skip to main content

AVNRT vs AVRT Differentiation — EECC MCQ

Instant feedback + full explanation. One question, done properly.

ModerateArrhythmia & ElectrophysiologyAVNRT vs AVRT DifferentiationEECC

A 28-year-old man with no structural heart disease presents with palpitations. ECG shows a narrow-complex tachycardia at 190 bpm with visible retrograde P waves in the ST segment (RP interval shorter than PR interval). Adenosine terminates the tachycardia with a visible retrograde P wave before termination. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Typical (slow-fast) AVNRT

The key distinguishing features are: (1) short RP interval (retrograde P waves visible in the ST segment, very close to the QRS), suggesting rapid retrograde conduction through the fast pathway; (2) termination with adenosine (confirms AV node involvement); (3) termination occurs after a retrograde P wave (block in the antegrade slow pathway). In typical (slow-fast) AVNRT, the tachycardia circuit uses the slow pathway for antegrade conduction and the fast pathway for retrograde conduction, producing pseudo-r' in V1 and pseudo-S in the inferior leads (representing the retrograde P wave). Orthodromic AVRT typically has a slightly longer RP interval (retrograde P in the early ST segment, further from QRS) as conduction travels through the ventricular myocardium to the accessory pathway.

Reference: ESC (2019): Guidelines on SVT Management