Wednesday, August 15, 2018

A Middle-Aged Man with Blunt Trauma and Hemopericardium

A Middle-Aged man had a single vehicle motor vehicle collision with significant energy.

He was hypotensive upon arrival.

A bedside ultrasound was done immediately.  Here are 3 clips.

There is pericardial fluid with echogenic material, diagnostic of hemopericardium with thrombus.

An ECG was recorded:
What do you think?

Sinus tachycardia.  There are Q-waves in II, III, aVF, and V3-V6.  There is ST elevation in the same leads.  The T-waves are inverted in V4-V6, and are beginning to invert in II, III, aVF.    This is diagnostic of subacute MI.

What do you conclude?

This explains everything.  There was subacute MI with myocardial rupture and hemopericardium that resulted in the patient becoming hypotensive and losing control of the vehicle.

The initial troponin returned at 74 ng/mL.  This is very high and cannot occur acutely.   In other words, this cannot be due to trauma.   The ECG cannot occur with trauma either (Q-waves, ST Elevation, T-wave inversion).  This confirms your diagnosis of non-traumatic myocardial rupture.

The patient was taken to the operating room where he could not be saved.  

You might think that death is inevitable from myocardial rupture, but it is not!

In 1994, from our institution (Hennepin), Plummer et al. published this case series: 

Emergency department two-dimensional echocardiography in the diagnosis of nontraumatic cardiac rupture.  23(6):1333-1342; June 1994.

In it, Dr. Plummer describes 6 cases of an apparent acute STEMI who presented with chest pain (3), SOB and weakness, and one with profound hypotension.   Rather than immediately receiving reperfusion therapy (which, at the time, was tPA), all underwent bedside ultrasound which uncovered hemopericardium.  One presented very hypotensive, 4 with Systolic BP 80-90, and one with SBP of 140.  All ECGs showed subacute MI.  All went to the operating room emergently.  2 survived neurologically intact.

Non-traumatic Myocardial Rupture

Differential of peri-infarct pericardial fluid
The differential includes 1) pericarditis with effusion or 2) hemopericardium.
1) Pericarditis with effusion
   a) If 3 weeks after MI, then Dressler's syndrome (Dressler's syndrome is also known as post-myocardial infarction syndrome, post-cardiac injury syndrome and postpericardiotomy syndrome--see this case), which is a late post-MI autoimmune pericarditis occurring about 3-4 weeks after the MI.  Dressler's syndrome appears to be quite rare, according to Shahar and Lichstein.  
   b) Nonspecific pericarditis
2) Hemopericardium would be due to myocardial rupture, which could be due to:
   a) Rupture of a coronary artery due to PCI or
   b) Free wall Myocardial rupture (see below, next paragraph). 

Also, not all rupture is of the free wall:

Large Transmural STEMI with Myocardial "Rupture" of Ventricular Septum

Myocardial rupture is not uncommon. It is found on 1% to 3.5% of autopsies of patients who died of MI. It is associated with transmural MI; since most STEMI are aborted with reperfusion therapy, it is not as common as it once was. It is more common in women, and in patients who have a first MI and have a good EF, as it requires a pump force from the healthy myocardium to produce high pressure which ruptures the infarcted myocardium. The "rupture" is not an explosion, rather a small tract through the myocardium which leaks blood into the pericardium, and kills by tamponade.
Myocardial rupture is usually preceded by postinfarction regional pericarditis (PIRP). PIRP is indicated on the ECG by 2 findings: 1) persistenly positive (upright) T-waves at 48 hours, or 2) premature reversal of inverted T-waves to positive deflection by 48 to 72 hours after STEMI. In contrast to re-occlusion of the infarct-related artery, this reversal should be gradual. There should be QS-waves indicative of completed transmural MI.
Patients who present with chest pain or cardiac arrest and have an ECG diagnostic of STEMI could have myocardial rupture. Obviously, administration of heparin and/or lytics is hazardous. These patients may survive. In a report of 6 cases at our institution (Hennepin County Medical Center), 2 survived with cardiac surgery. 5 of 6 presented with chest pain and an ECG indicating reperfusion therapy, but were detected by bedside ultrasound.

For more information, and several cases, see chapter 28 of Smith's "The ECG in Acute MI," starting on page 273, at this link.

For more cases related to myocardial rupture, go to this link.

Saturday, August 11, 2018

"Are these hyperacute T-waves?" - what is your recommendation for the team in these two cases?

Written by Pendell Meyers, edits by Steve Smith

When practitioners are learning a new ECG concept for the first time, they very appropriately must go through a stage where they titrate their mind to the new finding, going through stages of over and under-recognizing. In my experience this is a normal phenomenon in all of medicine, and especially in ECG interpretation.

As I have recently been promoting recognition of hyperacute T waves among my group, I am getting more and more ECGs texted to me very appropriately asking "are these T-waves hyperacute?"

So let's go over some hyperacute T-waves "ground rules":

 - There is no formal, universal definition of what constitutes a hyperacute T-wave. They could likely be defined as an elevation in the ratio of area under the ST-segment and T-wave compared to the area/size of the QRS complex. Although prior groups have described hyperacute T-waves simply as "tall and symmetric"(1), Smith et al showed that among patients with ischemic symptoms and at least 1mm STE in V2-V4, the absolute T-wave amplitude did not differ between patients with subtle LAD OMI and those with normal variant STE ("early repol"). When the T-waves in both groups were measured as a ratio of their preceding R-wave, those with subtle LAD OMI had proportionally larger T-waves than those with normal variant STE (T/R ratio = 0.7 for BER vs. 3.1 for LAD OMI) (2).

