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Hypoplastic Left Heart Syndrome (HLHS)
Single Ventricle Defect
HLHS is grouped into the category of single ventricle defects. In HLHS, the left side of the heart is severely underdeveloped, and the mitral and aortic valves are either entirely atretic (closed), or hypoplastic (small). As seen in the diagram below, the L) ventricle is tiny, and in HLHS, the first part of the aorta is very small, often only a few millimeters around.
Due to this, the L) side of the heart cannot provide circulation to the body.
The right side of the heart develops normally, and pumps blood to the lungs. However because the left side is so small, blood returning from the lungs into the L) atrium must pass through an atrial septal defect (see ASD chapter for more) to shunt into the right side of the heart.
The R) side must then pump blood to the lungs and out to the body, and a patent ductus arteriosus (see PDA chapter for more) is the only way blood can move through the heart to reach the body.
Once this begins to close however, circulation to the body will decrease, leading to very low blood flow to vital organs, that can lead in turn to shock.
Signs & Symptoms
Due to the above, we can expect to see:
☞ Reduced oxygen saturations, from blood mixing in the heart.
☞ Cyanosis
☞ Respiratory distress, as the lungs will be receiving a large amount of blood.
☞ Weak peripheral pulses depending on ductus arteriosus.
☞ Sleepiness, poor feeding, (and respiratory distress may worsen as the ductus closes.)
☞ Faint or no present heart murmur in newborns.
Signs of shock and progression include:
☞ Seizures
☞ Kidney failure,
☞ Liver failure
☞ Worsening cardiac function
Diagnosis
Diagnosis involves fetal echocardiograms, and HLHS is one of the most common cardiac defects found on screening ultrasounds. Early identifications facilitates prompt intervention at birth, with a team ready, at a hospital that can undergo aggressive newborn resuscitation.
Echo's give detailed information about the anatomy of the fetus, and function of the right ventricle, heart valves, ASD size, and size of PDA.
Cardiac catheterisation is not commonly used initially due to high risk in unstable newborns.
Treatment & Management
There are two stages.
1 | Stabilisation, and
2 | Operative / post-operative period.
Stabilisation is commenced immediately from brith to avoid neonate becoming unstable.
There is establishment of an umbilical line for medication administration and blood drawing. Prostaglandin will be administered to keep the ductus arteriosus patent from closing.
Oxygen is not routinely administered, as this promotes blood flow to the lungs and may steal away blood flow from systemic circulation, as well as place more demand on the stressed single right ventricle.
Intubation is undergone to balance blood flow to the body and to the lungs, as well as medication administration to support this.
Surgery is required thereafter. This is commonly undertaken in stages, to reconfigure the baby's cardiovascular system to be as efficient as possible. These do not correct the defect. These are considered palliative.
Norwood operation | week 1 of life
Only 75% of babies survive this surgery, and recovery can be form 4 - 6 weeks.
☞ The Right ventricle becomes the main ventricle pumping to the body.
☞ A neo aorta is fabricated from part of the pulmonary artery, and the original tiny aorta is enlarged to provide blood flow to the body.
☞ A tube graft is moved from an artery to the lung vessels to provide blood flow to the lungs.
Glenn Repair | 3-6 months of age
Fontan Operation | 2-3 years of age
Management
Many problems may occur as these children age into adolescence and adulthood. Fontan patients must have monitoring by cardiology specialists throughout their lives. Some people will experience low oxygenation levels that affect their physical abilities. Some may have weakening of the R) ventricle or leakage of one or more valves. 10% of these patients may develop protein losing enteropathy (albumin and other protein-rich materials leaking into the intestine) that required careful management. Fontan patients may develop liver or kidney function issues that also require monitoring.
Women who wish to become pregnant should be assessed and counselled before becoming pregnant, and if pregnancy occurs, this should be managed by a specialised medical teams skilled in managing pregnancy in women with cardiac defects.
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HLHS:
Surgical stages:
Fontan:
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