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Long-QT Syndrome
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Frequently Asked Questions
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1. WHAT IS THE LONG QT SYNDROME (LQTS)?

The long QT syndrome (LQTS) is causing an abnormality of the heart's electrical system. The mechanical function of the heart is entirely normal. The electrical problem is due to defects in heart muscle cell structures called ion channels. These electrical defects predispose affected persons to a very fast heart rhythm (arrhythmia) called "Torsade de Pointes" (TdP) which leads to sudden loss of consciousness (syncope) and may cause sudden cardiac death.

1.1. WHY IS THE DISEASE NAMED LONG QT SYNDROME?

The name of the long QT syndrome refers to the QT-interval measured on the electrocardiogram (ECG or EKG for the German term "Elektrokardiogramm"). Your specialist may refer to long QT syndrome as Romano-Ward syndrome or Jervell, Lange-Nielsen syndrome (see point 3).

2. WHAT IS THE QT-INTERVAL?

The duration of the QT-interval is a measure of the time required for depolarization and repolarization to occur. In long QT syndrome, the duration of repolarization is longer than normal. Thus, the QT-interval is prolonged. An interval above 440 milliseconds (msec) is considered prolonged. QT-prolongation in is due to overload of myocardial cells with positively charged ions during ventricular repolarization.

Picture 1: The QT-interval on the ECG.

2.1. WHAT IS THE CORRECTED QT-INTERVAL (QTc)?

The term "corrected" QT-interval may be misunderstood. It does not mean the measured QT-interval is incorrect, but adjusted for heart rate. The reason is that the QT interval is affected by the heart rate. QTc in concept is best compared to the Body Mass Index (BMI).

2.2. WHAT IS BORDERLINE QT?

Any QTc-interval above 440 milliseconds is considered prolonged.

Borderline QT shows a prolongation of QTc, but not prolonged enough to clearly make the diagnosis.

450 to 470 milliseconds is considered borderline. The average QTc for someone who has long-QT syndrome is 490 milliseconds.

A QTc at or above 480 milliseconds in females or 470 milliseconds in males, is probably a sign for long-QT syndrome, in the absence of drugs, electrolyte disturbance, or other conditions that might independently lengthen the QT-interval.

3. WHAT DOES MEDICINE KNOW ABOUT LONG QT SYNDROME?

The disease may be inherited (the genetic form) or acquired:

INHERITED: Inherited long QT syndrome was first clearly described in 1957. There are two variants, the autosomal dominant Romano-Ward (named by the doctors who first described the disease, O. Connor Ward and C. Romano) type and the autosomal recessive Jervell, Lange-Nielsen (Doctors A. Jervell, F. Lange-Nielsen) type. Inherited long QT syndrome is caused by mutations of at least 9 genes, and possibly more. Five different genes have so far been found. The location of a sixth gene is known, but the actual gene has not been found.

Jervell, Lange-Nielsen is associated with profound deafness and is inherited by autosomal recessive transmission. It occurs when both parents have one of the two genes known to cause Jervell, Lange-Nielsen and a child gets both abnormal genes, one from each parent. Statistically, each child of this couple has a 25% chance of getting both abnormal genes (the "homozygous" state), a 50% chance of getting just one abnormal copy (the "heterozygous" state) and a 25% chance of getting both normal genes and not having long QT syndrome. When a child does get both abnormal genes, they are "homozygous" if both parents have the same abnormal gene, or "compound homozygous" if one parent has one abnormal gene and the other parent has the second abnormal gene. Jervell, Lange-Nielsen is rare because it is not likely that both parents will have long QT syndrome.

The second and common form of the syndrome is Romano-Ward. In this form the hearing is normal. The patient inherits one abnormal copy of a long QT syndrome gene, and has one normal copy of that gene. It is, therefore, transmitted by autosomal dominant inheritance. Each child born to an affected parent has a 50% chance of receiving the abnormal copy and a 50% chance of receiving the normal copy.

ACQUIRED: Acquired long QT syndrome is most often due to the administration of medication. These medications are contraindicated in patients with the long QT syndrome, and a subsequent section will identify these drugs.