 - However, in my experience this is not enough. There is also morphology to consider. Hyperacute T-waves are fatter than normal T-waves and usually more symmetric (these characteristics increase the area under the STT as well).

 - Hyperacute T-waves are sometimes so impressive that they are diagnostic no matter the situation. Other times, you can only diagnose hyperacute T-waves by comparing the current questionable T-waves with a prior ECG.

 - Because hyperacute T-waves are part of the OMI Progression, they localize to the affected distribution and have focal reciprocal findings as well.

- Like other OMI findings, they are usually maximal in the area of worst ischemia, and diminish radially outward in all directions from the OMI epicenter.

- What appear to be hyperacute T-waves may be reciprocal to reperfusion T-waves in an opposite distribution. If so, the pain will be resolving or resolved (e.g. posterior reperfusion T-waves, T-wave in aVL after reperfusion in III, T-wave in III after reperfusion in aVL).

Here are two such cases I received recently. What would you tell the team?

Case 1: "45 y/o pt with chest pain. No prior EKG. Is V3 hyperacute?"

What do you think?

My response: "I do not think there is ECG evidence of occlusion. I would get serial ECGs to make sure there is no evolution or dynamic changes. Tell me more."

Why don't I think V3 is hyperacute?

Let's pretend for a second that we only have lead V3 to look at. The T-wave in V3 is indeed large compared to its QRS. I do not think it has the "wide" or "fat" appearance that most hyperacute T-waves have. Nor does it look like hyperK. There is no terminal QRS distortion or pathologic Q-waves. Considered alone, I would not be able to tell you whether this represents a hyperacute T-wave or not. In the right context of surrounding leads and features, it could be.

Now let's zoom out and consider it in context, because the context is what tells me that this T-wave is not hyperacute.

If V3 is indeed showing evidence of OMI, then its next-door neighbors should usually (but not always) help to corroborate this claim. As you get better at ECG's, you really can't help but personify them in your mind. Dr. Smith always says that "ECGs are like faces, you just have to recognize them."

Consider this analogy: You get a report from a single house that there might be an earthquake happening in that area. You call the house next door and they are acting normally, and they have no idea what you're talking about. The story is not corroborated by the next-door neighbor. Something doesn't fit.

V2 has small voltage and a relatively large T-wave, which again could theoretically be hyperacute out of context.

V4, however, is the model of what all V4's strive to be: tall, dark, and handsome R-wave, followed by an ST segment perfectly at baseline, with a perfectly proportional T-wave following. V4 disagrees with the idea of V3 being hyperacute. The next door neighbor has no idea what you're talking about.

There are no pathologic Q-waves, no terminal QRS distortion, no reciprocal changes, and no concerning ST morphology findings on the ECG.

Out of curiosity I ran it through the formula:

The closer the score is to the derived cutpoint of 18.2 (e.g. greater than 17.7 or less than 18.7) the more likely it is to represent a false negative or false positive.
So this is just barely positive!

I just did not think this was OMI based on ECG. So I told the team this, but reminded them that the ECG is not the only data point in the decision to perform emergent cath. The patient apparently did not look ill, limited US during pain was apparently unremarkable, and there was no hemodynamic or electrical instability.

They got several serial ECGs, all of which were unchanged. At some point the chest pain resolved.

Three troponins were negative.

Finally, a CT coronary angiogram (CTCA) was performed which showed normal coronaries.

The patient was appropriately discharged with chest pain of unknown cause.

Case 2: "40 year old man presenting with crushing chest pain described as 'like my other heart attacks', also missed dialysis. Is V3 hyperacute?"

What do you think?

My response: "I do not think there are hyperacute T-waves. I see no evidence of occlusion, but remember the ECG is not the only reason to activate. Would get serial ECGs and observe for evolution, assuming nothing else is concerning. Possible mild hyperK changes, would need baseline."

They immediately texted me back, saying "Does his troponin T of 1.21 change your interpretation?"

Generally, this troponin alone in the context of crushing chest pain is indeed an indication for the cath lab, no matter what the ECG shows.

My response: "Not about the ECG. But it should factor into the case as a whole. Where's the baseline? What's the story?"

Why do I think V3 isn't hyperacute?

Considered in isolation, V3 does have a large, tall T-wave which is big for its QRS complex. Like the last case, it is not fat or broad. By itself, it would be concerning but not diagnostic for a hyperacute T-wave.

So look next door: V2 has very high voltage followed by expected small STE and positive T-wave which is actually very small for such a large QRS complex. If V3 represented a hyperacute T-wave, V2 should at least hint that its T-wave is at least marginally concerning. But instead V2 is perfectly normal for its QRS.

V2 does not corroborate V3. Neither does V4.

Additionally, I think this represents a common mistake which happens most often in the transition lead. The "transition lead" is the precordial lead in which the QRS transitions from mostly negative QRS components to mostly positive. In this case, V2 is predominantly negative, and V4 is predominantly positive. Therefore V3 is the transition lead, and is almost isoelectric. Both V2 and V4 have considerable voltage.

You may ask "so where does all this voltage go between V2 and V4?", "why does V3 have such a small QRS then?" The way I answer this is to say that the voltage in V3 is "folded up" inside the QRS complex. This is sometimes the case in the transition lead, as the QRS is often isoelectric and has multiple conflicting component vectors. Most often, the transition lead simply has the same overall QRS voltage but with equal R and S components. Sometimes, however, the transition lead produces what appears to be a small QRS complex between two large high voltage QRS complexes. I think of this as the voltage being "folded up" into the transition lead QRS complex. This helps me understand why the T-wave appears so large in this lead. 

