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Electrocardiogram (ECG)

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Summary

An electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical voltage produced by the beating of the heart muscle in the form of a continuous strip graph. It is the prime tool in cardiac electrophysiology, and has a prime function in screening and diagnosis of cardiovascular diseases.

Measuring

Measuring an ECG can be as simple as placing electrodes at the centre of the wrist and on the forearm. This will not provide you the clearest signal possible, but is usually clear enough for electronic control or musical applications. For more precise measurements, the conventional 12-lead ECG configuration is used. The following section will provide an introduction to electrode placement in this configuration. However, it is recommended to use pre-existing software, like OpenBCI, to produce the ECG signal using this configuration.

12-lead ECG

In a conventional 12-lead ECG, ten electrodes are placed on a person's limbs and chest. The electrical voltages produced by the beating heart are then measured from twelve different leads (a type of vector or angle between electrodes) and is recorded over a period of time.

Four of the electrodes are placed on each limb and the other six are placed on the chest near the heart. The names of the electrodes and where they should be placed are as follows:

Electrode name Electrode placement
RA On the right arm
LA On the left arm
RL On the right leg
V1 Between ribs 4 and 5 to the right of the sternum
V2 Between ribs 4 and 5 to the left of the sternum
V3 Between leads V2 and V4
V4 Between ribs 5 and 6 in the mid-clavicular line
V5 In the left anterior axillary line, horizontally even with V4
V6 In the midaxillary line, horizontally even with V4 and V5

Electrode placement for ECG

When the voltages from the various leads are suitably processed, a graph of the voltage over time of the heart muscle beating is measured and produced. The graph produced is typically in the form of distinct waves: the P-wave, the QRS-complex, and the T-wave.

Graph of an ECG

Uses in musical applications

Electrocardiophone is an instrument that converts ECG signals to musical tone. This is done by amplifying the ECG signal and then using it to modulate an audio frequency oscillator and then playing that sound. It was developed primarily in the diagnosis of arrhythmias in medical patients.

External links & references