Date post: | 15-Jul-2015 |
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Health & Medicine |
Upload: | stanley-medical-college-department-of-medicine |
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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.