The Concertina Effect of Pre-excitation

A pt is admitted due to abdominal pain, No palpitations/syncope.

Figure 1

The ECG showed short PR interval (PRI), delta wave and widened QRS (WPW pattern) . After the 5th QRS there is progressive shortening of the PRI and further widening of the QRS. 

Figure 2

This appearance is referred as "concertina effect" of preexcitation.
Concertina form of pre-excitation is a reliable predictor of a relatively long refractory period and thus a marker of low risk of sudden death.


Knight, BP. Anatomy, pathophysiology and localization of accessory pathways in the preexcitation syndrome. In: UpToDate, Downey B (Ed), UpToDate, Waltham, MA. (Accessed on August 10,2015.)

Marco P et al.2009. Adding an Electrocardiogram to the Pre-participation Examination in Competitive Athletes: A Systematic Review. Curr Probl Cardiol ;34:586-662

Surawicz B and Knilans TK. 2008. Chou’s Electrocardiography in Clinical Practice. 6th ed. PA. Saunders-Elseiver

Vivek S et al. 2013. Concertina effect: a subtle but specific marker. BMJ Case Rep (



  1. NICE case! The principal differential diagnosis is between the Concertina Effect (that you show here) — and sinus rhythm with end-diastolic ( = end-cycle) PVCs that nearly coincide with the sinus-conducted QRS complexes. The fact that there is underlying sinus arrhythmia in this example makes it more difficult to assess — but I like lead aVR which to me clearly shows varying degrees of preexcitation for the negative delta wave in this lead. Thanks for presenting!

  2. The Concertina effect is one of those findings that, as you'd mentioned, reduce the risk of SCD associated with WPW given the implied long refractory period of the AP. Other findings include intermittent preexcitation (including "WPW alternans") as well as obliteration of preexcitation with exercise.