3.1. HOW COMMON IS INHERITED LONG QT SYNDROME?

The frequency is unknown but it appears to be a common cause of sudden and unexplained death in children and young adults. It is certainly much more common than previously thought. It may be as frequent as 1 in 5000 to 7000. This means, one of 5000 to 7000 newborns have the disease. The Jervell, Lange-Nielsen form is rare, but the Romano-Ward variant is being recognized with increasing frequency. In the USA, the presence of long QT syndrome is estimated to affect about 50.000 people and to cause as many as 3000 deaths each year. It is present in all races and ethnic groups, but it is not certain if the frequency is the same in all races.

4. WHAT ARE THE SYMPTOMS?

The usual symptoms are syncope (sudden loss of consciousness) or sudden death, typically occurring during physical activity or emotional upset. These most commonly begin in preteen to teenage years, but may present from a few days of age to middle age. The syncopal episodes are often misdiagnosed as the common faint (vasovagal event) or a seizure. Actual seizures are uncommon in long QT syndrome, but epilepsy is one of the common errors in diagnosis. 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. Importantly, 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 syndrome. Any young person that has an unexplained cardiac arrest should be considered for long QT syndrome, as well as those with unexplained syncope.

4.1. WHAT CAUSES THE SYMPTOMS?

Patients with long QT syndrome develop a very fast heart rhythm disturbance known as "Torsade de pointes". This is a form of ventricular tachycardia. This 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.

4.2. WHO IS AT RISK FOR SYMPTOMS?

Recently, a scheme for risk stratification among (untreated) patients with long-QT syndrome according to sex, genotype and prolongation of the QT-interval has been proposed.

Risk for cardiac event*

QTc at rest

Genotype

Sex

high (over 50%)

over 500 msec

LQT1

male/female

high

over 500 msec

LQT2

male/female

high

over 500 msec

LQT3

male

intermediate (30-49%)

over 500 msec

LQT3

female

intermediate

below 500 msec

LQT2

female

intermediate

below 500 msec

LQT3

female

intermediate

below 500 msec

LQT3

male

low (up to 30%)

below 500 msec

LQT2

male

low

below 500 msec

LQT1

male/female

* syncope, cardiac arrest or sudden death

5. HOW IS LONG QT SYNDROME DIAGNOSED?

The diagnosis is commonly suspected or made from the electrocardiogram (ECG). All children and young adults should have an ECG as part of their evaluation for an unexplained loss of consciousness episode. On the other hand, there is the possibility to check blood samples for known gene mutations that cause LQTS.

5.1. IS LONG QT SYNDROME ALWAYS OBVIOUS ON THE ECG?

It is generally estimated that approximately 10% to 12% of all patients with long QT syndrome show a normal QT-interval on their ECG. However, this does not mean that these patients are not affected by long QT syndrome. In such cases, a more profound evaluation is needed.

6. WHAT ARE KNOWN TRIGGERS IN LONG QT SYNDROME?

+ Swimming, running

+ Startle: An alarm clock, a loud horn, a ringing phone

+ Emotions: anger, crying, test taking or other stressful situations

+ Sudden death may also occur during sleep

6.1. CAN HEAT BE A TRIGGER IN LONG QT SYNDROME?

It has been noticed that several cardiac arrests occur during summer time. But it is not sure if it this may be an excess in statistical terms. It is however hard to define if these cardiac arrests are related to a specific "risk" due to heat or sweating or if it is mainly a reflection of increased physical activity, excitement and playing during the summer. The only advice patients with long QT syndrome are given is to avoid excessive fluid loss with sweating and to assume potassium supplements through diet.

6.2. CAN PREGNANCY BE A TRIGGER IN LONG QT SYNDROME?

The 9-month interval during pregnancy and the delivery itself are not associated with an increased occurrence of heart events in any of the LQTS women. However, it appears that the physical and emotional stress during the 9-month period after pregnancy (the postpartum period) may be a factor in triggering heart rhythm disorders in some vulnerable women with LQTS.


