Long QT Syndrome

Causes

Congenital LQTS is inherited and affects 1:2500 individuals. It is caused by an abnormality in the gene code for the ion channels. The abnormality of the ion channels slows the recovery phase of the heartbeat. At least 17 genes have been identified. The majority of the gene mutations are inherited in an autosomal dominant fashion.

Acquired LQTS can be caused by medications including certain antibiotics, anti-depressants, anti-nausea, or heart rhythm drugs. Sensitivity to these medications may be related to genetic causes. Electrolyte imbalances can also cause prolongation of the QT interval.

Symptoms

• Fainting (Syncope)

• Seizures

• Sudden cardiac arrest

There may be a family history of Long QT Syndrome or sudden unexplained deaths in family members under 50 years of age.

Nearly nearly half of patients with LQTS never have any symptoms. Those with symptoms of LQTS typically have their first episode by age 40.

Complications

Torsades de pointes. This is a life-threatening form of ventricular arrhythmia where the lower chambers of the heart beat fast and chaotically. This can lead to a faint or seizure. Generally, the heart returns to its normal rhythm. If this doesn't happen by itself ventricular fibrillation and sudden death will occur.

Sudden death. LQTS can explain some cases of sudden death in young people who otherwise appear healthy.

Unexplained fainting, drownings, seizures or other accidents. Long QT Syndrome can be responsible for some otherwise unexplained deaths in children and young adults.

Diagnosis

An EKG will show a prolongation of the QT interval. A detailed extended family history is also necessary. Other testing may include a Holter or event monitor, stress test, epinephrine provocation test, or echocardiogram. Genetic testing can confirm the diagnosis, although cannot identify all inherited cases of LQTS.

Treatment

Treatment for Long QT Syndrome involves medications, lifestyle changes, and possibly surgery or other procedures.

• Beta Blockers: medication that helps prevent against life threatening arrhythmias by slowing the heart rate
  
• Lifestyle changes: Avoiding triggers such as swimming, intense exercise, loud noises, emotional distress, and QT prolonging medications
  
• Implantable cardio-defibrillator (ICD): device that detects life-threatening arrhythmias and automatically shocks the heart back into a regular rhythm
• Left Cardiac Sympathectomy Denervation (LCSD) surgery: nerves are removed from the sympathetic nervous system to help control the heart rhythm

With correct diagnosis and common treatments, most LQTS deaths are preventable. Annual mortality for properly treated patients is less than 1%.

Sudden Arrhythmia Death Syndromes

Sudden Arrhythmia Death Syndromes (SADS) are genetic heart conditions that can cause sudden death in young, apparently healthy, people. In affected individuals, the heart's electrical system does not work properly which may result in an abnormal rhythm. There are approximately 4,000 SADS deaths each year in children, teens, or young adults. SADS conditions are: Brugada Syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), Long QT Syndrome, Short QT Syndrome, Timothy Syndrome, and Wolff Parkinson White (WPW).

Warning signs of SADS:

• Family history of unexpected, unexplained sudden death under age 40

• Fainting or seizure during exercise, excitement or startle

• Consistent or unusual chest pain and/or shortness of breath during exercise.

For more information on LQTS and SADS conditions please visit:

https://www.sads.org/What-is-SADS#.Yk42RC-B3rB

https://www.mayoclinic.org/diseases-conditions/long-qt-syndrome/symptoms-causes/syc-20352518

https://www.hopkinsmedicine.org/health/conditions-and-diseases/long-qt-syndrome-lqts