Hypoplastic left heart syndrome (HLHS)
In hypoplastic left heart syndrome (HLHS), the structures of the left heart are too small. As a result, the left ventricle cannot or can only partially contribute to supplying the body's circulation. Typically, there is a
- severe narrowing or obstruction of the aortic valve (aortic stenosis, atresia) and/or mitral valve (mitral stenosis, atresia)
- a poorly developed left pumping chamber (hypoplasia or aplasia)
- hypoplasia (underdevelopment) of the ascending aorta and the aortic arch and an intact ventricular septum (IVS).
Today, the term HLHS is used for extreme forms of left ventricular hypoplasia that result in a right ventricular-dependent circulation.
It is a critical, highly complex heart defect with ductus-dependent systemic circulation. The diagnosis is often made prenatally as part of a fine diagnosis. Subsequently, detailed counselling of the expectant parents about the therapeutic options, preferably by an experienced paediatric cardiologist, is recommended.
As a life-saving treatment approach, surgery is indicated for newborns with hypoplastic left heart syndrome, with the first surgical step, Norwood I surgery, usually within the first week of life. Ideally, the child should be treated by a neonatologist immediately after delivery and the diagnosis should be confirmed by a paediatric cardiologist using echocardiography. After intravenous administration of prostaglandins (5-10 ng / kg / min), the child should be transferred promptly for surgical treatment (DHZB emergency hotline: 030 4593-1000).
Timing:In the first few weeks of life, when the newborn baby is stable.
Two further operations are required at the age of 4-6 months and approx. 2 years until Fontan palliation is achieved.
Norwood 1 operation
The aim of the operation is to ensure that the only existing, fully developed right ventricle can supply the body and lung circulation with blood in equal measure.
Firstly, the trunk of the pulmonary artery (PA) is separated from the heart. Furthermore, the short-circuit connection from the pulmonary artery to the aorta (PDA) is severed (dashed line). The atrophied aorta is now cut open along the entire arc up to the narrowing point (ISTA) (dashed line). To ensure that the systemic circulation is adequately supplied with blood, the cut arch of the aorta is widened with a patch and connected at the root to the trunk of the pulmonary artery. This significantly widens the atrophied initial part of the aorta and also widens the narrow section behind the arch (ISTA). In order to supply the lungs with blood from a safe source, a plastic tube (shunt) is sutured between the branch of the aorta and the pulmonary artery.
The aim of the operation is achieved
The mixed blood from the ventricle now flows unhindered into the aorta, as the atrophied initial part and the constriction behind the arch have been widened with a patch. The blood supply to the lungs is ensured by the plastic tube between the aorta and pulmonary artery.
Glenn operation (Norwood stage 2)
The right ventricle, which normally only supplies the lungs with blood, supplies the entire body with blood after the Norwood 1 operation. This ventricle would certainly be overwhelmed for a longer period of time, as it normally only supplies the pulmonary circulation and not the systemic circulation. Another disadvantage is that only mixed blood flows in both circuits. The next step in separating the circulatory system is therefore the Glenn operation at the age of three to five months, in which the plastic tube is removed and the superior vena cava is connected directly to the right pulmonary artery. This procedure partially relieves the right ventricle, which previously had an increased workload, and the blood is passively channelled through the lungs by the venous pressure. As a result, the affected children experience a normal level of development.
The Glenn operation is favoured over the Hemifontan operation at the DHZC.
Fontan operation (Norwood stage 3)
The Glenn operation ensures that the deoxygenated blood from the superior vena cava flows directly into the lungs and no longer mixes with the oxygen-rich blood from the lungs in the common ventricle. However, the blood from the inferior vena cava has not yet been diverted because the pulmonary vessels were not yet ‘big enough’ to absorb all the blood from the systemic circulation. In order to better relieve the single ventricle, the blood from the inferior vena cava must also be channelled directly into the lungs instead of into the common ventricle.
There are various techniques for this. The most commonly used today is total cavopulmonary anastomosis (TCPC), in which a tube (tunnel) is led past the outside of the heart and connects the vein to the pulmonary artery. This type of venous blood supply to the lungs was first developed by the Frenchman Francis Fontan in the 1980s and the circulation that is achieved with it is also known as the Fontan circulation. During the Fontan operation, the inferior vena cava is connected to the pulmonary artery in the form of a Goretex tunnel outside the heart. The pulmonary and systemic circulation are thus completely separated from each other.
