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Anterior Wall M.I. With Second Degree AV Block, Type II, Rhythm Strip

Mon, 12/12/2011 - 15:33 -- Dawn
Anterior Wall M.I.; Second-degree AV Block, Type II, RBBB.  Aberrant conduction

This is a long MCL1, or V1, rhythm strip, in a patient with anterior-septal wall M.I.  It is often seen conducting as a 2:1 block, but when consecutive p waves are conducted, the PR intervals remain constant.  It is interesting that, when a p wave is not conducted, there sometimes occurs an escape beat with a right bundle branch block pattern: rsR' in V1.  The pathologic Q waves are probably significant for necrosis, and Type II blocks are usually fascicular blocks with a tendency to be permanent and progressive.  No 12 Lead ECG is available to enhance this rhythm strip.


Type II AV block?! PR intervals constant! Americans scare me - they are so knowledgeable.

And how "often" is it "seen conducting as a 2:1 block"? Only once, in the bottom strip. It's non-contributory, per se, for the diagnosis.

I've noticed, over the years, the alliterative allure of 2nd degree and 2:1 driving its users to diagnose type II block, almost as a clang association. The slender QRS and the longish PR intervals should have called for a more careful look at how "constant" the latter really are.

And another thing: can any early beats be called escape beats? If not, what is their true nature?


Dave Richley's picture

I suspect that this is type 1 AV block. In the epsiodes of 3:2 and 4:3 block there is a small but definite increase in PR from beat 1 to beat 2. This could still be type 2 block if the first QRS in every sequence is actually a narrow QRS escape, and not a conducted, beat but this would be unusual. The narrow QRS, the grouped beating and what looks like a prolonged PR interval in every beat point more towards type 1 rather than type 2, I think.


Dave R

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