Catecholaminergic Polymorphic Ventricular Tachycardia

What Is CPVT & What Causes It?

CPVT is a form of genetic heart disease. It is characterised by abnormal heart rhythms when stress hormones, in particular adrenaline or noradrenaline (also called catecholamines) are high. These are released when you exercise or experience intense emotion. Typically, these help to increase your heart and blood pressure so that your muscles get the extra oxygen they need when you are exercising or as a response to a stressful situation. However, if you have CPVT, this process doesn’t work in quite the same way. 

Instead, your heart will beat more rapidly. It can beat so quickly that there is no time for blood to fill the heart before the next beat. This means that while your heart is technically pumping, sufficient blood is not being moved around your body. If left untreated, your heart may stop beating entirely, potentially leading to sudden arrhythmic death syndrome.

This arrhythmia (irregular heartbeat) is a result of mutations in your genes that control certain cardiac proteins. Mutations to these genes then affect how calcium moves through your heart, leading to extra calcium in your heart’s electrical system.

The electrical system lets your heart know when and how fast it needs to beat in order to pump blood around the body. With the extra calcium, it beats faster and more often, which can then lead to palpitations, loss of consciousness and even sudden death.

Specialists have carefully examined cases of CPVT to better understand which genes play a role in this heart condition. Presently, mutations in the genes RYR2, CASQ2, CALM1, CALM2, TECRL and TRD have been identified as causing CPVT, with mutations in RYR2 thought to be responsible for most cases of CPVT. However, other genes may also play a role in the condition, and we may learn more about these through research in the future

Like all genetic mutations, the mutations that cause CPVT can be inherited from your parents or they may spontaneously occur when you are conceived. CPVT, unlike many other genetic heart conditions, can be autosomal dominant or recessive. Autosomal dominant conditions only require one copy of the gene to be mutated to cause the disease, while recessive conditions need both copies of the gene to be faulty. CPVT is a unique case because of the different genes at play. For instance, if the RYR2 gene contains the mutation, the condition will be autosomal dominant. However, if the CASQ2 gene is affected, it typically is autosomal recessive.

As a result of these inheritance patterns, CPVT genetic testing becomes more important than ever. This is because it allows you to not only confirm a diagnosis of CPVT but understand exactly which gene is affected. You and your healthcare team can then use this information to more accurately predict who else in your family may have the condition, including the likelihood of your children inheriting it.

Do You Have CPVT Symptoms?

There are a range of symptoms that can indicate CPVT. These will generally occur at some point during childhood, but there are instances where they may not become apparent until a later stage in life.

Typical symptoms include:

• Rapid heartbeat (palpitations)
• Fainting (syncope)
• Ventricular tachycardia (arrhythmia)

For many people with the condition, the first obvious sign is ventricular tachycardia, usually brought on by exercise. You may feel faint or lightheaded, and even be unpleasantly aware of your heartbeat. Unfortunately, because these symptoms can go away after a time, they may be ignored.

The ventricular tachycardia can then develop into ventricular fibrillation — this is where your heart’s ventricles quiver, making them unable to pump blood. This is a serious and life-threatening development, which can lead to sudden cardiac arrest and death. Without any other clear symptoms, this death may be the first and only symptom of the condition in an otherwise healthy young person. In fact, when left untreated, the mortality rate for CPVT could be as high as 30% by the age of 30.

This is why it is so important to not only pay attention to any symptoms that could indicate CPVT but to also get a diagnosis as early as possible. This allows you to begin CPVT treatment sooner and improve your life expectancy significantly.

Further, be aware that like all genetic heart diseases CPVT is variable. This means that while one individual in the family may have progressive heart issues, another individual in the same family may have none or just minor changes that can only be detected by an experienced cardiologist who is familiar with the disease.

How Is CPVT Diagnosed?

Unlike many other heart conditions, CPVT does not affect the structure of your heart, meaning some diagnostic tests cannot reveal if the condition is present. For instance, an ECG may show a typical heart. Additionally, because it shares symptoms with other heart conditions, like long QT syndrome and Brugada syndrome, genetic testing is often required to achieve an accurate diagnosis.

Because the arrhythmia caused by CPVT is only observable when there is adrenaline in your system, exercise stress tests or Holter monitors are often the best to look for those patterns of extra beats. Your physician, though, may suggest a number of other heart tests to get an overall picture of your heart’s health as well. Genetic testing can then follow up to confirm any suspicions of CPVT.

How Genetic Testing Can Help

Genetic testing is a vital element of a thorough medical evaluation for CPVT. This is because it can accurately diagnose the cause of CPVT. This then assists your physician in creating a custom treatment and management plan for you.

Furthermore, with genetic testing, you can help family members get diagnosed sooner, which is key to improving their prognosis. Your positive genetic test results can allow them to bypass other complex clinical tests and proceed .

Genetic testing needs to be conducted by an appropriately specialised cardiology and genetics service that understands how nuanced and subtle CPVT can be. Genetic testing is tailored to the individual, and interpretation of complex results can be challenging. Speak to your genetics service about what testing they can offer, and how they work with your health team to ensure you’re getting the most effective and timely treatment. 

Is CPVT in Your Family?

As CPVT can be genetically inherited, a family history of the condition, related symptoms or even sudden death can also be symptoms or signs that you may have the condition. If there are unexplained deaths or instances of healthy people experiencing a sudden cardiac arrest in your family, undiagnosed cases of CPVT may be the cause. Additionally, as CPVT can cause fainting, the presence of unusual deaths, like a strong swimmer drowning, may also indicate the condition is in your family.

Therefore, along with diagnostic and genetic testing, it can be worthwhile writing down any family members and their relevant health history if you suspect CPVT may be at play. You can then present these notes to your general practitioner, cardiologist or any other specialists working with you to help speed up your diagnosis for a better prognosis.

Thinking about your family health history, make a note of any:

• Sudden or unexplained deaths of otherwise healthy young people
• Sudden cardiac arrests without explanation
• Histories of fainting or arrhythmias