whst is the abnormality in this ecg

Reading File

Finding Sources

Reading File

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Now I have a clear view of the ECG. Here is the analysis:

ECG Abnormality: Wolff-Parkinson-White (WPW) Pattern

Patient details: Female, HR 68 bpm, 6-channel + rhythm strip recording.

Key Findings on This ECG

Looking across all leads, the tracing shows the classic triad of WPW:

Short PR interval - The PR interval is visibly shortened (< 120 ms). The P wave runs very quickly into the QRS, leaving minimal isoelectric baseline between them.
Delta wave - There is a characteristic slurred, slow upstroke at the very beginning of the QRS complex, most visible in the limb leads (I, II, aVF) and the lateral precordial leads (V4-V6). This represents early ventricular pre-excitation via the accessory pathway (Bundle of Kent) before the normal AV node conduction catches up.
Widened QRS - The QRS is slightly broad/prolonged due to the fusion of pre-excited myocardium (via the accessory pathway) and normally conducted myocardium (via the His-Purkinje system).
Secondary ST-T changes - Discordant ST-T changes are present, which are a secondary consequence of the abnormal depolarization sequence (not ischemia).

What Is WPW?

WPW is a ventricular pre-excitation syndrome caused by an accessory atrioventricular pathway (Bundle of Kent) that bypasses the AV node. This allows electrical impulses to reach the ventricles earlier than normal, producing the characteristic ECG findings above.

As stated in Pfenninger and Fowler's Procedures for Primary Care:

"WPW is an ECG pattern characterized by a short PR interval followed by a delta wave and a prolonged QRS duration... due to aberrant conduction of activation through an accessory pathway."

Clinical Significance

Feature	Detail
Prevalence	~1 in 10,000 individuals
Can be asymptomatic	Yes - often an incidental finding
Risk	Paroxysmal SVT (AVRT), rarely sudden cardiac death via pre-excited AF
Important caveat	ST segments cannot be used to assess ischemia in WPW
Pseudo-Q waves	Negative delta waves in some leads can mimic infarction - they are NOT true Q waves

Localizing the Accessory Pathway (Delta Wave Polarity)

Negative delta waves in V1 with positive delta in lateral leads suggests a left lateral accessory pathway (most common type).
On this ECG, the delta waves appear predominantly positive in the inferior leads (II, aVF) and in the lateral precordial leads, pointing to a likely left-sided pathway.

Next Steps

Ask about palpitations, syncope, or presyncope
Family history of sudden cardiac death
If symptomatic: refer to cardiac electrophysiology for risk stratification and possible radiofrequency catheter ablation (curative in >95% of cases)
Avoid AV node-blocking agents (verapamil, digoxin) if pre-excited AF is present - they can accelerate conduction down the accessory pathway and precipitate ventricular fibrillation

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