Thursday, September 1, 2011

What is the rhythm? Answer at the bottom.

An elderly woman presented with abdominal pain.  Here is her ECG:
























This is easily mistaken for atrial flutter because the waves have a fluttering, wavy, sawtooth appearance.  However, 3 things make atrial flutter impossible, 2 are related:
1) the rate of the waves is > 400
2) the QRS does not appear at the same part of the atrial wave cycle each time (which it must do in flutter)
3) the ventricular rate is irregularly irregular.  In atrial flutter, the ventricular rate can be regular if there is a constant ratio (2:1 block, 3:1 block etc).  It can also be regularly irregular, in which every QRS comes at a multiple of the atrial wave rate (if atrial wave rate is 300, it happens every 200 ms, and every R-R interval must be a multiple of 200ms)

2) and 3) are related: since 2) is true, 3) must also be true.

The woman had atrial fibrillation.  It was misdiagnosed as flutter, and this may have contributed to a delayed diagnosis of mesenteric embolism.

6 comments:

  1. Is it surprising that you have such well formed, large p-waves in atrial fibrillation? Doesn't this suggest that she is having organized activity in the atrium and thus organized atrial contractions rather than quivering?

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  2. I think that if it were truly organized, the "p" waves would all be identical and the QRS would occur at the same time on each cycle. So appearances are deceiving.

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  3. Doctor Smith: I had watched the Dr. K Wang's video: ''New K. Wang Video: Atrial Flutter A-Z''. The ECG showed at 16:15 was atrial flutter with variable AV block. However, the QRS did not appear at the same part of the atrial wave cycle. So, is it atrial flutter as Dr. Wang said or it is atrial fibrillation?

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    Replies
    1. Allen,
      Good question! I just looked at it and I am not 100% convinced that it is flutter. Flutter can occasionally have irregular conduction on the wave cycle when there is variable AV conduction. On the other hand, the baseline waves here are not uniform like you would expect from flutter. So it might actually be fibrillation.
      Steve Smith

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  4. Thank you for this interesting case.

    Sir, I hear that coarse fibrillation waves suggest left atrial enlargement. Is it true? Do you know any studies about this?

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    Replies
    1. Interesting question, but I don't know the answer.

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