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63 Year Old Male: “Dental Pain” — Discussion

2 comments

This is the discussion to "63 year old male: "Dental Pain". You may wish to review the case.

For starters, i think we all agree that the patient, with his signs and symptoms, needs to be transported. We have all had patients like this who don't want to go, even though we know they should. Patients say they don't want to go for different reasons… some want to use us as a "litmus test", gauging their need to go by our reaction. Others don't want to put us through the trouble. Some are afraid of not coming home, and some, just plain don't want to go. We have to do everything possible to convince them to go, and as we know, sometimes that requires quite a bit of persistence!

Now, about that 12 lead:

There is sinus rhythm, with a rate of about 80 and a normal PRI. The QRS is wide (124ms). There is Right Bundle Branch Block, with an rsR' in V1, and s waves in I and V6. 

Do we see any other abnormalities on the 12 lead? RBBB should have T waves appropriately discordant to the terminal portion of the QRS. There should be no ST elevation in the right precordials…  in fact, you might expect a slight bit of ST depression in V1 and V2 opposite the QRS. For the most part though, the ST segments are not deviated as they are in LBBB, which makes it possible to assess ST segments normally. Let's take a look in V1 and V2:

There is a slight amount of ST elevation in V1. This is not normal. V2 has concordant T waves, without ST elevation, which is also concerning.

Is this an anterior STEMI? Not so fast… let's see what the rest of the 12 lead shows:

There is ST elevation in aVR (about 2mm)  and slight ST elevation in V1, with ST depression in leads I,II,III,aVF and V3-V6. This constellation of "global" ST depression with ST elevation in aVR and V1 is typical for subendocardial ischemia. Could it be posterior STEMI? Not likely in this case. The anterior ST depression of posterior STEMI is usually maximal in V2-V4, and that is not the case here. It looks different as well. It helps me to visualize the direction of the ST segments. Think about where the ST depression is: inferior and lateral. What would be reciprocal to inferior and lateral depression? Rightward and superior ST elevation, which is exactly what we see here. This is what it looks like on the hexaxial reference system:

 

We see the direction of ST depression (blue arrows) and the reciprocal ST elevation (red arrows).  You can't have a STEMI in aVR, so you can see this is just opposite the diffuse ST depression. In the precordial leads, the lateral ST depression is opposed by the slight ST elevation in V1. This would not be considered a  STEMI.

This pattern of diffuse subendocardial ischemia could be due to a left main lesion, proximal LAD lesion, or 3 vessel disease. We can not tell from the ECG. People rarely survive long with a left main occlusion, which makes that unlikely (unless there was much collateral circulation). The most common issue is left main ACS, which is not a STEMI equivalent.

In the field, we treat this patient for ACS with our standard meds… For some agencies that carry Clopidogrel, probably not a good med for this patient in case he needs CABG. At the hospital, he won't get thrombolytics because it is not STEMI. Most likely he will be medically managed, with PCI to follow if medical management doesn't work, or his symptoms worsen.

Unfortunately, we don't have an outcome for this patient, but he crew was able to convince him to be transported.

For more information on subendocardial ischemia, read this great post by Dr. Smith.

Posted by on April 20, 2012 • Filed under: ems-topics, patient-management, training-development • Tagged: , , , , , , ,

64 year old female CC: Trouble Breathing – Conclusion

13 comments

Lots of great comments and it was good to see the depth of discussion on the appropriate treatment and transport for this patient!

This is the conclusion to 64 year old female CC: Trouble Breathing.

When we left off our crew was attending to an elderly female patient in respiratory extremis. Pulmonary edema was present and their initial 12-Lead was concerning.

Many readers correctly noted the normal sinus rhythm, a 1° AV Block, and a wide QRS. Other readers pointed out the apparent Left Bundle Branch Block due to a negative QS complex in V1. Only a few readers picked up on the abnormal presentation of the LBBB: lead I has an rS complex and there is right axis deviation! Right axis deviation is a very uncommon finding in LBBB [1].

Just as it is important to know what a normal 12-Lead looks like, we also need to know what our abnormal 12-Leads should normally look like. In the case of LBBB, we expect V1 to be negative and leads I/V6 to have broad, monomorphic R-waves.

We also expect the T-waves to be discordant with the dominant deflection of the QRS. A picture is worth a thousand words in this case:

In our case we have three troubling findings:

  1. An rS complex in Lead I with Right Axis Deviation, which is very uncommon in LBBB.
  2. Concordant ST-segments in leads V5 and V6.
  3. Excessive ST-segement elevation in leads V2 through V4.

Many readers stated that a Left Bundle Branch Block is a STEMI mimic and precludes an activation of a STEMI alert until an old 12-Lead is used in comparison. However, criteria exists to diagnose a STEMI in the face of a LBBB or Paced rhythm.

Additionally, this patient's 12-Lead does not show a normal LBBB, but rather a non-specific intraventricular conduction defect or IVCD. Dr. Garcia would encourage, "considering the company it keeps," [2] which includes acute myocardial infarction!