However, I am unable to find any literature that supports or denies this assertion.

You may also ask about the negative T-wave in aVL, wondering if this is a clue to inferior OMI. No, because the inferior leads do not show evidence of OMI, and the QRS in aVL is also negative, so it is not unexpected to have a negative T-wave at baseline. 

Here is the baseline ECG:

There are some differences, including lower voltage. The differences do not make the current ECG more concerning in my opinion.

Here is the repeat ECG:

I think there is no significant change.

Another repeat with no significant change:

I looked back in the patient's chart and found out that he had multiple similar visits, each time with missed dialysis followed by crushing chest pain and highly elevated troponins, always with similar ECGs. The first time, the cath lab was activated and the patient had normal coronaries, with absolutely no CAD. Each time, his troponin T elevated higher than 1.0 ng/mL with rise and fall diagnostic of MI, but obviously not of Occlusion MI. This is type 2 MI likely due to a variety of factors.

Warning: This is a bizarre case. It is highly unusual for a conventional troponin T level to be this high during an episode of crushing chest pain without ACS. 15% of patients with renal dysfunction have an elevated baseline troponin, but usually no more than 5x upper reference limit, sometimes up to 15x, but rarely higher (3). Conventional Troponin T of 1.0 ng/mL or greater is much more common in the setting of Occlusion MI than in Non-Occlusion MI. Without the history of the previous identical visits with completely negative cath recently, it would be completely appropriate to activate the cath lab based on crushing chest pain and such a highly elevated troponin, even in the absence of ECG findings.

The team found this information, and given no change in serial ECGs with this history, they admitted the patient for emergent dialysis. After dialysis, his symptoms resolved. The troponin rose and fell, peaked at 1.64 ng/mL. His baseline trop is unknown. No cath was performed.

Warning: I am not saying that a hyperacute T-wave must always have corroborating evidence in both neighboring leads. I am simply saying that checking both adjacent leads is a helpful step in determining whether findings in one lead are indicative of OMI when there are no other concerning or corroborating features. Here are some cases you might use to tell me I'm wrong because the hyperacute T-waves seem to have some surrounding leads which might not appear concerning to everyone:

30 yo woman with chest pain and a "normal ECG" by the computer, this one prehospital

In both cases, however, there are other concerning features even if one of the neighboring leads to the hyperacute T-waves is relatively normal.

Learning Points:

Only experience and time will make you better at distinguishing hyperacute T-waves from normal variants. See these many examples for comparison:

10 Cases of Anterior Hyperacute T-waves in V2-V3

10 Cases of Anterior/Lateral Hyperacute T-waves in V4-V6

10 Cases of Inferior Hyperacute T-waves

Missed hyperacute T-waves followed by death

Hyperacute T-waves that never manifested STE despite serial ECGs with total anterior wall infarction

30 year old with hyperacute T-waves diagnosed prehospital

Missed hyperacute T-waves followed by cardiac arrest during discharge

Hyperacute T-waves called "normal" by computer

Another prehospital hyperacute T-wave case

Hyperacute T-waves have no formal definition, and sometimes require comparison with prior ECGs and repeat ECGs.

Interrogate the neighboring leads to see if they corroborate a questionable finding.

The skill to detect subtle Occlusion MI must be developed simultaneously with the ability to weed out the mimics. We are trying to deliver immediate reperfusion to those with OMI and prevent unnecessary harm to those without.


1) Nikus K, Pahlm O, Wagner G, et al. Electrocardiographic classification of acute coronary syndromes: a review by a committee of the International Society for Holter and Non-Invasive Electrocardiology. J Electrocardiol 2010;43:91-103.

2) Smith et al. Electrocardiographic differentiation of early repolarization from subtle anterior ST-segment elevation myocardial infarction. Annals of Emergency Medicine 2012.

3) Vasudevan et al. Renal function and scaled troponin in patients presenting to the Emergency Department with symptoms of myocardial infarction. Am J Nephrol 2017;45:304-309.

K. Wang's comments:

Good cases and discussions of tall T waves in the precordial leads. Tall T waves in the precordial leads should make one think of three conditions, namely, hyperkalemia, hyperacute ischemia and normal variant. Typical examples of these three are illustrated in the "Atlas of Electrocardiography by K. Wang", page 171.
As can be clearly appreciated, they look different. The first two are symmetric while the normal variant is not (upstroke takes more time than the downstroke). In hyperacute ischemia. the upstroke is a straight line ,and, so is the downstroke, while they are "tented' in hyperkalemia. Of course, I have picked typical examples here. Unfortunately not all cases are typical and some fall in the borderline, making us agonize. But that's life! Still, one has to know what typical cases look like to start the discussion.

The beauty of Dr. Smith's ECG blog is that it is based on his years of clinical experience backed up by coronary angiography and patient outcome.

K. Wang.

Thursday, August 9, 2018

A 58 year old with Weakness and more than 4 mm ST Elevation in V3

This case was sent by Lou B, a paramedic and RN.

He writes:

"We were dispatched to a 58 yo male who had been out in the sun for 2-3 hours as a mailman. He stated he almost passed out, and bystanders called 911. They gave him water with salt, as he thought he was dehydrated."

"When we arrived, he was alert, sweating, and felt weak. Ambulated to ambulance for eval. 
Denied headache, chest pain, nausea / vomiting. No history, meds, or risk factors. Vitals were obtained, and placed on cardiac monitor, including a 12 lead EKG."

Here it is: 
The computer reads ***STEMI***
What do you think?

More from the medic:

"LifePak 15 interpretation was STEMI. Pattern looked to be BER. Transmitted to hospital with PCI."

