Introduction
Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a rare heart rhythm disorder. It can cause the heart to have periods of abnormally fast rhythm called arrhythmias.
Arrhythmias are more likely to happen when stress hormones are released into the body.
Stress hormones, including adrenaline and noradrenaline, increase heart rate and blood pressure when the body is physically or emotionally stressed. Doing this helps the body to get more energy and become more alert.
When a child has CPVT, their body does not respond to these stress hormones in the usual way. The hormones cause the heart to beat quickly and irregularly, which can be dangerous. This type of arrhythmia is called ventricular tachycardia (VT).
Signs and symptoms
Children with CPVT will usually have symptoms when they are doing physical activity, like sports. When their heart beats too fast and irregularly, there is not enough blood pumped through the heart. This causes the oxygen supply to the body and brain to get low and can make them lose consciousness or faint. This can be life-threatening if not treated.
Symptoms of CPVT will usually show up for the first time during late childhood to adolescence.
Diagnosis
CPVT can be difficult to diagnose because there are not usually any differences in the heart's structure. Your local doctor will refer your child to a heart specialist, known as a cardiologist, for testing.
The cardiologist will do tests in the hospital, including:
- an echocardiogram (ECG) to test the electrical activity of the heart while your child is resting
- an exercise stress test where your child has an ECG done while they are running on a treadmill
- an adrenaline challenge where adrenaline is given while the heart is being monitored.
The cardiologist will also take a detailed family history, or they may order genetic testing.
Treatment
Medications
Treatment of CPVT is usually with medications called beta-blockers. Beta-blocker medications block the effect of adrenaline on the heart, preventing it from beating faster.
The beta-blockers used to manage CPVT are:
- propranolol
- atenolol
- nadolol.
Lifestyle changes
Your child's cardiologist will talk to you about lifestyle changes that your family may need to make. For most children, this means avoiding energetic activities like competitive sports and swimming.
Implantable cardioverter defibrillator (ICD)
If beta-blockers do not work to manage your child’s heart rhythm, or your child has already had a serious heart episode, they may need to have an operation to implant a device to monitor their heart.
An implantable cardioverter defibrillator (ICD) can be implanted under the skin, underneath either the left collarbone or the ribcage.
An ICD is like a pacemaker, a device that uses electrical pulses to help keep the heart beating at an average rate and rhythm.
An ICD can also deliver an electrical impulse if it senses that the heart is beating in a way that could be dangerous. This can help get the heart pumping normally again.
Automatic External Defibrillator (AED)
An automated external defibrillator (AED) is a portable device that delivers an electric shock to make the heart rhythm regular again.
The AED works like an ICD, but it is an external machine. It has adhesive pads that must be applied to the chest for the shock to be delivered.
AEDs are pre-programmed to analyse the heart rhythm once the pads are applied to the chest. It will audibly tell the user what to do.
AEDs can be found in many public places, like the shops, in case of emergency.
Speak to your child’s cardiologist about whether this device should be used on your child.
Management
Causes of CPVT
Not all causes of CPVT are known. Some children have a gene that changes when they are developing during pregnancy. Genes are part of your DNA that decide what traits are passed down from parents to their children.
If your child has this gene, they may pass it down to any children they might have. Your child’s cardiologist will offer genetic testing to see if any family members carry the gene.
Siblings of children with this gene change do not usually have any problems.
Resources and more information
The Heart Centre for Children (at Westmead) is home to The Inherited Arrhythmia Clinic (IAC), a dedicated centre supporting children diagnosed with CPVT and their families. They offer a comprehensive range of services for families with this diagnosis and other arrhythmias.