Sgarbossa's criteria (and its modifications) for diagnosing STEMI in the face of LBBB or a Paced Rhythm has been covered in depth before so we'll only cover the positive criteria found on our 12-Lead:

  1. Is there ST-segment elevation ≥1 mm that is concordant with the QRS complex? Yes.

  2. Is there ST-segment depression ≥1 mm in leads V1, V2, or V3? No.
     
  3. Is there ST-segment elevation ≥5 mm, or ≥20% the depth of the S-wave, that is discordant with the QRS complex? Yes.

With 2 of the 3 criteria met (only 1 is required), we can be very confident that we're looking at a STEMI. Additionally, any concordant ST-elevation present should always suggest a STEMI.

The paramedic in this case recognized the concordant ST-elevation and the abnormal LBBB, called in a STEMI alert, and transported the patient to the PCI capable center. The patient improved significantly on the non-rebreather and CPAP was not necessary. Prior to arrival a second 12-Lead ECG was acquired:

Enroute the patient proved to be difficult for IV access, and received external jugular access in the ED. Labs were drawn while they waited for the cath lab team to arrive.

In the cath lab a 100% occlusion of the LAD was found and corrected with stenting.

For QA purposes an old ECG was retrieved after the call to compare to the field ECG:

Given this prior ECG, the new LBBB alone would likely cause a STEMI activation. However, in the absence of our more definitive changes this is a very weak criteria for activation [3].

Even without the prior ECG, we have an abnormal LBBB (most likely IVCD due to a peri-infarction block) with concordant ST-elevation and a patient presenting with signs of actue left sided heart failure: all of which point to an acute myocardial infarction!

This case highlights the importance of knowing what abnormal should normally look like and understanding that not every patient fits the protocol. We hope you enjoyed this case as much as we did, so be sure to continue the discussion below.

  1. Childers R, et al. Left bundle branch block and right axis deviation: a report of 36 cases. J Electrocardiol, 2000; 33 Suppl:93-102. [PubMed]
  2. The Art of Interpretation Series. http://www.12leadecg.com/
  3. Jain S, et al. Utility of left bundle branch block as a diagnostic criterion for acute myocardial infarction. Am J Cardiol, 2011; 107(8):1111-6. [PubMed]
Posted by on January 24, 2012 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , ,

80 year old male CC: Chest pain – Conclusion

22 comments

This is Part II of the conclusion to 80 year old male CC: Chest pain. For Part I see Excessive discordance as a marker of acute STEMI in LBBB.

First, let's take another look at the initial 12-lead ECG.

The first thing that catches my eye in this ECG is the strange morphology of the ST-segments and T-waves in the inferior leads (and lead aVL).

Could these be reciprocal changes to an acute anterior STEMI?

This ECG easily meets Sgarbossa's criterion of discordant ST-elevation > 5 mm, but is the ST-elevation excessively discordant when taking into account the depth of the S-wave?

Let's apply Dr. Smith's decision rule (that we learned about in the previous post). Do we see "excessive discordance" in this ECG?

Yes!

If this isn't evidence enough there are also significant changes in QRS voltage and ST/T morphology between the first and last 12-lead ECG.

Diagnosis: Acute anterior STEMI in the presence of LBBB.

See also:

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

Discordant ST-segment elevation in LBBB or paced rhythm

62 year old male CC: Chest pain

58 year old female CC: Chest pain

New left bundle branch block is a poor predictor of coronary occlusion (Dr. Smith's ECG Blog)

Posted by on December 29, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , ,

Excessive discordance as a marker of acute STEMI in LBBB

17 comments

This is Part I of the conclusion to 80 year old male CC: Chest pain.

As we have discussed on numerous previous occasions, the expected relationship between the QRS complex and the ST-segment and T-wave in the setting of left bundle branch should be one of discordance.

This is sometimes referred to as the rule of appropriate T-wave discordance.

That means that in the setting of left bundle branch block, negatively deflected QRS complexes can be expected to show ST-elevation and upright T-waves.

Positively deflected QRS complexes can be expected to show ST-depression and inverted T-waves.

That's why left bundle branch block is an anterior STEMI mimic.

It is normal for the ST-segments to be deflected opposite the S-waves in the right precordial leads (V1-V3).

However, there is a limit to how much discordance is appropriate.

Sgarbossa's criteria requires at least 5 mm of discordant ST-elevation in order to be significant.

However, this criterion is problematic because it does not take into account the rule of proportionality.

That's why it's the weakest of Sgarbossa's critiera.

Discordant ST-elevation of 5 mm (as a stand-alone finding) only indicates a 50% probability of AMI according to Sgarbossa's original scoring algorithm.

 

This ECG from a previous case post demonstrates the dilemma.

 

The ST-elevation in leads V1-V3 is well over 5 mm but the S-waves are so deep that they are running off the bottom of the ECG paper.

This patient was not experiencing acute STEMI.

Stephen Smith, M.D. (of Dr. Smith's ECG Blog) uses a modified criterion which considers the ST/QRS ratio.

He has found that when the ST-segment is deviated more than 0.2 the QRS complex it is both a sensitive and specific marker for acute STEMI in the setting of left bundle branch block (and probably also paced rhythm).

(Note: This has since been revised to 0.25 the QRS (download PDF here). However, I still think it terms of allowing 1 mm of ST-elevation for every 5 mm of S-wave depth. When I do this, I round up. In other words, if the S-wave is 18 mm deep, I round up to 20, which means that I would allow up to 4 mm of ST-elevation in that lead.)

