Against all expectations, it appears that these leads are actually called "high lateral leads". To be honest, I've never heard this expression in clinical medicine, but wikipedia says the following:

* The positive electrode for leads I and aVL should be located distally on the left arm and because of which, leads I and aVL are sometimes referred to as the high lateral leads.
* Because the positive electrodes for leads V5 and V6 are on the patient's chest, they are sometimes referred to as the low lateral leads.

So, there's a bit of redundancy in the IT text, I think. lateral and high-lateral??? makes little sense, if you think that lateral leads are I, aVL, v5 and v6, and high lateral leads are I and aVL.

The original text should either read "lateral leads" only, or "in lateral leads, more specifically high lateral leads"...

Or has my brain stopped functioning at this late hour (3 AM)?
Good night!

PS As for poor progression, I'd say 'limited'.

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Note added at 18 hrs (2010-03-12 01:15:50 GMT)
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oh, and re bi/diphasic, 'biphasic' is by far more commonly used, at least in the States.