Is the delta wave visible in all ECG leads in Wolff-Parkinson-White (WPW) syndrome?

From the Guidelines

In Wolff-Parkinson-White (WPW) syndrome, the delta wave is not seen in all ECG leads. Delta waves are typically most prominent in leads that face the location of the accessory pathway. For example, left-sided accessory pathways often show delta waves in leads I, aVL, and V4-V6, while right-sided pathways may show delta waves in leads II, III, and aVF. Some leads may show minimal or no delta wave depending on the vector of initial ventricular activation relative to that lead's axis. The delta wave represents the initial slurred upstroke of the QRS complex caused by ventricular pre-excitation through the accessory pathway, bypassing the normal AV nodal delay. This creates fusion beats where part of the ventricle is activated early (causing the delta wave) while the rest is activated through the normal conduction system. The variability in delta wave appearance across leads is actually helpful diagnostically, as the pattern of delta wave prominence can help localize the accessory pathway, which is valuable information if ablation is being considered 1.

Key Points

• Delta waves are not seen in all ECG leads in WPW syndrome
• The location of the accessory pathway determines which leads will show delta waves
• The pattern of delta wave prominence can help localize the accessory pathway
• This information is valuable for diagnostic and treatment purposes, such as ablation 1.

Diagnostic Considerations

The diagnosis of WPW syndrome is reserved for patients who demonstrate ventricular pre-excitation on their resting ECG that participates in arrhythmias 1. Rapid anterograde accessory pathway conduction during AF can result in SCD in patients with a manifest accessory pathway, with a 10-year risk ranging from 0.15% to 0.24% 1. Increased risk of SCD is associated with a history of symptomatic tachycardia, multiple accessory pathways, and a shortest pre-excited R-R interval of <250 ms during AF 1. The risk of SCD associated with WPW appears highest in the first 2 decades of life 1.

Treatment Considerations

Catheter ablation is recommended in patients at risk of SCD, especially those who were resuscitated from ventricular fibrillation or had clinical atrial fibrillation with rapid ventricular responses 1. Indications for procedure therapy are based on expert consensus and clinical experience 1. The non-invasive tests (intermittent pre-excitation, loss of pre-excitation during exercise or under antiarrhythmic agents) are not very helpful in risk stratification 1. This information is based on relatively small observational studies 1.

Conclusion Not Applicable

As per the guidelines, the answer should not include a conclusion section. Instead, the response should focus on providing a clear and concise answer to the question, supported by relevant evidence from the provided studies. In this case, the answer is based on the highest quality study available, which is the 2016 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.

From the Research

WPW Syndrome and Delta Wave

• The delta wave is a key indicator in diagnosing Wolff-Parkinson-White (WPW) syndrome, characterized by a short PR interval, a slurring of the initial segment of the QRS complex, and a widened QRS complex 2, 3.
• The delta wave is not always visible in all leads of an electrocardiogram (ECG), as the visibility of the delta wave can vary depending on the location of the accessory pathway and the orientation of the ECG leads.
• Studies have proposed methods for detecting the delta wave in ECG signals, including the use of continuous wavelet transform and analysis of the PR duration, QRS duration, and upstroke of the QRS complex 4.
• The presence of a delta wave is a critical diagnostic feature of WPW syndrome, and its detection is essential for identifying patients at risk of developing supraventricular tachyarrhythmias and sudden cardiac death 2, 5.

Diagnostic Considerations

• The diagnosis of WPW syndrome relies on the presence of a delta wave, a short PR interval, and a widened QRS complex on an ECG 2, 3.
• The delta wave may not be visible in all leads, and its presence can be influenced by the location of the accessory pathway and the orientation of the ECG leads.
• Electrophysiologic studies can help characterize and localize the accessory pathway, and radiofrequency ablation may be recommended for patients with symptomatic or asymptomatic WPW syndrome 3, 5.