The Role of Genetic Testing in Paediatric Cardiology: Personalised Treatment for Young Patients

Every year, millions of children around the globe are diagnosed with congenital heart defects and other paediatric heart conditions. Many of these heart disorders can be treated with surgical procedures or with medicines. But, sometimes, the treatment becomes complex as the causes may be genetic and are not fully understood.

Advances in genetic testing for heart diseases are providing unprecedented insights into the origins of hereditary heart disease.

In this blog, we’ll explore how genetic testing for cardiovascular disorders is revolutionising paediatric cardiology.

Role of Genes in Paediatric Heart Disorders

Paediatric cardiology focuses on heart diseases in children and is a rapidly advancing field. In this context, cardiovascular genetic testing plays an important role in identifying, diagnosing, and treating heart disorders.

A common question which intrigues one’s mind is, “Is heart disease genetic in children?”

For this, the answer is complex. This is because some heart diseases are strongly influenced by genetic factors while others may be caused by environmental factors and sometimes their combinations are leading causes of heart conditions.

Let’s discuss some genes that have been linked to childhood heart conditions.

1. NKX2-5 Gene

This gene encodes a homeobox transcription factor that forms the heart’s septum (the walls dividing the heart’s chambers) and the conduction system (which regulates heart rhythms).

Any mutations in the NKX2-5 gene are associated with a variety of Congenital Heart Conditions (CHDs), including atrial septal defect (ASD), tetralogy of Fallot, and arrhythmias.

2. GATA4 Gene

The GATA4 gene is a zinc finger transcription factor that is involved in regulating the development of the heart’s walls and valves.

It helps control the growth and differentiation of heart cells, including those that form the heart chambers and heart valves.

Any mutation in the GATA4 gene can disrupt normal heart development and lead to various congenital heart defects like atrial septal defects and atrioventricular septal defects.

3. TBX5 Gene

TBX5 encodes a transcription factor that encodes the formation of the left ventricle and the ventricular septum.

Any mutation in the TBX5 gene is the primary cause of Holt-Oram syndrome, a genetic disorder characterised by heart defects (like atrial septal defects and ventricular septal defects) and abnormalities in the upper limbs.

4. NOTCH1 Gene

The NOTCH1 gene produces a protein that helps activate the Notch signalling pathway.

This pathway plays an important role in the development of various organs and structures, such as the heart and blood vessels, as well as the formation of heart valves during the early stages of development.

Mutation in the NOTCH1 gene is involved in 4 to 10 per cent of bicuspid aortic valve cases, leading to an increased risk of complications such as aortic valve dysfunction, aortic dilation, and aortic dissection.

5. FOG2 Gene

FOG2 acts as a cofactor for GATA transcription factors and is essential for the proper development of the heart and the coronary vessels from the epicardium.

Mutations in FOG2 are associated with congenital heart defects and, more specifically, ventricular septal defects (VSD), as well as Tetralogy of Fallot.

6. MYH7 Gene

The MYH7 gene encodes a beta-myosin heavy chain protein that is part of the muscle fibers in the heart. This is a key component of the cardiac sarcomere responsible for muscle contraction within the heart.

Mutations in this gene can lead to conditions like hypertrophic cardiomyopathy and dilated cardiomyopathy.

7. KCNQ1 and KCNH2 Genes (Ion Channel Diseases)

The KCNQ1 and KCNH2 genes are involved in regulating the electrical activity in the heart by controlling ion channels.

The KCNQ1 and KCNH2 genes are both associated with heart conditions, particularly “Long QT Syndrome” (LQTS), as they encode subunits of potassium ion channels crucial for proper electrical signalling in the heart.

Common Genetic Conditions in Paediatric Cardiology

Congenital Heart Disease (CHD)

These are among the most common birth defects in the world. Often, genetic factors are implicated in cases such as bicuspid aortic valve, hypoplastic left heart syndrome, and tetralogy of Fallot. Identification of mutations that may have caused this defect has been improved through better diagnostic capability and treatment modalities.

The cost of congenital heart diseases in India depends on the treatment approach and the complexity of the case.

Cardiomyopathy

It is a condition in which the heart muscle becomes weak or enlarged. This may be inherited and may lead to heart failure or arrhythmias. Genetic testing is essential for the detection of mutations that cause the various types of cardiomyopathy, including dilated cardiomyopathy and hypertrophic cardiomyopathy, the latter two of which are treated if caught early.

Arrhythmias

Cardiovascular genetic testing can identify mutations responsible for inherited arrhythmias, such as Long QT syndrome or Brugada syndrome, which lead to dangerous heart rhythms. Early diagnosis through genetic testing will enable doctors to monitor and manage these conditions, which reduces the risk of life-threatening complications such as sudden cardiac arrest.

Familial hypercholesterolemia

Familial hypercholesterolemia is an inherited form of high cholesterol wherein children have a predisposed possibility of having heart disease if such a disorder is not identified or diagnosed early. With treatment and lifestyle changes, prevention of early-onset heart disease in children can now be possible.

How Genetic Testing Detects Paediatric Cardiac Conditions?

When we discuss current diagnostic approaches for paediatric heart conditions, we consider physical exams, echocardiograms, and MRI scans. There is no doubt that these methods have been providing valuable information; they sometimes may not detect genetic factors that are involved and are the primary reason behind cardiac problems in children. 

This is where genetic testing for heart diseases emerges as an innovative tool in paediatric cardiology that guides life-saving interventions and helps in generating future health planning for children.

The best paediatric cardiology surgeons in India refer several genetic testing methods depending on the case, and they are unto -

Cytogenetic testing

Cytogenetic testing focuses on analysing large-scale genetic changes, such as chromosomal abnormalities. These changes often underlie syndromic conditions associated with pediatric cardiac disorders.

