Describe it for my viva

Reading File

Finding Sources

Reading File

Finding Sources

I have everything needed. Let me now deliver a thorough viva-style ECG description.

ECG Description for Viva

Source: ECG-pedia.org, courtesy of A.A.M. Wilde, MD, PhD, AMC, The Netherlands.

Step 1 — Technical Adequacy

This is a standard 12-lead ECG recorded at 25 mm/s paper speed with standard calibration (10 mm/mV). All 12 leads are present: limb leads (I, II, III, aVR, aVL, aVF) in the upper panel and precordial leads (V1–V6) in the lower panel.

Step 2 — Rate and Rhythm

The rate appears rapid, approximately 150–180 bpm based on R-R interval spacing.
The rhythm appears regular.

Step 3 — Key ECG Features

Short PR Interval

The PR interval is visibly shortened (< 120 ms / 3 small squares), indicating that the atrial impulse reaches the ventricles faster than normal — bypassing the AV node via an accessory pathway.

Delta Wave

There is a characteristic slurred, slow upstroke at the beginning of each QRS complex — the hallmark delta wave — best seen in the limb leads. This represents early, abnormal ventricular activation through the accessory pathway before normal His-Purkinje conduction takes over.

Wide, Bizarre QRS Complexes

The QRS complexes are broad and abnormal-looking, wider than 120 ms, due to fusion of:

Early activation via the accessory pathway (delta wave component), AND
Normal activation via the AV node/His-Purkinje system

This is a fusion QRS — the hallmark of ventricular pre-excitation.

Secondary ST-T Changes

ST segments and T waves are discordant (pointing opposite to the main QRS deflection) — this is expected in pre-excitation and does not represent ischaemia.

Step 4 — Diagnosis

Wolff-Parkinson-White (WPW) Syndrome — antidromic AVRT or pre-excited tachycardia

The triad of:

Short PR interval
Delta wave
Wide QRS

...is classic for WPW pattern with pre-excitation. Given the rapid rate, this likely represents antidromic AV reentrant tachycardia (AVRT) — where antegrade conduction travels down the accessory pathway and retrograde conduction returns up the AV node — producing a wide-complex tachycardia that can mimic VT.

Step 5 — Accessory Pathway Localisation (Delta Wave Axis)

Delta waves appearing positive in the inferior leads (II, III, aVF) suggest a right anteroseptal or left-sided pathway.
Delta wave transition across the precordium helps further localise the pathway.

Step 6 — Clinical Significance & Viva Points

Feature	Detail
Mechanism	Congenital accessory atrioventricular pathway bypasses AV node delay
Risk	Atrial fibrillation conducted rapidly via accessory pathway → VF → sudden cardiac death
Do NOT give	AV-nodal blocking drugs (adenosine, beta-blockers, verapamil, digoxin) in pre-excited AF — these block the AV node, forcing all conduction through the accessory pathway, accelerating ventricular rate
Treatment	DC cardioversion if haemodynamically unstable; IV procainamide or flecainide if stable; definitive = electrophysiology study + radiofrequency ablation of accessory pathway
ECG in sinus rhythm	Short PR + delta wave + wide QRS (same triad, slower rate)

"WPW syndrome is characterized by a congenital accessory AV pathway that bypasses the AV node, allowing for early activation ('preexcitation') of the His–Purkinje system. ECG findings include a shortened PR interval and a delta wave — slurred upstroke and widening of the QRS complex. Management is with electrophysiology study and ablation." — Miller's Anesthesia, 10e

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