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 examples of Delta Waves
- 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)
- These changes are simply reciprocal to those seen in leads II, aVL, V5 and V6
History of the Delta wave
1930 – Wolff 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.
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 casesWolferth 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’
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)
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 »
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”
- Buttner R, Burns E. Wolff-Parkinson-White syndrome. LITFL
- Cadogan M. The history of Wolff–Parkinson–White syndrome LITFL
- Cadogan M. Who’s Afraid Of The Big Bad Wolff? LITFL
- Buttner R, Burns E. VT versus SVT with aberrancy LITFL
- Burns E. Puzzling Paroxysmal Palpitations LITFL
- Wolff L, Parkinson J, White PD. Bundle-branch block with short P-R interval in healthy young people prone to paroxysmal tachycardia. American Heart Journal. 1930; 5: 685-704 [Reprint: Ann Noninvasive Electrocardiol. 2006 Oct;11(4):340-53. PMID 17040283]
- Wolferth CC, Wood FC. The mechanism of production of short P-R intervals and prolonged QRS complexes in patients with presumably undamaged hearts: hypothesis of an accessory pathway of auriculoventricular conduction (bundle of Kent). American Heart Journal. 1933; 8: 297-311.
- Segers PM, Lequime J, Denolin H. L’activation ventriculaire précoce de certains cœurs hyperexeitables. Étude de I’onde Δ de I’électrocardiogramme. Cardiologia. 1944; 8(3-4):113-167.
- Hurst JW. Naming of the waves in the ECG, with a brief account of their genesis. Circulation. 1998 Nov 3;98(18):1937-42
- Buttner R. Delta wave. Eponym A Day. Instagram
ECG Library Basics
- 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.
- Zimmerman FH. ECG Core Curriculum. 2023
- Mattu A, Berberian J, Brady WJ. Emergency ECGs: Case-Based Review and Interpretations, 2022
- Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
- Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
- Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
- Hampton J, Adlam D. The ECG Made Practical 7e, 2019
- Kühn P, Lang C, Wiesbauer F. ECG Mastery: The Simplest Way to Learn the ECG. 2015
- Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
- Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest