ECG Blog #491 — VT until Proven Otherwise?

The ECG in Figure-1 was obtained from an older man with a history of coronary disease and chronic AFib (Atrial Fibrillation) — who was admitted acutely ill to the ICU (Intensive Care Unit) for septicemia. He was hemodynamically stable at the time this tracing was recorded.

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NOTE: The ECG in today's case looks similar to the tracing I presented a few weeks ago in ECG Blog #489. But is the answer the same?

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QUESTIONS:

• How would you interpret the ECG in Figure-1?
• How certain are you of your diagnosis?
• Did the fact that this patient was hemodynamically stable at the time this ECG was recorded influence your diagnosis?
• How would you treat this patient?

Figure-1: The initial ECG in today's case — obtained from an older man being treated in the ICU for septicemia. (To improve visualization — I've digitized the original ECG using PMcardio).

My Thoughts on Today’s CASE:

Applying the Ps, Qs and 3Rs (See ECG Blog #185) — the rhythm in Figure-1 is fast (~220/minute) — regular — with a wide QRS — and without clear sign of atrial activity. This defines the rhythm as a regular WCT (Wide-Complex Tachycardia). As per the LINKS to other cases that are found at the bottom of this page — the principal differential diagnosis is between:

• VT (Ventricular Tachycardia) — or —
• SVT (SupraVentricular Tachycardia) with either of the following: i) Preexisting BBB (Bundle Branch Block); or ii) Aberrant conduction as a result of the rapid rate.

On rare occasions — "something else" (ie, hyperkalemia, sodium channel blocker toxicity — or other toxicity) may result in a regular WCT rhythm. Given that this patient has been hospitalized in the ICU — presumably he is not hyperkalemic, such that the main consideration is to distinguish between VT vs SVT with either preexisting BBB or rate-related aberrant conduction. 

KEY Points to consider include the following:

• Statistically, in an unselected adult population — at least 80% of regular WCT rhythms without sign of atrial activity will turn out to be VT. Given that today's patient is an older adult with known coronary disease — the likelihood of VT is increased to ~90% even before we consider specific features of this ECG.
• QRS morphology may allow for greater precision in predicting WCT etiology — especially IF ECG features predictive of either VT or SVT are present. That said, even in cases in which QRS morphology is suggestive — it is rare to attain 100% certainty prior to our need to begin treatment.
• Hemodynamic stability during the WCT rhythm does not rule out VT. While true that patients with sustained VT are much more likely to decompensate than those who remain in a persistent SVT rhythm — these generalities do not always hold true. If LV function is good and the heart rate is not excessively rapid — then some patients in sustained VT may remain hemodynamically stable for a period of hours (or even longer).

What About Today's CASE?

When this case was sent to me — I found it surprising that this acutely ill patient with septicemia would be hemodynamically stable in this WCT rhythm — because the heart rate is so  very rapid (ie, ~220/minute).

• I thought the rhythm was fascicular VT — because QRS morphology resembled rbbb conduction in the chest leads (ie, with an all upright complex in lead V1 — an RS pattern in lateral lead V6 with terminal negativity consistent with rbbb-like conduction — and marked rightward axis deviation in the frontal plane).
• Given this patient's acutely ill status and the very rapid rate of his WCT rhythm — I probably would have moved to synchronized cardioversion. However, because this patient was hemodynamically stable — providers at the bedside reasonably opted for a trial of IV Amiodarone, being ready to cardiovert at any if time the patient became hemodynamically unstable.

PEARL #1: For as much as the rhythm in Figure-1 "looks" like VT — it's important to appreciate the limitations of our diagnostic accuracy from this single ECG. Confounding ECG features on this tracing include: 

• i) Lack of a clear triphasic rsR' pattern in lead V1 (instead there is an rR' pattern in lead V1 without descent of any S wave below the baseline — as illustrated in Figure-4 in the ADDENDUM below); 
• ii) Despite predominant negativity of the QRS in all 3 standard limb leads (leads I,II,III) — the lack of an all-negative QRS in either lead I and/or lead aVF means that we can not rule out a supraventricular rhythm (instead there is a tiny initial positive deflection in lead I and in each of the inferior leads); 
• iii) Lack of a completely monophasic R wave in lead aVR negates the value of this lead for predicting VT (instead there appears to be a tiny q wave = an initially negative deflection in this lead); 
• iv) Despite predominant negativity of the QRS in lateral chest lead V6 — the lack of an all negative QRS in lateral lead V6 negates the value of this lead for predicting VT (instead there is a small but-definitely-present initial R wave in this lead).

PEARL #2: Although each of the above ECG findings in PEARL #1 make a supraventricular rhythm less likely — none of them guarantee that the rhythm is VT. We need to remember that much of the time we will not be able to be certain if a regular WCT rhythm is VT or SVT at the time that we need to begin our treatment. Instead — we often need to formulate our best hunch as to what we think the rhythm is likely to be — and base our treatment decisions accordingly.

PEARL #3: Finding a prior ECG on this patient could prove invaluable — because if QRS morphology during the patient's baseline rhythm looks the same as during the WCT — this could prove that the WCT is not VT. 

• Unfortunately in today's case — this patient's baseline 12-lead ECG could not be found at the time it was needed.

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The CASE Continues:

Within minutes of beginning IV Amiodarone — the ECG shown in the bottom panel of Figure-2 was obtained. The patient remained hemodynamically stable.

