New local discovery to prevent cardiac arrest in athletes

Posted on 29 March 2017

The recent discovery of the CDH2 gene that causes sudden cardiac arrest in young people and competitive athletes means a disease that was previously difficult to diagnose, often manifesting in sudden death, can now be screened for. Dr Anil Kurian, a Mediclinic Heart Hospital cardiologist, discusses current genetic testing options and what CDH2 could mean for patients.

On Thursday 2 March 2017, the University of Cape Town (UCT), Instituto Auxologico Italiano, and the SA Medical Research Council, officially announced their discovery of the CDH2 gene after 15 years of research.

CDH2 has been identified as the gene causing arrhythmogenic right ventricle cardio-myopathy (ARVC) – a condition that predisposes young people and competitive athletes to sudden cardiac arrest.

The discovery, a world first, has been labelled as ‘probably the biggest breakthrough in South African cardiology since Dr Chris Barnard’s first heart transplant,’ by cardiology professor and Dean of Medicine at UCT, Prof Bongani Mayosi.

What is ARVC?

Dr Anil Kurian, Mediclinic Heart Hospital cardiologist, explains that ARVC is a genetic condition that abnormally alters the muscle tissue in the heart’s right ventricle, making the heart prone to arrhythmias (abnormal heart beat) under certain conditions.

‘Patients can be asymptomatic for most of their lives which is what makes diagnosis difficult, but it can happen that they develop palpitations, they could collapse, have atypical chest pain, shortness of breath, and sometimes sudden death,’ says Dr Kurian.

He explains that the condition can go largely undiagnosed and has a reported prevalence ratio of between 1:2000 to 1:5000. In South Africa alone, more than five young lives are claimed daily due to sudden cardiac arrest.

Who is at risk?

Gene mutations like CDH2, a result of an error in the replication process of a cell, can be caused by a number of factors. Some possible causes include radiation, exposure to certain medication, the presence of an autoimmune disease or an inherent (birth or familial) defect.

Dr Kurian says that high-intensity athletics seem to exacerbate the pre-existing mutation. ‘When these endurance athletes undergo  exercise, the catecholamine* release (adrenaline for example) is very high in the body at that time’. This release causes excessive pressure on the right side of the heart, in effect stretching the heart. When it stretches the right side of the heart in a person with this particular genetic problem, symptoms of palpitations and abnormal rhythms will present.

Young people are generally more likely to be competing athletes or sports players, so they’re likely to have higher levels of adrenalin in the body, along with other catecholamines*. Their right ventricle is, therefore, more likely to be under higher stress, creating the conditions for cardiac arrest.

‘If the right side of the heart is not under stress, even if the problem exists, they may not present with all the clinical signs,’ says Dr Kurian.

All carriers of the gene will have to be excluded from any competitive athletic activity because there’s currently no way of correcting the genetic defect. Dr Kurian advises that low-intensity or recreational sports (like golf, bowling, recreational cricket or yoga) are still ‘considered okay’.

Taking the test

Dr Kurian explains that while a number of methods are used to find the gene, for the patient it would involve a simple blood test. People suspected of being carriers, i.e. people who’ve presented with symptoms or who have family members who’ve succumbed to sudden cardiac arrest, can now be screened.

Prof Mayosi adds that family members who do not yet have symptoms can be screened allowing medical professionals to be able to advise them to avoid being involved in activities that could put them at higher risk of dying suddenly.

‘So far, we’ve already been able to offer care with regard to the symptoms ARVC presents with. So we treat the abnormalities in the rhythms, we ask patients to restrict exercise, we put them on medication that reduces pressure in the right side of the heart, or in some patients we implant devices such as cardiac defibrillators,’ says Dr Kurian.

He adds that once it becomes mainstream, the genetic test will provide the opportunity for healthcare providers to screen individuals who would’ve missed a correct diagnosis or were only diagnosed after sudden cardiac arrest. ‘We could pick the defect up earlier and have these patients treated in a preventative manner.’

‘This exciting research is going to be a stepping stone into preventing the disease. In future, with the advent of gene therapy, we could target this particular gene which will translate into correcting the problem,’ concludes Dr Kurian.

*Catecholamines are activated during exercise or due to another stimulus, such as fear or attack. These include adrenaline, noradrenaline and dopamine.