In a patient with history of recurrent syncope, Holter recording shows QT interval of 680msec. Which disease is suspected in this patient?
**Core Concept**
Prolonged QT interval is a hallmark of a specific cardiac condition characterized by delayed repolarization of ventricular myocytes. This condition increases the risk of life-threatening arrhythmias, particularly torsades de pointes.
**Why the Correct Answer is Right**
The prolonged QT interval in this patient is suggestive of Long QT Syndrome (LQTS). This condition is caused by mutations in genes encoding cardiac ion channels, particularly those involved in potassium (K+) and sodium (Na+) channel function. The most common affected gene is KCNQ1, which codes for the Kv7.1 potassium channel. In LQTS, the delayed repolarization of ventricular myocytes is due to impaired potassium channel function, leading to an increased risk of arrhythmias.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Brugada Syndrome is characterized by a distinct electrocardiographic pattern, including ST-segment elevation in leads V1-V3, with a risk of polymorphic ventricular tachycardia.
**Option B:** This option is incorrect because Wolff-Parkinson-White (WPW) syndrome is characterized by a short PR interval and a delta wave, resulting from an accessory electrical pathway between the atria and ventricles.
**Option C:** This option is incorrect because Hypokalemia can cause a prolonged QT interval, but it is not a specific disease like Long QT Syndrome.
**Clinical Pearl / High-Yield Fact**
The ECG hallmark of LQTS is a prolonged QT interval, particularly in the presence of a U-wave. A QT interval exceeding 440msec in males and 460msec in females is generally considered abnormal.
**Correct Answer:** C. Long QT Syndrome.