A 35-year-old man with recurrent episodes of palpitations and a regular narrow-complex tachycardia is diagnosed with atrioventricular nodal reentrant tachycardia (AVNRT) on electrophysiology study. Regarding the management and electrophysiological features of AVNRT, all of the following statements are correct EXCEPT:

Explanation

## Atrioventricular Nodal Reentrant Tachycardia (AVNRT): Mechanism and Management ### Pathophysiology of AVNRT **Key Point:** AVNRT is a reentrant tachycardia that uses **dual AV nodal pathways** (fast and slow pathways) — **NOT an accessory pathway**. This is the critical distinction from WPW-related SVT. **High-Yield:** AVNRT is the most common SVT in the general population (~60% of all SVTs), occurring in patients WITHOUT accessory pathways. ### Mechanism of AVNRT ```mermaid flowchart TD A[Sinus rhythm]:::outcome --> B[Impulse conducts down fast pathway]:::action B --> C[Slow pathway recovers]:::action C --> D{Premature atrial beat arrives}:::decision D -->|Fast pathway refractory| E[Conducts down slow pathway]:::action E --> F[Slow pathway conducts to ventricle]:::action F --> G[Impulse travels retrogradely up fast pathway]:::action G --> H[Reentry circuit established]:::outcome H --> I[AVNRT sustained]:::urgent ``` **Clinical Pearl:** The circuit in AVNRT is **entirely within the AV node** — it does not involve an accessory pathway. This is why AVNRT occurs in patients with normal pre-excitation ECGs and why it is distinct from WPW-related SVT. ### Acute Management of AVNRT | Intervention | Mechanism | Success Rate | Notes | |--------------|-----------|--------------|-------| | **Vagal maneuvers** (Valsalva, carotid massage) | Increase AV nodal refractoriness | 20–30% | First-line non-pharmacological | | **Adenosine IV** | Blocks AV nodal conduction | 90–95% | First-line pharmacological; rapid onset | | **Verapamil/Diltiazem** | Calcium channel blockade | 70–80% | Alternative if adenosine unavailable | | **Synchronized DC cardioversion** | Direct electrical termination | 100% | Reserved for hemodynamically unstable patients | **Mnemonic:** **AVN-DUAL** — AVNRT uses **Dual** AV nodal pathways (fast and slow), not an accessory pathway. ### Definitive Treatment: Slow Pathway Ablation **Key Point:** Radiofrequency ablation of the slow pathway is the definitive treatment for AVNRT, with a success rate >95% and a low recurrence rate (<5%). **Warning:** Slow pathway ablation carries a risk of **AV block** (1–2% incidence), which may be transient or permanent. Patients require informed consent and post-procedure monitoring. ### Why Option 2 is Incorrect Option 2 states that "AVNRT requires the presence of an accessory pathway." This is **false**. AVNRT uses dual AV nodal pathways and does NOT require an accessory pathway. Accessory pathways are found in WPW syndrome, not AVNRT. This is a fundamental mechanistic distinction that is frequently tested.