Runaway Heart: The Long and Short of Long QT Syndrome

Runaway Heart: The Long and Short of Long QT Syndrome

Imagine a young, apparently healthy person — an athlete, a teenager, someone in the prime of life — suddenly collapsing without warning. In many such cases, the culprit is a condition called Long QT Syndrome (LQTS) — a disorder of the heart’s electrical system that can cause fast, chaotic heartbeats, leading to fainting, seizures, or sudden cardiac death.

What Is Long QT Syndrome?

The QT interval is a measurement on an electrocardiogram (ECG) that represents the time it takes for the heart’s electrical system to recharge between beats. In Long QT Syndrome, this interval is prolonged — meaning the heart takes longer than normal to recharge. This creates a window of vulnerability during which a dangerous arrhythmia called torsades de pointes can occur, potentially degenerating into ventricular fibrillation and sudden cardiac arrest.

Congenital vs. Acquired LQTS

• Congenital LQTS — caused by inherited mutations in genes that encode cardiac ion channels (most commonly KCNQ1, KCNH2, and SCN5A). It is estimated to affect 1 in 2,000 people

• Acquired LQTS — caused by medications (including certain antibiotics, antipsychotics, and antihistamines), electrolyte imbalances, or other medical conditions

Warning Signs

• Unexplained fainting (syncope), especially during exercise or emotional stress

• Seizures

• Sudden cardiac arrest (sometimes the first and only symptom)

• Family history of unexplained sudden death, especially in young people

The Role of Genetic Testing

Genetic testing for LQTS can identify the specific mutation causing the condition — which has important implications for treatment (different LQTS subtypes respond differently to beta-blockers and other therapies), risk stratification, and family cascade testing. If a mutation is identified in one family member, other relatives can be tested to determine their own risk — potentially saving lives.