Some Types of Cytogenetic Testing are listed below.

1. Chromosomal Microarray Analysis (CMA)

It detects large genetic changes like deletions or duplications that may lead to complex congenital heart defects such as 22q11.2 deletion syndrome.

It identifies chromosomal abnormalities when a child has multiple congenital anomalies related to their heart as well as associated developmental delays.

Some conditions that can be diagnosed with CMA are-

• 22q11.2 Deletion Syndrome (DiGeorge Syndrome): It is associated with congenital heart defects such as tetralogy of Fallot and interrupted aortic arch.
• Turner Syndrome: Around 50% of children born with Turner syndrome have heart defects in the left side of the heart and aorta.
• Williams Syndrome: It is associated with supravalvular aortic stenosis.

Hence, by detecting these syndromes, heart conditions in children can also be analysed.

2. Karyotyping

It is a common genome-wide snapshot method that identifies structural changes in chromosomes, such as translocations or aneuploidy, such as trisomy 21 in Down syndrome.

It is often used for diagnosing syndromic conditions linked to cardiac abnormalities.

Some common conditions diagnosed with Karyotyping:

• Down Syndrome (Trisomy 21): It is linked to atrioventricular septal defects and ventricular septal defects.
• Patau Syndrome (Trisomy 13): It causes structural changes in the heart, like atrial septal defects.
• Edwards Syndrome (Trisomy 18): It leads to ventricular septal defects and other structural heart anomalies.

Molecular Genetic Testing

With this approach, smaller-scale genetic variations, such as mutations in individual genes, are examined. These genes can directly contribute to specific heart conditions.

Important Types of Molecular Genetic Testing are-

1. Whole-Exome Sequencing (WES)

It analyses all protein-coding genes in the genome to detect rare or new types of mutations linked to unexplained heart conditions.

It is useful when previous tests fail to identify a cause or when multiple genes are suspected to contribute to the condition.

WES helps in diagnosis of the following conditions:

• Noonan Syndrome: It is associated with multiple genes (PTPN11, RAF1, SOS1) and linked to pulmonary valve stenosis or hypertrophic cardiomyopathy.
• Barth Syndrome: It is an X-linked condition which causes dilated cardiomyopathy and is linked to the TAZ gene.
• Infantile Pompe Disease: It is a metabolic disorder causing hypertrophic cardiomyopathy and is linked to mutations in the GAA gene that breaks down glycogen into glucose in lysosomes.

2. Whole-genome sequencing (WGS)

It examines both coding and non-coding regions in genes and provides a complete understanding of genetic variations.

Though it is still emerging in terms of frequent clinical practices, it holds immense potential for identifying genetic causes of conditions which have remained undiagnosed through other genetic testing methods.

WGS is used when neither karyotyping nor WES provides answers, as it examines non-coding regions that may regulate heart development.

3. Preimplantation Genetic Testing (PGT)

It is used during in-vitro fertilisation (IVF) to screen embryos for specific genetic mutations or chromosomal abnormalities before implantation.

It helps families with a known risk of passing on heart-related genetic conditions to ensure healthier outcomes for the child.

Conditions Diagnosed with PGT-

• Marfan Syndrome: With PGT, testing for mutations in the FBN1 gene is done.
• Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT): Since the condition is associated with RYR2 or CASQ2 mutations, PGT identifies the mutation.

Benefits of Genetic Testing

Genetic testing allows doctors to pinpoint inherited conditions like hypertrophic cardiomyopathy or congenital heart defects, often before any noticeable symptoms appear. After the tests, interventions are planned accordingly. Let’s understand the aspects in brief.

• Once the reason has been finalised, it gives a further indication regarding adjustment in the medication dosages or even considering early surgical interventions.
• Genetic testing assesses familial risks and allows for early monitoring of children who are at high risk due to inherited conditions like Long QT syndrome or familial hypercholesterolemia.
• Screening newborns for specific genetic markers helps doctors detect congenital heart defects that may not be detected in their routine birth check-ups and also helps in predicting the progression of genetic disorders.
• Recent advancements in whole-exome sequencing have made it possible to detect rare genetic mutations linked to paediatric heart conditions and make better diagnostic precision and thus, faster results.

No doubt, evolutions in genetic testing are opening opportunities to new treatment options for complex heart conditions. At the best paediatric cardiology hospitals in India, It also develops new possibilities where paediatric cardiac conditions are not just treated, but also explored within their core.

Overcoming Challenges of Genetic Testing

Genetic testing is, undoubtedly, a powerful tool for understanding the cause of the disease, but it also has some challenges that need to be considered. 

• One of the most common issues is that of the interpretation of variants of uncertain significance. Variants of uncertain significance are genetic changes whose impact is not well understood. This leaves families in a grey zone and makes them unsure about how to proceed further with the treatment.
• It’s a very expensive test, sometimes unaffordable for most families. These tests are gradually becoming more affordable through advancements.
• “When can parents test asymptomatic children?” Such decisions shall be weighed on and in the heads of the individuals, along with proper genetic counselling.

Future of Genetic Testing in Paediatric Cardiology

The scenario of genetic testing is rapidly evolving with advanced technologies like whole-genome sequencing. They are providing even deeper insights into the genetic basis of heart conditions in children. In addition, artificial intelligence (AI), which is now making a significant transformation in medical treatment, is also influencing how genetic data is analysed and thus enables faster and more accurate diagnoses.

Moving towards the most exciting frontier- Gene-editing technologies like CRISPR. They hold the potential to correct genetic mutations even before they can lead to disease and its symptoms. These are still in their experimental stages, but, without any doubt, these advancements promise a future where genetic heart conditions can be treated at their genetic level.