Host:

If you are doing exercise, or are startled by a loud noise, and lead to severe heart rhythm abnormalities, which causes dizziness, seizures, and fainting, and even sudden cardiac arrest, you might have a rare genetic condition called "Long QT syndrome". Today we've invited Hong Kong Children's Hospital, Department of Paediatrics and Adolescent Medicine, Consultant, Dr. Kwok Sit-yee, to explain this to us. Hello, Dr. Kwok.

Dr Kwok Sit-yee:

Hello.

Host:

Can you share with us what does QT stand for? What type of disease is it?

Dr Kwok Sit-yee:

Long QT syndrome is a hereditary heart rhythm disease. The full name is Long QT syndrome. Actually, QT is difficult to explain. It is simply a name of a "waveform" in electrocardiogram (ECG). Every heart cell, in addition to its muscle function, electrical current coordination is also required to perform its function.

QT actually reflects the duration of the heartbeat from contraction to relaxation.For patients with long QT syndrome, the duration of QT is particularly long. So, the time of relaxation will be longer. If there are any premature beats falling in this period, it will cause arrhythmia and we would call it ventricular fibrillation. Simply, that is the period of time when the heart cannot beat. If for a long time the condition cannot be reversed, the patient will faint, there is even a risk of death.

Host:

What are the symptoms when a patient has an attack?

Dr Kwok Sit-yee:

Most of our patients with Long QT syndrome are presented with unexplained syncope. Some people may have seizures. Studies reveal that one in 10 people with Long QT syndrome have experienced a cardiac arrest and needed to be resuscitated. But about a quarter of people may not exhibit any symptoms.

Why Long QT Syndrome can be discovered is because when a patient receives an electrocardiogram or genetic testing during family screening, they find out they have this disease.

Host:

I have read some information that some patients, after being startled by an alarm clock, may have cardiac events, or even cardiac death. Why is that? What are the special circumstances that trigger the attack on these subtypes of long QT syndrome?

Dr Kwok Sit-yee:

I mentioned earlier this is one subtype of long QT syndrome, and the patient belongs to long QT type 2, and these are the specific triggering factors for this subtype. Different subtypes of long QT syndrome have different triggering factors. For example, for patients with long QT type 1, events would be triggered by strenuous exercise or emotional outburst. Like what you said, patients with long QT type 2 are responsive to very loud noises, including ringtones or alarm, which would trigger their cardiac events. For these patients, they are vulnerable before and after giving birth to a child, and they are sensitive to loud noise. Some patients with long QT syndrome may have cardiac events at sleep, and there are no special triggers.

Host:

Doctor, you mentioned some symptoms, such as cramps, they appear to be like epilepsy. Is it easily misdiagnosed?

Dr Kwok Sit-yee:

The convulsion you mentioned is a common reason why long QT syndrome patients first consult a physician. Studies have pointed out it usually takes half a year to diagnose long QT syndrome after their first presentation.

We have a patient who was one-year-old. He had seen many different doctors in the mainland and was diagnosed with epilepsy. He had tried many different medications for convulsion. However, the convulsions could not be cured. A lot of check-ups had been performed in Hong Kong, but it was just regarded as simple epilepsy. At one occasion, he injured his leg in a traffic accident and was admitted to the hospital. While he was on a heart monitor, his heart rhythm was very irregular. An electrocardiogram was performed and he was found to have Long QT syndrome. By then, it explains why he had convulsion in the past. After medical treatment and the use of defibrillator, the child didn't have any more seizures.

Host:

Heart disease is one of the leading causes of death worldwide. What is the different between long QT syndrome and commonly heard heart diseases?

Dr Kwok Sit-yee:

Commonly heard heart diseases are usually referring to the coronary artery diseases in adults. Coronary artery diseases can cause angina or a "heart attack", which is different from long QT syndrome. This is a genetic disease that leads to abnormal function of the ion channels in heart, and leads to heart rhythm problem. So, it is different from the commonly heard heart diseases.

Host:

Common heart diseases can come suddenly. Does this disease have some early symptoms?

Dr Kwok Sit-yee:

Most of times we will pay special attention to unexplained fainting, particularly when there is a shocking family history, such as sudden death in a very young family member. In addition to sudden death, we will also pay special attention to whether there are any family members who were involved in traffic accidents, and passed away early, in which the drivers may had passed out before having crash on driving, and also drowning. It is possible to have a heart event while swimming, and leave this world. These are the questions we would enquire on background history and family history.

If one has a family history, we will be alerted and do an electrocardiogram to check if a patient has long QT syndrome. We may even do more special tests to help them to find the causes.

Host:

Doctor, you mentioned that this is a genetic disease. Are chances that there are acquired factors?

Dr Kwok Sit-yee:

Yes, there are acquired factors. Hereditary long QT Syndrome is only one subtype. Another subtype is called acquired Long QT syndrome. So what patients will have this? These are patients who have taken medication that can prolong the QT interval. The examples are antibiotics, some psychiatric drugs or electrolyte abnormalities in the body, which lead to long QT intervals. But for these cases, the chances of experiencing cardiac events are lower. However, we will pay special attention as well.

Host:

Thank you doctor for sharing with us today. That's all for now. Goodbye.