Wednesday, January 7, 2009

If there is high suspicion for ischemia, do serial EKGs and pay attention to them!

Case 1)
This is the initial EKG of a 60 yo male with a couple days of stuttering chest pain. He is pain free at the time of the EKG at 2100.

At 2140, the patient had recurrent pain, and the following EKG was recorded:

If seen alone, this EKG would not look terribly abnormal. But compared to 40 minutes prior, there is ST elevation now where there was none before, and the T-waves are much taller.

This was not appreciated by the treating physician. Even with no change in the EKG, the patient should have at least been admitted for observation. Unfortunately, the patient was discharged and suffered significant loss of the anterior wall.

Case 2)
This is the initial ECG of another 60 yo man with chest pain that is now resolved.

There is left bundle branch block (LBBB) without any ST segment shift that would be suggestive of acute coronary occlusion (of LBBB with STEMI). Such shifts would be 1) concordant (same direction as QRS) ST elevation in inferior or lateral leads 2) concordant ST depression in leads V1-V3 (where the QRS is negative, ST depression would be concordant and this would be posterior STEMI) or 3) excessive ST elevation in leads with a negative QRS; excessive is greater than or equal to 20% of the preceding S-wave. This EKG has some T-waves that are suspicious for NSTEMI: in the presence of an upright QRS, these are positive T-waves in II and V6 and also biphasically positive (terminal portion upright) in I and aVL. T-waves, like the ST segment, should be opposite the QRS in LBBB without ischemia.

The patient was admitted to the CCU and had recurrent chest pain. The following ECG was recorded:
Now there is definite ST elevation, concordant with the QRS, in lead V5. There is also excessively discordant ST elevation in lead V2 (=25% the depth of the preceding S-wave). More importantly, these are all changes from the initial ECG. The patient's cardiologist did not see this change and the anterior wall was lost.

4 comments:

  1. Case 1:

    I think on the second ECG there is subtle STD in the inferior leads, especially compared to the first ECG, and a very small STE in aVL and maybe lead I.

    Case 2:

    1. What if we have an ECG with LBBB (and the patient has symptoms that are suspicious of ischaemic origin), and only see that there are no ST and T changes. For example in left leads (I, aVL, V5-6) where we expect STD and T inv., there are isoelectric ST and pos. T.
    Or, on the other hand, leads with net QRS<0 we see isoelectric ST's and concordant (negative) T's.

    OR

    2. The ECG when the patient is pain-free shows uncomplicated LBBB (appropriate and proportional ST and T wave changes), but then he/she has angina, and the ECG under tha angina shows isoelectric ST's etc. (as I wrote above).

    "That is the question..."

    Thanks for your answer!

    Márton

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  2. Excellent questions. I call this "relative" ST depression or elevation. Either relative to a previous ECG, if there is one, or relative to what should be the baseline ECG, if one does not have one. Such isoelectric ST segments in LBBB should make you very suspicious that it is relative ST elevation or depression, but it is not diagnostic because the specificity is inadequate.

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  3. Thanks, Dr. Smith!:-)

    May I have some more question about the Smith's rule (STE > S wave*0.2, or STD > R rave*0.2)?

    1.

    Can we use it in other conditions with secondary ST deviation (so not only in LBBB)? I mean ventricular rhythm (ventricular escape, VT, ventricular pacing), LVH, nonspecific intraventricular conduction block and WPW pattern.

    2.

    What about incomplete LBBB? As far as I know in incomplete LBBB we expect less ST-T deviation than in complete LBBB, so my intuition says that the 20% rule should be modified.

    3.

    In RBBB there are much less ST-T deviation than in LBBB, and in most cases the deviation is limited to right sided leads (and does not affect the left ones). Can we use the rule (or a modified edition of it) also in this situtation?
    (Yesterday, in the EM department where I work, I saw an ECG with RBBB: there were deep and broad S wave in V6 with 0.1 mV STE, and I didn't know if it is normal. Unfortunately, I can't remember if the patient had any symptoms.)

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  4. The new rule uses 0.25 ratio. See the upper sidebar for article published in annals of EM.
    1. No one is certain. I use it for paced rhythm, PVCs.
    2. I agree, probably lower ratio for incomplete LBBB. not certain
    3. RBBB is different. There should be no discordant ST deviation with one exception: leads V2 and V3 normally have up to 1 mm of discordant ST depression. Lateral leads should not have ST elevation. See RBBB under "labels (index)" on lower sidebar for many cases of RBBB where this is illustrated in depth.

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