Delta Wave Overview

The Delta wave is a slurred upstroke in the QRS complex. It relates to pre-excitation of the ventricles, and therefore often causes an associated shortening of the PR interval. It is most commonly associated with pre-excitation syndromes such as WPW.

The characteristic ECG findings in Wolff-Parkinson-White syndrome are:

  • Short PR interval (< 120ms)
  • Broad QRS (> 100ms)
  • A slurred upstroke to the QRS complex (the delta wave)
ECG Wolff-Parkinson-White WPW Delta wave
Delta wave: Premature excitation of the ventricles causes a slurred upstroke to the QRS

ECG examples of Delta Waves
Delta wave
delta wave positive deflection
  • Note that the remainder of the QRS remains normal — conduction still occurs through the AV node and this is the dominant pathway. On arrival to the ventricles, such conduction cancels out any pre-excitation that has occurred via an accessory pathway

Negative delta waves (e.g. seen in lead aVR)
delta wave negative deflection
  • These changes are simply reciprocal to those seen in leads II, aVL, V5 and V6

History of the Delta wave

1930Wolff L, Parkinson J, and White PD publish the eleven cases as definitive description of the syndrome – ‘Bundle Branch Block with Short P-R Interval in Healthy Young People Prone to Paroxysmal Tachycardia.’ A review of the literature confirmed and acknowledged the previously described cases as above. Wolff, Parkinson, and White erroneously thought that the wide QRS complex was caused by a type of bundle-branch block.

WPW 1930 Fig 6
Fig 6. Case III. WPW 1930

1933 – Wolferth and Wood suggested that the abnormal slurring of the initial part of the QRS complex, and prolongation of the QRS complex were not due to bundle-branch block but by:

…an actual acceleration of the passage of the impulse from the auricle to a section of the ventricle…in keeping with the possibility that an accessory pathway of AV conduction such as described by Kent between the right auricle and right ventricle could be responsible for the phenomenon manifested by these cases

Wolferth CC, Wood FC. 1933

1944 – Marcel Segers along with Lequime and Denolin are credited with proposing the Δ to represent the triangle shape at the base of the upsloping QRS complex. They described the ‘… deformation of the PQ segment is the result of a supplementary electrical deflection that we propose to call Δ‘ . This became more commonly described as the ‘delta wave’

Delta wave 1944 Segers Fig 10

However, Segers et al actually proposed that the Δ wave was a discrete and autonomous wave between P and Q. They did state that the wave could fuse with the base of QRS complex (figure C) to form a slurred upstroke, and attributed the Δ wave fusion with the bundle branch phenomenon of WPW (Figure D)

1944 Segers et al Delta wave origin
Fig 1 (a, b, c, d) Segers et al 1944

Schéma a: Onde Δ représentée par une simple inclinaison du segment PQ.

Schéma b ; Tracé avec onde Δ complètement autonome : le point Q se marque nettement après Δ , et dans ces conditions les intervalles PQ et QRS gardent en réalité une valeur normale.

Schéma c : Tracé avec onde Δ formant un « pied » accolé à QRS : l’onde Q correspond au point d’inflexion séparant Δ et R. Le pointillé montre l’évolution de l’onde Δ se poursuivant pendant toute la durée du complexe ventriculaire, selon l’hypothese de Eckey et Schäfer; cette onde diphasique viendrait se superposer au complexe ventriculaire normal et déterminerait ainsi le décalage de ST et la déformation de T.

Schéma d: Les ondes Δ et QRS sont complètement fusionnées en un complexe unique et élargi du type bloc de branche (syndrome de Wolff, Parkinson et White); le point Q et le sommet R ne sont plus visibles et l’onde T se présente en « forme d’escalier »

Segers et al 1944

Diagram a: Δ wave represented by a simple tilt of the PQ segment.

Diagram b; Plot with completely autonomous Δ wave: the Q point is clearly marked after Δ , and under these conditions the PQ and QRS intervals actually keep a normal value.

Diagram c: Plot with Δ wave forming a “foot” attached to QRS: the Q wave corresponds to the point of inflection separating Δ and R. The dotted line shows the evolution of the Δ wave continuing throughout the duration of the complex ventricular, according to the hypothesis of Eckey and Schäfer; this diphasic wave would come to be superimposed on the normal ventricular complex and would thus determine the shift of ST and the deformation of T.

Diagram d: Δ and QRS waves are completely fused into a single, enlarged bundle-branch block-like complex (Wolff-Parkinson-White syndrome); the Q point and the R vertex are no longer visible and the T wave appears in a “staircase shape”

Segers et al 1944

Further reading


Original articles

Review articles

ECG Library Basics

Advanced Reading



LITFL Further Reading



BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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