"ER doc stated possible BER.  On arrival, cardiologist reviewed and activated the Cath lab for an exploratory cath."
"The cath was negative. Enzymes were and remained negative. Patient left AMA after cath."

"Is there an "upper age" limit to where we shouldn't suspect BER?"

My response:

"I think it is very worrisome for STEMI."

It meets STEMI criteria even for a male under age 40, with STE 2.84 mm in V2 and 4.08 mm in V3.  There is STE also in I and aVL, with reciprocal STD in lead III, so it appears to be a proximal LAD occlusion.

However, one must always entertain that it is normal variant ST Elevation, especially when there are no symptoms of MI, as in this case.

Here are the features which must be present if you would interpret normal variant STE in V2-V4 (also known as early repolarization).  I recommend only using the LAD occlusion vs. early repol formula when they are fulfilled: 

The iPhone app "subtleSTEMI" takes you through them

There is no lead with more than 5 mm STE at the J-point (see on the side that V3 has 4.08 mm)
There is upward concavity in all of V2-V6
There are no Q-waves
There is minimal inferior ST depression (less than 1 mm of summed inferior STD)
There is no ischemic T-wave inversion
There is no precordial ST depression
There is no terminal QRS distortion: Best Explanation of Terminal QRS Distortion in Diagnosis of Electrocardiographically Subtle LAD Occlusion

Since there is less than 1 mm of summed inferior ST depression, this ECG meets these criteria, so it could be early repol.

Comment: I hesitate to use this formula to deny cath lab activation to those whom you think have a STEMI.  I advocate it mostly to make you reconsider a diagnosis of benign ST elevation when the value is high.  If this patient had chest pain and the value suggested early repol, I would be very hesitant to act on it.

4-variable formula

Validation of 4-variable formula (it is now established as superior to the 3-variable formula):

Explanation of 4-variable formula: 

12 Cases of Use of 3- and 4-variable formulas to differentiate normal STE from subtle LAD occlusion

Computerized QTc was 375 ms
STE60V3 = 6.5 (!)
QRSV2 = 16
RAV4 = 14

Value = 20.24 
(The cutoff of 18.2 is best, and this is far above that cutoff, supporting acute LAD occlusion)

The cath lab was activated.

--The coronaries were clean (this is not the gold standard, however, as some patients with ischemic ST elevation may have clean coronaries).
--Troponins were negative (this is very strong evidence against ischemic ST elevation, but not the best)
--All subsequent ECGs before the angiogram were identical
--Unfortunately, we do not have the ECGs from after the angiogram [this is the gold standard -- if there is no evolution of the ECG, then the ST elevation is baseline.  Ischemic ST elevation will always evolve (resolution of STE +/- development of T-wave inversion, +/- development of Q-waves)].

Dominance: Right
LM: A 5 mm vessel which bifurcates into the LAD and LCx coronary artery. The LM coronary artery is free of disease 
LAD: A type 3 LAD, which gives rise to usual septal perforators and diagonal branches. The LAD and its major branches are free of disease
LCX: A non-dominant vessel that is moderate caliber in size, which gives rise to several OM branches and continues to complete its course in the AV grove as a small vessel. The LCx and its major branches are free of disease
RCA: A dominant vessel witch gives rise to the PDA and PLA. The RCA and its major branches are free of disease

Note that the angiographer does not just say that there is no obstructive coronary disease.  He/she says that the vessels are free of disease.  This makes the possibility of acute MI even more remote.

There was no post cath ECG, which if unchanged would absolutely confirm that this is his baseline ECG.  However, given that all vessels are "free of disease," it is almost certain that this is the patient's baseline ECG, and it is a scary one.

Learning point:

Some patients have scary baseline ECGs.  Thus, the 4-variable formula does have false positives.  Even if you suspect early repol, you may need to activate the cath lab, or at least do an emergent formal bubble contrast echo.  You might find a previous identical ECG, and that is also helpful.

Here is another similar case of scary early repol for whom I did not activate the cath lab.  

How did I avoid it?

Anterior ST elevation with large broad T-wave: what is the diagnosis?

K. Wang's comments:

A good case. 
It's important and useful to note that
1) Over 90% of healthy young men have up to 3mm ST elevation  in one or more precordial leads normally (Atlas of Electrocardiography by K. Wang, 
    (pages 222-224).
2) There are three causes of tall T waves; hyperkalemia, hyperacute ischemia and normal variant (Atlas of Electrocardiography by K. Wang, page 171). 
    The first two are symmetric, the last one, the normal variant, is asymmetric in that the upstroke takes more time than the downstroke.
This case turned out to have both.
K. Wang.