Let's examine each of these QRS complexes separately.

We'll start with the positively deflected QRS complex marked 'A'.

As you can see, the R-wave measures 10 mm. The J-point (relative to the PR segment) is depressed 3 mm. Therefore, the ST/QRS ratio is 0.3 (which is higher than 0.2). Hence, this finding would strongly suggest acute STEMI.

Now let's look at the negatively deflected QRS complex marked 'B'.

In this example the S-wave measures 10.5 mm. The J-point (relative to the PR segment) measures 3.5 mm. Therefore, the ST/QRS ratio is 0.33 (which is higher than 0.2). Hence, this finding, would strongly suggest acute STEMI.

In Part II we'll apply Dr. Smith's decision rule to the our recent case study.

See also:

80 year old male CC: Chest pain

80 year old male CC: Chest pain – Conclusion

Discordant ST-segment elevation in LBBB or paced rhythm

62 year old male CC: Chest pain

58 year old female CC: Chest pain

Posted by on December 29, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , , ,

80 year old male CC: Chest pain

23 comments

Here’s a case submitted by a faithful reader who wishes to remain anonymous.

It’s a great case and destined to be one of my favorites!

EMS is called to evaluate a 80 year old male patient with a chief complaint of chest pain.

On arrival the patient is found sitting on his living room couch. He appears acutely ill and anxious.

Onset: 2 hours prior to EMS arrival
Provoke: Pain unrelieved after SL NTG x5
Quality: Severe substernal pressure
Radiate: The pain does not radiate
Severity: 8/10
Time: Several previous episodes but “never this bad”

Skin is cool, pale, and diaphoretic.

Breath sounds: clear

No JVD or peripheral edema noted.

Past medical history: CABG x3, CHF, angina, renal insufficiency, LBBB

Meds: Numerous but unavailable at the time of evaluation

Allergies: Penicillin

Vital signs:

RR: 20
Pulse: 108
BP: 150/80
SpO2: 99 on RA

The cardiac monitor is attached.

A 12-lead ECG is captured.

What is your impression?

*** UPDATE ***

Here are the serial 12-lead ECGs.

See also:

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

Discordant ST-segment elevation in LBBB or paced rhythm

62 year old male CC: Chest pain

58 year old female CC: Chest pain

Posted by on December 28, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , , ,

58 year old female CC: Chest pain – Conclusion

9 comments

Here’s the conclusion to the 58 year old female with chest pain and left bundle branch block.

To refresh your memory here is the 12-lead ECG.

And for those of you who requested lead V4R.

This ECG meets all 3 of Sgarbossa’s criteria to identify acute STEMI in the presence of left bundle branch block.

Keep in mind, it only has to meet one criterion in one lead!

(Please note: One criterion has been modified from its original form. Instead of discordant ST-elevation > 5 mm we are looking for discordant ST-elevation > 0.2 the depth of the S-wave. This is known as the ST/QRS ratio. Credit to Dr. Smith of Dr. Smith’s ECG Blog.)

Angiography revealed 100% occlusion of the LCX and 99% occlusion of the RCA.

Thanks to everyone who commented on the case!

See also:

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II

“New” LBBB – What’s the big deal?

Discordant ST-segment elevation in LBBB or paced rhythm

Sgarbossa’s Criteria – New Graphic

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

Posted by on July 25, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , ,

58 year old female CC: Chest pain

22 comments

Here’s another case study from an international reader who wishes to remain anonymous.

Presenting Complaint – Chest Pain

History of Present Complaint – 58 year old female, nil cardiac history, mild smoker, social drinker and overweight.

Complaining of acute central chest pain @ rest. Awoken by pain.

On Arrival – Sat upright on settee (Editor’s note: One of you Brits will have to interpret that for me!)

On examination:

Alert, orientated and communicable (GCS 15)
Pale, cool dry skin.

Nil SOB, clear bi-lateral air entry – nil adventitious breath sounds
R/R 19, SpO2 99%

H/R 68 and irregular, BP 125/74

Temp 36.8
B.M 7.2 (Editor’s note: B.M. is BGL measured in millimoles. 1 mmol/L of glucose is equivalent to 18 mg/dL. Hence, this patient’s sugar is about 130).

C/O chest pain.

O – Acute. Awoken from sleep.
P – Nothing makes pain better. Not affected by breathing
Q – Non specific compressing type pain
R – Central chest pain radiating left arm
S – Pain score 6/10
T – 30 mins
I – No pain intervention sought.

Slight nausea, nil vomit

The cardiac monitor is attached.

A 12-lead ECG is captured.

How would you treat this patient?

See also:

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II

“New” LBBB – What’s the big deal?

Discordant ST-segment elevation in LBBB or paced rhythm

Sgarbossa’s Criteria – New Graphic

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

Posted by on July 23, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , ,

62 year old male CC: Chest pain

10 comments

62 year old male presents to the emergency department complaining of chest discomfort.

Past medical history is significant for dyslipidemia and ulcerative colitis. Also prior history of significant tobacco use.

Maternal history of CAD. Maternal and paternal history of CVA.

