**Core Concept**
WPW (Wolff-Parkinson-White) syndrome is a rare disorder characterized by the presence of an accessory electrical pathway in the heart, known as a bypass tract or Kent bundle. This abnormal pathway allows for premature contractions of the ventricles, leading to tachyarrhythmias. The pathophysiology involves an abnormal conduction of electrical impulses through the bypass tract, bypassing the normal atrioventricular (AV) node.

**Why the Correct Answer is Right**
The bypass tract in WPW syndrome typically connects the atria to the ventricles, allowing for anterograde conduction (from atria to ventricles) but not retrograde conduction (from ventricles to atria). This results in a pre-excitation of the ventricles, leading to a short PR interval and a wide QRS complex on the electrocardiogram (ECG). The bypass tract is often located in the left lateral or right posterior regions of the heart.

**Why Each Wrong Option is Incorrect**
**Option A:** WPW syndrome is characterized by an accessory electrical pathway, which is true. However, the location of the bypass tract can vary, and it's not limited to the left lateral region.

**Option B:** WPW syndrome is associated with an increased risk of atrial fibrillation, which is true. The abnormal conduction pathway can lead to rapid ventricular rates during atrial fibrillation.

**Option C:** WPW syndrome is often diagnosed using an ECG, which is false. The ECG may show a short PR interval and a wide QRS complex, but it's not the definitive diagnostic tool. Other tests like electrophysiology studies (EPS) or imaging studies like echocardiography or cardiac MRI may be required to confirm the diagnosis.

**Clinical Pearl / High-Yield Fact**
WPW syndrome is a potential cause of sudden cardiac death in young athletes, making it an important condition to recognize and manage. The presence of a short PR interval and a wide QRS complex on the ECG should raise suspicion for WPW syndrome.

**Correct Answer: C. WPW syndrome is often diagnosed using an ECG.**