Which pattern is commonly referred to as 'rabbit ears' on the ECG?

Which pattern is commonly referred to as 'rabbit ears' on the ECG?

• A. Notched R waves
• B. Wide QRS
• C. Sinus tachycardia
• D. Peaked T waves

Answer: (A)

Rabbit ears describe the notched R waves in the QRS complex. This notch creates two small peaks in the R wave, giving a pattern that looks like two ears. It’s classically seen in left bundle branch block, where activation of the left ventricle is delayed, producing broad, notched R waves in lateral leads such as I, aVL, V5 and V6. The important point is that the two-peak, notched appearance of the R wave is what earns the “rabbit ears” description. The other options don’t produce that specific look: a wide QRS is a broader sign of conduction delay but doesn’t specify the notched, two-peak R wave; sinus tachycardia is about faster rate; peaked T waves are tall, sharp T waves typical of hyperkalemia.