital defect murmurs not be heard for several days after birth?

Pulmonary vascular resistance (PVR) remains high.

The most common type of ASD

Secundum 87% of these close by age 4. Spontaneous closure is dependent upon size. Ones that do not close spontaneously can be closed using transcatheter devices.

Most common congenital heart defect

VSD

Congenital heart defects that can result in a significant increase in blood flow to the pulmonary circulation (possibly leading to Eisenmenger's syndrome)

VSD, ASD, PDA

When does cyanosis occur?

When the absolute level of reduced hemoglobin in the capillary bed exceeds 3 g/dL.

Effect of O2 on respiratory problems

Will increase O2 saturation

Effect of O2 on congenital heart defects

Will not alter the deficiency

What are the most common cyanotic congenital heart disease lesions?

tetralogy of Fallot (TOF) transposition of great vessels (TGV)