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 ECG 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 challenge posed by U waves in the context of supraventricular tachycardia.
• To emphasize the importance of differentiating U waves from P waves for accurate arrhythmia diagnosis.
• To highlight how U waves can mask typical slow-fast AVNRT.

Main Methods:

• Case presentation of a 40-year-old woman with regular narrow-complex tachycardia.
• ECG analysis revealing a positive deflection after the T wave, suggesting a long RP tachycardia.
• Electrophysiological study to determine the activation sequence and intervals.

Main Results:

• The electrophysiological study showed a short VA interval.
• An H-A-V activation sequence, characteristic of typical slow-fast AVNRT, was identified.
• The U wave following the T wave created a pseudo-long RP interval, initially suggesting a different tachycardia type.

Conclusions:

• U waves can mimic retrograde P waves, complicating tachycardia diagnosis.
• Higher heart rates exacerbate the challenge of distinguishing U waves from P waves.
• Accurate differentiation is essential for correctly identifying arrhythmias like AVNRT and guiding treatment.