The fetal heart is already formed during the first trimester. The first heartbeats can be detected in week 5-6 of gestation. Normally, during week 10, the heart is already anatomically complete. From this stage onwards it undergoes mainly processes of growth.
Congenital heart defects are caused by non-optimal cardiac development during fetal development. The prevalence of this condition is 8 in 1,000 births. There are various heart defects which occur in various levels of severity. Milder defects have little to no clinical manifestation, whereas severe defects may be lethal
Various factors may cause congenital heart defects, such as diseases during pregnancy (diabetes, rubella, etc.), alcohol consumption during pregnancy, the use of certain medication that is not meant to be used during pregnancy, and other factors. This article will discuss congenital heart defects caused by genetic mutations.
Heart defects can manifest in the pulmonary artery, the aorta, the interventricular septum, the atria, and more. Congenital heart defects are typically divided in two main groups: heart defects as an isolated finding, and heart defects as part of a range of symptoms.
Which gene mutations can cause congenital heart defects?
In most cases, congenital heart defects are caused by a combination of genetic and environmental factors. The diagnosis of a heart defects indicates a higher risk for genetic or chromosomal disorders. Therefore, the diagnosis of a heart defect through a fetal heart ultrasound scan requires also preforming amniocentesis.
When heart defects are an isolated finding, most chances are that this defect did not develop due to a genetic disorder. however, in special cases, the specific gene mutation that caused the heart defect can be detected.
Here are the main factors that can be diagnosed via genetic testing:
- Chromosome abnormalities – such as Down syndrome (trisomy 21).
- Microdeletion and microduplication syndromes – microdeletions in the long arm of chromosome 22 are detected in 10% of fetuses suffering from heart defects. In addition, microdeletions in chromosome 7 are prevalent. Therefore, a FISH test is required whenever heart defects are detected.
- Genetic disorders with a simple inheritance (mostly autosomal dominant inheritance) – tuberous sclerosis, Holt Oram syndrome, Char syndrome, Ellis Van Creveld syndrome, and more.
How is this condition diagnosed?
It is important to note that different genetic tests do not diagnose heart defects, but the genetic mutations which cause for the defect. The heart defects themselves are diagnosed through echocardiography, or a fetal cardiac ultrasound, performed by a pediatric cardiologist around week 24 of gestation.
This test is not offered routinely, but only when specific indications exist, such as a suspected heart defect in the fetus following abnormal results in an anomaly scan, diagnosis of heart defects linked to conditions such as spina bifida or hydrocephalus, increased nuchal translucency, high levels of amniotic fluid, a family history of heart defects, and more.
There are various gene mutations that can cause congenital heart defects. In some cases, the defect develops due to multiple mutations in several genes that occur simultaneously. Among those genes are: TBX5, TAB2, EVC, and more.