The patient’s only medication is Lipitor but he took an aspinin en route to the hospital.

Onset: Patient states the pain started that morning and became progressively worse since lunch time
Provoke: Nothing makes the pain better or worse
Quality: Sharp and nonpleuritic
Radiate: The pain radiates down the right arm to the bicep
Severity: 7/10
Time: Patient states he experienced a similar pain in his right upper chest several days prior while playing tennis. He stopped exercising and the pain resolved.

The pain makes the patient feel “a little clammy.” He denies shortness of breath. He states that he feels “a little dizzy” but denies palpitations. He had a negative stress test 3-4 years ago.

He has a known history of left bundle branch block.

The patient’s skin is warm and dry.

Breath sounds clear bilaterally. No JVD. Neuro exam normal.

Vital signs:

Resp: 18
Pulse: 60
BP: 140/72
SpO2: 98 on RA

A 12-lead ECG is captured and presented to the ED physician within 5 minutes of arrival.

An “old” ECG is pulled from the computer system for comparison.

What is your impression?

*** UPDATE ***

After oxygen and nitroglycerin the patient reports a significant decrease in pain.

An additional 12-lead ECG is captured.

There is now slightly less ST-elevation in leads V3 and V4.

Remember that a secondary ST-segment abnormality (as opposed to a primary ST-segment abnormality) should not “improve” with oxygen and nitroglycerin!

In other words, if this ST-elevation was caused just by the LBBB, it shouldn’t be “getting better”. Changing ST-segments suggest the dynamic supply vs. demand characteristics of ACS!

Now, let’s go back to the initial 12-lead ECG. Is the ST-elevation in the anterior leads cause for concern?

Go back and read Identifying AMI in the presence of left bundle branch block (or paced rhythm).

Remember, discordant ST-elevation = or > 5 mm is the least specific of Sgarbossa’s criteria! That’s why we use the modified rule that I learned from Dr. Stephen Smith of Dr. Smith’s ECG Blog.

That criterion states that discordant ST-elevation should not be more than 0.2 (or 20%) the depth of the S-wave in the setting of left bundle branch block (ST/QRS ratio).

Using that criterion, how does this ECG measure up? Let’s take a look.

The patient was ultimately cathed and angiography revealed 100% occlusion of the LAD.

Final thought:

Does it get any more difficult that that? If Dr. Smith’s decision rule works this great, shouldn’t we be shouting it from the rooftops?

See also:

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II

Discordant ST-segment elevation in LBBB or paced rhythm

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

58 year old female CC: Chest pain

58 year old female CC: Chest pain – Conclusion (meets all 3 of Sgarbossa’s criteria)

Posted by on May 19, 2010 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , ,

94 year old female CC: Chest Pain

4 comments

Here is an interesting case submitted by Billy Eskridge.

EMS is called to an assisted living facility to evaluate a 94 year old female complaining of chest pain.

History of present illness:

Approximately 1 hour prior to EMS arrival, the patient had complained of a headache. A nurse gave the patient a Lortab. About 15 minutes later the patient started complaining of chest discomfort.

The nurse gave the patient two 0.4 mg NTG tablets over 20 minutes with no relief of the chest pain. The patient requested to be seen by a physician.

Paramedic evaluation:

Patient is slightly confused and lethargic but states that she feels “sick all over.” The nurse states this is unusual for the patient.

Past medical history:

Complex medical history including hypertension, aortic stenosis, and mitral regurgitation

Vital signs:

Resp: 24
Pulse: 68
BP: 184/72
SpO2: 85 on RA

The cardiac monitor is attached.


A 12-lead ECG is captured.


Here are the computer measurements and interpretive statements.

Billy Eskridge asks the following questions:

Since this patient has an internal pacemaker and wide QRS complexes, is it possible to identify the ST/T changes of ischemia or acute injury?

I have also observed that not every beat is paced, and that there are come supraventricular beats which are also wide complex, showing a LBBB.

I know that there are certain tricks for diagnosing acute MI in LBBB, but I’m not familiar with them.

I am also aware that normal ST changes in wide complex rhythms can be used for diagnosis of MI if an old 12 lead is available to compare the current one to, but is this valid for both paced and supraventricular rhythms with a BBB?

If this rhythm was paces every beat without any apparent conduction abnormality can you scan it for AMI?

Discussion:

In the first place, even though the pacing spikes seem to “disappear” occasionally in the rhythm strip, it shows 100% pacing. I suspect that the pacing spikes are simply lining up perfectly with the lines on the graph paper, but regardless, we can rest assured that it’s 100% paced because there is no change whatsoever in the R-R interval or QRS morphology.

In this case, the 12-lead ECG shows a fairly typical looking paced rhythm consistent with a pacing lead in the apex of the right ventricle. Namely, it shows LBBB morphology in lead V1 with a left axis deviation. It also shows negative concordance in the precordial leads, which is a common finding with paced rhythms.

You will note that the ST-segments and T-wave are deflected opposite the main deflection of the QRS complex (which is also the terminal deflection of the QRS complex). This is consistent with a “normal” paced rhythm and the “rule of appropriate T-wave (and ST-segment) discordance” with LBBB or paced rhythm.

