Long QT Syndrome – Symptoms and Causes
Overview
Long QT syndrome (LQTS) is a heart rhythm disorder characterized by irregular, chaotic heartbeats that can potentially be life-threatening. This condition affects the electrical signals responsible for normal heart function.
LQTS can be either congenital (present at birth due to genetic changes) or acquired later in life from certain medications, health conditions, or mineral imbalances in the body.
People with LQTS may experience sudden fainting episodes and seizures. Young individuals with this condition face a higher risk of sudden cardiac death. The syndrome’s name comes from the prolonged QT interval visible on an electrocardiogram (ECG).
Treatment options include:
- Lifestyle modifications
- Medications to prevent dangerous heart rhythms
- Medical devices or surgical interventions when necessary
Early diagnosis and proper management are essential for those affected by LQTS to reduce risks and maintain heart health.
Signs and Symptoms
Long QT syndrome (LQTS) often causes fainting without warning. This happens when the heart beats irregularly for a brief period.
Emotional triggers like excitement, anger, or fear can lead to fainting episodes. Exercise or sudden startling noises such as ringtones may also trigger these episodes.
Before losing consciousness, some people experience:
- Blurry vision
- Feeling lightheaded
- Heart palpitations (pounding heartbeats)
- Weakness
LQTS can sometimes cause seizures in affected individuals. Symptoms may appear in babies during their first few months of life, or later in childhood. Most people born with this condition show symptoms by age 40.
These symptoms can occur during sleep as well. Some people with LQTS have no noticeable symptoms.
In these cases, the condition might be discovered during routine heart tests like an electrocardiogram or through genetic testing done for other reasons.
When Medical Care Is Needed
Schedule a checkup if you experience fainting spells or feel your heart racing or pounding unusually.
It’s important to inform your healthcare provider if any of your close family members (parents, siblings, or children) have been diagnosed with long QT syndrome. This condition often runs in families and can be passed down genetically.
If you have a family history of unexplained fainting or sudden death, especially at a young age, mention this to your doctor. Early detection can lead to better management of the condition.
What Causes Long QT Syndrome
Causes of Congenital Long QT Syndrome
Congenital long QT syndrome happens when you’re born with genetic changes that affect your heart’s electrical system. These DNA changes are passed down through families.
There are two main types of congenital long QT syndrome:
Romano-Ward syndrome: This is the more common type. It occurs when a person inherits a single altered gene from one parent (autosomal dominant inheritance). Only one altered gene is needed to develop this condition.
Jervell and Lange-Nielsen syndrome: This rare form is more severe and typically appears early in life. Children with this syndrome also experience deafness. It occurs when a child inherits altered genes from both parents (autosomal recessive inheritance).
The genetic changes in long QT syndrome affect how the heart recharges between beats. Instead of resetting quickly after each heartbeat, the electrical system takes longer to recover.
This delayed recovery is what creates the “long QT interval” that gives the condition its name.
Unlike some heart problems, long QT syndrome doesn’t change the shape or structure of the heart. Instead, it affects only the electrical signals that coordinate heartbeats.
Causes of Acquired Long QT Syndrome
Acquired long QT syndrome develops later in life due to medications or health conditions. Unlike the congenital form, acquired long QT syndrome can often be reversed when the cause is identified and addressed.
Medications that can cause long QT syndrome:
- Certain antibiotics (erythromycin, azithromycin)
- Antifungal medications for yeast infections
- Water pills (diuretics) that lower potassium or other minerals
- Heart rhythm medications (anti-arrhythmics)
- Some mental health medications for depression or anxiety
- Certain stomach medications
Medical conditions that can trigger long QT syndrome:
| Condition | Description |
|---|---|
| Low body temperature | Below 95°F (35°C), called hypothermia |
| Mineral imbalances | Low levels of calcium, magnesium, or potassium |
| Adrenal gland tumor | Called pheochromocytoma, usually non-cancerous |
| Brain issues | Stroke or bleeding in the brain |
| Thyroid problems | Underactive thyroid (hypothyroidism) |
If you take any medications, including over-the-counter drugs, it’s important to tell your healthcare provider about all of them. More than 100 different medications can potentially cause QT interval prolongation in otherwise healthy people.
For people with acquired long QT syndrome, addressing the underlying cause—whether stopping a medication or treating a medical condition—often resolves the problem.
Risk Factors
Several factors can increase the chance of developing long QT syndrome:
- Family History: Having a parent, sibling, or child with the condition.
- Previous Cardiac Arrest
- Medication Use: Taking certain medicines known to extend QT intervals.
- Gender Factors: People born female who take specific heart medications have a higher risk.
- Digestive issues: Severe vomiting or diarrhea that changes mineral levels in the body
- Eating Disorders: Conditions like anorexia nervosa that disrupt normal mineral balance.
Complications
Long QT syndrome (LQTS) typically allows the heart to return to a normal rhythm after an episode. However, several serious complications can occur if the heart’s rhythm isn’t corrected quickly.
Torsades de pointes is a dangerous fast heartbeat where the lower heart chambers (ventricles) beat rapidly and irregularly. This condition:
- Reduces blood flow from the heart
- Causes sudden fainting without warning
- May lead to full-body seizures if prolonged
- Can progress to ventricular fibrillation if not self-correcting
Ventricular fibrillation is a life-threatening heart rhythm where the ventricles quiver instead of pumping effectively. Without prompt intervention using a defibrillator, this condition can quickly result in:
- Lack of blood flow to vital organs
- Brain damage
- Death
Sudden cardiac death refers to an unexpected, rapid loss of heart function. LQTS has been linked to sudden cardiac death in otherwise healthy young people. It may explain some previously unexplained events, including:
- Mysterious fainting episodes
- Unexplained drownings
- Seizures with no apparent cause
Prevention
You cannot prevent congenital long QT syndrome (LQTS) from occurring. If LQTS runs in your family, consider talking to your doctor about genetic screening options. This testing can help determine your risk.
For those diagnosed with LQTS, proper treatment helps manage the condition and prevent dangerous heart rhythms that lead to complications.
To prevent acquired LQTS:
- Attend regular medical checkups
- Communicate openly with your healthcare provider about all medications you take
- Avoid medications that can affect your heart rhythm or extend the QT interval
Maintaining a good relationship with your healthcare team is essential for managing this condition effectively. They can help you identify and avoid potential triggers that might worsen your condition.
Most people with LQTS can lead normal, active lives while minimizing the chance of serious complications.
