ECG OF THE WEEK

Idhayachandran. N.

Prof. Sundar’s unit.

• A 24 year old male patient came to the OPD with complaints of chest pain for the past 2 hours.

• Pain was retrosternal, pricking type, not aggravated by exertion or relieved by rest.

• No h/o DM/HT.

• Smoker & consumes alcohol occasionally.

• O/E:

– conscious, oriented, afebrile,

– hydration fair

– comfortable at rest.

• CVS,RS,ABD,CNS-Normal.

ECG

• Rate - 60/min.

• Normal sinus rhythm.

• PR interval - 160 ms.

• QRS duration - 100 ms.

• QT interval - 400 ms.

• Right axis deviation.

• No signs of RVH or LVH.

• T wave inversion in L1and aVL. Q wave in aVL.

• Negative P wave in L1 and aVL.

INTERPRETATION

• T wave inversion and QS in L1 and aVL might suggest lateral wall infarction.

• This is an artefact due to reversal of the two upper limb leads.

• L1, aVL, V5 and V6 all have similar axes.

• The morphology of QRS complex should be identical in all these leads.

• If the polarity of QRS in L1 is opposite to that of the left precordial leads (V5 and V6), as in this case, arm lead reversal should be suspected.

• Reversal of arm leads is the most common lead placement error and is the easiest to recognize because of negative P wave in L1.

• In patients with AF or unrecognizable P waves, if the polarity of QRS in L1 is different from that of left precordial leads V5 and V6, arm lead reversal is suspected.

• In case of reversal of arm leads the morphology of complexes in the limb leads resembles dextrocardia.

• However dextrocardia and reversal of arm leads can be differentiated on the basis of QRS complexes in the precordial leads.

• In dextrocardia as we progress from V1 to V6 QRS complex becomes progressively smaller and displays mostly QS or rS in V5 or V6.

• In reversal of arm leads the progression of QRS from V1 to V6 is normal.

ECG

•→

Lead ILead I

RA RALA LA

LLLL

--

+ +

-+

- -

+-

+ +

• If one of the standard limb leads is almost a straight line, the right leg cable was probably switched with other limb cables.

• In the augmented unipolar limb leads, if the lead aVL shows all negative deflection, the right arm cable has been switched with the left arm.

• If the lead aVf shows all negative deflection, the right arm cable has been switched with the left leg.

• Reversal of the left arm cable and the left leg cable is difficult to recognize without having a previous normal ECG for comparison.

• If the precordial leads are misplaced, the ECG might resemble infarction pattern.