Home ECG Test Kit

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Home ECG Test Kit
University of Pittsburgh Senior Design BioE
1160/1161
James Cook Carmen Hayes Joe Konwinski April 18,
2005 Mentor Mingui Sun, PhD
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Problem Statement

• Heart disease
• 2nd leading cause of death
• Number 1 killer of women
• Limitation of Diagnosis
• In 2003, of the 700,000 Americans that died, only
  148,000 were diagnosed
• Individuals remain unaware of the symptoms of
  heart attack or dismiss them

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Introduction

• Develop a small device that can
• Cleanly amplify the electric activity of the
  heart
• Save the amplified signal onto a portable memory
  solution
• Produce a program that can
• Analyze the ECG data and give heart-risk feedback
  to the user
• Be Sold Over-the-Counter
• Be User Friendly and Safe

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Purpose

• Purpose is
• To assess heart risk of seemingly HEALTHY, middle
  to upper aged individuals
• To give a cheaper/ less demanding alternative for
  healthy patients
• Purpose is NOT
• To replace a health professional in assessing
  heart risk of ILL or HEAVY RISK individuals

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• Let Us Be Frank.

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Market

• Whats There
• Marquette MARS PC Holter Monitoring Review
  System--11,500
• Burdick Vision Holter Analysis
• System
• --6,000
• All Marketed Devices are For Use By
• Health Care Professionals

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Market Size

• Based on the 2000 Census, the population of
  both sexes ages 40 was 119,386,252 (42 of
  population).
• Family history
• Hypertension (estimated 28 million adults)
• Obesity (estimated 41 million adults)
• Smoking (estimated 20 million adults)

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Constraints

• Economic
• Time
• Money
• Regulatory
• False positive
• False negative
• Patient misuse

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Project Outline

• Hardware Group
• Develop Miniature ECG Amplifier
• Decide Proper Electrode Placement/Management
• Research Methods on Implementing a Portable
  Memory Solution
• Software Group
• Understand the Mechanism behind ECG diagnoses
• Develop a Computer Algorithm to Interpret
  Imported ECG Signal

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Hardware Development

• Develop a Miniature ECG Amplifier

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Hardware Development

• Development of Miniature ECG Amplifier
• Deciding on Chips
• Bread-Board Model
• PCB development
• Testing PCB model

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Hardware Development

• Deciding on chips
• Size
• Power Consumption

Chip Quiescent current Supply voltage
INA332 450µA 2.7 - 5.5 V
OPA2336 20µA 2.3 - 5.5V
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Hardware Development

• Breadboard PCB

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Hardware Development

• Electrode placement
• Normally has 12 leads, each one takes a picture
  of the heart from a different aspect.

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Hardware Development

• Normal Recording

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Hardware Development

• Einthovens Triangle

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Hardware Development

• Goal Detect P, R, S, and T waves

R
T
P
S
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Hardware Development

• Implementing Portable Memory
• Current Solution
• Microchips PIC18F2455
• 10-bit A/D Converter

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Hardware Development
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Hardware Development
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Hardware Development
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Heart Disease ECG Timing
Clinically, the electrocardiogram is a powerful
tool in diagnosing certain types of heart disease.

• Heart block (1st,2nd,3rd degree)
• Timing irregularity in PR interval
• Bundle branch block
• Long QRS interval
• Arrhythmia
• Heart rate too fast or slow (lt60 gt100 BPM)
• Myocardial Ischemia
• Depressed ST segment

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Software Development
Signal Conditioning

• Moving median filter (nfs) to calculate baseline

• Locate areas of muscle contraction using
  threshold detector (0.4V from baseline)
• Find largest gap of continuous data between
• contractions for use in further analysis
• If largest gap is smaller than 12 sec,
• prompt user to recollect data and to try
• to relax his/her body

• Subtract baseline from data
• Use Butterworth 2nd order lowpass (fl 15 Hz)
  to remove high frequency noise

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Software Development
ECG Analysis

• Peak-detector algorithm locates peaks/valleys in
  the ECG along with their amplitudes and
  derivatives

• K-means cluster analysis locates cluster
  centroids and groups data points with centroids
  to minimize sum of squares

• Heuristics based on derivatives, amplitudes, and
  relative locations of peaks/valleys give each
  cluster a label (i.e. P, Q, R, S, T)
• Need to test at least 40 normal patients before
  this step is complete

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Software Development
User Feedback

• Calculate peak-to-peak timing and important
  slopes of ECG
• Statistical analysis calculates a percent risk
  of each disease and, by weighting each disease, a
  total risk of disease

• User is given feedback consisting of
• Type Subtype Risk
  Weight
• Heart Block 1st degree 92 2
• 1st degree heart block is caused byIt results
  inIt is usually treated by
• 2nd degree 10 5
• 2nd degree heart block
• 3rd degree 0.2 40
• 3rd degree heart block
• TOTAL RISK 11

1st degree heart block is diagnosed when the PR
interval is greater than 0.2 seconds
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Criteria for Success
Completing

• Design of on-chest ECG hardware
• Ability to detect peak-to-peak time intervals
  programmatically

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Successes

• Nearing completion of the computer program
• Developed a miniature ECG amplifier
• Verified that signal peaks can be detected with
  chest-mounted electrodes

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Future Work

• Finish computer program
• Design and implement flash memory storage
• Create a working prototype

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Acknowledgements

• Dr. Mingui Sun
• Dr. Marc Simon
• Drs. Hal Wrigley and Linda Baker for their
  generous donation

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Questions?