What are the key clinical features to consider when diagnosing congenital Long QT Syndrome in a young patient?

When diagnosing congenital Long QT Syndrome (LQTS) in a young patient, several key clinical features and diagnostic considerations are paramount.

Clinical Presentation:

• The most common symptom is syncope (fainting), which can be triggered by exercise, emotional stress, or auditory stimuli such as an alarm clock ³, (Khan, 2002), (Ching and Tan, 2006), (Crotti et al., 2008).
• Patients may also experience palpitations ¹, (Khan, 2002).
• Seizures are another important feature and can sometimes lead to a misdiagnosis of epilepsy (Khan, 2002), (Ching and Tan, 2006).
• In severe cases, the first manifestation might be sudden cardiac arrest or sudden death (Khan, 2002), (Ching and Tan, 2006), (Crotti et al., 2008).
• It is important to note that some individuals with congenital LQTS can be asymptomatic (Ching and Tan, 2006).

Diagnostic Considerations:

• A family history is crucial, particularly a history of sudden unexplained death in young family members, or a history of syncope or seizures within the family ³, (Khan, 2002), (Ching and Tan, 2006), (Crotti et al., 2008).
• The hallmark diagnostic finding is a prolonged QT interval on an electrocardiogram (ECG), specifically a corrected QT (QTc) interval (Khan, 2002), (Ching and Tan, 2006), (Crotti et al., 2008). Specific thresholds, such as a QTc greater than 480 ms in children, are significant (Khan, 2002).
• Other ECG abnormalities may include T-wave alternans or notched T waves (Khan, 2002), (Ching and Tan, 2006).
• The Schwartz Score is a diagnostic scoring system that incorporates ECG findings, clinical symptoms, and family history to assess the likelihood of LQTS (Khan, 2002).
• Genetic testing can confirm the diagnosis by identifying specific mutations in genes encoding cardiac ion channels, with LQT1, LQT2, and LQT3 being the most common types (Ching and Tan, 2006), (Crotti et al., 2008).