94 year old female CC: Chest Pain

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

4 Comments

  • Geoff says:

    Thanks again for the great information. It's taken me a couple times to read through, but it is starting to make sense. Just to one thing though, with LBBB or a paced rhythm, you do or don't need the criteria for STEMI in two contiguous leads?

  • Tom B says:

    Geoff – The original criteria is a scoring system. It only required one of the relevant findings in one lead, but if multiple criteria were present, the score would go up, increasing the probability of AMI.You can see the original scoring criteria HERE.You can see that concordant ST-elevation in a single lead is the most specific isolated finding (probability of AMI 88%).Often you will see mutiple criteria met in the same ECG, or one criterion met in two or more contiguous leads, but this need not be the case! In THIS example, you can see concordant ST-depression in leads V3 and V4 (more obvious in lead V3).The original criteria specifies "ST-depression in lead V1, V2 or V3" but you will note that these leads pretty much always show negative QRS complexes in the setting of LBBB.In other words, the ST-deviation is in the same direction as the terminal deflection of the QRS complex, which is bad.So I use a modified form of Sgarbossa's criteria. Basically, any concordant ST-segment (depression or elevation) and any discordant ST-segment greater than 0.25 the QRS complex.Tom

  • john says:

    sinus rhythm with 1st degree AV block, acute anterolateral and inferior wall MI, and Left posterior fascicular block.

  • Paul says:

    John, the ST elevation you are seeing in the anterolateral leads is normal with a ventricular pacemaker. Refer to the Sgarbossa criteria for more information about ST changes indicative of MI in the presence of LBBB/paced rhythms.

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