Comment by KEN GRAUER, MD (8/9/2018):
Our thanks to Lou B for this insightful case. The “MORAL” of this story reminds me of the valuable lesson I was long ago taught regarding the diagnosis of acute RLQ pain: If acute appendicitis is found 90-95% of the time that you call for surgical consultation — then you are not calling the surgeon often enough (ie, you are missing too many cases of acute appendicitis). The same is true regarding the ECG in Figure-1 — the correct answer (as emphasized by Dr. Smith— is that in view of the worrisome findings on this tracing, you have to rule out acute STEMI until you prove otherwise.
  • I don’t feel bad at all that the cath turned out to be totally normal (ie, free of disease!). Instead, I find it both humbling and highly informative to know that despite the worrisome appearance of this 12-lead tracing — it is all the result of a repolarization variant.
Dr. Smith has expertly detailed the abnormal findings in this case, including a 4-variable formula value = 20.24 (above the 18.2 cutoff). I’ll add the following points from a qualitative perspective regarding my interpretation.
  • Leads V2 and V3 are the first findings that “caught my eye”. Both leads show more-than-the-usual amount of J-point ST elevation — and — T waves that look to be disproportionately tall compared to respective QRS complexes in these 2 leads. Repolarization variants canclearly produce the same picture — but the onus is on us to prove that this appearance is the result of a repolarization variant, rather than the other way around.
  • My “Go-To” Lead whenever I contemplate acute LAD occlusion is lead aVL. Lack of ST elevation in aVL makes me question the diagnosis of acute LAD occlusion. But there is clear ST elevation in lead aVL in Figure-1.
  • Mid- or more distal LAD occlusions do not always produce reciprocal ST-T wave depression in the inferior leads. But proximal LAD occlusions almost always do! So once I’ve detected some ST elevation in lead aVL — I simultaneously look next at all 3 inferior leads (II,III,aVF), to see if there are reciprocal ST-T wave changes. Reciprocal changes are not uniformly seen in lead II — and even when seen, they tend to be more modest than in leads III and aVF. But I especially look for that magic mirror-image” picture of reciprocal change between leads III and aVL — which IF present, to me means acute STEMI until proven otherwise.
  • To clarify what I mean by “mirror-image” reciprocal change — I’ve outlined in BLUE in the Bottom of Figure-1 the mirror-image picture of leads III and aVL. Note that the mirror-image of the ST-T wave in lead III looks virtually identical to the upright image of the ST-T wave in lead aVL — and vice versa.
  • NOTE: The T waves in lead III and/or lead aVF may sometimes normally be inverted — especially when the axis is leftward, and the QRS complex in these leads is predominantly negative. But it is rare in my experience to normally see the mirror-image reciprocal picture (with some ST depression) that we see here in lead III of Figure-1. The shape of the ST-T wave in lead aVF also looks atypical for a normal variant.
What Else Can WLearn from this Case? Knowing that the cath in this case was entirely normal — it is worthwhile going back to the initial ECG in Figure-1. Factors against acute STEMI include: ithe fact that there is at least some ST elevation in so many leads on this tracing! (ie, leads I, II, aVL, and V1-thru-V6). Acute STEMI is more likely to localize; iithere is healthy R wave progression and the QTc looks relatively short (these are 2 qualitative features that are incorporated into Dr. Smiths 3- and 4-variable formulas, which I find to be helpful in reducing the likelihood of acute STEMI); and iiithis 58yo man was not having chest pain. That said, the ECG abnormalities that we do see on this tracing clearly justify ruling out acute occlusion.
  • SUGGESTION: Given that we now know the ECG in Figure-1 is the “normal” ECG pattern for this patient — it may be helpful to give him a miniature photocopy of his ECG to carry on his person in the event he ever again presents to an ED because of acute symptoms. Ready availability of his “baseline tracing” may avoid another future cath ...
Figure-1: Initial ECG on the 58yo man in this case at the time EMS arrived (TOP tracing). Bottom — For illustrative purposes, I have inserted the “mirror image” of leads III and aVL outlined in BLUE (See text).

Tuesday, August 7, 2018

12 Year Old Asthmatic with Intermittent Dyspnea Unresponsive to Albuterol---What is it, and Why Now?

This case was written by one of our great Hennepin 2nd year residents, Aaron Robinson, with lots of comments and edits by Smith.

Thanks to Dr. Smith and Dr. Travis Olives for being part of this case. 

A 12 year old girl with a history of mild intermittent asthma presented to the emergency department with worsening shortness of breath over the past couple of days. She is up to date on her vaccinations and has no PMHx besides asthma and a noncontributory family history. She does not identify any specific triggers for her asthma. Initial screen in triage revealed normal vitals signs and a normal temperature. Upon interviewing the patient and her mother, they state that the patient has been having worsening shortness of breath in the past week, but her neb treatments (which typically eliminate her issues) haven't been working. The child appeared anxious, but overall nontoxic during her initial emergency department evaluation. Her mother had given her two albuterol neb treatments prior to arrival, without improvement. 

What was puzzling to the emergency physicians was the history and physical. On first glance, things seemed consistent with worsening asthma, but there was something that didn't fit. The child didn't have any wheezing on exam, but but this was not so unusual in that asthma frequently lacks wheezing. What was more unusual for asthma was that there was also no history of cough, (which is almost universally present in asthma).  

It was further digging in the history that piqued the emergency physicians' interest: the abrupt onset of the shortness of breath, with no apparent trigger, as well as the lack of even minimal improvement with albuterol. When questioned further, the patient said "I feel like I need to keep taking a deep breath and I get really nervous, then it goes away." These episodes have increased in frequency over the past few weeks. This unusual history prompted the emergency physician to broaden the differential and consider other pathology.

So, an ECG was ordered and is pictured below.
What do you see?

There is a short PR interval at 101 ms, even for a 12 year old.  Normal PR for a 12 year old ranges from 106 ms to 176 ms.  Here it is 101 ms.  

Furthermore, the computer reads a QRS duration of 117 ms, which is long even for an adult, but far too long for a 12 year old (normal = 87 ms).

In this case, the computer did interpret "ventricular pre-excitation/WPW [Delta Waves]"

But it might not always do so.

This is a textbook example of Wolff-Parkinson-White (Type B, see below). 
The PR interval is short (101 ms) and there are obvious delta waves, most notable in leads I, II, V1, V5, and V6. This is a pre-excitation syndrome, which predisposes the patient to runs of SVT (AVRT). The black arrows indicate the delta waves in the annotated ECG below.

