Cardiac Inherited Disease Registry

LONG QT SYNDROME

INFORMATION FOR FAMILIES

Background

Long QT syndrome (LQTS) is an uncommon hereditary disorder characterised by abnormal electrical activity in the heart. It affects mostly children and young adults causing frequent faints or collapse resulting in sudden death. The most common form of LQTS is inherited in a dominant pattern, which means that each child of an affected parent has a 50% chance of inheriting the disorder. Once a diagnosis is made, treatment is available. However, an accurate diagnosis can be difficult, because not all people affected by LQTS become ill and display symptoms.

Usually, LQTS can be seen on an electrocardiogram (ECG). Every heartbeat is triggered by an electrical signal that tells the heart’s muscle cells to contract. After contracting, these cells must recover – or relax – before the next heartbeat is initiated. The amount of time needed by these cells to recover can be measured on an ECG and this is called the QT interval. During the last part of this interval, the heart is vulnerable and electrically unstable. People with LQTS have an abnormally long QT interval. If the next electrical signal arrives before the muscle cells have completed their recovery period a dangerously fast heart rate can occur leading to a fall in blood pressure and loss of consciousness.

People with LQTS are sometimes identified after an unexplained fainting episode. These episodes are usually associated with surges of adrenaline, such as with sudden loud noises, intense emotional reactions, awakening from sleep or during intense physical activity, especially swimming. Currently, the primary treatment for LQTS is a beta blocker medication, which inhibits the effects of adrenaline on the heart. Some patients (not the majority) may benefit from pacemakers or implantable defibrillators or surgical resection of a group of nerves connecting the brain and the heart. Everyone with LQTS should avoid medications that are known to prolong the QT interval. A list will be provided with this information sheet.

Screening family members

Since the gene runs in families, screening of family members is very important, yet this is complex and time consuming. Not only are the tests difficult to interpret, but the family members may be spread across New Zealand and the rest of the word. Centralised registries – such as the International LQTS Registry based in Rochester, New York and the registry such as we are establishing in the Auckland region – are vital. These help achieve successful family screening programmes, and allow dissemination of new information to affected family members and their clinicians. They also permit useful research studies into this common yet widespread disease.

Research

Scientific breakthroughs – including the recent discoveries of six groups of genes that cause LQTS – may soon lead to better therapies and ultimately a cure. It seems likely that different forms of LQTS, caused by the different genes, may benefit from “gene-specific” therapies yet to be developed. Much of the current research into LQTS aims to improve the reliability of the tests we use to make the diagnosis – some people who carry the abnormal genes can be have a normal QT interval on the routine ECG. Exercise tests and 24 hour ECG monitoring show considerable promise and are already useful clinically. It is likely your physician may request either or both of these during evaluation of your family. Other research is at a molecular level – identifying the gene defects and the effects these have on the heart muscle cells. Only about 60% of affected families will have a gene defect that has thus far been identified.

Genetic diagnosis

Until very recently, genetic diagnosis has only been available by sending blood overseas. At present these genetic analyses are time consuming and very expensive. Now a significant proportion of families will be able to receive a genetic diagnosis within New Zealand. Laboratories exist in Wellington, Christchurch and Auckland. Your supervising physician, after discussion with yourself, will send your blood for genetic testing to the facility that seems most appropriate for your case at that time.

Other sources of information

There are a number of physicians in New Zealand who have a special interest in the management of families with long QT syndrome and some of these are listed below. There are many web sites to visit, of varying quality. A good start is www.SADS.org.

Physicians with skills in the management of long QT syndrome

Dr Ian Crozier, Cardiologist, Christchurch Hospital, Christchurch

Dr Joanne Dixon, Clinical Geneticist, Wellington Hospital, Wellington

Dr Spencer Heald, Cardiologist, Waikato Hospital, Hamilton

Dr David Heaven, Cardiologist, Middlemore Hospital, Auckland

Dr Margaret Hood, Cardiologist, Green Lane Hospital, Auckland

Dr Nigel Lever, Cardiologist, Wellington Hospital, Wellington

Dr Hugh McAlister, Cardiologist, Waikato Hospital, Hamilton

Dr Jon Skinner, Cardiologist, Green Lane Hospital, Auckland

Dr Warren Smith, Cardiologist, Green Lane Hospital, Auckland

National Long QT Registry in New Zealand

We are in the process of developing this registry and it is not yet truly national. A significant registry exists in Wellington under the care of Joanne Dixon and a new registry, based in Auckland, is being developed as part of the inherited cardiac disease service. This is co-ordinated by Jackie Crawford (Senior Cardiac Technologist) and Drs Jon Skinner and John French. Ultimately we hope to amalgamate these registries to form a national service.

If you have any other questions you would like to ask, please do not hesitate to contact the registry co-ordinator and/or discuss your queries with your Specialist.

If you have any queries regarding your rights as a participant in the Cardiac Inherited Disease Registry you may phone the Health Advocate Trust: Phone (09) 623 5799 Auckland

Or contact Mata Forbes RGON; Co-ordinator/Advisor, Maori Health Services, Auckland Healthcare Services Ltd, Auckland Hospital Grafton; Mobile 021 348 432

Work Phone (09) 307 4949 Ext. 7972.

This study has received Ethical Approval from the Auckland Ethics Committee: AKX/02/00/107