Certified Medical Assistant (CMA AAMA)Procedures, Examinations and DiagnosticsMedium
A medical assistant places all 12 leads for an EKG and notices that lead aVR shows a predominantly upright (positive) QRS complex, which is unusual. What does this most likely indicate?
- AAn indication that the patient is experiencing a myocardial infarction
- BNormal sinus rhythm with no cause for concern
- CCorrect placement confirming accurate limb lead positioning
- DPossible reversal of the right arm and left arm electrodes
Show answer & explanationAnswer & explanation
Correct answer: D. Possible reversal of the right arm and left arm electrodes
Lead aVR normally displays a negative deflection because it views the heart from the right shoulder, away from the main electrical vector. A positive aVR complex is a classic sign of arm lead reversal and should prompt a recheck of electrode placement before assuming a cardiac abnormality.
Why the other options are wrong
- A. MI is diagnosed through other criteria, not primarily by aVR polarity alone.
- B. A positive aVR is abnormal and should not be dismissed as normal.
- C. Correct placement produces a negative aVR, not positive.
aVR Lead Polarity Check
Lead aVR should normally show a negative QRS deflection; a positive aVR suggests limb lead misplacement, commonly right/left arm reversal.
- aVR views heart from right shoulder
- Normally negative deflection
- Positive aVR = check for arm lead swap
Memory trick: aVR Always Reversed (negative)—if it's not, arms are switched.