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Wednesday, 12 March 2014

#ECGclass - Spring4 - When ECGs go bad!

Welcome to another weekly case on ECGclass. :)
If you are new to either @ECGclass, #ECGclass, or this blog - please click  here to find out what it's all about! 

ECG class is delighted to welcome our second guest speaker of the term!

A big welcome to Simon Ross Deveau.

Simon can be found on Twitter @sydeveau or via his ECG blog:  Bits and Pieces from an ED Nurse
As an ED nurse, Simon has come across a variety of ECG problems in the ED.
Problems range from ED staff doing them wrong, ambulance crews querying ischaemia/ST deviation, and people being referred in with abnormal ECGs, who go on to have normal ECGs when electrodes and leads are positioned correctly. 

So this weeks ECG class looks at a case of mistaken identity.
What happens when ECGs are done wrong?

Thank you Simon! :)
Here goes, and have fun…..…

Please use the Hashtag #ECGclass if joining in on Twitter!

If you want to ask the patient any questions, or request any further investigations this can  be done by the hashtag during the course of this evening. 

Alternatively, if referring to this blog at a later date, please leave comments below.

#ECGclass Spring4

Q1.      What is the correct electrode position of the precordial leads?

Correct precordial lead positioning:
V1    L sternal border, 4th intercostal space. 
V2    R sternal border, 4th intercostal space 
V4    Midclavicular line, 5th intercostal space. 
V5    Anterioraxillary line
V6    Midaxillary line
V3    Midway between V2 & 4.


Q2.     What technical error does the ECG below show?

The ECG above shows leads RA & LA to be reversed. 

Lead I is –ve and aVR is +ve = general R direction of cardiac impulse. 

The differential diagnosis here would be right sided heart (dextrocardia/dextroposition).


Q3.     How about this one?

This ECG shows reversal of V1-V6. 
Note the RS progression in reverse.


Q4.    Are we worried about this ECG?

Note that lead I shows normal sinus rhythm.   
Remember to treat the pt not the ECG!  

This is VT artefact from movement.


Q5.    At least this one doesn’t need defibrillating, but it there correct lead placement?

Note the amplitude of lead I > II . This is always suspicious. 
The P wave in Lead III has a small +ve  deflection at the end. This is Abdollah Sign 
(The amplitude of the P wave in lead I greater than in lead  II and/or  a P wave terminal positive component in lead III).
Abdhollahs sign = LA & LL reversal.


Q6.    What about this ECG?

Image thanks to

Normal sinus rhythm! 
All the above ECGs could well have come from the same patient so remember to treat the patient, not their ECG! 
If ECG  looks wrong, then redo - If in doubt throw it out!


Q7.    What general rules could you use to check for correct electrode placement?

  • aVR negative. 
  • II & III same general direction ( +ve  or –ve but not one of each).
  • I, II & III not all isoelectric. 
  • Amplitude II > I.

Discussion and Background

Incorrect lead and pad positioning on ECGs.

Correct placement of leads is important as an ECG captures a 180degree ‘picture’ of the
heart. This picture will be inaccurate if the leads are not ‘looking’ at the correct point. While
the majority of ECGs may be done by non-medical staff it is important that those reading an ECG can identify areas that may suggest an error in obtaining the ECG, rather than some cardiac pathology.


Limb leads = arm & leg leads (RA, LA, LL, N)
Precordial leads = V1-V6 (posterior leads = V7-V11 & right side leads = V1R-V6R)
Augmented (Goldberger's) leads = aVR, aVA, aVL, aVF

Colour coding is not universal.  American systems use different colours (so Ride Your Green Bike, starting with right arm and moving clockwise will not work). 
Many systems have replacement clips that attach to the electrodes and these may mean that the red RA electrode has a green clip on it.

Problems with Misplacement 

Incorrect lead placement by as little as 20-25mm from standard placement results in clinically significant ECG changes, including: ST depression in lateral leads; R and S wave amplitude across all leads (Hill and Goodman, 1987; Herman, Ingram et. al., 1991; Lateef, Da Nimbkar et. al., 2003; Perbody and Ornato, 1993)

Herman et. al. (1991) in a small scale experiment found deliberate misplacement of ECG
electrodes produces ST segment changes of ≥1mm in 47% of participants, as well as other changes, resulting in incorrect diagnosis in 60% of patients.

Hill and Goodman (1987) showed that misplacement by 1 intercostal space vertically, or
15mm horizontally, significantly altered R and S wave amplitude; leading to incorrect
diagnosis of pericarditis and ischaemia and a missed MI in a single case.

Nelwan, Meij, et. al. (2001) and Madias (2006) state that body position for recording of an
ECG will change both the amplitude and axis of QRS complexes. 

