ECG Blog #460 — A Wide Tachycardia ...

I was sent the ECG in Figure-1 — initially told only that it was obtained from an older man with “palpitations”.

• The cardiology team thought the rhythm was an SVT (SupraVentricular Tachycardia) — with QRS widening as a result of aberrant conduction.

QUESTION:

• Do YOU agree that the rhythm is consistent with an SVT, in which there is QRS widening because of aberrancy?
• How would you treat this patient?

Figure-1: The initial ECG in today's case. (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 ~160/minute, without clear sign of atrial activity.

• Clinically — The 1st priority in assessing this patient would be to determine hemodynamic status! (because IF this patient was 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 two) — 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!
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• In Today's CASE — All that we initially knew was that the patient was an "older adult" — but we were not told if he had underlying heart disease. So before looking at QRS morphology — statistical odds were ~80% likelihood of VT.

PEARL #2: Assessment of the frontal plane axis and consideration of QRS morphology in the 12-lead tracing during the WCT rhythm can increase (or decrease) statistical likelihood of VT from our initial estimate of ~80% (See ADDENDUM below for user-friendly criteria I favor for this purpose).

• Finding extreme axis deviation in the frontal plane during the WCT would strongly favor VT. 
• 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. 
• In Today's CASE — The 12-lead tracing in Figure-1 does not satisfy this “extreme” axis deviation criterion — because the axis is normal (ie, The net QRS deflection is positive in both leads I and aVF — therefore the axis lies between the normal range of 0-to-90 degrees). 

Perhaps the most helpful criterion for assessing QRS morphology during a regular WCT rhythm — is whether QRS morphology resembles a typical conduction block? (ie, typical RBBB; typical LBBB — or bifascicular block with either RBBB/LAHB or RBBB/LPHB).

• As emphasized in ECG Blog #204 — Focus on the 3 KEY leads ( = leads I,V1,V6) facilitates recognition of RBBB and LBBB within seconds. That said — whereas somewhat atypical QRS morphology does not necessarily indicate VT  — the finding of a completely typical QRS morphology for RBBB or LBBB may greatly increase the likelihood of a supraventricular rhythm.

In Today's CASE — QRS morphology is very atypical for either RBBB or LBBB. As a result — the WCT rhythm in Figure-1 has to be assumed VT until proven otherwise!

• ECG #1 is not consistent with LBBB — because while the QRS is all positive in lead V6, there is no predominant negativity in the anterior leads.
• ECG #1 is not consistent with RBBB — because: i) Lead V1 lacks a triphasic morphology; — ii) Lateral leads I and V6 lack any terminal S wave; — and, especially because: iii) The QRS is almost all positive in all 6 chest leads (there is no more than a tiny initial q wave in leads V3,V4,V5).

PEARL #3: If ever there is concordance of QRS complexes in all 6 chest leads (ie, all 6 chest leads are either entirely positive or entirely negative) — this is virtually diagnostic of VT.

• The sensitivity of this criterion not good — such that it will be rare that you will see positive or negative QRS concordance in all 6 chest leads during a regular WCT rhythm. That said, if ever you do — then you have essentially made the diagnosis of VT. 
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• In Today's CASE — Those tiny initial q waves in leads V3,V4,V5 mean that positive concordance is not strictly present. That said — given how tiny these 3 precordial q waves are, I interpreted the almost all positive QRS in leads V1-thru-V6 as supportive of presumed VT (albeit not diagnostic).
• The only exceptions that I'm aware of to the above-cited morphologic criteria for VT are: i) IF the rhythm is antidromic AVRT — in which case 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); — ii) If the baseline ECG during sinus rhythm manifests a widened and very abnormal QRS morphology as a result of prior infarction, cardiomyopathy and/or preexisting bundle branch block; — and, iii) If there is some toxicity (such as hyperkalemia) which widens and distorts QRS morphology.
• Conclusion: Assuming none of the above exceptions exist — the ECG in Figure-1 has to be presumed VT until proven otherwise. 

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CASE Conclusion:

Today's patient was hemodynamically stable in association with the ECG in Figure-1.

