A 76 yo male had Chest Pain followed by a cardiac arrest. He was resuscitated in the field, and had hypotension annd electrical storm in the ED.

There is a QRS duration of 120 ms, with a wide R-wave in lateral leads (but also a Q-wave). This is either an incomplete LBBB or a very wide left anterior fascicular block. There is concordant ST depression in precordial leads.
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Posterior leads were applied (V4=V7, V5=V8, V6=V9) for the following ECG:

There is now clearly concordant ST elevation. Whether LBBB or not, ST elevation of 0.5 mm or more in just one lead is enough for the diagnosis of posterior STEMI.

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Electrical storm continued, with 8 defibrillations.

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Unfortunately, there was a storm outside, too. A huge snowstorm, and the cath lab personnel could not get to the ED fast enough.

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Tissue plasminogen activator was given and 30 minutes later the patient stabilized with a BP of 130/70. Echo showed a posterolateral wall motion abnormality. Later cath showed 3-vessel disease but the exact culprit could not be established. The troponin I peaked at 40 ng/ml.

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Unfortunately, in spite of therapeutic hypothermia, the patient died of cerebral anoxia.