What Is SADS?
Sudden Arrhythmia Death Syndrome or Sudden Adult Death Syndrome as the title implies, culminates in a person dying very suddenly and unexpectedly.
Sudden death in the family is particularly traumatic for the relatives and friends of the victim as this type of death can occur in an apparently fit and healthy young person who has shown absolutely no sign of illness.
In some sudden arrhythmia deaths there are no signs at all on autopsy testing, this is due to faults within the electrical activity of the heart, which cannot be detected after death.
One such condition is called the Long QT Syndrome (LQTS).
With the Long QT Syndrome the only symptoms to watch out for are fainting spells or sudden death, it is therefore extremely important that anyone with any symptoms of syncope (fainting) should be screened for the condition, early identification can reduce the mortality rate.
Long QT Syndrome (LQTS) is an abnormality of the heart electrical system. The mechanical function of the heart is normal however the electrical problem is due to defects in heart muscle cell structures called ion channels. These electrical defects pre-dispose affected persons to a very fast heart rhythm (arrhythmia) called ‘torsade de pointes’ which leads to sudden loss of consciousness (syncope) and may cause sudden cardiac death. The QT refers to an interval measured on the electrocardiogram (ECG).
This syndrome can be inherited or acquired.
Inherited Long QT Syndrome - This was first clearly described in 1957 as two variants - the autosomal dominant Romano-Ward type and the autosomal recessive Jervell, Lange-Nielsen type.
Acquired Long QT Syndrome - This version is most often due to the administration of medications. These medications are contraindicated in patients with the Long QT Syndrome, and a subsequent section will identify these drugs.
How common is inherited Long QT?
The frequency of Long QT is unknown but it appears to be a common cause of sudden and unexplained death in children and young adults. It is much more common than previously thought – possibly as frequent as 1 in 5,000, and may cause 3,000-4,000 sudden deaths in children and young adults each year in the United States. Estimations for Australia are more difficult to obtain.
What are the symptoms of Long QT?
The usual symptoms are sudden loss of consciousness (syncope) or sudden death, typically occurring during physical activity or emotional upset. These most commonly begin in pre-teen to teen-age years, but may present from a few days of age to middle age. The syncopal episodes are often misdiagnosed as the common faint or a seizure. Actual seizures are uncommon in Long QT syndrome. Sudden loss of consciousness during physical exertion or during emotional excitement should strongly raise the possibility of the Long QT Syndrome.
A family history of unexplained syncope or sudden death in young people should also raise suspicion. About one third of individuals who have the Long QT Syndrome never exhibit symptoms, and therefore, the lack of symptoms does not exclude a person or family from having Long QT. Any young person that has an unexplained cardiac arrest should be considered for Long QT, as well as those with unexplained syncope.
What causes the symptoms?
People with Long QT syndrome develop a very fast heart rhythm disturbance known as 'Torsade de pointes'. The rhythm is too fast for the heart to beat effectively, so the blood flow to the brain falls precipitously causing the sudden loss of consciousness. In most instances, there is no warning prior to syncope.
Common triggers and consequences of the arrhythmias
Triggers include swimming; running; a startle such as an alarm clock, a loud horn or ringing phone; anger, crying, tests or other stressful situations. Sudden death may occur during sleep. Consequences include car accidents; apparent drowning; dizziness or near fainting after exercise or sports.
How is Long QT Syndrome diagnosed?
Diagnosis of Long QT is commonly suspected or made from the ECG. It is often recommended that all children and young adults should have an ECG as part of their evaluation for an unexplained loss of consciousness episode. Sometimes no testing, or only neurological testing with an electroencephalogram (EEG) is done. It may be necessary to request that an ECG be done and specifically evaluated for QT prolongation.How is Long QT syndrome inherited?
Long QT is commonly inherited by autosomal dominant transmission.
This means that it affects boys and girls equally, and that each child of an affected parent has a 50% chance of inheriting the gene. In a large family approximately 50% of the children would inherit the gene. In usual size families it can range from all to none as each child has an independent 50/50 chance of inheriting the gene.
It is extremely important that all family members be tested for the syndrome once a family member is identified as a Long QT Syndrome patient. The testing should include the parents, all siblings, any children of the affected individual, and all relatives of the affected parent.
It is extremely important that all patients be identified early in order to prevent the tragic and unnecessary sudden deaths that may occur.
How do you treat Long QT?
Beta blocker medications are the mainstay of therapy for most patients with the Long QT Syndrome. These medications are effective in about 90% of affected subjects. New information regarding the genetics of the syndrome suggests that a subset of patients might be treated with other drugs, either instead of or in addition to the beta blocker medications.
This can be discussed with a physician and it depends upon the gene type which you have. In patients who do not respond to medication, the insertion of a pacemaker or the automatic defibrillator, or the surgical cutting of certain nerves in the neck, called cervico-thoracic sympathectomy, can be utilised.
All patients with symptoms should be treated, and because it is not possible to predict which patients are vulnerable to the syncope and sudden death, and sudden death often occurs with the first episode, asymptomatic patients, especially children, should also be treated.
For more information about SADS please visit www.sads.org.au