ECG Diagnosis of Wide Complex Tachycardia

Written by Sam Parnell

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Several ECG features can help differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy. When in doubt, assume wide complex tachycardia (WCT) is VT, especially for patients with history of coronary artery disease or structural heart disease.

Why does this matter?
When patients with wide complex tachycardia present for medical care, initial evaluation should focus on hemodynamic stability. All patients with hemodynamic instability should be managed with urgent electrical cardioversion. For patients who are stable, correct diagnosis of wide complex tachycardia will guide the appropriate management and disposition.  However, differentiating ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy isn’t easy.

It’s shocking how complex the diagnosis of wide complex tachycardia can be…
This was a case report and review article in JAMA Internal Medicine focusing on the diagnostic approach to wide complex tachycardia. The authors described several ECG features that are strongly associated with ventricular tachycardia. In addition, they highlighted the importance of reviewing the patient’s medical history, as nearly 90% of patients with wide complex tachycardia and a history of myocardial infarction will be in ventricular tachycardia.

ECG factors associated with VT include:

  1. AV dissociation (P waves marching through at a slower rate, capture beats, or fusion beats)

  2. QRS positivity in lead aVR

  3. QRS concordance throughout the precordium

  4. QRS duration longer than 160 ms

  5. A broad and notched intrinsic deflection (initial portion of the QRS)

An example ECG from the article showing VT and several features associated with VT is shown below. 

From cited article

These ECG features can help differentiate VT from SVT with aberrancy. However, when in doubt, err on the side of caution by assuming the patient is in VT, especially if the patient has a history of coronary artery disease or structural heart disease.

Source
Diagnostic Approach to Wide Complex Tachycardia. JAMA Intern Med. 2021 Sep 1;181(9):1231-1233. doi: 10.1001/jamainternmed.2021.3189.

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