Wednesday, December 22, 2010

ECG Interpretation Review - #8 (Tachycardia, Acute Changes)

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QUESTION: Interpret the 12-lead ECG and accompanying Lead II rhythm strip.  These were obtained from a patient with new-onset dyspnea, but no chest pain.
  • What do you see in addition to the tachycardia?
Figure 1 (ECG reproduced from ECG-2014-ePub )
Note - Enlarge by clicking on Figures -









         





INTERPRETATION:  Look first at the lead II rhythm strip. There is some baseline artifact and lead wander. The rhythm itself is rapid and irregularly irregular.  The QRS complex is narrow. There are undulations in the baseline - but no definite P waves are seen. This is Atrial Fibrillation with a rapid ventricular response. Regarding intervals - there are no P waves (ergo no PR interval). The QRS is of normal duration; the heart rate is too fast to assess the QT.  The mean QRS axis is normal and close to zero (almost a null QRS vector in lead aVF). There is no definite chamber enlargement (though we might suspect LVH from the relatively deep S waves in leads V1,V2).
  • Q-R-S-T Changes: -  A large Q wave is seen in lead III; there may be a small q wave in lead II.  QS complexes are seen in leads V1 and V2, with a suggestion of smaller q waves in other precordial leads. Transition is slightly delayed and occurs between V4-to-V5.  There is ST elevation in lead III, with hyperacute T waves in this lead and in aVF. Moreover, there is marked ST coving and elevation across the precordial leads (with "frowny" configuration). As suggested in Figure 2 - this is sometimes referred to as "tombstone" ST elevation because of its associated clinical implications (often a large infarct with correspondingly guarded prognosis).
Figure 2 - Toombstone ("Frowny" ) ST Segment Elevation
(Reproduced from ECG-2014-ePub )
CLINICAL IMPRESSION:  In addition to rapid A Fib - We worry about acute extensive anterolateral (if not apical) MI in this patient without chest pain.
  • Up to 1/3 of all infarcts are "silent" MIs (ie, not associated with chest pain). Instead there may be dyspnea, mental status changes, GI symptoms, flu-like illness, or no symptoms at all (Of the non-chest-pain symptoms - acute dyspnea is by far the most common associated with acute MI ). Bottom Line: Always consider obtaining a 12-lead ECG in older patients who present with new-onset dyspnea. 
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Final Point:  Note how QRS morphology changes in several leads (especially in leads III and V3). This could be due to aberrant conduction (which is common in atrial fibrillation when the rate is rapid) - or - it may be the result of movement artifact in this patient with acute shortness of breath.



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6 comments:

  1. Nice post. So while it's apparent this patient needs to be a cardiac facility, I am interested to know if you would treat the A-Fib RVR with Cardizem (pending stable BP & tolerates a fluid bolus), electricity if unstable, or if you're suspecting an AMI to withhold the drugs. I'd want to slow it down to get a better 12-L interpretation as well as take away the heart's increased irritation of beating so fast/irregular (for the sake of increased ischemia if the patient is truly having an MI).

    Your opinion?

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  2. Thanks for your excellent question. As is often the case - there is a "trade-off". Given the very rapid ventricular response of A Fib in this case - it would seem preferable to slow this down - and potential benefit by use of an agent like IV Cardizem (my choice) would seem to far outweigh any potential detriment from using this drug in this circumstance - Ken Grauer, MD (ekgpress@mac.com)

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  3. Why not also inferior STEMI (not only antero-lateral STEMI)?
    Thanks a lot.

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    1. @ Stillicho — Thank you for your comment. You'll note that I included the possibility of "apical" MI in my differential. This term,"apical" is not used as much currently — but it indicates a stemi picture in which there is both inferior and anterior ST elevation. Although we don't see ST elevation in lead II ... the changes we do see in leads III and aVF are clearly consistent with inferior wall involvement. I suspect there may be mid-LAD occlusion of an LAD with "wraparound" accounting for acute inferior lead changes.

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  4. Hello doctor... How lateral wall MI? Can't see any STe in lateral leads..
    From your experience,do you feel there is any chance that after slowing this rhythm, the STT changes can resolve?
    Thanks

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  5. The ST segment is elevated in V5 (which is a lateral lead), and it may be hyperacute in V6. Some call this an "extensive anterior MI" — others call in "anterolateral". Probably doesn't matter. Looks like an LAD culprit. ST-T wave changes may improve once the tachycardia is controlled — but the working diagnosis has to be acute anterior STEMI until proven otherwise.

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