A Concealed Typical AVNRT: U Wave Contribution in Simulating Long RP Supraventricular Tachycardia

Area of Science:

• Cardiology
• Electrophysiology
• Medical Diagnostics

Background:

• Accurate P wave identification on electrocardiograms (ECGs) is crucial for diagnosing supraventricular tachycardias.
• U waves can be mistaken for retrograde P waves, leading to misinterpretation of the RP interval.
• This diagnostic challenge can obscure the underlying mechanism of tachycardia, such as atrioventricular nodal reentrant tachycardia (AVNRT).

Purpose of the Study:

• To illustrate the diagnostic difficulties in identifying supraventricular tachycardias when U waves mimic P waves.
• To emphasize the importance of recognizing U waves in the context of rapid heart rates.
• To highlight the potential for U waves to mask typical slow-fast AVNRT.

Main Methods:

• Case report of a 40-year-old woman presenting with regular narrow-complex tachycardia.
• Analysis of ECG findings showing a positive deflection after the T wave, suggesting a long RP tachycardia.
• Electrophysiological study to determine the activation sequence and intervals (VA interval, H-A-V sequence).

Main Results:

• The patient presented with tachycardia that mimicked a long RP interval due to a deflection following the T wave.
• Electrophysiological study confirmed a short VA interval and an H-A-V activation sequence.
• These findings are characteristic of typical slow-fast AVNRT.

Conclusions:

• U waves can pose a significant diagnostic challenge in supraventricular tachycardias, especially at higher heart rates.
• Misinterpretation of U waves as P waves can lead to a pseudo-long RP interval, obscuring the diagnosis of AVNRT.
• Recognizing the impact of U waves on ECG interpretation is essential for accurate arrhythmia diagnosis.