Long QT Syndrome

Recent report in Mumbai Mirror prompted me to post this. Click here to read the full story

Definition

Long QT syndrome or LQTS is a heart rhythm disorder that can potentially causes fast, chaotic heartbeats. The rapid heartbeats, caused by changes in the part of the heart that causes it to beat, may lead to fainting. In some cases the hearts rhythm may beat so erratically that it can cause sudden death.

History.

The first case of LQTS is back in the 19th century where a deaf mute girl was described. She died after her teacher yelled at her. When the parents were told about her death, they told that her older brother who also was deaf mute died during similar circumstances in his school during a fight. This was before the ECG was invented but is likely the first described case of Jervell and Lange Nielsen syndrome. In 1959, the first case documented by ECG was described Jervell Lange and Nielsen. Romano, in 1963, and Ward, in 1964, separately described the more common variant of LQTS with normal hearing, later called Romano Ward Syndrome.

Causes

The Chambers of Heart - Image Courtesy Mayoclinic.com

The heart beats about 100,000 times a day to circulate blood throughout the body. To pump blood, the heart’s chambers contract and relax. These actions are controlled by electrical impulses created in the sinus node, a group of cells in the upper right chamber of your heart. The impulses travel through the heart and cause it to beat.

After each heartbeat, the heart’s electrical system recharges itself in preparation for the next heartbeat. In LQTS, however, the heart’s muscle takes longer than normal to recharge between beats (a process known as repolarization). The electrical disturbance can be seen on an ECG.

Symptoms

About half of those affected with LQTS don’t have any signs or symptoms. They might be aware of their condition only from results of an ECG performed for an unrelated reason or because they have a family history of long QT or because of genetic testing results.

For people who do experience signs and symptoms of LQTS, the most common symptoms include:-

• Fainting:- This is the most common sign of LQTS. In people with LQTS, fainting spells (syncope) are caused by the heart temporarily beating in an erratic way. Syncope may happen when one is excited, scared or during exercise. Fainting in people with LQTS can occur without warning, such as losing consciousness after being startled by a ringing telephone.

• Seizures:- If the heart continues to beat erratically, the brain becomes increasingly deprived of oxygen. This can the cause generalized seizures. Due to this, some people with LQTS have been wrongly diagonised as having a seizure and even have been treated with anti epileptic medicines.

• Sudden Death:- Normally, the heart beat returns to its normal rhythm. If this doesnot happen spontaneously and if paramedics don’t arrive in time to convert the rhythm bac to normal with an external defibrillator, sudden death will occur.

Types of QT Syndrome

There are two types of QT syndrome:-

• Inherited Long QT Syndrome

At least 12 genes associated with LQTS have been discovered so far, and hundreds of mutations within these genes haven been identified. Mutations in three of these genes account for about 75 percent of long QT Syndrome

Doctors have described two forms of inherited long QT syndrome:-

• Romano-Ward Syndrome:- This more common form occurs in people who inherit only a single genetic variant from one of their parents. This type of LQTS affects about one in 2500 people.
• Jervell and Lange-Nielson syndrome:- Sings and symptoms of this rare form usually occur earlier and are more severe than in Romano-Ward syndrome. It is seen in children who are born deaf and have LQTS because they inherited genetic variants from each parent.

Additionally, Scientists have been investigating a possible link between Sudden Infant Death Syndrome (SIDS) and LQTS. It has been discovered that about 10-15 percent of babies wwith SIDS had a genetic defect or mutation for LQTS.

• Acquired Long QT Syndrome

More than 50 medications, many of them common, can lengthen the QT interval in otherwise healthy people and cause a form of acquired LQTS known as drug induced LQTS. Medications that can lengthen the QT interval and upset heart rhythm include certain antibiotics, anti depressants, antihistamines, diuretics, heart medications, cholesterol lowering drugs, diabetes medications and well as some anti fungal and anti psychotic drugs

Tests and Diagnosis

If doctor suspects that you have LQTS, the following tests may be carried out to confirm diagnosis:-

• An Electrocardiogram (ECG):- An ECG measures electrical impulses as they travel through the heart.
  

  Image courtesy Mayoclinic.com

  Patches with wires attached to the skin measure these impulses, which are displayed on a monitor or printed on paper as waves of electrical activity. An ECG measures electrical impulses as 5 distinct waves. Doctors label these waves as P, Q, R, S and T. The waves labeled Q through T show electrical activity in the heart’s lower chamber. The space between the start of the Q wave and the end of the T Wave (the QT interval) corresponds to the time taken by the hearts lower chamber to electrically discharge and then recharge (repolarization). By measuring the QT interval, doctors can tell whether it occurs in a normal amount of time. If it takes more than normal, it is called a prolonged QT interval. This test may be taken while at rest or while exercising by running on a treadmill or pedaling a stationary bike.