Another important finding is that the larger the QRS complex, the more pronounced the secondary ST-T wave abnormality in the opposite direction. This is also true with strain patterns with left ventricular hypertrophy (LVH).

However, there are limits as to the expected amount of discordant ST-segment elevation in the presence of LBBB or paced rhythm.

According to Sgarbossa’s Criteria, discordant ST-elevation (that’s ST-elevation that is opposite the main deflection of the QRS complex — in other words, ST-elevation in a lead with a negative QRS complex) > 5 mm is suggestive of AMI.

The problem is that QRS complexes with extremely deep QRS complexes will show more ST-elevation, and that’s normal for LBBB and paced rhythm. For example, if you have a QRS complex in the right precordial leads with an S-wave that is 50 mm deep, you can have 5 mm of discordant ST-elevation and the ST-elevation is only 10% the depth of the QRS complex, which is fine.

Dr. Smith and colleagues from Hennepin County Medical Center propose a modified rule for discordant ST-elevation where you look for discordant ST-elevation that is 0.20 (or 1/5) the depth of the QRS complex. See: Excessive discordance as a marker of acute STEMI in LBBB.

This 12-lead ECG shows a normal looking paced rhythm with appropriate T-wave discordance and ST-segments that are normal looking within the context of paced rhythms.

See also:

78 year old male CC: Chest pain

78 year old male CC: Chest pain – Discussion

Posted by on December 30, 2009 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , ,

Right bundle branch block – Part II

9 comments

Once you’ve identified a RBBB on the 12 lead ECG, the next thing you want to do is determine whether or not you’re dealing with a normal RBBB or an abnormal RBBB (or new RBBB).

You may remember this graph from my previous post: Who benefits the most from reperfusion therapy?


It shows that patients with “new BBB” receive the most benefit in terms of lives saved per 1000 treated with fibrinolytics (based on the FTT Collaborate Group). We often here it claimed that patients with “new LBBB” receive the highest benefit from prompt reperfusion therapy, but it’s worth pointing out that the FTT Collaborative Group did not distinguish between LBBB and RBBB.

Generally speaking, RBBB does not mimic or obscure the ECG diagnosis of acute STEMI the way LBBB does. However, sometimes it can (remember the update to Funky Trouble-Looking RBBB with AMI).

So how do we know what’s “normal” for right bundle branch block? We use the concept of “appropriate T wave discordance”. This concept usually comes up in the context of discussing LBBB, but it’s also useful for RBBB (and paced rhythms, ventricular rhythms, non-specific IVCD, and so on).

For RBBB, the concept is that when the terminal deflection of the QRS complex is positive, the T wave should be negative. Likewise, when the terminal deflection is negative, the T wave should be positive.

You may recall this graph from my previous post: Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria – Part II.


The blue and red arrows show the expected relationship between the terminal deflection and the T wave with RBBB.

Remember, the terminal deflection is the last deflection in the QRS complex.

Consider the following case.

EMS is contacted for a 77 year old male complaining of chest pain. On arrival, you find the patient lying supine on the couch. He is ashen in color and diaphoretic with absent radial pulses. He responds sluggishly but appropriately and states that he is having severe sub-sternal chest pain.

His shirt is cut off and the combo-pads are applied, revealing the following heart rhythm.


It appears to be sinus rhythm with wide QRS complexes and occasional PVCs.

A 12 lead ECG is captured.


Using the concept of “appropriate T wave discordance” is there anything about this ECG that bothers you?

See also:

Right bundle branch block – Part I

Right bundle branch block – Part II

Right bundle branch block – Part III

Posted by on July 10, 2009 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , ,

“Funky Trouble Looking” RBBB with AMI

1 comment

You might remember from my intro that my inspiration for starting the Prehospital 12 Lead ECG blog was the Capnography for Paramedics blog.

You might also recall from my Superlative Hieroglyphicist Award that author of the Capnography for Paramedics blog Peter Canning keeps an active blog called Street Watch: Notes of a Paramedic.

Of course, you probably didn’t need me to tell you that, because he’s been around the blogosphere a lot longer than I have! :)

Regardless, Peter posted a most interesting case study today called “Funky Troubling Looking” — Right Bundle Branch Block and MI that is similar to the case I posted on 11/29/08.

It also dovetails nicely with my recent posts on Sgarbossa’s Criteria.

While Sgarbossa’s Criteria is generally used to identify AMI in the presence of LBBB or paced rhythm, I also discussed the “rule of appropriate T wave discordance” which can be applied to RBBB if it is well understood.

In other words, if you think in terms of the terminal deflection of the QRS complex, and not the main deflection.

*** UPDATE 12/21/08 ***

Here’s an interesting case sent to me by Thomas Bernesser of Mint Hill Fire and Rescue.

50 year old male with an acute onset of sub-sternal chest pain and dyspnea. He states he was at rest when the sharp, tight feeling began in the center of his chest and radiated to his left side. A 10 on 10 with the pain. He also remarked of left arm pain and tingling. He c/o of associated nausea and diaphoresis along with the pain and dyspnea. He had taken two of his own SL NTGs prior to EMS arrival without any relief. He had a past history of multiple MIs with stent placement, the last being in October of this year.

