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Personal HeartPersonal HeartAttack DetectorAttack Detector

NirNir GluzmanGluzmanAlexei Alexei IolinIolin

March 3, 2005March 3, 2005

Technion Israel Institute of TechnologyDepartment of Electrical Engineering

VLSI Systems Research Center & Laboratories

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Did you know?Did you know?More than 1.2 million Americans will suffer a heart attack, where about 502,000 of these people will die!340,000 of them in ER or they reach a hospital.

Surviving a heart attack depends on the treatment that is given within the first hour of the heart attack.

Most common reason for treatment delay is patient unawareness.

Source: American Heart Association, 2004 estimation.

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The solutionThe solution

Personal HeartPersonal HeartAttack DetectorAttack Detector

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AGENDAAGENDAECG waveform.Heart attack & ST-Elevation.Project objective.System block diagram.Background on wavelets.DWT and filter-bank.Detection of ECG Characteristic points with DWT.SIMULINK implementation. Summary.

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ECG waveformECG waveformECG = Electrocardiogram

Recording of hearts electrical activity.Measures rate and regularity.Used to diagnose diseases.

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Basic ECG complex

ECG waveformECG waveform

R

P

Q

S

T

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Heart attack(Myocardial Infarction)

An event that results in permanent damage to the heart.myocardium = heart muscle.infarct = die.

Heart attack & STHeart attack & ST--ElevationElevation

Q-waves and inverted T-wavesare two diagnostic wave forms seen in old heart attacks and new heart attacks respectively.

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ST-Elevation (STEMI)Elevation of ST-segment relative to PR or TP segment.

ST-elevation is a sign for coming heart attack (acute myocardial infarction).Short PR interval - very difficult for computer algorithms to find the isoelectric reference level.

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Develop a chip for measuring Develop a chip for measuring STST--elevationelevation and and alerting the user to heart attackalerting the user to heart attack. . Detection algorithm is implemented in Detection algorithm is implemented in hardwarehardware for for power efficiency. power efficiency.

Project objectiveProject objective

Winter semester objectiveWinter semester objectiveDevelop an algorithm for detection of ECG characteristic points.Develop an algorithm for detection of ST-elevation. Implement the above in SIMULINK for feasibility demonstration.

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System block diagramSystem block diagramBiosensors

A/D

DWT algorithm fordetection of ECG characteristic points

Detection ofST-Elevation

ST-Elevationalert

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Background on waveletsBackground on waveletsFourier Transform (FT)Fourier Transform (FT)

Break down a signal into constituent sinusoids ofdifferent frequencies.Transform the view of the signal from time-base to frequency-base.

Source: Wavelet applications using MATLAB toolbox, SIPL.

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Background on waveletsBackground on waveletsShort Time Fourier Transform (STFT)Short Time Fourier Transform (STFT)

Analyze a small section of a signal, based on FT and using windowing.STFT maps a signal into a two-dimensional function of time and frequency.

Source: Wavelet applications using MATLAB toolbox, SIPL.

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Background on waveletsBackground on waveletsWavelet Transform (WT)Wavelet Transform (WT)

STFT with variable size window.Long time intervals when low frequency information is needed.Short time intervals when high frequency information is needed.

Source: Wavelet applications using MATLAB toolbox, SIPL.

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Wavelet main advantageWavelet main advantageLOCAL ANALYSIS

Sinusoid with a small discontinuity

0 2 0 4 0 6 0 8 0 1 00- 1

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0

0 .5

1

time

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20 40 60 80 100

Wavelet coefficients

Wavelet transform can help to detect Wavelet transform can help to detect signal discontinuities !!signal discontinuities !!

time

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c

a

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e

0 10 20 30 40 50 60 70 80 90 1000

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Fourier coefficients

frequency

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DWT and FilterDWT and Filter--BankBankCWT is continues in two means: Scale/frequency. Time shift (position).

CWT is very hard for implementation by hardware.Discrete Wavelet Transform (DWT) chooses only a subset of scales and positions, based on power of two (dyadic choice).Mallat was the first to implement DWT by two channel subband coder (filter bank).Filter bank can be easily implemented by hardware.

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DWT and FilterDWT and Filter--BankBankMallatMallatss fast implementation for DWTfast implementation for DWT

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Detection of ECG Characteristic points with DWT

Algorithm is based on the article:Detection of ECG characteristic points

using wavelet transform (1995)

The article uses a CWT algorithm and implements it on a 486-DX33 PC with C-language.

Based on Mallats work we develop a system that implements the detection algorithm with DWT.

1919Source: Estimation of QRS complex power spectra for design of a QRS filter,

IEEE Transaction of biomedical engineering, Nov. 1984

Power spectrum of QRS complex, P- and T-waves

QRS complex can be separated from otherinterfering signals

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SIMULINK implementation

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SIMULINK implementationFilter bank outputFilter bank output

Time [sec]4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5

-0.5

0

0.5

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1.5R

TP

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ECG originalsignal

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ECG approx.

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SummaryDWT algorithm for ECG characteristic points detection was presented.

Algorithm is implemented with filter-bank.

Detection of ECG characteristic points is a crucial stage before calculating ST-elevation.

Project involves utilization of sophisticate signal processing algorithm for medical problem.

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Questions?Questions?

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ECG is a representation of an electrical activitycreated by depolarization and repolarization of the

atria and ventricles

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Existed solutions for Existed solutions for heart monitoring & heart attack alertheart monitoring & heart attack alert

Holter heart monitorContinuous recording of heart rhythm during normal Continuous recording of heart rhythm during normal activity.activity.HolterHolter monitoring is used monitoring is used to determine how the to determine how the heart responds to normal heart responds to normal activity.activity.

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Heart rate monitoring for sport activities

Heart rate gives a precise measurement of exercise intensity.Very common with professional athletes and amateurs.

Source: Polar Electro.

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Triage Cardiac PanelTriage Cardiac PanelDiagnosis of heart attack based on blood test.Results delivered in approximately 15 minutes.

Source: Biosite inc.

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Automated External Defibrillator Automated External Defibrillator (AED)(AED)

Jump-start a heart that has stopped beating, almost always due to a heart attack.The machine won't give a shock unless it detects that a person's heart has stopped beating and is just fluttering.

Source: Philips HeartStart Defibrillators.

Personal HeartAttack DetectorDid you know?ECG waveformECG waveformHeart attack & ST-ElevationProject objectiveSystem block diagramBackground on waveletsBackground on waveletsBackground on waveletsDWT and Filter-BankDWT and Filter-BankDetection of ECG Characteristic points with DWTSIMULINK implementationSIMULINK implementationSummaryQuestions?Existed solutions for heart monitoring & heart attack alert