QUESTIONS:

• What is learned from comparison of today initial ECG — with the repeat ECG obtained within minutes after beginning IV Amiodarone?

Figure-2: Comparison between the initial ECG — with the repeat ECG obtained within minutes of starting IV Amiodarone.

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ANSWER:

Surprisingly, the very rapid WCT rhythm seen in today's initial ECG has dramatically slowed in ECG #2 to another regular, wide rhythm.

• Comparing QRS morphology during the WCT rhythm ( = the upper tracing in Figure-1) — with QRS morphology shortly after initiation of IV Amiodarone — Isn't QRS morphology in virtually every lead remarkably similar?

PEARL #4: ECG features in ECG #2 now look much more in favor of an SVT with aberrant conduction because: 

• i) Lead V1 in ECG #2 now manifests a typical triphasic morphology for supraventricular conduction because there is a small initial r wave — followed by an S wave that descends below the baseline — that finishes with a tall, pointed terminal R' ( = a taller "right rabbit ear" ).
• ii) The tiny initial r waves that we barely saw in ECG #1 — are now much more evident (and much more consistent with supraventricular conduction with RBBB/LAHB).
• iii) Leads V4,V5 and especially V6 in ECG #2 — now manifest significantly taller narrow R waves that are strongly suggestive of a supraventricular rhythm.

KEY Point: Despite the above morphologic features of ECG #2 that strongly suggest a supraventricular rhythm — P waves are not seen! As a result — I was not yet certain that the rhythm in ECG #2 was now supraventricular.

• PEARL #5: Did you notice that the rate of the regular wide rhythm in ECG #2 is almost half that of the initial rapid WCT rhythm? — almost as if ECG #1 represented a reentry SVT rhythm, that as a result of the AV nodal blocking effect of Amiodarone — was now only conducting every-other-impulse to the ventricles.
• Alternatively — the rhythm in ECG #2 could represent junctional tachycardia with preexisting RBBB/LAHB. Although an automatic junctional tachycardia is not a common rhythm in adults — today's clinical situation (ie, a "sick" patient with multiple underlying disorders) is perhaps the most common setting in which we encounter fast junctional rhythms.

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The CASE Continues:

Since the patient remained hemodynamically stable with the rhythm in ECG #2 — IV Amiodarone was continued. A few minutes later — the rhythm in ECG #3 was observed.

• To facilitate comparison in Figure-3 — I've put the 3 ECGs in today's case together.

QUESTION:

• What do we learn from ECG #3?

Figure-3: Comparison of the 3 ECGs in today's case.

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ANSWER:

The rhythm in ECG #3 is faster than it was in ECG #2 — and is now irregularly irregular without P waves. This patient with a known history of chronic AFib — is now back in AFib with a rapid ventricular response. The 5th beat in leads V1,V2,V3 that is wider and different in morphology from the rest of the tracing is a PVC.

• Treatment of this patient with IV Amiodarone was effective! Although the end result of this treatment is still suboptimal (ie, recurrence of this patient's chronic AFib — now with a rapid ventricular response) — the "good news" is that: i) The rate of the rhythm in ECG #3 is slower than it was in ECG #1; and, ii) We now know that the rhythm in ECG #1 was not VT (because AFib is a supraventricular rhythm and QRS morphology in ECG #3 is virtually identical to QRS morphology during ECG #1).

CASE Follow-Up.

• Comparison of QRS morphology in the 3 tracings shown in Figure-1 was found to be the same as this patient's QRS morphology in prior baseline tracings. This confirms that the initial ECG in today's case was not VT. 
• Instead — today's initial rhythm most likely represents a reentry SVT in which QRS widening is the result of preexisting RBBB/LAHB.
• This patient continued to have a stormy course — but seemed to be gradually improving over time as his septicemia was treated. His AFib is chronic. Rate control will hopefully be optimized once his underlying conditions improve.
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• Editorial Comment: What I especially liked about this case — is that it keeps us humble. I truly thought the initial ECG was VT. But "not all patients read the textbook" — and over time, serial ECGs confirmed a supraventricular etiology (with preexisting RBBB/LAHB). Truly — we often have to begin treatment of wide tachycardias before we are certain of the rhythm etiology. A trial of IV Amiodarone was reasonable given hemodynamic stability of the patient — and providers were able to confirm a supraventricular etiology.

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Acknowledgment: My appreciation to Andrea D'Angelo (Naples, Italy) for allowing me to use this case and these tracings.

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ADDENDUM (8/9/2025):

Figure-4: QRS morphology in lead V1 that suggests a supraventricular etiology (from my ACLS Pocket Brain-2013).

 

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Additional Relevant ECG Blog Posts to Today’s Case: 

• ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the Ps, Qs, 3R Approach.
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• 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 #220 — Review of the approach to the Regular WCT (Wide-Complex Tachycardia).
• ECG Blog #489 — in which the initial ECG looks similar to that in today's case (but for which the answer is different).
• ECG Blog #196 — Reviews another regular WCT.
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• ECG Blog #263 and Blog #283 — Blog #361 — Blog #384 — and Blog #460 — and Blog #468 — 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 — more regular WCTs.
• ECG Blog #475 — Aberrant SVT?
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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. 
• A series of 3 challenging tracings with QRS widening (See My Comment at the bottom of the page in the March 6, 2025 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.