• In view of this patient's hemodynamic stability — medical therapy was initially tried. There was no response to vagal maneuvers, nor to 3 doses of Adenosine. This was followed with several Amiodarone boluses — again with no response.
• Some clinical history was obtained — which revealed that the patient has known coronary disease (S/P CABG — with ejection fraction of ~35%).

At this point — the cardiology team still suspected a supraventricular etiology for today's rhythm. That said, plans were made for synchronized cardioversion given lack of response to medical treatment. Before this could be done — the patient spontaneously converted to sinus rhythm.

Final Reflections on Today's CASE:

• The ECG in Figure-1 strongly suggests VT. That said — clinicians often need to begin treatment before they are 100% certain of the rhythm diagnosis. In today's case — a trial of medical therapy was reasonable since the patient was hemodynamically stable.
• It's important to appreciate that the odds that today's rhythm was VT immediately increased as soon as it was learned that the patient has significant underlying heart disease.
• Given that multiple doses of antiarrhythmic medication were given — there should have been adequate time in this patient with known significant coronary disease — to obtain a prior ECG. This could have been insightful if a prior tracing were to show a preexisting conduction defect in sinus rhythm with the same QRS morphology as seen in Figure-1. 
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• While nothing is 100% — the sequence and choice of treatment options should be influenced by relative probability of the differential diagnosis.
• Several doses of Adenosine were given in today's case. This drug is extremely effective for converting reentry SVT rhythms. It may also convert a certain number of patients with idiopathic VT. That said, by definition — today's patient does not have idiopathic VT, because he has known coronary disease. (See ECG Blog #197 — for review of idiopathic VT).
• Although the effects of Adenosine wear off within 30-90 seconds, and most patients tolerate this drug surprisingly well — Adenosine is not benign (See ECG Blog #402). As a result — I would not have risked using Adenosine in today's case ( = my opinion) given virtual nil chance of it working.
• That said — the fact that both vagal maneuvers and 3 doses of Adenosine failed to convert today's rhythm is yet more evidence in favor of VT.
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• IV Amiodarone (bolus and drip) — is an appropriate medication to try in today's case, given that this patient was hemodynamically stable. An advantage of this medication — is that it may be effective for both VT and SVT rhythms. As I lack full details from today's case — I do not know if it ultimately was the Amiodarone that converted today's WCT to sinus rhythm.
• IF the decision is made for a trial of medical therapy — the provider should stay at the bedside, ready to immediately cardiovert if at any time during the treatment process the patient's hemodynamic status deteriorates.
• Alternatively — a decision could have been made to sedate the patient and immediately cardiovert, given the 90+% likelihood of VT in this patient with known coronary disease.
• While important to engage in thoughtful discussion about cases like this — ultimately, "Ya gotta be there" to know which therapeutic option(s) might be best, given the particulars of any given case. I offer the above as retrospective reflection to stimulate discussion on actions to consider.
• My understanding is that the decision was made for today's patient to be formally evaluated by EP cardiology — with consideration given to ablation and/or insertion of an ICD (Implantable Cardioverter Defibrillator).
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• For more on evaluation and management of the regular WCT — See the ADDENDUM below.

 

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Acknowledgment: My appreciation for the anonymous submission of this case.

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Additional Relevant ECG Blog Posts to Today’s Case:

• ECG Blog #185 — Reviews my System for Rhythm Interpretation — with use of 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. 
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• ECG Blog #422 and Blog #425 — Cases with Congenital Heart Disease in Adults.
• ECG Blog #220 — Review of the approach to the regular WCT ( = Wide-Complex Tachycardia).
• ECG Blog #196 — Another Case with a regular WCT.
• ECG Blog #263 and Blog #283 — Blog #361 — and Blog #384 — More WCT Rhythms ...
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• 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).
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• 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.
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• ECG Blog #211 — WHY does Aberrant Conduction occur?
• ECG Blog #301 — Reviews a WCT that is SupraVentricular! (with LOTS on Aberrant Conduction).
• ECG Blog #445 and Blog #361 — Another regular WCT rhythm ...
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• 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 — Criteria to distinguish VT vs Aberration.
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• ECG Blog #133 and ECG Blog #151— for examples in which AV dissociation confirmed the diagnosis of VT.
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• 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. 
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• 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.

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ADDENDUM (12/13/2024):

• I've reproduced below from ECG Blog #361 — 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.

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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.