ECG Interpretation Summary: ECG Challenge-Heart Patient With a Racing Pulse
ECG Interpretation Summary: ECG Challenge-Heart Patient With a Racing Pulse
Published on: Medscape, July 18, 2025
Key Points – Numbered Summary
1. Heart Rhythm:
• Regular rhythm at a tachycardic rate of 132 bpm
2. QRS Morphology:
• Wide QRS complex (duration: 0.16 sec)
• QRS has an RBBB-like appearance, especially a broad tall R wave in lead V1
• However, this morphology is not typical for standard right bundle branch block (RBBB)
3. QRS Axis:
• Extreme left axis deviation
• Seen as positive QRS in lead I and negative in leads II and aVF
4. P Waves and AV Dissociation:
• Occasional P waves are seen, but they are not consistently associated with QRS complexes
• This confirms AV dissociation, a classic feature of ventricular tachycardia (VT)
5. ST-T Wave Changes:
• Subtle changes in ST-T segments are present, which may reflect:
• Abnormal ventricular activation
• Superimposed atrial activity (P waves)
6. QT/QTc Intervals:
• Prolonged at 380/560 msec
• But when corrected for the widened QRS, adjusted QT/QTc becomes 300/445 msec, which is considered normal
7. Differential Diagnosis Consideration:
• Though the QRS and axis could suggest fascicular VT (originating from the left posterior fascicle),
• The presence of coronary artery disease (CAD) and prior MI makes scar-related reentry VT more likely
8. Final Diagnosis:
Ventricular Tachycardia (VT)
Supported by:
• Wide QRS
• AV dissociation
• Extreme axis deviation
• History of structural heart disease
9. Peer Response:
• 56% of respondents correctly identified the rhythm as ventricular tachycardia
• Other less likely choices included:
• Sinus tachycardia with RBBB (13%)
• AV reentrant tachycardia (AVRNT) with RBBB (16%)
10• The key difference between ventricular tachycardia (VT) and supraventricular tachycardia (SVT) with aberrant conduction lies in their origin and ECG features. In this case, VT is favored due to several hallmark findings:
• AV dissociation, where P waves are not linked to QRS complexes, strongly supports VT and essentially excludes SVT.
• The QRS morphology, while resembling RBBB, is atypical and more consistent with abnormal ventricular activation.
• An extreme left axis deviation, uncommon in SVT but typical in VT, especially with prior MI or structural heart disease, further supports VT.
• Additional features such as ST-T changes, subtle QRS variation, and prolonged QTc all point to a ventricular origin.
In contrast, SVT with aberrancy typically shows regular PR intervals, consistent bundle branch block patterns, and occurs in patients without significant heart disease.
Thus, this ECG represents classic scar-related reentrant VT, not SVT with aberrant conduction.
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