Sunday, April 23, 2017

A 16 year old girl with altered mental status and possible overdose

A 16 year old girl presented with altered mental status, probably due to alcohol intoxication, but also with possible overdose.

As part of her workup, she had an ECG:
The computer interpreted this as Left Bundle Branch Block
The overreading physician confirmed this read.
2 subsequent identical ECGs were confirmed as left bundle branch block, by different physicians.
What do you think?

This ECG was texted to me in real time by the resident, asking what it was.
My immediate reply: WPW

Notice the very short PR interval and the profound delta waves.  This is clearly NOT left bundle branch block.

Case continued

The patient awoke from her intoxication without complications.  She and her mother denied ever having palpitations, tachycardia, chest pain, or shortness of breath.


Asymptomatic WPW.


The management of asymptomatic WPW is beyond the scope of this blog.  Suffice it to say that there is a very high incidence of serious events in untreated children with this ECG finding.

See this publication: 

The Natural History of Asymptomatic Ventricular Pre-Excitation: A Long-Term Prospective Follow-Up Study of 184 Asymptomatic Children.  Journal of the American College of Cardiology.  Volume 53, Issue 3, 20 January 2009, Pages 275–28.

Such cases should all be referred to cardiology, pediatric cardiology, or an electrophysiologist, avoid exercise until follow up, and call 911 for chest pain, SOB, or palpitations.

Computer interpretations:

The computer is often wrong, but leads to serious diagnostic momentum.  What would the overreading physicians have interpreted had the computer:

1) Given some other diagnosis?  
2) Given no diagnosis at all?  
3) Or if the physicians read the ECG first, then looked at the computer interpretation?

I don't know. How did you interpret it?  Correctly?  Or as LBBB?

I will be presenting an abstract at SAEM on the diagnosis of atrial dysrhythmias by computer and by overread, compared to a new neural network, machine-learning algorithm.  When the standard diagnostic algorithm falsely diagnosed atrial fibrillation, the physician corrected it only half the time.  By the way, the new algorithm performed far better.

Learning Point

1.  Blind yourself to the computer interpretation until you make your own.
2. Only then look at the computer interpretation.
3. Then look back at the ECG if the computer sees something (accurate or not) that you did not.


  1. Great case for illustrating a number of basic concepts that remain all-too-often overlooked. My comments are aimed at enhancing Dr. Smith’s excellent discussion.

    i) The 1st thing to do in assessment of any ECG is to ensure that the patient is stable. Once done, the next thing to do is to spend 2-3 seconds (which should be all that it takes) to look at a long lead II rhythm strip with specific attention directed at determining IF an upright P wave with fixed (and normal) PR interval precedes each QRS complex. Amazingly, this 1st step remains ignored by many (including many “experienced” interpreters). Following this 1st step will immediately reveal if there is or is not a sinus rhythm. Doing so in this tracing would have immediately revealed that although the rhythm is sinus — the PR interval is far too short to be conducting through normal pathways. Given the wide QRS — the diagnosis of WPW becomes obvious.

    ii) In a pediatric (as well as young adult) population (such as in this case) — LBBB is rare, and virtually NEVER occurs without associated underlying heart disease. If one accepted the computerized report diagnosis of LBBB — this should still have immediately prompted inquiry as to WHY an otherwise healthy 16yo should have LBBB? In contrast, WPW is encountered much more often than complete LBBB in an otherwise healthy pediatric population. Awareness of this relative prevalence provides another clue to the diagnosis here.

    iii) Computerized ECG reports CAN be helpful — but only if used correctly. For the expert interpreter (which I define by one who has interpreted MANY THOUSANDS of tracings over MANY years in MANY clinical situations) — one’s speed for accurate interpretation may be significantly increased by using the computerized report (with additional benefit of a neatly typed report compared to the often difficult-to-read handwriting of the busy clinician). Expert interpreters may choose to look at the computer report before they look at the actual ECG. But 99+% of all non-cardiologist clinicians interpreting ECGs in a clinical setting do not meet these “expert interpreter” qualifications. Non-expert interpreters (even if they are “skilled” interpreters) should NEVER look at the Computer report before they complete their unbiased interpretation of the ECG. Doing so only predisposes to the embarrassing error made in this case … AFTER the less-than-expert interpreter has completed his/her unbiased interpretation — then looking at what the computer says may ENHANCE accuracy by sometimes suggesting a conclusion or finding not initially thought of.

    iv) The article by Santinelli et al that Dr. Smith references here is EXCELLENT. I’ll add to the findings of this study, the clinical reality that AGE at discovery of asymptomatic WPW provides very helpful insight as to the relative likelihood that significant arrhythmia might occur in the future. In general, the risk of developing a significant arrhythmia is highest in childhood (as per this case and the article by Santinelli et al) — it is moderate in 20-40 year olds — and it is much less if WPW is only incidentally discovered after 40-50yo. This IS helpful — because it means that incidental discovery of WPW in a 50 or 60 or 70-year old patient who gives no suggestion of prior arrhythmia in their history need NOT be referred to an EP (or other) cardiologist! In contrast — in 2017, it is prudent to refer virtually any child or teenager with even asymptomatic WPW to an EP cardiologist. What to do for the asymptomatic 30-year old who has WPW incidentally discovered could be debated, with perhaps informed consent joint decision-making as an option — but that becomes a more complex decision-making issue. However, the 16-year old in this case should definitely be referred.

    THANKS again to Dr. Smith for posting this case!

  2. Interesting. I probably would have called it a retrograde p with AIVR- except for the rate and the clinical presentation.

  3. I also fell into the LBBB trap. I normally read like you say in the "lessons learned" section of this post, but this time I accidentally saw the interpretation caption before reading the EKG.


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