Electrocardiograms from active electrodes located on the chest can be used to determine the damage to cardiac tissue caused by coronary occlusions, or for diagnosing ventricular hyper­trophy. These determinations are possible because these electrodes respond to electrical activity directly beneath them, whether the activity is moving towards or away from the electrode.

The six chest leads normally used in a 12-Lead ECG are known as leads V1 through V6, and occur in an almost horizontal plane that is best described as being parallel to the floor when the subject is standing.  Recordings from a normal, healthy heart usually show a biphasic QRS from either the V3 or the V4 lead positions. The lead that yields R and S waves of equal magnitude, in opposite directions, is the lead that overlies the anterior edge of the interventricular septum, also known as the transition point. A shift in the transition point results from an abnormal orientation of the heart around a vertical axis that is perpendicular to the horizontal plane of the chest leads, and is an indication of an anatomical or pathological deviation. 

In this experiment, students will record electrocardiograms from the six standard chest lead positions on multiple subjects and determine the transition point of the each subject.

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When recording electrocardiograms from chest leads or augmented limb leads, the active electrode on the chest or limb is referenced against an indifferent point that is formed by the joining of the limb leads at the indifferent input of the recording channel.  A three-way indifferent electrode cable (Part Number: C-ECG-IE) is now available from iWorx/CB Sciences.  Use all three snap leads of this cable to form the indifferent point needed for recording an electrocardiogram from the chest leads.  Use two of the three snap leads to connect the limb electrodes needed to form the indifferent point used for the recording of electrocardiograms from augmented limb leads.  View more information in the Tech Note.

Special Offer to iWorx Users  
The 3-way Indifferent Electrode Cable is required to perform the Chest Lead Electrocardiograms experiment discussed above.  For a limited time, iWorx is offering its iWorx users a 50% discount on purchase of the cable.
 

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Download the installer, settings files, and manuals for Chest Lead Electrocardiograms and other experiments recently published in the iWorx newsletter.

On this page we have also accumulated a host of links to informative, external physiology Web sites and conveniently categorized them into major sub categories for easy reference.   

Each lab includes a topical overview, background, equipment set-up and lab procedure, quiz questions, and an interactive LabPlayer that displays recorded data from real experiments and allows students to manipulate and record data just as they would in a "wet" lab.  Data can be captured and logged in an online Lab Journal that can be later copied to a new document or sent via email.  Labs are further enhanced with animations, diagrams, and video clips. 

The virtual labs can be accessed on a CD or from the Web and are designed specifically for student self-learning environments.

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