Wednesday, December 22, 2010

LAD occlusion in the setting of paced rhythm

An 80 yo male presented with chest pain.

There is clearly a ventricular paced rhythm. Normally in a paced rhythm, the QRS is all negative from V1-V6 because the pacing wire is in the apex of the RV and thus all depolarization goes away from the apex.
In the above ECG, the QRS in V2 is positive and all others are negative, as in the patient's previous ECG below. This implies some problem with lead placement. Nevertheless, leads V1, V3, and V4 have excessively discordant ST segments.
Though there is not a lot of data to support it, the ratio used for left bundle branch block seem to be applicable to paced rhythm. An ST/S ratio in V1-V4 > 0.20 is, I believe, quite specific for LAD occlusion. V2, though suspect because of the positive QRS, has a concordant ST segment, which is diagnostic of STEMI.

Previous ECG 2 months prior:

The emergency physician needed to do some persuasion with the interventionalist, but succeeded and the patient was taken for angiography and PCI of a 100% LAD occlusion.

This is the ECG 2 days later:

This is a much more difficult ECG because only complexes 4 and 5 are paced now. The precordial leads have an RBBB morpholoyg, with some minimal persistent ST elevation in v2 and V3 with T-wave inversion, suggestive of reperfusion.

Ischemic symptoms and a paced ECG with excessive discordance in V1-V4, with ST/S ratio > 0.20, is anterior STEMI until proven otherwise.


  1. I have encountered similar situations where subtle EKG findings, especially in setting of BB or paced rhythm, are not often appreciated by cardiologists. It seems we in the EM community are often more up to speed on this than our cardio colleagues.

  2. This ecg also seems to show STE in aVR, but it is difficult to tell on my computer screen.
    Would you agree?
    My understanding is STE in aVR is associated with occlusion of the left main coronary artery and carries a very bad prognosis, so could this have been used, in addition to the criteria you presented, when talking to the cardiologist?

  3. Yes, there is concordant ST elevation in aVR. But this was not a left main issue. Which points out what I have stated before which is that ST elevation in aVR is not specific for left main ACS. In my view, the literature on this is not particularly good: it does not show whether STE in aVR is independently predictive of left main (independent of STE in V1, or widespread ST depression), and there is no good data to show its sensitivity and specificity.

    In general, if STE in aVR is greater than STE in V1, that is a better predictor of Left Main occlusion. Also, if there is STE in aVR and aVL (both), that is also better.

    Amal Mattu states these are both highly specific. I'd like to know which paper(s) he bases this on and read them again. I have yet to see a convincing study that these findings are highly reliable, and, as far as I can tell, I've read them all.

    1. In V1 V2 V3 remember Scarbossa's Criteria for the hidden MI ; /

    2. I'm using the modified Sgarbossa criteria. See my paper on the right-hand side from annals of emergency medicine.