Atrioventricular Nodal Reentrant Tachycardia (AVNRT) on ECG

Introduction

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common type of supraventricular tachycardia (SVT). It is caused by reentry within the atrioventricular (AV) node, leading to rapid heart rates. Understanding its ECG characteristics is key to accurate diagnosis and treatment.

ECG Characteristics of AVNRT

1. Regular, Narrow QRS Complex Tachycardia

   • The QRS complex is typically narrow (<120 ms) unless there is aberrant conduction.

2. P Waves Hidden or Retrograde

   • In typical AVNRT, retrograde P waves are often embedded within or follow the QRS complex (appearing as pseudo-S waves in the inferior leads or pseudo-R waves in lead V1).

3. Heart Rate Between 140-250 bpm

   • AVNRT is characterized by a sudden onset and termination, often triggered by premature atrial beats.

4. RP Interval

   • The RP interval (time between the R wave of the QRS complex and the preceding P wave) is usually short in typical AVNRT (<90 ms), whereas it is longer in atypical AVNRT.

Differential Diagnosis

• Atrioventricular Reentrant Tachycardia (AVRT): Distinguished from AVNRT by the presence of a bypass tract (e.g., Wolff-Parkinson-White syndrome).
• Atrial Tachycardia: P wave morphology differs, and tachycardia is not usually abrupt in onset.
• Sinus Tachycardia: Gradual onset and presence of normal P waves.

Treatment Options

• Acute Management:
  • Vagal maneuvers (e.g., Valsalva maneuver, carotid sinus massage)
  • Adenosine (rapid IV push) is the first-line pharmacologic treatment.
  • Beta-blockers or calcium channel blockers if adenosine is ineffective.
• Long-term Treatment:
  • Catheter ablation of the slow pathway is highly effective in recurrent cases.
  • Medications such as beta-blockers or calcium channel blockers in patients who are not candidates for ablation.

Conclusion

AVNRT is a common type of supraventricular tachycardia characterized by a narrow QRS tachycardia with absent or retrograde P waves. ECG interpretation and appropriate treatment strategies are essential for managing this condition effectively.

Source recommendations

1. American Heart Association (AHA) Guidelines on Supraventricular Tachycardia

1. https://www.ahajournals.org/doi/10.1161/cir.0000000000000311
2. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate
3. https://professional.heart.org/en/science-news/-/media/028ddd505f514ea2b3a4e74bb72e3557.ashx
4. https://pubmed.ncbi.nlm.nih.gov/26409259/
5. https://professional.heart.org/en/science-news/guideline-for-the-management-of-adult-patients-with-supraventricular-tachycardia

2. European Society of Cardiology (ESC) Guidelines on Supraventricular Tachycardia

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
2. https://academic.oup.com/eurheartj/article/41/5/655/5556821
3. https://pubmed.ncbi.nlm.nih.gov/31504425/
4. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2019/09/10/12/36/2019-ESC-Guidelines-for-Supraventricular-Tachycardia
5. https://pubmed.ncbi.nlm.nih.gov/14563598/