Long QT Syndrome
Long QT syndrome is a rare problem with the heart's electrical system. It is estimated to affect 1 in 5,000 people and result in 3,000 deaths within the United States each year. As the heart pumps blood, its electrical system needs to recharge between beats. In people with Long QT syndrome, the heart's electrical system takes too long to recharge. This makes the heart susceptible to problematic rhythms, often referred to as arrithymias which can cause the heart to stop pumping blood throughout the body. If the heart enters into one of these problematic rhythms it may cause a person to become lightheaded or faint. If the heart does not return to its normal rhythm, it may lead to death.
Long QT syndrome is caused by a defect in a set of very small channels (ion channels) within the heart. These channels allow extremely small, electrically charged particles (ions) to move in and out of the heart's cells. The movement of these electrically charged particles is responsible for both generating and recharging the heart's electrical signals. In people with Long QT syndrome, as the heart recharges, the small channels in the heart's cells don't open and close properly to let the particles move at the correct times. Researchers are still not certain how these channels are connected to the dangerous heart rhythms associated with Long QT syndrome, but it is known that the defective channels make the heart's electrical system unstable as it recharges. When the heart is unstable, it can enter into a problematic heart rhythm.
Problematic heart rhythms come about when the electrical signals in the heart become disorganized and cause the heart to pump blood inefficiently. A few heart rhythms often associated with Long QT syndrome are Torsades de Pointes, ventricular fibrillation, and ventricular tachycardia. If the heart falls into any of these three rhythms death can occur within only a few minutes.
Events that spark the body to release adrenaline are often cited as events that may cause people with Long QT syndrome to experience life-threatening heart rhythms. Terefore, it is usually recommended that people with Long QT syndrome avoid high intensity physical activities and try to remain calm during highly emotional events.
About half those with long QT syndrome don't have any signs or symptoms.
For people who do experience signs and symptoms of long QT syndrome, the most common symptoms include:
Fainting. This is the most common sign of long QT syndrome. In people with long QT syndrome, fainting spells (syncope) are caused by the heart temporarily beating in an erratic way. These fainting spells may happen when you're excited, angry, scared, or during exercise. Fainting in people with long QT syndrome can occur without warning, such as losing consciousness after being startled by a ringing telephone.
Signs and symptoms that you're about to faint include lightheadedness, heart palpitations or irregular heartbeat, weakness and blurred vision. If you think you're about to faint, sit or lie down and tell someone near you about your symptoms. However, in long QT syndrome, such warning signs before fainting are unusual.
Seizures. If the heart continues to beat erratically, the brain becomes increasingly deprived of oxygen. This can then cause generalized seizures. In fact, some people with long QT syndrome have been misdiagnosed as having a seizure disorder and have even been treated with anti-epileptic medications.
Sudden death. Normally, the heart returns to its normal rhythm. If this doesn't happen spontaneously and paramedics don't arrive in time to convert the rhythm back to normal with an external defibrillator, sudden death will occur.
Signs and symptoms of inherited long QT syndrome may start during the first months of life, or as late as middle age. Most people who experience signs or symptoms from long QT syndrome have their first episode by the time they're age 40. Most LQTS-related deaths occur in people ages 11 to 30.
Rarely, signs and symptoms of long QT syndrome may occur during sleep or arousal from sleep. Some doctors believe that inherited LQTS-causing mutations likely explain about 10 percent to 15 percent of sudden infant death syndrome (SIDS).
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