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==Lead reversals== | ==Lead reversals== | ||
{{multiple image | |||
| align = right | |||
| direction = vertical | |||
| width = 200 | |||
| image1 = E000566.jpg | |||
| caption1 = A Normal ECG | |||
| image2 = E000567.jpg | |||
| caption2 = right arm - right leg reversal | |||
| image3 = E000563.jpg | |||
| caption3 = left arm - left leg reversal | |||
| image4 = E000564.jpg | |||
| caption4 = left leg - right leg reversal. | |||
| image5 = E000568.jpg | |||
| caption5 = v3 - v2 reversal | |||
| image6 = E000565.jpg | |||
| caption6 = left - right reversal | |||
}} | |||
Lead switches are a common mistake when ECGs are made and can lead to wrong diagnoses. Common mistakes are: | Lead switches are a common mistake when ECGs are made and can lead to wrong diagnoses. Common mistakes are: | ||
* '''Left-right arm reversals''' lead to a negative complex in lead I with a negative P wave in lead I. They are one of the most common causes of right axis deviation on the ECG! | * '''Left-right arm reversals''' lead to a negative complex in lead I with a negative P wave in lead I. They are one of the most common causes of right axis deviation on the ECG! | ||
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* '''Chest lead reversals''' lead to inappropriate R wave progression (increase-decrease-increase) and are often easily recognized. | * '''Chest lead reversals''' lead to inappropriate R wave progression (increase-decrease-increase) and are often easily recognized. | ||
Therefore '''any right axis or small signal in an extremity lead''' should be reason enough to check lead positioning. A previous ECG can be very helpful. | Therefore '''any right axis or small signal in an extremity lead''' should be reason enough to check lead positioning. A previous ECG can be very helpful. | ||
More specific patterns with every lead reversal: | More specific patterns with every lead reversal: | ||
*right and left arm electrodes: | *right and left arm electrodes: | ||
**inversion of lead I | |||
**reversal of leads II and III | **reversal of leads II and III | ||
**reversal of leads aVR and aVL | **reversal of leads aVR and aVL | ||
*right leg and right arm: | |||
**diminished signal in lead II | |||
*left arm and left leg: | *left arm and left leg: | ||
**reversal of leads I and II | **reversal of leads I and II | ||
**reversal of leads | **reversal of leads aVL and aVF | ||
**inversion of lead III | **inversion of lead III | ||
*right arm and left leg: | *right arm and left leg: | ||
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It is possible to distinguish lead reversal and [[w:Dextrocardia|dextrocardia]] by watching the precordial leads. Dextrocardia will not show any R wave progression in leads V1-V6, whereas lead reversal will. | It is possible to distinguish lead reversal and [[w:Dextrocardia|dextrocardia]] by watching the precordial leads. Dextrocardia will not show any R wave progression in leads V1-V6, whereas lead reversal will. | ||
<gallery> | |||
Image:cableReversal1.png|Right and left arm lead reversal can be distinguished from the (much rarer) dextrocardia by examination of the precordial R wave progression. | |||
Image:cableReversal2.png|Right arm and left leg lead reversal. Lead II now measures the signal between the left and right leg, which is remote from the heart. | |||
Image:dextrocardia.jpg|A patient with dextrocardia (and previous inferior myocardial infarction) | |||
Image:Situs_inversus.jpg|Another patient with dextrocardia | |||
</gallery> | |||
{{clr}} | {{clr}} | ||
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</gallery> | </gallery> | ||
{{clr}} | |||
==References== | ==References== | ||
<biblio> | <biblio> | ||
#Garcia pmid=19804517 | #Garcia pmid=19804517 | ||
</biblio> | </biblio> | ||