He’s pale, diaphoretic, clutching his chest, looks very uncomfortable and anxious. His initial BP was 92/50, a little tachy between 100-110 and a respiratory rate at about 18/minute.

And on to the EKGs, I ran numerous serial EKGs and they were all identical – including the ones done in the ED at the receiving facility. Just based on his presentation alone I was convinced that he was having a significant cardiac event, but the EKG was a little less convincing for me. Each one of the interpretations made reference to ST elevation in the inferior leads and diagnosed an Acute MI. While I do note elevated segments, the EKG just strikes me as odd. I’m not seeing the classic ST elevation above baseline coming off the S wave of the complex. I might be missing something but I found it interesting nonetheless and wanted to share it with you.

Just so you know, he was worked up in the ER for an MI and sent to the cath lab. He was cathed and came back clean, no signs of occlusion. So, definitely a false MI identification for the Philips MRx.

There’s no perfect solution for patients with baseline abnormalities on the 12 lead ECG. One interesting point for this case is the absence of a definite TP segment as a baseline for ST segment measurement due to the sinus tachycardia.

Normally, we don’t think of RBBB as distorting the ST segment in a discordant direction (which is why LBBB is so problematic). However, both of these cases demonstrate that RBBB can can be challenging when evaluating a chest pain patient.

One final note. Mr. Bernesser advised me that this ECG also fooled the computer at the hospital, which I’m assuming used the GE-Marquette 12SL interpretive algorithm, so it wasn’t just the Philips monitor that gave the >>>> ACUTE MI <<<< message.

Posted by on December 20, 2008 • Filed under: Uncategorized • Tagged: , , ,

Identifying STEMI in the presence of LBBB – Sgarbossa’s Criteria – Part II

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In Part I, we discussed Sgarbossa’s Criteria for identifying AMI in the presence of LBBB. We also talked about the “rule of appropriate T wave discordance” for bundle branch blocks and other forms of abnormal depolarization (like ventricular rhythms or paced rhythms).

You will recall that I drew a distinction between a QRS complex’s main deflection and its terminal deflection, even though they are one in the same for LBBB. I explained that it’s helpful to think in terms of the terminal deflection, because then you can apply the “rule of appropriate T wave discordance” to RBBB as well as LBBB.

And so you can!

Let’s look at an ECG.

This is from one of my “old” 12 lead ECG classes. In those days, I cropped the computer measurements and interpretive statements because I didn’t want the students to “cheat”. Nowadays, whether it’s EMS or firefighting, I’ve come to believe in reality-based training. In real life, for good or bad, you get an interpretive statement.

But, this ECG is a good example of an important concept.

So let’s look at this ECG. It’s a sinus rhythm. It has a normal axis. We know that for several reasons.

The QRS complex is smallest in lead aVL, so the perpendicular lead on the hexaxial reference system is lead II. Lead I is almost equiphasic so the perpendicular lead is aVF. The value of lead II is 60 degrees and the value of lead aVF is 90 degrees, so the frontal plane axis is somewhere between 60 and 90 degrees.

Or, to do it the “easy” way, lead I and lead aVF are both positively deflected, so we know we’re in the left inferior quadrant.

Or, because leads I, II, and III are all positive, so we know the axis is normal.

It really doesn’t matter what method you use. I use all three for every ECG.

The QRS duration is wide. When supraventricular rhythms are wide, we look at lead V1 to see if it shows RBBB or LBBB morphology. This ECG shows a terminal R wave in lead V1, which is RBBB morphology. Next we check lead I and look for a terminal S wave. We find one!

This is a simple RBBB.

You will notice that in many leads, the T wave is deflected the same direction as the QRS complex (II, III, aVR, aVF, V2, V3, V4, V5, and V6). In other leads, the T wave is deflected opposite the main deflection of the QRS complex (aVL, V1). I did not list lead I because the QRS complex is close to equiphasic.

So, how should these T waves be deflected?

The answer is, they should be deflected opposite the terminal deflection of the QRS complex, and so they are!

Look at the following image.

As you can see, when the terminal deflection of the QRS complex is negative, the T wave is positive. When the terminal deflection is positive, the T wave is negative. In other words, even if the main deflection of the QRS complex is positive, as long as the terminal deflection (or last deflection) is negative, the T wave is positive.

That’s why I’m encouraging you to always think in terms of the terminal deflection, even though for LBBB, the terminal deflection is also the main deflection.

There is method to this madness!

Although not part of Sgarbossa’s Criteria, the “rule of appropriate T wave discordance” can help you pick up on AMI in the setting of RBBB (or bifascicular block) because an inappropriately concordant ST segment and/or T wave can tip you off that something is wrong!

For example, this case from Dr. Smith’s ECG blog.

In the last lesson, we introduced Sgarbossa’s Criteria. Let’s take a look at a graphic that shows exactly what we’re looking for.

The first example shows > 1 mm of concordant ST segment elevation (and a concordant T wave). Both are abnormal for LBBB.

The second example shows > 5 mm of discordant ST segment elevation and a discordant T wave. Discordant ST segment elevation > 5 mm is abnormal for LBBB (with one very important caveat) but a discordant T wave is normal for LBBB!

In the last example, there is concordant ST segment depression in the right precordial leads, which is abnormal for LBBB, but a discordant T wave, which is normal for LBBB.

