During routine ultrasound examinations during pregnancy, special attention is paid to the baby’s heart. In this context, it may be determined that a child—despite functional heart valves and a well-functioning heart chamber—already has a significantly undersized left side of the heart while still in the womb. This underdevelopment can be so severe that the heart is unable to supply the body with blood after birth. Other terms for this spectrum of malformations include functional left heart hypoplasia, hypoplastic left heart complex, or borderline left ventricle.
Affected children can often only be helped after birth through complex and repeated cardiac surgery. And only some of these children will develop normal circulation (two-chamber circulation) over time.
If your unborn child has been diagnosed with this serious condition, a non-invasive drug treatment can be used to achieve significant growth of the left side of the heart, even shortly before the end of pregnancy.
A non-invasive drug treatment method that can help unborn children with undersized left heart structures even shortly before the end of pregnancy was developed by Prof. Thomas Kohl at the DZFT almost 10 years ago: chronic intermittent maternal-fetal hyperoxygenation, known as “oxygen therapy” or the “Kohl procedure” for short. The procedure is very simple and achieves significant catch-up growth of undersized left heart structures even in the last weeks of pregnancy.
The principle of oxygen therapy is easy to understand: before birth, the pulmonary vessels of the unborn child are still narrow. This makes sense, as the child is not yet breathing independently but exchanges oxygen and carbon dioxide via the placenta. Immediately after birth, however, these vessels must expand significantly so that the oxygen contained in the air can enter the child’s blood via the airways and alveoli. The strongest trigger for this vital dilation of the pulmonary vessels is oxygen itself. We make use of this mechanism in “oxygen therapy.”
When a pregnant woman inhales a concentrated form of oxygen, a small portion of it passes through the placenta to her unborn child. In many cases, this small amount is sufficient in babies with a too small aortic arch to lead to a pronounced dilation of their pulmonary vessels and an increase in pulmonary blood flow.
This automatically causes the blood to return to the left atrium via the pulmonary veins and from there preferentially through the left side of the heart into the aorta.
The significantly stronger inflow into the aorta stimulates growth primarily in the undersized areas of the left ventricle, its valves, and the downstream aorta.
A controlled study* published in December 2016 confirms that the Kohl procedure can prevent the otherwise necessary surgical intervention on the aortic arch in the majority of affected children. The study involved 48 fetuses with the corresponding diagnosis. The unborn children were divided into two groups: one group received prenatal oxygen therapy, the other did not.
The result was clear. After birth, 75% of the babies who had not been treated with the Kohl procedure required heart surgery. In contrast, only 20% of newborns who received oxygen therapy required surgical treatment on the aortic arch.
Other areas of the left heart, such as the mitral valve, the aortic valve, and the left ventricle, also showed faster growth under oxygen therapy—a vital advantage of the new treatment for children with hypoplastic left heart syndrome.
The study thus confirms our observations of children with this condition treated at the DZFT to date.
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*Zeng S et al. Sustained maternal hyperoxygenation improves aortic arch dimensions in fetuses with coarctation. Sci Rep 6, 39304; doi: 10.1038/srep39304 (2016)
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