BIPOLAR EKG

Now we will show the design of the stages that has a basic bipolar electrocardiograph from the diagram of blocks and the corresponding circuits

Bipolar Leads

Fig 1. Einthoven´s triangle [2]

Well, the 2 leads situated on the right and left wrist (or shoulders), AVr and AVL respectively, and the lead situated on the left ankle (or left lower abdomen) AVf, make up a triangle, known as "Einthoven’s Triangle"[1].

• information between AVr and AVl is known as lead l.

• Information between AVr and AVf is known as lead ll

• Information between AVl and AVf is known as lead lll

As shown below the shape of the signal changes according to the position and record of the signal with respect to two leads

Fig 2. Bipolar derivates of Electrocardiogram

MATHEMATICAL CALCULATIONS FOR THE FILTERS USED IN THE ECG DESIGN

FILTER NOTCH

Cutting frequency of 60 Hz.

FILTER NOTCH

Cutting frequency of 50 Hz.

BANDPASS FILTER

HIGH PASS FILTER

LOW PASS FILTER

INSTRUMENTATION AMPLIFIERS INA128

GAIN OF 1000

SCHEMATIC DRAWING

As you can see, we do a impedance coupling with buffer of each lead RA,LA and LL, After we apply the Wilson circuit and connect the node RA,LA and LL to each INA128 to get the bipolar signal of EKG.

Now connect to a new dip switch to select the filter that you want apply according to the last design of notch filter of 50 Hz and 60 Hz. the last step is connect the filtered signal with the ofsset and then to the MOC to separate the patient from the electrical source.

the output of the circuiti is the 5 pin optocoupler, and you can see your signal in the oscilloscope

---

RESULTS

Here we will show with images the results obtained from de EKG in each of the bipolar derivations. These derivations record the potential difference between two electrodes located in different extremities.

DI derivation

DI is a connection between electrodes located on the left arm and on the right arm. When the left arm is in a positive force field with respect to the right arm, in DI a deflection is registered upward (positive).

DII derivation

DII is the connection between the electrodes located in the left leg and the right arm, when the left leg is in a positive force field with respect to the right arm, an upward deflection is registered in this shunt.

DIII derivation

DIII is a connection between the left leg and the left arm. When the left leg is in a positive force field with respect to the left arm, a positive deflection is registered in DIII.

GLOSARY

ECG: is a simple, noninvasive procedure. Electrodes are placed on the skin of the chest and connected in a specific order to a machine that, when turned on, measures electrical activity all over the heart [1]

QRS COMPLEX: The waves are the different curvatures that take the tracing of the ECG up or down. They are the product of the action potentials that occur during cardiac stimulation and are repeated from one heartbeat to another, except alterations.

The electrocardiographic waves have been called P, Q, R, S, T in that order and are joined together by an isoelectric line.

The QRS complex consists of a set of waves representing the depolarization of the ventricles. Its duration oscillates between 0.06 s and 0.10 S. It takes several morphologies depending on the shunt. [2]

TERMINOLOGY ELECTROCARDIOGRAPHIC:

A electrocardiographic shunt is intended to measure the current that flutye in a straight line from one electrode to another.

There are several electrocardiographic shunts that allow you to see the heart signals from different points of view. The waves can be recorded because the electricity of the heart spreads throughout the body in a homogeneous way.

INA128: Is low-power, general purpose instrumentation amplifiers offering excellent accuracy. The versatile 3-op amp design and small size make these amplifiers ideal for a wide range of applications.[3]

FILTER NOTCH: A notch filter is typically an aggressive filter that strongly attenuates the power over a narrow region of the spectrum.  For example, a notch filter at 60 Hz / 50 Hz is used to filter out power line noise with minimal disruption to the rest of the signal. [4]

BAND PASS: is an electronic device or circuit that allows signals between two specific frequencies to pass, but that discriminates against signals at other frequencies. Some bandpass filters require an external source of power and employ active components such as transistors and integrated circuits; these are known as active bandpass filters. [5]

Wilson Network: its a circuit createdwith a central terminal of Wilson, of potential zero.

BIBLIOGRAPHICAL REFERENCES

[1]"Bipolar Leads - ECG Lead Placement - Normal Function of the Heart - Cardiology Teaching Package - Practice Learning - Division of Nursing - The University of Nottingham", Nottingham.ac.uk, 2018. [Online]. Available: https://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/bipolar_leads.php. [Accessed: 01- Sep- 2018].

[2] [2]"Ondas del Electrocardiograma", My-ekg.com, 2018. [Online]. Available: http://www.my-ekg.com/generalidades-ekg/ondas-electrocardiograma.html. [Accessed: 02- Sep- 2018].

[3]INA12x Precision, Low-Power Instrumentation Amplifiers. Texas instruments, 2018, p. 1. http://www.ti.com/lit/ds/symlink/ina129.pdf

[4]"Notch filter | BIOPAC", BIOPAC Systems, Inc., 2018. [Online]. Available: https://www.biopac.com/knowledge-base/notch-filter/. [Accessed: 08- Sep- 2018].

[5]M. Rouse, "What is bandpass filter? - Definition from WhatIs.com", WhatIs.com, 2006. [Online]. Available: https://whatis.techtarget.com/definition/bandpass-filter. [Accessed: 08- Sep- 2018].