With this finding, the ED physicians were immediately concerned that this patient wasn't having worsening asthma but was in fact having runs of symptomatic SVT. The patient was placed on the cardiac monitor. CXR was within normal limits, and bedside cardiac ultrasound did not reveal any grossly noticeable abnormalities. Initial troponin was negative, and chemistry was remarkable for hypokalemia (K=2.8), which places the patient at increased risk of dysrhythmia (how does it do so?  see below). Magnesium was normal. Potassium chloride supplementation was given PO. 

The hospital caring for her did not have advanced pediatric cardiac care and there was concern given the patient being increasingly symptomatic. The decision was made to transfer her to the nearby university hospital that had advanced pediatric cardiology for definitive care. She was transferred in stable condition. She never had any runs of SVT during her ED stay.

Follow up:

Follow up on the patient's transfer to a pediatric hospital with cardiac specialists:

The patient had a repeat chest XR and a formal echocardiogram the day of transfer, both of which were negative. No sign's of Ebstein's anomaly on echo. Why did they look for this? See below for an explanation. She was discharged with 24-hour Holter monitoring. She had multiple runs of SVT as well as multiple triplets and quadruplets of PACs that correlated with her symptoms. They took her to EP lab, where they performed a small ablation. Post-ablation, no further runs of SVT were seen and she no longer met criteria on ECG for WPW. No further AVRT could be induced in EP lab. The hypokalemia, as described above, was likely secondary to her albuterol use as we suspected. She is doing very well. 

Why did they look for Ebstein's anomaly?
Ebstein's Anomaly: Basically, it's a critical congenital heart defect that causes "atrialization" of the right ventricle. The atrioventricular valve is displaced inferiorly and the RV size is very small. The valve leaflets are abnormal, and describes as "plastered" to the RV. About half of patients also have an ASD or PFO. 

Why does this matter in our patient? About half of patients with Ebstein's also show evidence of WPW on ECG. Cardiac physicians were screening for this in this case. Remember cardiac anatomy: a thick, fibrous ring known as the anuli fibrosi cordis electrically insulates the atria from the ventricles. In MOST patients, the AV node is the limiting factor with its refractory period, and why atrial fibrillation usually can't degenerate into ventricular fibrillation. This is, of course, barring the fact that no accessory pathways exist, unlike our patient. Because of the severely displaced right-sided AV valve, the anuli fibrosi cordis is at risk of being disrupted, and why ~50% of patients with Ebstein's have WPW. 

Learning Point

In this case, the ECG is not at all difficult.  The computer even accurately diagnosed it.  

The learning point is that even children's symptoms may sometimes be explained by the ECG.  I (Smith) always obtain and ECG on children with chest pain that does not have a clear explanation, as they may have myocarditis and even myocardial infarction (from coronary dissection, previous Kawasaki's disease (which may be unknown), coronary anomalies).  And I even get just one troponin in these cases.  

Any child (just like adults) with episodes of palpitations, lightheadedness, syncope, or pre-syncope could have any of WPW, HOCM, long QT, Brugada, or Arrhythmogenic RV dysplasia.  Any child with unexplained dyspnea could have MI, myocarditis, congenital heart disease, RV hypertrophy from pulmonary hypertension, and more.  The ECG is simple, cheap, and non-invasive.  Nevertheless, in one major study of syncope in children in the ED, 58% did not get an ECG recorded!

Just this week, the New England Journal of Medicine [379(6):524-534; Aug 9, 2018] published an article which found that 42 of 11,168 asymptomatic adolescents screened for athletic activity had a variety of disorders that are associated with sudden death (36 detected by ECG, for 0.32%, or 1 in 300), including 5 HOCM, 2 Arrhythmogenic RV dysplasia, 1 dilated cardiomyopathy, 3 long QT, 2 with coronary anomaly, 3 with dangerous bicuspid aortic valve, and 26 with WPW (1 in 400).

If asymptomatic children have this many significant abnormalities, then children with unexplained symptoms would have many more, though this number is not known (as far as I can tell).

The only danger to recording an ECG is misinterpretation.  Especially not recognizing normal variants as normal.  

Wolff-Parkinson-White Syndrome

The Wolff-Parkinson-White Syndrome is a pre-excitation syndrome that is manifested by dysrhythmias due to an accessory pathway between the atria and the ventricles (i.e. The Bundle of Kent, or atrioventricular bypass pathway). It is more grossly typed as an Atrio-Ventricular Reentrant Tachycardia, or AVRT. It's classically defined by the appearance of the "delta wave" on EKG, which is the slurred upstroke of the QRS and the presence of a short PR interval. Because the accessory pathway goes through abnormal tissue, the conduction is not fast like the AV node/Purkinje network. When the SA node fires, the slowed conduction through the accessory pathway initially is responsible for the delta wave. Generally, the AV pathway predominates overall, and the patient is without issue. However, when a reentrant circuit is formed between the AV node and accessory pathway, a patient can enter SVT and be stable or symptomatic/unstable. Conduction occurs in orthodromic (most cases) or antidromic (~5% of WPW) conduction. 

Orthodromic (latin "correct") conduction is conduction anterograde the AV node (the normal way) and retrograde up the accessory pathway. This causes the QRS to be narrow because the initial depolarization is as it usually is.

Much less commonly, antidromic reentry is exactly the opposite: anterograde conduction through the accessory pathway and retrograde up the AV node. This abnormal conduction causes the QRS to be wide and can be difficult to distinguish from ventricular tachycardia. Thankfully, it is less common. 

Depending on the location of the accessory pathway, the sinus EKG manifestations of WPW will vary. 

