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#27730 - 02/02/08 11:20 AM
Re: ECG Recording Formats
[Re: Geoff Hannis]
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Mr R J Ling
Mr R J Ling
Unregistered
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Hi Geoff,
The standard arrangement of each ECG lead position is traditional. The frontal leads aren't arranged in any particular order, anatomically speaking, for any particular reason. The displayed lead orientations allow comparison between lead orientations over time.
However organisation of displayed leads in the Cabrera format takes into account the logical progression of the ECG signal through the anatomy of the heart initially in the frontal plane (aVL, I, -aVR, II, aVF, III) and then into the transverse plane (V1, V2, V3, V4, V5, V6).
Research has shown that the Cabrera sequence gives more accurate indication of where infarctions occur in the heart and also the frontal axis (orientation) of the heart can be more easily determined.
Apparently the use of an inverted aVR (-aVR or maVR) improves diagnosis and allows better estimation of the risks associated with inferior (lower) and lateral (side) myocardial (heart muscle) infarction (heart attack).
Cabrera is a more logical and more effective format to use, clinically speaking, according to the literature. The reason clinicians don't use Cabrera routinely is that the use of standard format is somewhat ingrained in the cardiology profession.
From the papers, etc, that I've read in the past, I think manufacturers include the Cabrera format, as well as the standard one, because they're being "encouraged" to provide this function by clinical recommendations.
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#27733 - 02/02/08 01:52 PM
Re: ECG Recording Formats
[Re: ]
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Geoff Hannis
Hero
Registered: 12/02/04
Posts: 3046
Loc: the path less trodden
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Here's a bit more that I've found:-
"If a coronary artery is occluded, the transport of oxygen to the cardiac muscle is decreased, causing an oxygen debt in the muscle, which is called ischemia. Ischemia causes changes in the resting potential and in the re-polarization of the muscle cells, which is seen as changes in the T-wave. If the oxygen transport is terminated in a certain area, the heart muscle dies in that region. This is called an infarction. An infarct area is electrically silent since it has lost its excitability."
And ...
"As we know, the ten connections which generate the well-known and commonly used 12-lead ECG, consists of "leads" I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6. The main reason for recording all 12 leads is that it enhances pattern recognition. This combination of leads gives the clinician an opportunity to compare the projections of the resultant vectors in two orthogonal planes and at different angles. This is further facilitated when the polarity of the lead aVR can be changed. For instance, the lead -aVR is now included in many ECG recorders."
With Cabrera the inverted aVR would look very similar to aVF (or even lead II) in a strong heart. Pattern recognition it must be, then (notice the order of the leads in the Frontal Plane, as mentioned by Richard, within the circle shown at the aVF link, for a graphical depiction of where Cabrera is coming from).
No doubt you're right, Richard. I should imagine that it would be relatively easy these days (ie, as kit is "software driven") for ECG manufacturers to include every and all possible lead arrangements (eg, Cabrera, Einthoven, Frank, Goldberger, McFee-Parungao, Nelson, SVEC, Wilson and all the rest ... and there are many). Then the cardiologists could no doubt play to their hearts' content! 
Edited by Geoff Hannis (02/02/08 02:44 PM)
Edit Reason: How could I forget Goldberger!
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#27735 - 02/02/08 03:29 PM
Re: ECG Recording Formats
[Re: Geoff Hannis]
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Mr R J Ling
Mr R J Ling
Unregistered
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Actually Geoff, from memory, some of the methods you mention use less connections to the patient and rely on different lead positions to derive the standard leads, i.e. there are other motives why they're used, e.g. to reduce the connections to the patient.
10 electrode placement is already based upon the Einthoven, Wilson and Goldberger configurations combined to give different "views" in a 12 lead ECG. The standard display format has evolved to become the de-facto standard.
The bottom line is that the Cabrera display format is produced directly from the standard 10 electrode placement and it is considered to be effective in improving the diagnostic capability of standard 12 lead diagnostic ECG.
Again, off the top of my head and as far as I'm aware, Cabrera doesn't need a different electrode configuration or changes in the number of patient connections, compared to the standard configuration.
Nothing more than inverting aVR and then displaying the augmented and limb leads, in the order (aVL, I, -aVR, II, aVF, III) that the ECG in the frontal plane propagates.
Along with displaying the precordial leads (V1-V6), that, as standard, are already displayed in the order corresponding to the direction of propagation of the ECG in the lateral plane.
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#27999 - 16/02/08 10:32 PM
Re: ECG Recording Formats
[Re: Geoff Hannis]
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Mr R J Ling
Mr R J Ling
Unregistered
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Originally Posted By: The ECG Complex:
1912
Einthoven addresses the Chelsea Clinical Society in London and describes an equilateral triangle formed by his standard leads I, II and III later called 'Einthoven's triangle'. This is the first reference in an English article I have seen to the abbreviation 'EKG'.Einthoven W. The different forms of the human electrocardiogram and their signification. Lancet 1912(1):853-861
1934
By joining the wires from the right arm, left arm and left foot with 5000 Ohm resistors Frank Wilson defines an 'indifferent electrode' later called the 'Wilson Central Terminal'. The combined lead acts as an earth and is attached to the negative terminal of the ECG. An electrode attached to the positive terminal then becomes 'unipolar' and can be placed anywhere on the body. Wilson defines the unipolar limb leads VR, VL and VF where 'V' stands for voltage (the voltage seen at the site of the unipolar electrode). Wilson NF, Johnston FE, Macleod AG, Barker PS. Electrocardiograms that represent the potential variations of a single electrode. Am Heart J. 1934;9:447-458.
1942
Emanuel Goldberger increases the voltage of Wilson's unipolar leads by 50% and creates the augmented limb leads aVR, aVL and aVF. When added to Einthoven's three limb leads and the six chest leads we arrive at the 12-lead electrocardiogram that is used today.
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