# Case Report: Adenosine-induced atrioventricular dissociation: unmasking monomorphic tachycardia as a diagnostic challenge in a neonate

## TL;DR

A neonate with a fast heart rhythm was correctly diagnosed with ventricular tachycardia using adenosine and ECG analysis, highlighting the importance of accurate diagnosis in infants.

## Contribution

Demonstrates adenosine-induced AV dissociation as a diagnostic tool for neonatal ventricular tachycardia.

## Key findings

- Adenosine-induced AV dissociation confirmed ventricular tachycardia in a neonate with monomorphic tachycardia.
- ECG analysis revealed prolonged QRS duration and delta wave-like slurring, supporting the VT diagnosis.
- Low-energy cardioversion and β-blocker prophylaxis effectively managed the tachycardia.

## Abstract

Neonatal monomorphic tachycardia poses a diagnostic challenge. This report demonstrates how adenosine-induced AV dissociation confirmed ventricular tachycardia.

A 3-day-old preterm neonate (34 + 2 weeks) presented with refractory monomorphic tachycardia (217 bpm; QRS 92 ms) initially diagnosed as SVT based on 1:1 retrograde P-waves. Adenosine administration induced atrioventricular dissociation without termination—a finding inconsistent with SVT. Retrospective ECG analysis revealed prolonged QRS duration during tachycardia (92 ms vs. 60 ms post-cardioversion) and delta wave-like slurring, confirming VT diagnosis. Synchronized cardioversion (0.5 J/kg) restored sinus rhythm, followed by metoprolol prophylaxis.

This case highlights that monomorphic tachycardia in neonates may represent VT. Adenosine's role in inducing AV dissociation is pivotal for diagnosis, and low-energy cardioversion with β-blocker maintenance offers an effective rescue strategy. Clinicians must reassess ECG features dynamically to avoid misclassification.