Baranchuk and Shaw (2009) report that ECGs taken with the patient sitting upright compared to lying down are unlikely to affect diagnosis due to QRS differences. They do suggest that ECGs taken in positions other than lying down are annotated to alert people to differences in QRS complex.

Inter-rater reliability

McCann, Kelly et. al. (2013) suggest that minimal inter-rater reliability exists, even between
“experts”. They found differences of up to 120mm in electrode placement, with greater
difference in women than men. This may be because it is traditional for precordial leads to be placed inferior to breast tissue, rather than at the ‘correct’ anatomical landmark.
As breast tissue will reduce current, therefore reducing amplitude of ECG complexes,
pragmatically placement on abdominal wall inferior to breast tissue in women produces
higher amplitude complexes.

General Rules to Confirm Lead Placement

  • aVR is generally negative. aVR may be positive in patients with a heart on the right side of their chest (dextrocardia/dextroposition), however this is uncommon (around 1/12-20000 live births) (Haththotuwa and Dubrey, 2013)
  • Leads II and III are generally similar in orientation (either + or -) if one is +ve and the other – ve then there is likely to be misplaced leads. It is possible for one to be isoelectric and the other + or -.
  • If leads I, II and III are all isoelectric then this is incorrect, as electrical impulses are not moving in any defined vector…and remember that all tests need to be used in conjunction with patient assessment and a patient with no organised cardiac activity probably needs CPR rather than discussion about cardiac vectors on a 12 lead ECG…
  • P wave amplitude in lead II greater than lead I. No Abdollah’s sign (amplitude of the P wave in lead I greater than in lead II and/or P wave terminal positive component in lead III). This shows a LL & LA reversal.
For serial ECGs it is important they are recorded with electrodes in  the same place, as altering electrode placement may change electrical morphology and cause the appearance of altering cardiac pathology.

Precordial Lead Position

V1 4th intercostal space right sternal margin
V2 4th intercostal space left sternal margin
V3 between V2 and V4
V4 5th intercostal space mid-clavicular line
V5 same axial plane as V4 anterior axillary line
V6 same axial plane as V4 and V5 mid-axillary line

V7 same axial plane posterior axillary line
V8 mid clavicular line (close to the inferior angle of the scapular)
V9 between V9 and V11
V10 4th intercostal space left sternal border
V11 4th intercostal space right sternal border

So there you have it.  Thanks to all who joined in!  

Hope you found this useful. 
Please do feedback any comments to @ECGclass or @sydeveau.

And don't forget - if you fancy leading a class - just get in touch! 
'Till next week.

Credit to Baranchuk and Shaw (2009) for the ECGs used in the cases above.

Additional Reading
Koppikar, S; Shaw, C; Baranchuk, A (2014). A tale of an abnormal ECG. Journal of
Electrocardiology 47(1) pp. 123-125.

Baranchuk and Shaw (2009) & Batchvarov and Malik (2007) below have many examples of
lead misplacement.

Baranchuk, A; Shaw, C; Alanazi, H; Campbell, D; Bally, K; Redfearn, D P; Simpson, C S;
Abdollah, H (2009). Electrocardiography Pitfalls and Artifacts: The 10 Commandments.
Critical Care Nurse 29(1) pp. 67-73.

Batchvarov, V N; Malik, M; Camm, A J (2007). Incorrect electrode cable connection during
electrocardiographic recording. Europace 9(11) pp. 1081–1090.

Haththotuwa HR, Dubrey SW (2013). A heart on the right can be more complex than it first
appears. BMJ Case Reports Online:
201046.full.pdf (Accessed 8/2/14).

Herman MV; Ingram DA; Levy JA; Cook JR; Athans RJ, (1991). Variability of ECG lead
placement: a method to improve accuracy and reliability. Clinical Cardiology 14(6) pp. 469–

Hill N, Goodman J (1987). Importance of accurate placement of precordial leads in the 12-
lead electrocardiogram. Heart Lung 16(5) pp. 561–566.

Lateef F, Da Nimbkar NZ, Min F (2003). Vertical displacement of praecordial leads alters
ECG morphology. Indian Heart Journal 55(4) pp. 339–43.

McCann, K; Holdgate, A; Mahammad, R; Waddington, A (2007). Accuracy of ECG
electrode placement by emergency department clinicians. Emergency Medicine Australasia 19(5) pp. 442–448.

Madias JE (2006). Comparability of the standing and supine standard electrocardiograms and standing sitting and supine stress electrocardiograms. Journal of Electrocardiology 39(2) pp. 142-149.

Nelwan SP, Meij SH, van Dam TB, Kors JA (2001). Correction of ECG variations caused by
body position changes and electrode placement during ST-T monitoring. Journal of
Electrocardiology 34(suppl) pp. 213-216.

Perbody M, Ornato J (1993). Recognition of electrocardiographic lead misplacements.
American Journal of Emergency Medicine 11(4) pp. 403–5.


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