Chest pain, left bundle branch block, and excessively discordant ST-segment elevation

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 stroke.

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:

  • RR: 18
  • HR: 60
  • NIBP: 140/72
  • SpO2: 98% on room air

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


Sinus rhythm and left bundle branch block. There is discordant ST-segment elevation in the anterior leads but is it excessively discordant? Could this be LAD occlusion?

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



The “old” ECG shows far less ST-segment elevation in the anterior leads.

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

An additional 12-lead ECG is obtained.


There is slightly less ST-segment elevation in leads V3 and V4 but this is still abnormal when compared to the old ECG.

serial ecgs

Generally speaking, secondary ST/T wave abnormalities (as opposed to the primary ST/T wave changes associated with ischemia) should not improve with oxygen and nitroglycerin.

Dynamic ST/T-wave changes usually (but not always) suggest the dynamic myocardial oxygen 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?

Smith’s modification to Sgarbossa’s criteria indicates that ST-segment elevation in left bundle branch block, measured at the J-point, should be no more than 0.25 the depth of the S-wave.

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

smith modification to sgarbossa criteria

The patient was ultimately sent to the cardiac cath lab where angiography revealed 100% occlusion of the LAD.

Further Reading

New left bundle branch block (LBBB) and dyspnea at Dr. Smith’s ECG Blog

Identifying Acute STEMI in the Presence of Paced Rhythm at JEMS

Making Sense of Sgarbossa’s Criteria – Chest Pain and Left Bundle Branch Block at ECG Medical Training


Meyers H, Limkakeng A, Jaffa E et al. Validation of the modified Sgarbossa criteria for acute coronary occlusion in the setting of left bundle branch block: A retrospective case-control study. American Heart Journal. 2015;170(6):1255-1264. doi:10.1016/j.ahj.2015.09.005.

Cai Q, Mehta N, Sgarbossa E et al. The left bundle-branch block puzzle in the 2013 ST-elevation myocardial infarction guideline: From falsely declaring emergency to denying reperfusion in a high-risk population. Are the Sgarbossa Criteria ready for prime time?. American Heart Journal. 2013;166(3):409-413. doi:10.1016/j.ahj.2013.03.032.

Smith S, Dodd K, Henry T, Dvorak D, Pearce L. Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule (PDF). Annals of Emergency Medicine. 2012;60(6):766-776. doi:10.1016/j.annemergmed.2012.07.119.

Updated: 03/31/2016


  • Christopher says:

    Comparing the two I see that P-mitrale is now present, so LAE (look at the data, the P axis also shifted). Change in the shape/size of the ST segment in the inferior leads, and flattening in the high lateral leads of the ST segment. Morphological changes in II, aVF, aVR, and V5 perhaps explainable through lead placement.Following Sgarbossa's 3 criteria:1. >=1mm STE concordant? No.2. >=1mm STD V1-V3? No.3. >=5mm STE discordant? Yes.The STE in V2-V4 appears to have increased over time and appears to be greater than would be expected for the S-waves.The criteria support calling the MI in the face of LBBB. Patient presentation also supports this.Differentials I'm considering include cholecystitis, liver problems, chest/rib pain, and atypical presentation of an AMI.

  • Christopher says:

    Typo: *looking at the data, the P axis also shifted.Also, it looks like there is new notching present, which I seem to recall having some significance.

  • Tom B says:

    Great reply, Christopher! Speaking of how much ST-elevation is appropriate for the size of the S-wave, what is our cut-off?Remember, the least specific of Sgarbossa's criteria is discordant ST-elevation = or > 5 mm! I'll give you the answer (since it's changed recently).According to recent data out of Hennepin County Medical Center (with credit to Dr. Stephen Smith of Dr. Smith's ECG Blog) the cut-off is 0.2 (or 20%) the depth of the S-wave! So would this ECG qualify based on the modified criteria?Tom

  • Christopher says:

    Using a lil image wizardry it appears the ST segment is >=5mm STE and >20% the size of the preceding S-wave.The image below shows two areas (green 20% of the preceding S-wave).LBBB 20% of S-wave

  • Tom B says:

    Well done, Christopher! I'll add the update and my own graphic now. After all, the case has been up for at least 10 minutes! LOL! :)Tom

  • Terry says:

    Thanks Tom this Sgarbossa criteria has been a real eye opener for me. Can't tell you how many times I have said or been told you can't dx an MI with a BBB or all new LBBB is an MI until proven otherwise. Keep up the good work.

  • Tom B says:

    Terry -I completely understand! That's an important myth to "bust"! It's unfortunate that we indoctrinate paramedics this way, but the reality is that it's misunderstood by many ED physicians.One of the ways the "myth" got started is the fact that AMI used to be diagnosed with Q-waves on the 12-lead ECG, and LBBB can obscure Q-waves.Now that we're in the reperfusion era, it's ST-elevation that is important, and of course LBBB also causes ST-elevation whether acute STEMI is present or not, so it does change the "rules" and it makes the dx more challenging (but as you've seen, certainly not impossible).The final complication is that previous studies that led to the creation of "new LBBB" as a criterion for reperfusion therapy were based on a rise and fall of cardiac biomarkers, not an acute occlusive thrombus in an epicardial coronary artery confirmed by angiography! In other words, the studies combined STEMI and NSTEMI. That's why the work done in Minneapolis is so important. You may recall that almost half of LBBB had no culprit artery in the Larson study! That's one of the reasons I pay attention when they come up with a modified criterion that works! Tom

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