Hypoplastic left heart is one of the most severe heart defects with cyanosis and is also Hypoplastic left heart syndrome called. This is understood as the underdevelopment of the entire left side of the heart. These include the mitral valve (the valve between the left atrium and the left ventricle), the left ventricle (the left main chamber), the aortic valve (the valve of the aorta) and the aorta with the aortic arch. The heart valves may be narrowed (stenotic) or completely closed (atretic). Since the left side of the heart is not functioning, the baby is dependent on the right side of the heart alone for blood supply to the body and lungs.
What are the effects of hypoplastic left heart syndrome?? The child is doing well in the womb. It usually grows normally. After birth, the connections between the right and left heart, which are present in every baby, close. These are the foramen ovale (hole between the right and left atria) and the ductus arteriosus (vessel between the pulmonary and coronary arteries). This happens in the first hours of life until about the third day of life. In hypoplastic left heart syndrome, blood backs up in the left atrium because it can no longer drain through the foramen ovale into the right atrium. In this heart defect, the right main chamber pumps its blood not only into the lungs, but also into the systemic circulation via the ductus arteriosus. If the ductus arteriosus closes, which happens in every newborn, the systemic circulation receives hardly any blood and the baby suffers circulatory shock. The child dies undetected within a short period of time. Life-saving is then the infusion with the drug prostaglandin to open the ductus arteriosus again.
Any child with an HLHS is cyanotic (blue) or very pale, usually there is labored breathing. On examination, a very fast heartbeat (tachycardia) and very weak pulses are then noticed.
How Hypoplastic Left Heart Syndrome is treated?
A child with HLHS has the best chance of being treated if the diagnosis is known before birth. The delivery is then planned in a center experienced in the care of these children.
After birth, the patient is immediately started on the drug prostaglandin as a continuous infusion. This usually succeeds in reopening the ductus arteriosus and stabilizing the circulation within a few hours.
To dilate the foramen ovale a cardiac catheter intervention can be performed. Here, a catheter is advanced to the heart via the umbilical vein or a vein in the groin. This directs from the right to the left atrium. There, a balloon sitting on the catheter is inflated, widening the hole in the partition between the atria. This procedure is also called Rashkind procedure.
Unfortunately, in HLHS there is no way to stimulate the left side of the heart to grow, so the only option for these children, besides a heart transplant, is to have the right side of the heart do all the work in the long run via a three-stage surgical procedure. The operations are very complex and you can read the details in the section surgical techniques. The most important steps are listed here
1. Norwood operation (or as a variant of it, the Sano operation)
In this case, the outlet from the right main chamber is made by connecting the pulmonary artery to the small aorta, the small aortic arch is widened, the partition between the atria is removed, and finally blood is directed to the lungs via an aortopulmonary shunt. This operation is performed in the first 10 days of life. Is technically for the surgeon the most difficult step of the operations.
At the age of 4-6 months, the large vein of the upper half of the body (vena cava) is sutured to the right pulmonary artery. This operation is a good relief of the right main chamber. The children usually thrive afterwards. Oxygen saturation is around 85% in the best case, meaning the child remains somewhat cyanotic, but is doing sost well.
3. Total cavopulmonary anastomosis (TCPC)
The third operation is done at the age of about 3 years (2-4 years). This also involves connecting the large vein in the lower half of the body to the pulmonary artery. There are different techniques, the most common today is the total cavopulmonary anastomosis (TCPC), where a tube (tunnel) is passed outside the heart and connects the vein with the pulmonary artery. This way of feeding the venous blood to the lungs was first invented by the Frenchman "Francis Fontan" in the 1980s and this is how the circuit is called Fontan circulation.
Since the late 1990s, another treatment option has been developed in which the goal is also a fontan cycle, but in which the first step of treatment is a stent implantation into the ductus arteriosus and a throttling of the pulmonary blood flow with a surgically placed Pulmonary artery banding of the right and left pulmonary artery is. With this technique, parts of the Norwood operation and the Glenn operation can then be done in a single operation, which can be done in about 4. is carried out during the first month of life. The completion of the Fontan circuit is then the same as described above. This procedure also requires a great deal of experience, not only of the surgeon, but also of the pediatric cardiologist.
Living with hypoplastic left heart syndrome
To support the heart, some children need permanent medication and the blood is made a little thinner with Marcoumar (anticoagulant) or aspirin (inhibition of platelets – thrombocytes) so that blood clots do not form. Children with HLHS are no longer cyanotic (blue) after the third operation and, although they are missing one half of their heart, they can bear weight surprisingly well. Nevertheless, it must be taken into account that the heart of a child with HLHS ages more rapidly. Therefore, all major centers that care for such patients have developed follow-up programs to detect and treat deterioration at an early stage. This happens primarily with medicines, some patients expects however possibly also a heart transplantation.