ECG Blog #531 — WCT: What to Do?

I was sent the ECG in Figure-1 — with the question, "VT or SVT"?

• The sender wanted to know, "Adenosine or Amiodarone"?
• The patient was hemodynamically stable at the time the ECG in Figure-1 was recorded, so although synchronized cardioversion could be perfectly appropriate — it would seem reasonable to try medical therapy.

QUESTION:

• How would YOU interpret the ECG in Figure-1?

Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio).

My Thoughts:

The ECG in Figure-1 shows a regular WCT (Wide-Complex Tachycardia) at ~135/minute, without clear sign of sinus P waves.

• As always when confronted with a regular WCT without clear sign of sinus P waves — the principal differential is between VT (Ventricular Tachycardia) — vs some form of SVT (SupraVentricular Tachycardia) with QRS widening from either preexisting bundle branch block or rate-related aberrant conduction.

I looked more closely at the rhythm in Figure-1:

• KEY Point #1: Statistically — at least 80-90% of regular WCT rhythms without clear sign of sinus P waves will turn out to be VT (with this figure increasing to over 90% if the patient is "older" and has underlying heart disease). This of course means that sometimes (ie, 10-20% of the time) — the WCT rhythm in front of you will be supraventricular. But it especially means that we should assume VT until proven otherwise (especially if your patient is "older" and known to have underlying heart disease). — (See ECG Blog #361 — for more on assessment of the regular WCT).
• 
  
• KEY Point #2: QRS morphology in Figure-1 is perfectly consistent with LBBB conduction (ie, Monophasic upright QRS complex in left-sided leads I and V6 — and predominantly negative QRS in lead V1, as well as in other anterior leads that all manifest a very steep S wave downslope). So, although we still need to assume VT until proven otherwise — this perfectly consistent QRS morphology for LBBB conduction clearly reduces the likelihood of VT (See ECG Blog #204 — for more on the QRS morphology of LBBB conduction).
• 
  
• KEY Point #3: There does appear to be sign of some form of atrial activity — as the narrow, pointed peak to the T waves in lead aVF looks too pointed for a naturally occurring T wave — which makes me suspicious that an underlying P wave is peaking the T wave (RED arrows in Figure-2). And if these RED arrows are P waves — they are upright, and therefore not the negative P waves of retrograde conduction that are seen with reentry SVT rhythms. Instead — these upright P waves would have a surprisingly long PR interval for this tachycardia rhythm, which suggests the Bix Rule discussed in ECG Blog #227, in which when a P wave is seen near the middle of the R-R interval, tihs often means there is 2:1 AV conduction.
• 
  
• KEY Point #4: The most commonly overlooked arrhythmia (by far!) — is AFlutter (Atrial Flutter) with 2:1 AV conduction — especially when the ventricular rate is close to 150/minute (range between 130-160/minute). As a result, the BEST way to avoid overlooking AFlutter — is to always think AFlutter until proven otherwise whenever you have a regular SVT without clear sign of sinus P waves, when the ventricular rate falls within the above rate range (See ECG Blog #287 — for review of why AFlutter is so commonly overlooked) — (And for another Step-by-Step example of my "Thought Process" for uncovering AFlutter — See my discussion in the November 12, 2019 post in Dr. Smith's ECG Blog).

Figure-2: In today's case — the lead that most made me suspect underlying atrial activity was lead aVF (RED arrows).

KEY Point #5: My "Go-To" leads when I am trying to identify subtle (partially hidden) atrial activity — are leads II, III, aVF; lead aVR; and lead V1. IF none of the above leads suggest atrial activity — then I’ll survey the remaining 7 leads as I look for atrial activity. That said, AFlutter will almost always provide ready evidence of atrial activity in one or more of my “Go To” leads.

• KEY Point #6: The BEST way to quickly find partially hidden atrial activity is to use calipers. Calipers instantly make you smarter! (and in my experience those clinicians who do not use calipers will commonly miss the diagnosis of complex rhythms).
• Since the most common conduction ratio of untreated AFlutter is 2:1 — the way in which I look for hidden flutter waves is to carefully set my calipers at precisely HALF the R-R interval of the regular SVT rhythm.

