ECG Interpretation: ECG Blog #371 — Palpitations Since Childhood ...

The ECG in Figure-1 is from a man in his 30s — who overall has been healthy, except for a history of "intermittent palpitations" that he has had since childhood. Episodes typically last less than 2 minutes — but this time, he presented to the ED (Emergency Department) because of ongoing symptoms lasting a number of hours.

The patient consumed alcohol at a party the night before.
He was hemodynamically stable with ECG #1.

QUESTION:

What is the rhythm in Figure-1?

Figure-1: The initial ECG in today's case. The patient was hemodynamically stable in association with this rhythm. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:

I have presented similar ECGs to the one in today's tracing on several occasions (most recently in ECG Blog #284). The importance of being able to look at the ECG in Figure-1 — and make an immediate presumptive diagnosis is such, that periodic review is merited.

QUICK "Take": The QRS complex in ECG #1 is obviously wide — and P waves are absent (ie, Emergency providers will instantly consider some form of VT = Ventricular Tachycardia). But the rhythm is not regular ...

KEY diagnostic features regarding today's rhythm include:

Point #1: On close observation — the R-R interval varies from 1 beat-to-the-next (ie, the rhythm is irregularly irregular! — and P waves are absent).
Point #2: QRS morphology varies a bit throughout the tracing (ie, some beats are wider — and at least slightly different in shape than other beats).
Point #3: At certain points — the rhythm is exceedingly fast (ie, some R-R intervals are barely more than 1 large box in duration — which corresponds to a ventricular rate that at times exceeds 250/minute!). At other times — the R-R interval is nearly twice as long.
Point #4: Clinically, despite the exceedingly rapid rate — the patient was hemodynamically stable at the time that ECG #1 was recorded.
Point #5: The patient describes a longstanding history of intermittent palpitations. He presented to the ED a number of hours after a party, at which he consumed an unspecified amount of alcohol alcohol.

My IMPRESSION:

The rhythm in Figure-1 is almost certain to be very rapid AFib in a patient with WPW.

Although VT may at times be somewhat irregular — it is generally not as irregularly irregular as the rhythm in Figure-1, except in the case of PMVT (PolyMorphic VT). That said — PMVT almost always occurs in older patients with significant underlying heart disease — and, the patient will usually not be hemodynamically stable in such cases!
The other entity to consider in a younger adult with a rhythm such as the one shown in Figure-1 — is CPVT (Catecholaminergic PolyMorphic VT). As discussed in ECG Blog #363 — this rare genetic disorder almost always presents in association with emotional stress or with exercise (ie, CPVT is usually "induced" by catecholamine discharge).
NOTE #1: While CPVT can not be ruled out in today's case — the longterm history of intermittent, short-duration palpitations in a young adult who presents following alcohol consumption with the exceedingly rapid, irregularly irregular rhythm shown in Figure-1 — is much more likely to be the result of very rapid AFib in a patient with WPW.
NOTE #2: Surprisingly, it is not uncommon for patients in AFib with WPW to be hemodynamically stable — despite having exceedingly rapid ventricular rates. Many of these patients with WPW are younger adults who tolerate rapid ventricular rates.

Today's CASE Continues:

Because the patient was hemodynamically stable in association with the rhythm in Figure-1 — a trial of antiarrhythmic medication was contemplated. Among the drugs used for treatment of presumed very rapid AFib with WPW — are IV Procainamide, Amiodarone, and Ibutilide. Discussion of the pros and cons of these various agents extends beyond the scope of this ECG Blog.

While medical trial of an antiarrhythmic agent can at times be undertaken (assuming the clinician remains at the bedside throughout the process) — synchronized cardioversion is often favored for treatment of AFib with WPW, given the exceedingly rapid ventricular response with this arrhythmia.
The treatment approach in today's case was changed by the overseeing clinician to administer prompt synchronized cardioversion. The resultant rhythm after cardioversion is shown in Figure-2. — What do YOU see?

Figure-2: The repeat ECG in today's case — obtained following synchronized cardioversion. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the Post-Cardioversion Tracing:

Synchronized cardioversion was successful — with restoration of normal sinus P waves in lead II of Figure-2.

QUESTION:

Did YOU see the delta waves in Figure-2? If not — LOOK at Figure-3.

Figure-3: Delta waves in the post-conversion tracing are subtle! (RED arrows). A KEY clue to the diagnosis of WPW lies within the RED rectangle in lead V1.

A Closer Look at Figure-3:

The delta waves in the post-conversion tracing are subtle!

