ECG system

Discussion in 'The Projects Forum' started by alexpanrui, Jan 6, 2010.

  1. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    So far as I know, a 12-lead ECG system is able to generate waveforms on Lead I, II, III, aVR, aVL, and aVF. A 5-lead ECG system is also able to provide all these information.
    So what is the difference between a 12-lead and a 5-lead ECG system?
    What are Lead I, II, III, aVR, aVL and aVF for?
    For heart rate estimation, is it feasible to analyze Lead II only?
    Thank you guys.
     
  2. t06afre

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    May 11, 2009
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  3. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    thanks, buddy...i will go through book......and still open for other suggestions.....thanks
     
  4. KMoffett

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    Dec 19, 2007
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    Yes. Are you looking for a circuit?

    Ken
     
  5. alexpanrui

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    Feb 25, 2008
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    ummmm..... thanks for your reply...Im currently not looking for a circuit. I just wanna figure out how thing's working?
     
  6. KMoffett

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    Actually a three "wire" ECG input is needed...RA, LA, and LL. "3 Lead" is the clinical term for an ECG that reads "Leads" I, II, and III.

    Ken
     
  7. whatsthatsmell

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    Oct 9, 2009
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    True, but just looking at Lead II requires only two wires - RA and LL.
     
  8. KMoffett

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    Sort of true, but in the normal ECGs, a RL driver is included to reduce offset and environmental noise. They are a differential amps after all and need a reference. Not that you couldn't get by with just a ground and a signal input.

    Ken
     
  9. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    There's something confusing me. The output from a ecg monitor is just one waveform showing P,Q,R,S,T. But for a 3 "wire" system, there are 3 different waveforms for leads I, II, III. How do these 3 different waveforms add up together to produce a single waveform? And what about aVR, aVL and aVF in a 12-lead system?
     
  10. KMoffett

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    Dec 19, 2007
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    ECG monitors can have one ECG tracing or multiple traces.
    The different "leads" are just signals from different combinations of electrodes on the body connected to the three differential amplifier wires.

    Google: differential amplifier

    This is done by having multiple differential amplifiers, or one amplifier and switching in different electrode combinations:

    Lead I: RA>LA referenced to RL
    Lead II: RA>LL referenced to RL
    Lead III: LA>LL referenced to RL
    aVR: (LA+LL)>RA referenced to RL
    aVL: (RA+LA)>LA referenced to RL
    aVF: (RA+LA)>LL referenced to RL

    Did you read chapter 15 in the link that t06afre posted earlier? If so, was it too complex to grasp?

    Ken
     
  11. t06afre

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    May 11, 2009
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    You may also try Google for more information. But as far as I know the link I gave you is one of the best free (and legal) Ebook on this topic.
     
  12. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    Thank you guys. I will do some more research on my own. With your help, I have a better understanding now.
     
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