Type A Wolff-Parkinson-White. An example is below:
Photo from LITFL: Wolff-Parkinson-White Type AType A Wolff-Parkinson-White has a dominant R wave in V1, indicating a left-sided accessory pathway.
How can you tell?The large upright R-wave in V1 is analogous to a right bundle branch block.
The initial depolarization is on the left (left sided pathway, just like in RBBB when the left bundle is the only working fascicle, the depolarization is from left to right)

Type B Wolff-Parkinson-White. Another example from the fantastic LITFL example is below:
Type B Wolff-Parkinson-White has a "negative delta wave" in V1 and a predominant S wave, indicating a right-sided accessory pathwayThe patient in this case appears to have a Type B WPW.

In this case, it has an LBBB-type morphology, with monophasic R-waves in I, V5 and V6.
This is because the right sided pathway leads to right to left activation, as you get in LBBB.

Notice also that in both types, there are ST-T abnormalities that could mimic ischemia.  These are "secondary" ST-T abnormalities, secondary to an abnormal QRS.  Whenever you see abnormal ST-T, you should ascertain whether the QRS is the source (secondary) or whether the QRS is relatively normal (ST-T are "primary", due to pathology such as ischemia.

How did hypokalemia affect this case? 
This patient has had an accessory pathway for some time.  It did not just suddenly appear.  So why did she start having symptoms?  Most likely, it was due to hypokalemia.  Hypokalemia can trigger premature atrial beats (PAB).  The initiation of a re-entrant rhythm, whether in AVNRT or AVRT (atrio-ventricular reciprocating tachycardia, in WPW), is through a PAB.  Normally, in sinus rhythm, the beat is conducted down BOTH the AV node and the accessory pathway.  The 2 together create a fusion beat, the delta wave the result of conduction down the accessory pathway, and the remaining narrow complex beat the result of conduction down the Purkinje fibers.  If there is a PAB which occurs when one of these pathways is refractory, then it will be blocked in that pathway and proceed down the other.  Then it will be able to travel back UP the pathway that was initially blocked as that one will no longer be refractory.  Then it can make an endless loop.  PABs do not require hypokalemia but can happen for many reasons.  Beta blockers are fairly good at suppressing PABs and therefore may be used to prevent initiation of SVT.

"Concealed WPW"
Interestingly, the delta wave may not always be seen! If the accessory pathway is far enough from the SA node, the depolarization from the SA node may not reach the accessory pathway by the time the AV node depolarizes. This results in no delta wave! However, you can "uncover" the accessory pathway by slowing the rate down in these patients. Another way that WPW can be concealed is in the very rare (~15% of all WPW patients) retrograde-only conduction, in which the accessory pathway ONLY allows retrograde conduction, which obviously wouldn't show a delta wave on sinus EKG but still predisposes the patient to re-entry tachycardias. 

For more on concealed conduction:

Treatment in the acute setting is largely focused on SVT and electrolyte optimization. Vagal maneuvers and/or chemical conversion can be attempted in stable patients (adenosine, CCB, etc) in SVT. Unstable patients should get DC cardioversion immediately. If the patient has antidromic conduction, extreme caution must be taken as to not mistake this for ventricular tachycardia (it's VT until proven otherwise). In the most recent ACLS update, the AHA states that one may "Consider adenosine ONLY if the patient is in a stable, wide complex, REGULAR, MONOMORPHIC tachycardia." This is because adenosine will break antidromic WPW (or SVT with aberrancy), but obviously will NOT correct ventricular tachycardia. Adenosine should NEVER be tried in a patient with a WIDE complex IRREGULAR rhythm. This may be the feared atrial fibrillation with WPW, a rhythm that, if AV nodal blockade occurred, the fibrillation waves from the atria will be directed solely down the accessory pathway, and the patient will very likely decompensate into ventricular fibrillation. 

Definitive treatment of WPW can be through radio-frequency ablation of the accessory pathway in the electrophysiology lab or medical management. More can be found below.

Life in the Fast Lane does an outstanding job reviewing WPW and can be found here, including examples of WPW Type A and Type B EKGs.