• Ambulatory ECG monitoring:-This test, also called Holter monitoring is used to monitor the heart for rhythm irregularities during normal activity for an uninterrupted 24 hour period. During the test, electrodes attached to the chest are connected to a portable recorder that is attached to a belt or is carried by a shoulder strap. The recorded information can then be analyzed to check for heart rhythm irregularities, such as prolonged QT intervals.

• Event ECG Recording:- This is similar to ambulatory ECG except that you need to wear a portable ECG recorder for days or weeks as it records your heart rhythms.

While some people with suspected LQTS have a visibly lengthened QT interval on an ECG, others dont making the condition more difficult to diagnose. Other testing may then be necessary.

• A nonexercise (Medication) stress test:- This ECG test is performed while a medication is given that stimulates the heart in a way similar to exercise. In this test, doctors monitor the effects of the adrenaline on the way your heart recharges. (Adrenaline is a substance that the body releases in response to stress.) This test can in some patients unmask a condition known as concealed QT syndrome which is a normal QT interval at rest, although they still have the syndrome. In some people with LQTS, fainting spells are triggered by sudden bursts of adrenaline in the body such as are experienced during intense exercise or emotional upset.

• An Electroencephalogram (EEG):-This test looks for neurological causes of fainting, such as a seizure disorder. The procedure measures the waves of electrical activity the brain produces. Small electrodes attached to the head pick up the electrical impulses from the brain and send to the EEG machine, which records brain waves.

• Genetic Testing:- A genetic screening test for five of the most common genes associated with LQTS is available. These five genes explain about three out of every four cases of LQTS. Therefore, its possible to test negative with the genetic test but still have LQTS. If the genetic test is positive, then family members can be tested to prove definitively whether they inherited the same genetic mutation.

In addition, doctor will need to know medical history and details of medications taken by the patient.

Complications

Prolonged QT intervals may never cause any problems. However, physical or emotional stress may cause the heart’s rhythm to spin out of control. A prolonged QT interval may trigger a particular irregular heart rhythm (arrhythmia) called torsades de pointes (twists of the points) in which hearts ventricles beat fast, making the waves on an ECG monitor look twisted. When this arrhythmia occurs, less blood is pumped from the heart and less blood reaches the brain causing a person to faint.

If a torsades de pointes episode is short – lasting less than one minute – the heart can correct itself seconds later, and one regains consciousness on own. However, if episode persists, it can lead to life threatening arrhythmia called ventricular fibrillation.

In ventricular fibrillation, the ventricles beat so fast that heart quivers and ceases pumping blood. Unless the heart is shocked back into a normal rhythm by a device called a defibrillator, ventricular fibrillation can lead to brain damage and death.

Treatments and Drugs

Treatment for inherited LQTS can involve medications, medical devices surgery or lifestyle changes. The goal of the treatment is either to prevent the LQTS heart from ever beating out of control or to prevent sudden death. It is often possible to eliminate drug induced LQTS by simply switching medicines with doctors advice.

Medications

Medications used to treat LQTS include:-

• Beta Blockers:- Examples of this heart drug include nadolol and propranolol. These drugs slow the heart rate and prevent the dangerously fast heartbeats that can come about i times of stress, fear or exertion for pople with LQTS.
• Potassium:-Potassium is a mineral in the body, derived from the diet, thats important for the health of heart’s electrical system. Potassium supplements may improve the heart’s recharging system and may be helpful for people with certain form of LQTS.

Medical Devices and Surgical Procedures

Doctors may consider two other treatments

• A pacemaker or implantable cardioverter defibrillator (ICD):- These devices can monitor for fatal arrhythmia and if necessary stop it. Each device is implanted under the skin of the chest and will correct heart’s rhythm if it detects a disrupted heart rhythm
• Left Sided Sympathetic denervation surgery:- In this procedure, specific nerves in the chest are surgically cut. These nerves are part of body’s sympathetic nervous system, which controls automatic functions in the body including regulation of heart rhythm. This surgery is generally reserved for people considered at high risk of sudden death.

Lifestyle Changes

In addition to medications or surgery, the doctor is most likely to recommend lifestyle changes to reduce your symptoms. These could include avoiding strenuous exercise or contact sports, reducing loud and startling noises and staying away from situations that could make one excited or angry.

Coping and Support

LQTS can be a worrisome condition because of its serious potential outcomes. Families with inherited LQTS may find it helpful to talk to a cardiologist with expertise in diagnosing and treating LQTS, a genetics counselor, a psychiatrist or psychologist as well as other families with the condition. Several websites provide help for families with the disorder.

Sources

MayoClinic.Com

Wikipedia

QTS Syndrome.Ch

Texas Heart Institute and St. Luke’s Episcopal Hospital

Filed under: Long QT Syndrome, Medical World , Ambulatory ECG monitoring, arrhythmia, • An electroencephalogram (EEG), ecg, Event ECG recording, Genetic testing, lqts, qt interval, qts, syncope