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Left axis deviation

Previous Inferior Wall M.I. and Left Axis Deviaton

Fri, 01/17/2014 - 21:39 -- Dawn

If you are teaching frontal plane axis to your students, you will need to teach them HOW to determine the axis - usually beginning with the QRS axis and then adding the P and T waves.  But, you also need to teach them WHY we measure axis, to provide relevance to something that may seem challenging to beginners.  There are many ECG interpretations that rely heavily or are dependent upon the determination of the axis.  

This ECG is a great example of left axis deviation.  The cause is readily discernible, if your students know the ECG signs of myocardial infarction. This patient had an inferior wall M.I. in the distant past, and now has pathological Q waves in Leads II, III, and aVF.  Pathological Q waves in related leads in a patient with history of M.I. are a sign of necrosis, or permanent damage, in that part of the heart.  The inferior wall has lost an extensive amount of tissue, which is now electrically inactive as well as mechanically inactive.  (You may also find it helpful to show students videos of ventriculograms showing normal LV function and hypokinesis of the LV due to M.I.)  Because of the loss of electrical activity in the inferior wall, the "mean" electrical direction (or axis) is AWAY from the inferior wall.  That is, the electricity travels AWAY from II, III, and aVF and TOWARD I and aVL.

Many of the blogs and webpages listed in our "Favorites" address the subject of axis determination.  Here is one from Cardio Rhythms Online if you would like a review.




jer5150's picture

Jason's Blog: ECG Challenge of the Week for July 8-15. Which lead do both of these ECGs share a “common-thread”?


Two more ECGs classified under the general heading:  “Tracing suggestive of   ____ ”.  I  like ECGs that strongly favor a very specific clinical disorder.

Recently I performed these ECGs on two different patients.  They were both recorded a little more than an hour apart and exemplified a common electrocardiographic theme I noticed during that work shift.

The primary goal of this week’s blog is not to determine the name of each ECG’s rhythm but rather what each ECG is virtually diagnostic of.

This sign is commonly referred to by one of two names:  (1.)  Either by the lead that it appears in or (2.) eponymously named after the doctor who is credited with first describing it.  

jer5150's picture

Jason's Blog: ECG Challenge of the Week for June 10-17. Why did the ventricular rate abruptly decrease?


From June 10, 2012:   As is the case with all practical blogs, I’m encouraging ECG Guru members to engage in active group participation.  Share your thoughts, observations, impressions, findings, and interpretations.  Feel free to compare notes with one another and pick each other’s brains.

Please post your comments and inquiries and I guarantee I'll respond to them in a timely manner as soon as they are received (usually within a few short hours).  All questions will be answered and the interpretation (accompanied by laddergram) will be revealed on Sunday, June 17 2012 at which time I will post a brand new Case of the Week. 

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