Difference between revisions of "Technical Problems"

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m (Artifacts)
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==Lead reversals==
 
==Lead reversals==
 
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'''. This leads to a negative complex in lead I with also a negative P wave in lead I. It is one of the most common causes of right axis deviation on the ECG!
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* '''Left-right arm reversals'''this lead to a negative complex in lead I with also a negative P wave in lead I. It is one of the most common causes of right axis deviation on the ECG!
* '''Arm - foot switches''' lead to a very small or 'far field' signal in leads II or III.
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* '''Arm-foot switches''' lead to a very small or 'far field' signal in leads II or III.
* '''Chest lead reversal''' lead to inappropiate R wave progression (increase - decrease - increase) and are often easily recognized.
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* '''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.
 
<div style="float:right">
 
<div style="float:right">
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More specific patterns with every lead reversal:
 
More specific patterns with every lead reversal:
 
*right leg and right arm:
 
*right leg and right arm:
**Hardly any signal in lead II.
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**diminished signal in lead II
*right and left arm electrodes;
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*right and left arm electrodes:
 
**reversal of leads II and III
 
**reversal of leads II and III
 
**reversal of leads aVR and aVL
 
**reversal of leads aVR and aVL
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<gallery perRow="4">
 
<gallery perRow="4">
 
Image:Noise_move.png|Movement artifacts
 
Image:Noise_move.png|Movement artifacts
Image:ECG_Parkinson.png|Increasing movement artifacts in a Parkinson patient. The patient was in sinus rhythm! (which doesn't show on this short recording)
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Image:ECG_Parkinson.png|Increasing movement artifacts in a Parkinson's patient. The patient was in sinus rhythm (which doesn't show on this short recording)!
 
Image:BaselineDrift.png|Baseline drift. The amplifier in the ECG machine has to re-find the 'mean'. This often occurs right after lead connection and after electric cardioversion.
 
Image:BaselineDrift.png|Baseline drift. The amplifier in the ECG machine has to re-find the 'mean'. This often occurs right after lead connection and after electric cardioversion.
 
Image:cardioversion_from_afib.jpg|Cardioversion from atrial fibrillation to sinus rhythm, with clear baseline drift.
 
Image:cardioversion_from_afib.jpg|Cardioversion from atrial fibrillation to sinus rhythm, with clear baseline drift.
 
Image:electric_noise_ecg.png|Electrical interference from a nearby electrical appliance. A typical example is a 100 Hz background distortion from fluorescent lights. Not to be confused with [[Atrial_Fibrillation|atrial fibrillation]].
 
Image:electric_noise_ecg.png|Electrical interference from a nearby electrical appliance. A typical example is a 100 Hz background distortion from fluorescent lights. Not to be confused with [[Atrial_Fibrillation|atrial fibrillation]].
Image:electric_noise_ecg2.jpg|Another example of an artefact caused by an electrical appliance. The patients rhythm is regular. This strip shows 10 QRS complexes.
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Image:electric_noise_ecg2.jpg|Another example of an artifact caused by an electrical appliance. The patients rhythm is regular. This strip shows 10 QRS complexes.
 
File:DVA2162.jpg|An artifact that was originally diagnosed as a VT
 
File:DVA2162.jpg|An artifact that was originally diagnosed as a VT
 
</gallery>
 
</gallery>

Revision as of 06:26, 17 January 2010

Author(s) J.S.S.G. de Jong
Moderator J.S.S.G. de Jong
Supervisor
some notes about authorship

Lead reversals

Lead switches are a common mistake when ECGs are made and can lead to wrong diagnoses. Common mistakes are:

  • Left-right arm reversalsthis lead to a negative complex in lead I with also a negative P wave in lead I. It is one of the most common causes of right axis deviation on the ECG!
  • Arm-foot switches lead to a very small or 'far field' signal in leads II or III.
  • 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.

More specific patterns with every lead reversal:

  • right leg and right arm:
    • diminished signal in lead II
  • right and left arm electrodes:
    • reversal of leads II and III
    • reversal of leads aVR and aVL
  • left arm and left leg:
    • reversal of leads I and II
    • reversal of leads aVR and aVF
    • inversion of lead III
  • right arm and left leg:
    • inversion of leads I, II and III
    • reversal of leads aVR and aVF

It is possible to distinguish lead reversal and dextrocardia by watching the precordial leads. Dextrocardia will not show any R wave progression in leads V1-V6, whereas lead reversal will.

Artifacts

Artifacts (disturbances) can have many causes. Common causes are:

  • Movement
  • Electrical interference