It would be extremely easy to overlook the diagnosis of WPW from ECG #2 — because we do not see evidence of WPW in any of the limb leads.
A KEY clue that the patient in today's case may have WPW — is forthcoming from realization that the R wave in lead V1 is abnormally tall (See the QRS within the RED rectangle in lead V1 of Figure-3). Normally, the QRS complex is predominantly negative in right-sided lead V1 — because the predominant vector of ventricular depolarization is normally directed away from this right-sided lead, and toward the left-sided leads V5,V6 (See ECG Blog #81 and Blog #153 — for the LIST of diagnostic entities to consider with a Tall R Wave in Lead V1).
Recognizing the Tall R Wave in Lead V1 — should prompt you to look that much closer at the initial part of the QRS complex in all 12 leads on this post-conversion tracing. Doing so reveals subtle-but-unmistakable slurring (ie, delta waves) in the initial part of the QRS complex in leads V2, V3 and V4 (RED arrows in Figure-3).
To Emphasize: You will not always see delta waves in all 12 leads of a given ECG. This is because conduction over the AP (Accessory Pathway) may only be partial (ie, with a smaller or larger percentage of impulses instead traveling over the normal AV nodal pathway). Given no more than minimal QRS prolongation in the post-conversion tracing — there is only partial preexcitation at this time.
P.S. (Beyond-the-Core): IF you look really close at the very beginning of the QRS complex in leads V5,V6 of Figure-3 (best seen on ipad if you "stretch" the screen to magnify) — and, also look in limb leads II,III,aVF — I believe there is a little positive "rounded nubbin" deflection (less than 1 little box long) that occurs just before the negative deflection (q wave) in these leads. I fully acknowledge that I am only seeing this in retrospect — but I believe this very small rounded "nubbin" that occurs just before the q wave in these 5 leads represents a very small delta wave.

Case CONCLUSION:

Today's patient was referred to EP Cardiology. A left-sided lateral wall AP was found on EP study — and successfully ablated.

Presumably the alcohol consumed at the previous evening party, is what precipitated the episode of AFib — which becaue of the AP, was able to conduct with an exceedingly rapid ventricular response.

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Beyond-the-Core: Can You Localize the AP?

Although localization of the AP in a patient with WPW is not essential for the non-EP-cardiologist (ie, It is more than enough to recognize and refer a patient with WPW-related arrhythmias) — I find it interesting and gratifying to identify the probable location of the AP.

For the EP cardiologist — localization of the AP before EP study is more than academic, as it facilitates and expedites localization of the AP during EP study. In addition — knowing the AP location helps in planning the EP study procedure, as well as in patient discussion — since risks of catheter ablation and likely success rates are based in part on localization of the AP.
Over the years — I've studied many algorithms that have been proposed for predicting AP location on the basis of EP findings. I have synthesized what I find the BEST from these programs in my ECG Blog #76.
KEY Point: ECG localization of the AP is optimally accurate when there is complete preexcitation. Accuracy will be less when there is only partial preexcitation (as occurs in the post-conversion tracing in Figure-3 in today's case) — because delta wave features are reduced. That said — my algorithm nevertheless did well for predicting AP localization in today's case.

Applying My Algorithm (from my ECG Blog #76):

The 1st Step in my algorithm — is to determine where Transition occurs in the chest leads (ie, Between which 2 leads does the R wave become more positive than the S wave is deep). Since the R wave in lead V1 of ECG #2 (in Figure-3) is predominantly positive — this tells us that: i) The AP is LEFT-sided; — and, ii) We should begin with Step A-1 from my ECG Blog #76.
Step A-1 — is to measure the sum of delta wave polarities in the 3 inferior leads. As per my "P.S." above — I believe that the tiny rounded "nubbin" that occurs just before the q wave in each of the inferior leads in Figure-3, is the delta wave in these leads. Since this nubbin is positive — the sum of inferior lead polarities in Step A-1 = +3 — which suggests that there is likely to be an AnteroLateral LV Free Wall AP.

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NOTE: In the Addendum below — I've reproduced in Figures-4, -5, -6 and -7 (from my ECG-2014-ePub) — those Sections that review the basics for ECG diagnosis of WPW — and — assessment of the common arrhythmias expected with WPW.

CLICK HERE — to download a PDF of the content in these 4 figures.

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Acknowledgment: My appreciation to Magnus Nossen (from Fredrikstad, Norway) for the case and this tracing.

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Related ECG Blog Posts to Today’s Case:

ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
ECG Blog #185 — Review of the Ps, Qs, 3R Approach for systematic rhythm interpretation.

NOTE: The following blogs and reference materials provide more info on WPW:

Predicting AP Location with WPW from the ECG — See ECG Blog #76.
ECG Blog #153 — Reviews the ECG Diagnosis of WPW (as well as implications when WPW is found in an asymptomatic patient).
ECG Blog #284 — Reviews a case similar to today's Very Fast AFib.
ECG Blog #18 — Reviews another case of Very Fast AFib.
ECG Blog #37 — Lead misplacement and Very Fast AFib.
ECG Blog #81 — Reviews a case of subtle WPW (presenting as a Tall R in Lead V1).
ECG Blog #87 — Reviews a case of WPW with intermittent AP conduction.
ECG Blog #121 — Reviews a case of subtle WPW (with illustration of the Concertina Effect).
ECG Blog #157 — Can you diagnose ischemia and/or infarction when there is WPW?
For the case I presented in the March 11, 2020 post in Dr. Smith's ECG Blog — which illustrates similar ECG findings as seen in today's case (ie, very fast AFib + WPW).
See My Comment in the June 1, 2020 post in Dr. Smith's ECG Blog — in which I discuss the various types of VT (ie, monomorphic, polymorphic, pleomorphic, bidirectional).

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ADDENDUM (3/29/2023):

I've reproduced in Figures-4, -5, -6 and -7 (from my ECG-2014-ePub) — those Sections that review the basics for ECG diagnosis of WPW — and — assessment of the common arrhythmias expected with WPW.