Hypoplastic left heart disease

The hypoplastic left heart disease is a congenital heart malformation which represents about 1% of all heart anomalies. It is the most common cause of death for heart disease within the first month of life.

As for morphology, the left ventricle is too small or absent, mitral and aortic valves are atretic or severely hypoplastic, the ascending aorta and the aortic arch are hypoplastic, the left atrium is small and there are often other cardiovascular malformations: interatrial defect in 15% of the cases, interventricular defect in 10% and coarctation of the aorta, which is the most frequent combined anomaly.
The disease is well tolerated during fetal life thanks to supersystemic pulmonary resistances and a prevalent right ventricle which ensures a normal pressure of perfusion into the descending aorta and the placenta through the ductus arteriosus, whereas the disease becomes intolerable after birth because of the inversion of the relation of the systemic and pulmonary resistances and the closing of the ductus arteriosus, which causes a dramatic drop in the systolic flow and in the pressure into aorta and a situation of shock.





Hypoplastic left heart syndrome. There is an atresia of mitral valve and aortic valve, left ventricle is virtual, ascending aorta is hypoplastic. The ductus arteriosus is the only way for the aorta to receive blood.


 

 

The survival of these patients depends on the size of the ductus arteriosus which permits the right ventricle to keep the right flux into the aorta and on the presence of a wide interatrial defect which allows the decompression of the left ventricle. The medical treatment consists of mechanical ventilation and oxygen therapy, infusion of prostaglandin immediately after birth, in order to maintain the ductus arteriosus open, and atrioseptostomy to decompress the left atrium and improve oxygenation.
From a surgical point of view there are two alternatives:

  • Norwood procedure
  • Cardiac transplant

The Norwood procedure followed by the Fontan procedure

  • The first phase of the Norwood procedure, undertaken immediately after birth, consists in the resection of the trunk of the pulmonary artery, closure of the distal end by a patch and binding of the ductus arteriosus; a shunt is carried out on the right between the subclavian artery and the right pulmonary artery and a connection of the proximal pulmonary artery with the ascending aorta and the aortic arch.

  • The second phase of the Norwood procedure performed at the age of six months, consists in creating a pulmonary shunt between the superior vena cava and the right pulmonary artery.

  • The third phase consists in a modified Fontan procedure, at the age of 18 months.

 

The best candidate for the last stage of the Norwood procedure must present the following hemodynamic characteristics: not restrictive interatrial communication, adequate tricuspid valve, a not obstructed anastomasis between the pulmonary aorta and descending aorta, low vascular resistances and adequate right ventricular function.

At present some authors report a rate of survival of 76% at the age of 1 month, 58% at the age of 12 months, 54% at the age of 4 years. Others report significantly lower data. At present there are still controversial theories about which procedure should be applied.

Some parents might choose a third alternative: let nature run its course.

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