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Normal 12-Lead Demonstrating Good R Wave Progression

Dawn's picture
Wed, 01/29/2014 - 23:05 -- Dawn

Do you need a good example of normal precordial R wave progression for your collection?  It is important to teach your students what "normal" looks like, as a reference for the abnormal ECGs you will teach them later.  

This 3-channel 12-lead ECG offers a normal frontal plane axis, as evidenced by Lead II having the tallest R wave of all the limb leads.  It also demonstrates a normal "Z" axis.  That is, the direction of depolarization on the horizontal plane is normal.  This is seen in the progression of the QRS complexes from a negative V1 to a positive V6.  Each of the chest leads should have an R wave.  V1 normally has a small R wave, and a deeper S wave.  The R wave reflects the depolarization of the septum, which flows TOWARD the V1 electrode.  The S wave reflects the ventricles depolarizing, dominated by the left ventricle, which depolarizes AWAY from V1.

V6 will be all or nearly all positive, reflecting that the same heart is depolarizing TOWARD the V6 electrode, located in the 5th ICS in the mid-axillary line.  When we evaluate the leads V2 through V5, we should see an orderly progression between the negative V1 and the positive V6.  When viewed as an R-S ratio, we could say the R waves are becoming larger and the S waves smaller as we progress across the chest from right to left.  Other factors, however, will affect the overall size of the QRS, such as the size and contents of the chest, and how close the electrode is to the heart.  For that reason, the overall amplitude of V2 and V3 is usually larger, given their close proximity to the heart.  V6 is smaller overall than V5 because it is farther from the heart, and more chest contents (lungs) are between the heart and the electrode.  

Once your students understand what the ECG "should" look like, it is time to teach the abnormalities.  Poor R wave progression (a not-very-helpful term) can be caused by a number of things, such as electrode misplacement, anterior M.I. with pathological Q waves, and chamber enlargement.  For an excellent discussion of poor R wave progression, visit Life In the Fast Lane.

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Comments

ekgpress@mac.com's picture
     As per Dawn - this week’s Instructor Collection ECG features a normal tracing - which is good to include among one’s personal tracing collection. I’ll add a few selected comments to Dawn’s discussion:
  • Although referral to “R Wave Progression” and “PRWP” (= “Poor” R Wave Progression) - remain as entrenched terms in both the literature and in common clinical usage - there is a better terminology. The problem with “PRWP” as a descriptive term - is that a variety of contradictory conditions may qualify as manifesting “poor R wave progression” - including LVH - RVH - pulmonary disease - anterior or anteroseptal infarction - various conduction defects including LBBB/LAHB/IVCD - cardiomyopathy - chest wall deformities - normal variants - and lead misplacement. Thus, LITTLE is learned by saying a patient has “poor R wave progression”. Far better in my opinion is to describe the area of Transition, as well as specific ECG findings (ie, QS complex in leads V1,V2,V3) - instead of just saying, “PRWP”. For those interested - this LINK provides free download of Sections 09.1-thru-09.11 from my ECG-2014-ePub which reviews this subject in detail.
  • Finally - Lead V6 is not necessarily in the 5th IC space. This represents a change from prior recommendations for precordial lead placement. Instead - leads V5,V6 should both be placed level with lead V4. This is now preferred to the 5th intercostal space - because the course of each intercostal space is variable (Kligfield et al - AHA/ACC Recommendations. JACC 49:1109-1127, 2007). For those interested - this LINK provides free download of Sections 03.0-thru-03.11 from my ECG-2014-ePub, which reviews the Technical Mishaps and other Lead Derivation/Placement issues. See Section 03.9 for the parts referring to precordial lead placement of leads V4,V5,V6.

Ken Grauer, MD  www.kg-ekgpress.com   [email protected] 

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