## Diagnostic Approach to AVRT **Key Point:** Electrophysiological study (EPS) with programmed atrial stimulation is the gold standard investigation for diagnosing AVRT and identifying the accessory pathway location. ### Why EPS is Definitive 1. **Direct pathway identification**: EPS can precisely locate the accessory pathway (Kent bundle) and confirm the reentrant mechanism. 2. **Reproducibility**: Programmed stimulation reliably induces and terminates the tachycardia, confirming the diagnosis. 3. **Therapeutic advantage**: EPS is both diagnostic and therapeutic — radiofrequency ablation can be performed in the same session. ### Clinical Context This patient has classic features of AVRT: - Regular tachycardia at 180 bpm (typical for AVRT) - Normal resting ECG (accessory pathway may not be evident in sinus rhythm if concealed) - Reproducible, paroxysmal episodes **High-Yield:** In AVRT with an **overt** accessory pathway (Wolff-Parkinson-White syndrome), the resting ECG shows a short PR interval and delta wave. However, **concealed** pathways (like this case) have a normal resting ECG, making EPS essential for diagnosis. ### Role of Other Investigations | Investigation | Role in AVRT | | --- | --- | | **EPS** | Gold standard; diagnostic and therapeutic | | **Echocardiography** | Excludes structural heart disease; not diagnostic for AVRT | | **Holter monitor** | May capture episodes but cannot diagnose mechanism | | **CXR/Biomarkers** | Rule out other causes of palpitations; non-specific | **Clinical Pearl:** The regular rate at exactly 180 bpm and the normal resting ECG in a young woman with palpitations are classic red flags for AVRT with a concealed pathway — EPS is the next logical step.
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