Ventricular Pre-excitation

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Pre-excitation is a condition in which an accessory pathway exists between the atria and the ventricles, often referred to as the bundle of Kent. When the accessory pathway conducts in an anterograde direction, the ventricles are “pre-excited,” yielding the characteristic delta wave on the ECG. Because of the accessory pathway, patients are at risk for developing antidromic (wide complex, anterograde conduction through the accessory pathway and retrograde conduction through the atrioventricular node) or orthodromic (narrow complex, anterograde conduction through the atrioventricular node and retrograde conduction through the accessory pathway) reentrant rhythms. When dysrhythmias occur involving the accessory pathway, it is referred to as the Wolf-Parkinson-White syndrome.

 

Depiction of orthodromic and antidromic atrioventricular reentrant tachycardias possible with the Wolf-Parkinson-White syndrome. The red bars in panel A represent possible locations of the accessory pathway (type A, between LA and LV; type B, between RA and RV). The blue line in panel B represents orthodromic conduction (narrow complex) and the blue line in panel C represents antidromic conduction (wide complex). RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.

Examples

ECG Showing Ventricular Pre-excitation

Ventricular Pre-excitation

This ECG displays the classic features of pre-excitation: the delta wave, shortened PR interval, and slightly widened QRS. The dominant R wave in V1 is consistent with a left-sided accessory pathway, referred to as "Type A."
ECG Showing Ventricular Pre-excitation

Ventricular Pre-excitation

This ECG displays the classic features of pre-excitation: the delta wave, shortened PR interval, and slightly widened QRS. The dominant S wave in V1 is consistent with a right-sided accessory pathway, referred to as "Type B."
ECG Showing Ventricular Pre-excitation

Ventricular Pre-excitation

Ventricular preexcitation with shortened PR, delta waves, and slightly prolonged QRS.
ECG Showing Ventricular Pre-excitation

Ventricular Pre-excitation

This is the post-conversion ECG of patient that was discovered to be in atrial fibrillation with rapid ventricular response and was noted to have a more-rapid-than-usual rate with changing QRS morphologies consistent with pre-excitation (i.e., Wolf-Parkinson-White). Notice the short PR interval, delta wave, and slightly widened QRS complex.
ECG Showing Atrioventricular Reentrant Tachycardia

Orthodromic Atrioventricular Reentrant Tachycardia

This narrow complex tachycardia converted to sinus rhythm with adenosine. She was subsequently discovered to have a left-sided lateral accessory pathway with retrograde conduction that was successfully ablated (i.e., orthodromic atrioventricular reentrant tachycardia or orthodromic reciprocating tachycardia). This tachycardia is virtually indistinguishable from atrioventricular nodal reentrant tachycardia and can be safely treated with atrioventricular nodal blocking agents. It is important to keep orthodromic accessory conduction on the differential for narrow complex tachycardia and always obtain a post-conversion ECG to look for evidence of pre-excitation.
ECG Showing Antidromic Atrioventricular Reentrant Tachycardia

Antidromic Atrioventricular Reentrant Tachycardia

This wide complex tachycardia is essentially indistinguishable from ventricular tachycardia. Antidromic atrioventricular tachycardia is a macro reentrant circuit in which the signal travels anterograde through accessory pathway and retrograde through the atrioventricular node. Antidromic conduction was subsequently confirmed via an electrophysiology study.
ECG Showing Atrial Fibrillation with WPW

Atrial Fibrillation with WPW

Note the inconsistent QRS morphologies owing to variable transmission of signals from the atria to the ventricles via anterograde conduction through the atrioventricular node and the accessory pathway. The rate approaches 300 bpm at times. Rates this fast are not seen with atrial fibrillation unless an accessory pathway exists. This patient was electrically cardioverted.
ECG Showing Atrial Fibrillation with WPW

Atrial Fibrillation with WPW

Note the inconsistent QRS morphologies owing to variable transmission of signals from the atria to the ventricles via anterograde conduction through the atrioventricular node and the accessory pathway. The rate approaches 300 bpm at times. Rates this fast are not seen with atrial fibrillation unless an accessory pathway exists. This patient was electrically cardioverted.
ECG Showing Atrial Fibrillation with WPW

Atrial Fibrillation with WPW

Notice the more-rapid-than-usual rate for atrial fibrillation and changing QRS morphologies consistent with pre-excitation (i.e., Wolf-Parkinson-White). This patient was electrically cardioverted and admitted for a successful accessory pathway ablation.

References

  1. Wagner GS, Strauss DG. Marriott’s Practical Electrocardiography. 12th ed. Lippincott Williams & Wilkins; 2014.
  2. Moore EN, Spear JF, Boineau JP. Recent Electrophysiologic Studies on the Wolff-Parkinson-White Syndrome. New England Journal of Medicine. 1973;289(18):956-963.
  3. Benson DW, Cohen MI. Wolff-Parkinson-White syndrome: Lessons learnt and lessons remaining. Cardiology in the Young. 2017;27(S1):S62-S67.