13-02-2013, 11:20 AM
ECG Simulation Using MATLAB
ECG Simulation.pptx (Size: 1.73 MB / Downloads: 33)
Introduction
Electrocardiogram (ECG) is a nearly periodic signal that reflects the activity of the heart. A lot of information on the normal and pathological physiology of heart can be obtained from ECG. However, the ECG signals being non-stationary in nature, it is very difficult to visually analyze them. Thus the need is there for computer based methods for ECG signal Analysis. One of the important technology used is simulation of ECG using MATLAB.
Importance Of ECG
ECG reflects the state of cardiac heart and hence is like a pointer to the health conditions of a human being.
ECG, if properly analyzed, can provide us information regarding various diseases related to heart. However, ECG being a non-stationary signal, the irregularities may not be periodic and may show up at different intervals.
By studying ECG, Doctors can diagnose the disease and prescribe the required medications.
Electrocardiogram (ECG)
An ECG is a series of waves and deflections recording the heart’s electrical activity from a certain “view”. Many views, each called a lead, monitor voltage changes between electrodes placed in different positions on the body.
Each cardiac cell is surrounded by and filled with solutions of Sodium (Na+), Potassium (K+), and Calcium (Ca++). The interior of the cell membrane is considered to be negative with respect to outside during resting conditions.
When an electric impulse is generated in the heart, the interior part becomes positive with respect to the exterior. This change of polarity is called depolarization. After depolarization the cell comes back to its original state. This phenomenon is called repolarization. The ECG records the electrical signal of the heart as the muscle cells depolarize (contract) and repolarize.
Effects Of Noise
In routinely recorded ECGs, many types of noise and artefact are present. Noise is defined to be part of the real signal that confuses analysis (e.g. muscle movements) and artefact is defined to be any distortion of the signal caused by the recording process, such as electrode movement.
Noise problems in the environment have gained attention due to the tremendous growth of technology that has led to noisy engines, heavy machinery, high speed wind buffeting and other noise sources.
The problem of controlling the noise level has become the focus of a tremendous amount of research over the years.
Three types of predominant noise that commonly contaminate the signal are baseline wander (BW) noise, electromyographic (EMG) interference, and 50 or 60 Hz power line interference. Among them power line interference is a significant source of noise. Cables carrying ECG signals from the patients to the monitoring equipment are susceptible to electromagnetic interference (EMI) from the 50/60Hz power line noise.
How To Remove Noise
Many attempts have been made to detect and eliminate noise sources and artefacts from the actual electrocardiographic signals. Analogue or digital filters are widely used to reduce the influence of interference superimposed on the ECG.
The goal for ECG signal enhancement is to separate the valid signal components from the undesired artifacts, so as to present an ECG that facilitates easy and accurate interpretation.