I illustrate this approach in Figure-3 — in which I've added colored arrows to 4 additional leads:

• PINK arrows in lead II highlight where I strongly suspect flutter waves are hiding.
• YELLOW arrows in leads III and aVR ( = 2 more of my "Go-To" leads) highlight even more subtle atrial activity (ie, I suspect the tiny upright deflection at the beginning of some QRS complexes in lead III is the beginning of a flutter wave — as I suspect the slow upslope of the last part of the QRS in lead aVR reveals where the 2nd negative flutter wave in this lead is hiding).
• To Emphasize: Flutter waves are very subtle in leads III and aVR — but it is the perfect regularity of 2:1 AFlutter in lead aVF with the strong suggestion of supraventricular LBBB conduction that makes me all-but-certain that the underlying rhythm in Figure-3 is 2:1 AFlutter.
• P.S.: I fully admit that I do not see flutter waves in lead I — but the YELLOW arrows clearly show where 2:1 flutter waves might be hiding.

Figure-3: It is the RED arrows in lead aVF that convinced me the underlying rhythm in today's case is AFutter with 2:1 AV conduction. Less obvious in leads II,III,aVF — I strongly suspect the colored arrows in those leads highlight where flutter waves are hiding.

 

= = = = = = = = = = = = = = 

Final Point #7: A deceptively easy but all-too-commonly-forgotten way to demonstrate hidden atrial activity is to use a Lewis Lead. Once familiar with the technique (that is described in Figure-4) — it should take no more than seconds to apply a Lewis Lead for assistance with the problematic arrhythmia you are working with.

Figure-4: How to record a Lewis Lead.

CASE Conclusion:

To return to the 2nd question I was asked by the sender of today's case:

• Since today's patient was hemodynamically stable — I thought an initial attempt at medical treatment was reasonable.
• For the reasons discussed above — I was virtually certain the rhythm in today's ECG was AFlutter with 2:1 AV conduction (If uncertain about the rhythm — a vagal maneuver could be tried to bring out flutter waves or a Lewis Lead may have made flutter waves more visible).
• While Adenosine could have been used — this drug is not effective for cardioverting AFlutter (Instead — IV Adenosine would act as a "chemical Valsalva" to slow the ventricular response, which most likely would have revealed underlying flutter waves).
• I would have instead favored IV Amiodarone — which may be effective for both VT and SVT rhythms.

Providers treated this patient with IV Amiodarone. The patient remained hemodynamically stable — and within 2 hours sinus rhythm was restored. The diagnosis of AFlutter was confirmed.

• Unfortunately — the patient was an older man with significant underlying comorbidities. He did not survive the hospitalization.

= = = = = = = = = = = = = = 

Extra Credit:

Return for a moment to the ECG in Figure-3. Did you notice the markedly coved, hyperacute-appearing ST-T waves in leads V4,V5?

• My initial concern on seeing the ST-T wave appearance in leads V4,V5 — was that whatever the etiology of the regular WCT rhythm, the "cause" of this rhythm might be an ongoing acute MI.
• That said — both QRS widening and tachycardia are notorious for affecting ST-T wave appearance (ie, In today's case — underlying flutter waves might be superimposed, thereby producing the "picture" we see in Figure-3).
• I did not think the markedly peaked ST-T waves in leads V1,V2,V3 of Figure-3 looked abnormal — as they appeared to be "proportional" given how deep the anterior S waves are. But the shape of the ST-T waves in leads V4,V5 clearly suggested the possibility of an underlying ongoing MI.
• 
  
• Bottom Line: First priority in today's patient was to determine the etiology and treat the WCT rhythm — and then repeat the ECG once converted to sinus rhythm to rule out the possibility of an ongoing infarction. This was done — and by Troponins and follow-up tracings an acute MI was ruled out (and the peaked ST coving in leads V4,V5 resolved once sinus rhythm at a controlled rate was restored). An acute infarction was not the reason for this patient's unfortunate demise. 

================================== 

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

==================================

 

Relevant ECG Blog Posts to Today’s Post: 

• See ECG Blog #185 — for review of the Systematic Ps, Qs, 3R Approach to Rhythm Interpretation.
• ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
• 
  
• ECG Blog #204 — Reviews a user-friendly approach to the ECG Diagnosis of conduction defects (ie, LBBB — RBBB — IVCD).
• 
  
• ECG Blog #287 — Working through the diagnosis of AFlutter (with Audio Pearls, PDF, Lewis Lead).
• The November 12, 2019 post in Dr. Smith's ECG Blog — in which I review my approach to a Regular SVT rhythm.