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ECG interpretation delta wave pre-excitation WPW pattern features

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WPW Wolff-Parkinson-White ECG delta wave short PR wide QRS

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Based on my systematic analysis of the ECG image you provided, here is a detailed interpretation:

ECG Analysis

Machine parameters: Heart Rate 90 bpm | 6-channel + 1 rhythm | 10 mm/mV | 25 mm/sec

Primary Abnormality: Wolff-Parkinson-White (WPW) Pattern / Ventricular Pre-excitation

The ECG shows the classic triad of WPW:
FeatureFinding
PR intervalShort (< 120 ms) — visible across leads I, II, III, aVF
Delta waveSlurred, slow upstroke at the beginning of the QRS complex — most visible in inferior and precordial leads
QRS durationWidened (> 120 ms) due to pre-excitation of ventricular myocardium

Mechanism

In WPW, an accessory pathway (Bundle of Kent) bypasses the AV node and directly connects atrial to ventricular myocardium. This causes:
  1. Early ventricular activation → short PR (no AV nodal delay)
  2. Slow initial conduction through non-specialized myocardium → delta wave (slurred upstroke)
  3. Fusion of pre-excited and normal His-Purkinje activation → wide QRS
This is confirmed by Braunwald's Heart Disease: "Sinus rhythm ECG showing a short PR interval and delta wave classic for Wolff-Parkinson-White syndrome (WPW)."

Accessory Pathway Localization (from delta wave polarity)

  • The delta waves appear upright in the inferior leads (II, III, aVF) and have a pattern consistent with a right anteroseptal or left-sided accessory pathway — but formal localization requires the full 12-lead precordial views (V1–V6), which are not shown in this 6-channel strip.

Secondary ST-T Changes

  • Discordant ST-T changes (ST depression / T-wave inversion in some leads) — these are secondary repolarization abnormalities due to abnormal depolarization, NOT primary ischemia.

Clinical Significance

⚠️ Important: WPW predisposes to:
  • AVRT (AV re-entrant tachycardia) — the most common arrhythmia
  • Pre-excited atrial fibrillation — potentially life-threatening (very short R-R intervals can degenerate to ventricular fibrillation)
  • Sudden cardiac death (rare but possible)
Management: Electrophysiology (EP) study + radiofrequency catheter ablation of the accessory pathway is curative. Avoid AV-nodal blocking agents (digoxin, verapamil, diltiazem) if pre-excited AF is suspected, as they can accelerate conduction down the accessory pathway.
Here is a reference WPW ECG from the medical literature for comparison:
WPW ECG — short PR, delta wave, wide QRS
Source: Braunwald's Heart Disease, p. 512
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