If you have a patient with signs and symptoms consistent with ACS and the ECG shows LBBB with concordant ST segment elevation, then chances are excellent that you are dealing with a STEMI.

Likewise, if you have a patient with signs and symptoms consistent with ACS and the ECG shows LBBB with concordant ST segment depression, especially in the right precordial leads, then chances are excellent that you are dealing with a STEMI.

The original criteria didn’t take into account the depth of the S wave, and as we know from other STE-mimics like LVH, the deeper the S wave, the higher the ST segment elevation. So a blanket statement that 5 mm of discordant ST segment elevation indicates acute STEMI in the setting of LBBB is not helpful in those situations where the S wave is > 50 mm deep like the example below.

Stephen Smith, M.D. of Dr. Smith’s ECG Blog has suggested that a more sensitive and specific marker is discordant ST-elevation > 0.2 the depth of the S wave (ST/QRS ratio).

See also:

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

“New” LBBB – What’s the big deal?

Sgarbossa’s Criteria – New Graphic

Discordant ST-segment elevation in LBBB or paced rhythm

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)

58 year old female CC: Chest pain

58 year old female CC: Chest pain – Conclusion (meets all 3 of Sgarbossa’s criteria)

Posted by on December 15, 2008 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , , ,

Identifying STEMI in the presence of LBBB – Sgarbossa’s Criteria – Part I

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There has been a lot of discussion lately about identifying AMI in the presence of LBBB (see Dr. Bearemy’s “My Emergency Medicine Blog” here and a recent thread on the EKG Club). I’ve also been receiving a lot of emails offlist, so I think a full discussion is in order.

In my recent post Who benefits the most from reperfusion therapy? I posted a graph that demonstrates how patients with new bundle branch block benefit the most from reperfusion therapy.

*** Important Update ***

Recent evidence suggests that new (meaning previously undetected) LBBB patients do not “rule-in” for AMI at any greater rate than any other group of patients! That’s why it’s so important for health care practitioners to understand Sgarbossa’s criteria! Those are the patients who need immediate reperfusion therapy in the cardiac cath lab!

*** End Update ***

The problem is that in many prehospital 12 lead programs (and regional STEMI systems), patients with LBBB or a QRS duration > 0.12 sec (120 ms) are excluded! In other words, patients with wide QRS are taken to the local community hospital without interventional capability. Or, the cath lab is not activated while EMS is still in the field.

Why would you exclude the very patients who stand to benefit the most from prompt, expertly performed PCI at a cardiac center?

Simple.

It’s too difficult to figure out whether or not the BBB is new! The ECG diagnosis of STEMI can be difficult in the setting of BBB.

In False Positive Cardiac Cath Lab Activations I reviewed Larson, Menssen, Sharkey et all, False-Positive” Cardiac Catheterization Laboratory Activation Among Patients With Suspected ST-Segment Elevation Myocardial Infarction, JAMA 2007;298(23):2754-2760.

I quoted:

Patients with new or presumably new left bundle-branch block had an inordinately high prevalence of false positive catheterization laboratory activation (almost half did not have a culprit artery). Patients with a previous myocardial infarction or previous coronary bypass surgery had a significantly higher prevalence of no culprit artery, likely because of abnormal baseline ECG results.

This is obviously a big problem, and subjecting all patients with LBBB and signs and symptoms of ACS to an emergent cath or the risks associated with thrombolytic therapy is not the answer, as some authors have suggested.

If only there was some kind of algorithm that could help distinguish between patients with LBBB and acute STEMI from patients with LBBB who are not experiencing acute STEMI.

But there is such an algorithm! It’s been around for over 10 years!

The GUSTO investigators Sgarbossa et al., Electrocardiographic Diagnosis of Evolving Acute Myocardial Infarction in the Presence of Left Bundle-Branch Block. N Eng J Med 1996; 334(8):481-487 published an algorithm which has come to be known as “Sgarbossa’s Criteria”.

The criteria seems complicated but it’s really not. Like anything else, it’s a tool. A very important tool for a critical subset of patients.

The original paper contains a flow chart from which the patient receives a score. I’m not going to publish the flow chart, because it’s not something you need to memorize.

Here is the criteria. A patient is presumed to be experiencing an evolving AMI if any of the following are present.

  1. ST segment elevation = or > 1 mm that is concordant with the QRS complex.
  2. ST segment depression = or > 1 mm in leads V1, V2, or V3.
  3. ST segment elevation = or > 5 mm that is discordant with the QRS complex.

It is the last criterion that has caused the most controversy and requires qualification.

However, before we address the third criterion, we have to dispose of a common misunderstanding.

What do we mean by concordant and discordant? The short answer is, concordant means “the same direction” and discordant means “the opposite direction”.

The rule of appropriate T wave discordance

In the presence of abnormal ventricular depolarization (left bundle branch block, right bundle branch block, paced rhythm, ventricular rhythms) the T wave should be deflected opposite the terminal deflection of the QRS complex (appropriate T wave discordance).

What is the terminal deflection?

The terminal deflection is the last deflection, or wave, of a QRS complex.

Please take the time to learn this! It is extremely important!

Take a look at the following image.

