Sunday, February 5, 2023

ECG Blog #361 — Another WCT Rhythm ...

The ECG in Figure-1 is from a middle-aged man — who had just received thrombolytic therapy for presumed acute infarction. No other history available.

  • How would YOU interpret this ECG?
  • How certain are you of your answer?

Figure-1: ECG obtained from a middle-aged man following thrombolytic therapy. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:
The ECG in Figure-1 — shows a regular WCT ( = Wide-Complex Tachycardia) at ~140/minute, without clear sign of atrial activity.
  • Clinically — The 1st priority in assessing this patient would be to determine hemodynamic status. This is because IF this patient was hemodynamically unstable with this ECG — then regardless of what the rhythm happens to be — synchronized cardioversion would become immediately indicated!
  • On the other hand — IF the patient is completely stable with this rhythm, then by definition — You have at least a “moment of time” to more thoroughly contemplate the etiology of this rhythm.

PEARL #1: As emphasized in many other blog posts (ie, ECG Blog #220 and Blog #196, to name just 2) — the differential diagnosis of a regular WCT rhythm without clear sign of atrial activity should be assumed to be VT (Ventricular Tachycardia) until proven otherwise.
  • Taking all comers in an unselected adult population — statistical likelihood that a regular WCT without atrial activity will be VT is at least 80%.
  • If the patient is at least middle-aged, and especially if there is a history of underlying heart disease — then statistical likelihood that a regular WCT without atrial activity will be VT increases to ~90%. To Emphasize — This is a 90% likelihood of VT even before you look at the ECG!

  • In today's case — Given that the patient was just treated with thrombolytic therapy for a presumed acute MI — the odds that the rhythm in Figure-1 is VT are at least 90% (even before you look at the ECG).

PEARL #2: Use of QRS morphology in the 12-lead tracing during the WCT rhythm can help to refine the statistical likelihood estimate from 80-90% — to an even more precise figure (See ECG Blog #42 for specific criteria I favor for this purpose). This is especially relevant for today’s tracing — because the QRS morphology in Figure-1 is exceedingly atypical for a supraventricular rhythm. Looking at specific ECG findings in today's case:
  • There is extreme axis deviation in the frontal plane during the WCT. This is highly unlikely with a supraventricular rhythm. To Emphasize: By “extreme” axis deviation — the QRS must be entirely negative in either lead I or lead aVF. Even a small positive deflection in either of these leads negates the reliability of this criterion. The 12-lead tracing in Figure-1 satisfies this “extreme” axis deviation criterion — because the QRS is all negative in each of the 3 inferior leads! 

  • The QRS is all positive in right-sided lead aVR. This usually indicates that the origin of the WCT rhythm is from the left ventricular apex — which implies that the rhythm is VT (because supraventricular conduction does not originate from this anatomic location).

  • The QRS is all negative in leads V3-thru-V6. The finding of an all negative QRS in lead V6 — greatly increases the likelihood of VT (for a similar reason as does an all positive QRS deflection in right-sided lead aVR). Seeing an all negative QRS not only in lead V6 — but in each of the last 4 chest leads (ie, in leads V3-thru-V6) overwhelmingly favors VT.

  • Although an all positive QRS in lead V1 can be associated with RBBB-conduction — the lack of additional deflections (ie, there is no triphasic rSR’ complex in lead V1) — is more consistent with VT than with an SVT rhythm.

  • To Emphasize: There are exceptions to the above-cited morphologic criteria. These exceptions are limited to: i) If the rhythm is antidromic AVRT — in which the impulse travels forward over an AP (Accessory Pathway) in a patient with WPW, therefore resulting in a regular WCT rhythm that resembles VT (For more on the various arrhythmias in patients with WPW — See ECG Blog #18); and, ii) If the baseline ECG during sinus rhythm manifests a widened and very abnormal QRS morphology as a result of “scaring” from prior infarction(s). 
  • BOTTOM Line: Other than these 2 exceptions — it’s hard to imagine how the regular WCT rhythm in Figure-1 could be supraventricular (ie, I'd estimate a 98-99% likelihood that the rhythm in Figure-1 was VT).