Comment by KEN GRAUER, MD (8/7/2018):
Our thanks to Drs Robinson, Olives and Smith for this thought-provoking case. As per Dr. Smith — one of the KEY points is that certain symptoms in children may be explained by an ECG. Clinicians have been fascinated by WPW for years. Many aspects of diagnosis and management remain controversial. In the interest of academic pursuit — I’ll add the following comments.
  • As noted — the diagnosis of WPW in this case is not difficult. There is obvious PR interval shortening — and, prominent delta waves are seen in virtually every lead on this tracing. But the diagnosis of WPW is often much more subtle. Delta waves are not always seen in as many leads as we do here. Some patients (especially older adults) develop some initial slurring of the QRS complex in a number of leads without there being any AP (Accessory Pathway). And, most importantly — is appreciation that in patients with WPW, conduction may be entirely down the AP — entirely down the normal AV nodal pathway — or  any relative percentage amount between these 2 possibilities. For example, if the relative amount of preexcitation is minimal (say 80-90% of impulses travel down the normal AV nodal pathway) — then delta waves may be difficult to recognize, and the QRS complex may not be overly wide (See ECG Blog #121).
  • Conduction properties of the AP may vary for a variety of reasons. These include decreased ability to conduct in one or both directions over the AP as the patient ages — certain medications — autonomic stimuli, among others. This changing propensity to conduct over the AP is a major reason why risk of a potentially life-threatening WPW-related tachyarrhythmia is clearly less in adults over 35-40 with WPW who had not had previous symptomatic arrhythmias. As a result — older adults who have remained asymptomatic from their WPW over the balance of their lives do not necessarily need referral to a cardiologist. In contrast, given recent advancements in technology and the continually enhanced diagnostic and therapeutic prowess of experienced EP cardiologists — infants and children, and probably also teenage and young adult competitive athletes merit referral for full assessment in 2018, even when the patient is asymptomatic. NOTE: For more on assessment and management considerations in patients with asymptomatic WPW (including risk stratification) — Click HERE: ECG Blog #153.
Clinical Relevance of PInterval Shortening:
The reason the PR interval is short with WPW — is that the AV node is bypassed.
  • With normal conduction in sinus rhythm — the electrical impulse slows down as it passes through the AV node on its way to the ventricles. As a result — most of the PR interval normally consists of the time it takes for the impulse to traverse the AV node. The electrical impulse arrives at the ventricles sooner with WPW — because the relative delay that occurs when passing through the AV node is avoided by conduction over the AP.
  • This is the reason the QRS complex with WPW will usually be wide when the rhythm is AFib or AFlutter — because in both of these arrhythmias, the impulse does not have to travel through the normal AV nodal pathway. Instead, entry into the ventricles can be accomplished much faster traveling anterograde over the AP. Absence of passage through the AV node with AFib and AFlutter also enables much faster ventricular rates to be achieved (depending on the refractory period of the AP — and not dependent on the refractory period of the AV node).
  • In contrast, ~95% of AVRT is orthodromic — because the path to the ventricles passes over the normal AV nodal pathway. As a result — the QRS complex will usually be narrow in AVRT.
How to Recognize WPW in Patients with AFIB:
As alluded to above — the principal WPW-related Arrhythmias are: iA regular reentry SVT AVRT (AtrioVentricular Reciprocating Tachycardia)iiAFiband iiiAFlutter. While some WPW patients may be extremely symptomatic with episodes of AVRT — it is especially AFib (and not AVRT) that is most likely to be potentially life-threatening.
  • Adenosine is potentially problematic if given to a patient with WPW who is in AFib — but, Adenosine IS useful to treat WPW patients with AVRT. The “good news” — is that you’ll often be able to recognize that a patient with AFib has WPW. This facilitates knowing when to avoid Adenosine (and when to also avoid Verapamil/Diltiazem).
For example — How would you interpret the arrhythmia shown in Figure-1?
Figure-1: How would you interpret this arrhythmia? (See text).
ANSWER: The rhythm is irregularly irregular. No P waves are seen. The QRS complex is wide. Therefore, even without seeing a complete 12-lead ECG — the above findings are virtually diagnostic of AFib.
  • How fast is the rate of this AFib?
ANSWER: In places — the rate of the AFib seen in Figure-1 is between 250-300/minute (ie, the R-R interval in places is barely more than 1 large box in duration — which corresponds to a ventricular rate ~300/minute). The only way AFib results in a ventricular response this fast — is if impulses are bypassing the longer refractory period of the AV node — which means that there must be an AP!
  • Recognition of the ECG features in Figure-1 are virtually diagnostic of AFib + WPW. These features are: iexceedingly rapid AFib (over 220/minute in parts of the tracing); iiQRS widening (due to anterograde conduction over the AP); and, iiimarked variability in the R-R intervals over this rhythm strip.
  • For more on the basics of WPW-related arrhythmias — Click HERE: Section 12.
  • Excellent teaching points made by this case include the likelihood that the cause of this 12-year old girl's shortness of breath was not asthma. And, while transfer to a facility with expertise in pediatric cardiology is the intervention of choice — it should be emphasized that we’ve not yet proved a sustained arrhythmia (AVRT, AFib, AFlutter) is the cause of this patient’s symptoms. Holter studies have demonstrated that not only sustained tachyarrhythmias — but also brady rhythms and isolated PACs and PVCs may also be the cause of palpitations. Comprehensive risk assessment by EP cardiology is needed to determine if AP ablation is or is not the recommended management for this patient at this time.
Beyond-the-Core: A number of ways for classifying WPW types have been proposed. A step beyond division into Types A & B — is to use morphology of delta waves in multiple leads on the ECG to predict the probable location of the AP. Having studied numerous proposed algorithms for predicting localization of the AP — I synthesized those I found most helpful into a user-friendly method that is surprisingly accurate (though clearly not perfect). My method takes minimal time.
  • I do not try to memorize the Algorithm in my method. Instead — I simply turn to ECG BLOG #76 whenever I want to attempt my prediction.
Take another look at the initial ECG in this case (Figure-2):
Figure-2: Initial ECG on the 13yo girl in this case (See text).
  • Click on the link to ECG Blog #76.
  • The 1st Step in the Algorithm depends on where Transition occurs (ie, where the QRS complex in the chest leads becomes more positive than negative).
  • Transition in Figure-2 occurs between leads V4-to-V5. This means that we begin with STEP B-5 — which immediately tells us we are dealing with a right-sided AP.
  • We now need to measure the delta wave frontal plane axis — which we do by looking at delta wave polarity in leads I and aVF. Note that the delta wave in both leads I and aVF is positive — which means that the delta wave frontal plane is positive. According to the Algorithm — this predicts the AP will be localized to the Anterolateral RV Free Wall.
  • NOTE: I labeled this last set of comments as “Beyond-the-Core” — because precise localization of the AP is not critical information for providers who are not the EP cardiologist caring for the patient. But: i) It’s fun to be able to quickly and with surprisingly good accuracy predict localization of the AP; and, iiI think it helpful to appreciate how the EP cardiologist knowing the likely location of the AP prior to performing EP study can facilitate more rapid isolation of the AP during EP study. 

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