**Core Concept**
Syncope refers to transient loss of consciousness due to inadequate cerebral perfusion. Diagnosis involves identifying the underlying cause—whether cardiac, neurological, or vasovagal—through appropriate testing that evaluates hemodynamic stability, arrhythmias, or autonomic function.

**Why the Correct Answer is Right**
PET (Positron Emission Tomography) scan evaluates cerebral blood flow and metabolism, primarily used in detecting stroke, epilepsy, or neurodegenerative diseases. It does not assess cardiac arrhythmias, autonomic dysfunction, or hemodynamic instability—key contributors to syncope. In contrast, tilt table testing evaluates autonomic responses, Holter monitoring detects arrhythmias, and electrophysiological testing identifies re-entrant arrhythmias. PET has no role in diagnosing or ruling out the causes of syncope.

**Why Each Wrong Option is Incorrect**
Option A: Electrophysiological testing is useful to identify arrhythmias like ventricular tachycardia or re-entrant circuits that can cause syncope.
Option B: Tilt table testing assesses autonomic dysfunction, especially in vasovagal syncope, by measuring blood pressure and heart rate changes during upright posture.
Option D: Holter monitoring detects intermittent arrhythmias (e.g., bradycardia, atrial fibrillation) that may trigger syncope.

**Clinical Pearl / High-Yield Fact**
Always remember: syncope is primarily a hemodynamic event. Tests assessing cardiac rhythm (Holter, electrophysiology) or autonomic function (tilt table) are first-line; neuroimaging like PET is not indicated unless there is a known neurological cause such as stroke or seizure.

✓ Correct Answer: C. PET Scan