CASE Conclusion:
Unfortunately — I do not have follow-up on today's patient. That said — it's hard to imagine how today's rhythm could not be VT.
  • ClinicallyImmediate cardioversion would be indicated IF this patient was at all unstable hemodynamically. Even if stable — prompt electrical carioversion would clearly be an appropriate action for a rhythm such as that shown in Figure-1.
  • Alternatively — a trial of antiarrhythmic therapy (ie, with IV Amiodarone or Procainamide) — could be appropriate IF the patient was tolerating the arrhythmia.
  • Although Adenosine is used by many in selected cases for treating a regular WCT rhythm of uncertain etiology — I would not lose time by trying Adenosine in today's case. This is because today's patient by definition has underlying coronary disease (ie, He was just treated with thrombolytic therapy for presumed acute MI). Adenosine may work in the treatment of selected Idiopathic VT rhythms (as per ECG Blog #197) — but Adenosine will not work with ischemic VT.
  • IF at any time during the treatment process the patient's hemodynamic status deteriorates — then immediately cardiovert! 

  • For more on evaluation and management of the regular WCT — See the ADDENDUM below.


Acknowledgment: My appreciation to Dradam Ahmen (from Nouakchott, Mauritania) for the case and this tracing.





ADDENDUM (2/5/2023):
  • I've reproduced below from ECG Blog #196 — a number of helpful figures and my Audio Pearl on assessment of the regular WCT rhythm.


Figure-2 : My LIST #1 = Causes of a Regular WCT (Wide-Complex Tachycardia) of uncertain Etiology (ie, when there is no clear sign of sinus P waves).

Figure-3: Use of the "3-Simple Rules" for distinction between SVT vs VT.

Figure-4: Use of Lead V1 for assessing QRS morphology during a WCT rhythm.

ECG Media PEARL #13a (12:20 minutes Audio) — reviews “My Take” on assessing the regular WCT (Wide-Complex Tachycardia), when sinus P waves are absent — with tips for distinguishing between VT vs SVT with either preexisting BBB or aberrant conduction.


Additional Relevant ECG Blog Posts to Today’s Case:

  • ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the Ps, Qs & 3R Approach.

  • ECG Blog #210 — Reviews the Every-Other-Beat (or Every-Third-Beat) Method for estimation of fast heart rates — and discusses another case of a regular WCT rhythm. 

  • ECG Blog #220 — Review of the approach to the regular WCT ( = Wide-Complex Tachycardia).
  • Regular WCT (Wide-Complex Tachycardia).
  • ECG Blog #196 — Reviews another Case with a regular WCT rhythm.
  • ECG Blog #263 and Blog #283More WCT Rhythms ...

  • ECG Blog #197 — Reviews the concept of Idiopathic VT, of which Fascicular VT is one of the 2 most common types. 
  • ECG Blog #346 — Reviews a case of LVOT VT (a less common idiopathic form of VT).

  • ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD). 
  • ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the Video Pearl in this blog post.
  • ECG Blog #211 — WHY does Aberrant Conduction occur?

  • ECG Blog #197 — Review of Fascicular VT.
  • ECG Blog #301 — Reviews a WCT that is SupraVentricular! (with LOTS on Aberrant Conduction).

  • ECG Blog #323 — Review of Fascicular VT.
  • ECG Blog #38 and Blog #85 — Review of Fascicular VT.
  • ECG Blog #278 — Another case of a regular WCT rhythm in a younger adult.
  • ECG Blog #35 — Review of RVOT VT
  • ECG Blog #42 — Review of criteria for distinguishing VT vs Aberration.

  • ECG Blog #133 and ECG Blog #151— for examples in which AV dissociation confirmed the diagnosis of VT.
  • Working through a case of a regular WCT Rhythm in this 80-something woman — See My Comment in the May 5, 2020 post on Dr. Smith’s ECG Blog. 
  • Another case of a regular WCT Rhythm in a 60-something woman — See My Comment at the bottom of the page in the April 15, 2020 post on Dr. Smith’s ECG Blog. 

  • Review of the Idiopathic VTs (ie, Fascicular VT; RVOT and LVOT VT) — See My Comment at the bottom of the page in the September 7, 2020 post on Dr. Smith’s ECG Blog.
  • Review of a different kind of VT (Pleomorphic VT) — See My Comment in the June 1, 2020 post on Dr. Smith’s ECG Blog.


  1. Dr. I was impressed that the DI and AVL derivation is positive

    1. The rhythm is VT — so depending from where in the ventricles the rhythm originates, you may see some leads abnormal and others not so much ... The ALL NEGATIVE complexes in the inferior leads and in V3-V6 tell us this rhythm is VT ... — :)