ECG Case 016

Main Abnormalities

• Narrow complex tachycardia at ~ 150 bpm
• Right axis deviation = just rightward of +90 degrees
• Pseudo-R’ waves in V1-2 = retrograde P waves superimposed on the terminal QRS causing peaking of the J-point
• No clear sinus P waves or flutter waves seen

Pseudo R’ waves

Differential Diagnosis

When you see a regular narrow complex tachycardia at 150 bpm, you should think of four main diagnoses:

• Atrial flutter with 2:1 block (especially in elderly, IHD, CCF)
• AV-nodal reentry tachycardia (“SVT”)
• Orthodromic AV reentry tachycardia in WPW
• Sinus tachycardia — should see P waves but may be hidden in the T waves (e.g. with concurrent 1st degree AV block). There should also be some HR variability compared to the other 3 rhythms

The patient’s young age and presence of retrograde P waves (pseudo R’ waves) suggest a paroxysmal reentry tachycardia involving the AV node — either AVNRT (“SVT”) or orthodromic AVRT.

The next step is a therapeutic trial of vagal maneouvres and/or adenosine… (see Quiz ECG 017).

Further Reading

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.
• Wiesbauer F. Little Black Book of ECG Secrets. Medmastery PDF