Long QT syndrome (LQTS) is a heart condition where the electrical system that controls the heartbeat takes longer than normal to recharge between beats. This delay shows up as a prolonged QT interval on an electrocardiogram (ECG). The syndrome can be inherited or acquired, and it affects how the heart rhythm behaves, sometimes leading to dangerous arrhythmias.
The **signs of long QT syndrome** can vary widely. Many people with LQTS may have no symptoms at all and might never know they have it unless tested. However, when symptoms do appear, they often relate to abnormal heart rhythms caused by this delayed electrical recovery.
Here are the main signs and symptoms you might notice:
– **Fainting spells (syncope):** This is one of the most common signs. Fainting often happens suddenly without warning and may be triggered by physical exertion, emotional stress, or sudden loud noises. It occurs because abnormal heart rhythms temporarily reduce blood flow to the brain.
– **Palpitations:** People with LQTS may feel their heart racing or pounding irregularly. These palpitations happen when the heart beats erratically due to disrupted electrical signals.
– **Lightheadedness or dizziness:** Before fainting episodes or during arrhythmias, individuals might feel dizzy or unsteady.
– **Seizures:** In some cases, if blood flow drops significantly during an arrhythmia episode, seizures can occur due to lack of oxygen in the brain.
– **Sudden cardiac arrest:** Although rare, LQTS can cause life-threatening arrhythmias like torsades de pointes—a specific type of polymorphic ventricular tachycardia—that lead to sudden collapse and require immediate medical attention.
Other less specific symptoms include:
– **Shortness of breath**
– **Fatigue**
– **Chest pain**
These symptoms are not unique to LQTS but could accompany episodes related to abnormal rhythms in affected individuals.
The triggers for these signs depend on whether someone has congenital (genetic) LQTS or acquired forms:
1. In *congenital* LQTS types such as LQT1, fainting often occurs during exercise; in others like LQT2 it may be triggered by emotional stress; while some types show events during sleep or rest periods.
2. *Acquired* long QT syndrome usually results from medications that affect cardiac ion channels—certain antibiotics, antidepressants—or electrolyte imbalances like low potassium or magnesium levels which prolong repolarization time in heart cells leading to similar symptoms.
On an ECG test—the primary diagnostic tool—long QT syndrome shows as a prolonged QT interval beyond normal limits adjusted for heart rate (corrected QT interval). Sometimes subtle changes in T-wave shape also hint at risk for dangerous arrhythmias even before symptoms appear clinically.
Because many patients remain symptom-free until a serious event happens unexpectedly—such as syncope during sports activity—it’s important for those with family history of sudden unexplained death or known genetic mutations linked with ion channel defects (*KCNQ1*, *KCNH2*, *SCN5A*) to undergo screening tests including ECGs regularly even if asymptomatic.
In children especially who present with unexplained fainting episodes accompanied by palpitations or seizures without other causes identified should raise suspicion for possible underlying long QT syndrome requiring specialist evaluation through detailed electrophysiological studies alongside genetic testing if indicated.
Signs indicating urgent concern include:
– Repeated fainting spells
– Palpitations associated with dizziness
– Prolonged corrected QT intervals over 500 milliseconds on ECG
Such findings warrant close monitoring because they increase risk for torsades de pointes—a potentially fatal ventricular tachycardia characterized by rapid irregular heartbeat causing collapse—and sudden cardiac death without prompt treatment interventions such as beta-blockers medication use and sometimes implantable cardioverter defibrillators (ICDs).
In athletes undergoing intense training regimens who develop borderline prolonge
