Understanding Long QT Syndrome (LQTS) on ECG

Introduction

Long QT syndrome (LQTS) is a condition affecting the electrical system of the heart, leading to an increased risk of fast, chaotic heartbeats (arrhythmias). These arrhythmias can cause fainting (syncope), seizures, or sudden cardiac arrest.

What is the QT Interval?

The QT interval on an electrocardiogram (ECG) represents the time it takes for the heart's ventricles to contract and then recover. It consists of: - QRS complex: Ventricular contraction - ST segment: Initial recovery phase - T wave: Final recovery phase

A prolonged QT interval means that the heart muscle takes longer than usual to recharge between beats. This increases the risk of dangerous arrhythmias such as torsades de pointes, which can lead to sudden cardiac death.

Causes of Long QT Syndrome

LQTS can be inherited (congenital) or acquired.

1. Congenital LQTS

• Genetic mutations affecting ion channels in the heart
• Three common subtypes: LQT1, LQT2, LQT3
• Frequently diagnosed in young individuals with a family history of sudden cardiac death

2. Acquired LQTS

• Medications (e.g., antiarrhythmics, antibiotics, antidepressants, antipsychotics)
• Electrolyte imbalances (low potassium, magnesium, or calcium)
• Bradycardia
• Medical conditions such as hypothyroidism or chronic kidney disease

Diagnosing Long QT Syndrome

• ECG measurement: QTc (corrected QT interval) is used to adjust for heart rate variations.
  • Normal QTc: Male < 450 ms, Female < 460 ms
  • Borderline QTc: 450–480 ms
  • Prolonged QTc: > 480 ms
• Genetic testing in suspected congenital cases
• Provocative testing (e.g., exercise stress test)
• Family history assessment

Treatment Options

1. For Congenital LQTS

• Beta-blockers (first-line treatment for LQT1 and LQT2)
• Implantable cardioverter-defibrillator (ICD) for high-risk patients
• Lifestyle modifications (avoiding triggers like stress, certain medications, and intense exercise)

2. For Acquired LQTS

• Stopping the causative medication
• Correcting electrolyte imbalances (replenishing potassium and magnesium)
• Temporary pacing in severe cases

Conclusion

Long QT Syndrome is a serious but manageable condition. Early diagnosis and appropriate treatment significantly reduce the risk of life-threatening arrhythmias. If you have symptoms like fainting, seizures, or a family history of sudden cardiac death, consult a cardiologist immediately.

Source recommendations

1. American Heart Association Guidelines for Long QT Syndrome

1. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/conduction-disorders
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
3. https://www.jacc.org/doi/10.1016/j.jacc.2017.10.053
4. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191096
5. https://newsroom.heart.org/news/caution-recommended-on-covid-19-treatment-with-hydroxychloroquine-and-azithromycin-for-patients-with-cardiovascular-disease-6797342

2. European Society of Cardiology Guidelines on Ventricular Arrhythmias and Sudden Cardiac Death

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
4. https://pubmed.ncbi.nlm.nih.gov/36017572/
5. https://www.sciencedirect.com/science/article/pii/S2405500X22010945