7. WHAT IS THE THERAPY?

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. However, a new study (Association of Long QT Syndrome Loci and Cardiac Events Among Patients Treated With Beta Blockers: JAMA. 2004;292:1341-1344) shows that among treated patients with LQT2 and LQT3 genotypes, there still is a high rate of cardiac events.

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 your 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 can be utilized.

Another procedure, mainly used in Europe, is the surgical cutting of certain nerves in the neck, called left cardiac sympathetic denervation.

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.

7.1. DO GENERIC BRANDS OF BETA BLOCKERS ALSO PROVIDE A COMPLETE PROTECTION AGAINST LONG QT SYNDROME?

Most of the studies in the medical literature confirm that no major differences exist between brand and generic drugs. However it is fair to recognize that occasional reports have raised concern that certain generic brands may be less effective than brand name products (see: Cervera Barba EJ. [Increase of arterial pressure caused by generic atenolol]  Aten Primaria. 2001 Feb 15;27(2):146-8).

8. WHEN SHOULD A CHECK FOR LONG QT SYNDROME BE CONSIDERED?

+ Sudden and unexplained loss of consciousness during childhood and teenage years

+ Sudden and unexplained cardiac arrest or cardiac arrhythmia during childhood and teenage years

+ Unexplained sudden deaths in the family

+ Epilepsy in children

9. CAN AN AUTOPSY REVEAL LONG QT SYNDROME?

There are two ways to make a diagnosis for QT syndrome. The first is to check if the QT-interval on the ECG of a suspected patient is prolonged. Because the heart stopps beating when death occurs, this possbility is out of question - except an ECG of the dead person already exists, of course.

The only possibility would be to check body fluids of the dead person - in this case blood - for the known gene mutations that cause QT syndrome.

10. ARE THERE CORRELATIONS WITH OTHER DISEASES?

Recent research suggests that a prolonged QT-interval could be an important cause for Sudden Infant Death Syndrome (SIDS).

Mutations in the KCNJ2 gene are associated with Andersen syndrome (AS). AS is a rare, inherited disorder characterized by periodic paralysis, skeletal developmental abnormalities and a prolonged QT-interval (see point 2) with ventricular arrhythmias. Because of the prolongation of the QT-interval, AS is considered a subtype of long QT syndrome.

Furthermore, mutations in the CACNA1C gene are associated with Timothy syndrome. This disease is also characterized by a prolongation of the QT-interval, syndactyly (a condition in which two or more of the fingers or toes are joined together), hypoglycemia, hypothermia, mental retardation and cardiac malformation.

11. ARE THERE GENDER DIFFERENCES IN LONG QT SYNDROME?

Studies show there are significant gender differences in genotyped LQTS patients relative to age of first episode, syncope, cardiac arrest and sudden death.  Males seem to have a higher risk of cardiac events (meaning syncope or blackout spells, cardiac arrest and sudden death) during childhood (with an average earlier age of onset in males at 8 years old vs.14 years in females), through puberty.   Studies reveal females have an increased risk relative to males during adulthood.  Where sudden death occurred, males died on average at 13 years whereas females at 20 years.   Males had a 32 % incidence of sudden death as a first episode in comparison to 9% in women.  Studies showed that only a few males had a first cardiac event after 15 years of age whereas about half of the females had a first cardiac event after 15 years of age.

12. IS SPORTS RESTRICTED?

Competitive sports should be avoided. Actually there is very little knowledge how sports affect a well treated patient with long QT syndrome. It is known that especially LQT1 type patients have an increased risk during exercise, but to a smaller degree also LQT2 type patients. This is especially seen in untreated individuals with long QT syndrome.

12.1. IS TRAVELLING BY AIRPLANE RESTRICTED?

Travelling often means stress, which to some degree affects people including patients with long QT syndrome. Some airplanes have defibrillators onboard. Well treated long QT syndrome patients should have a low risk as long as they follow their treatment. Of course, the risk will never be zero but low. However it is recommended to discuss your travel plans with your specialist(s). It may be useful to do some research about the public health systems of the country you are travelling to prior to your journey.


Also see: Long QT Syndrome Message Board - General Questions

Last update: May 2005


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