You will notice that each of these QRS complexes is labeled according to the waves are present. If the wave is large, it gets a capital letter. If the wave is comparatively small, it gets a lowercase letter.

I could talk about this image for a long time, but for now, I just want you to notice that an Rs complex is positively deflected while an rS complex is negatively deflected, even though both of them contain only an R and an S wave. But the terminal deflection of each is negative, because they both end in an S wave!

Why is this important?

When teaching Sgarbossa’s Criteria, students always get confused as to whether or not the ST segments and T waves should be deflected opposite the main deflection of the QRS complex or opposite the terminal deflection.

Well, guess what?

With LBBB, the terminal deflection is the main deflection!

So why are we splitting hairs?

Because if you learn to think in terms of the terminal deflection, you can use the rule of appropriate T wave discordance for RBBB, too!

Let’s start by looking at a patient with a normal LBBB.

I have no idea why the GE-Marquette 12SL interpretive algorithm is giving the “data quality prohibits interpretation” message for this ECG. There’s a little bit of artifact in the inferior leads, but it’s not that bad!

This is a normal looking LBBB. We know the frontal plane axis is around 0 degrees, because the QRS complex is isoelectric in lead aVF. Therefore, the perpendicular lead in the hexaxial reference system is lead I. Since lead I is positively deflected, we can place the frontal plane axis at 0 degrees. A physiological left axis deviation (0 to -30) is normal for left bundle branch block.

To put it another way, a negative QRS complex in lead III is normal for LBBB, but it should be upright and monomorphic in lead I.

Now, let’s look at the QRS complexes and the T waves.

You will notice that in every lead, the T wave is deflected opposite the QRS complex! This is “appropriate T wave discordance” in the presence of left bundle branch block.

To help illustrate this point, consider the following graphic.

The blue arrow shows the direction of the terminal deflection of the QRS complex (which is also the main deflection in the setting of LBBB). The red arrows shows the direction of the ST segment and the T wave.

This is what we mean by “appropriate T wave (and ST segment) discordance” with LBBB. Note that with RBBB, the T wave should be discordant, but the ST segment should remain isoelectric. This is why RBBB is usually not listed as a STE-mimic.

With LBBB, there is also a discordant shift of the ST segment, which is why it’s one of the most common STE-mimics! ST segment elevation in the right precordial leads (V1-V3) is a normal finding for LBBB!

In Part II, we’ll look at the “rule of appropriate T wave discordance” as it applies to RBBB and talk more about Sgarbossa’s Criteria.

See also:

Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II

80 year old male CC: Chest pain

Excessive discordance as a marker of acute STEMI in LBBB

80 year old male CC: Chest pain – Conclusion

“New” LBBB – What’s the big deal?

Sgarbossa’s Criteria – New Graphic

Discordant ST-segment elevation in LBBB or paced rhythm

Found on the Lifenet Receiving Station (LBBB with concordant ST-depression in leads V3 and V4)

62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)

58 year old female CC: Chest pain

58 year old female CC: Chest pain – Conclusion (meets all 3 of Sgarbossa’s criteria)

Posted by on December 13, 2008 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , , , , , , , , , ,

The Only Constant Is Change

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In this excellent article from the March 2007 Journal of the Emergency Medical Services, Tim Phalen discusses the importance of performing serial 12 lead ECGs.

Here are some of the highlights.

“Acute myocardial infarctions (AMIs) aren’t like broken bones and, therefore, ECGs aren’t static like X-rays. If an EMS crew were treating a hip fracture and could somehow perform the X-ray on scene, what would it show? A broken hip, of course. And if the X-ray wasn’t performed until the patient arrived at the emergency department (ED), would the broken hip still be visible?

Absolutely.

When dealing with a fracture, whether the X-ray is obtained immediately, in 10 minutes or in 10 hours, the interpretation and diagnosis usually won’t change. But what’s true for X-rays isn’t necessarily true for ECGs. In fact, an ECG can significantly change in a very sort period of time — as can the corresponding interpretation.”

“[I]t can be difficult to determine if the presence of LBBB on the ECG of a suspected AMI patient is preexisting or is a new onset. If the LBBB is infarct-induced, it has a high mortality rate — up to 60%. Therefore, the patients who may need reperfusion the most are the least likely to receive it. However, dynamic changes on serial ECGs shed light on the situation. A hallmark of infarct is change over time. If a patient has had an LBBB for the past 15 years, it’s not likely to change much during the next 15 minutes. But when changes occur in a short period of time, suspect AMI.”

Those are some excellent points.

It’s also helpful to understand the expected appearance of baseline abnormalities. For example, the rule of “appropriate T-wave discordance” states that with bundle branch blocks and paced rhythms, the T-wave should be deflected opposite the terminal deflection of the QRS complex. So LBBB is an abnormal finding, but discordant T-waves (and ST-segments) within the context of LBBB are a normal finding (to a point).

On the other hand, while baseline abnormalities like LBBB or paced rhythm may cause a discordant shift of the ST-segment and T-wave, the ST-segment should not be moving! A moving ST-segment suggests dynamic changes in supply v. demand characteristics.

In other words, ischemia.

Posted by on October 27, 2008 • Filed under: ems-topics, patient-management • Tagged: , , , , , , , , , , , , , , , ,