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

Problem Statement  Heart disease 2 nd 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

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

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

Let Us Be Frank….

Market What’s 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

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)

Constraints  Economic Time Money  Regulatory False positive False negative Patient misuse

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

Hardware Development Develop a Miniature ECG Amplifier

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

Hardware Development Deciding on chips Size Power Consumption Chip Quiescent currentSupply voltage INA µA V OPA µA V

Hardware Development Breadboard PCB

Hardware Development Electrode placement Normally has 12 leads, each one takes a “picture” of the heart from a different aspect.

Hardware Development Normal Recording

Hardware Development Einthoven’s Triangle

Hardware Development Goal: Detect P, R, S, and T waves P R S T

Hardware Development Implementing Portable Memory Current Solution: Microchip’s PIC18F bit A/D Converter

Hardware Development

Heart Disease & ECG Timing  Heart block (1 st,2 nd,3 rd degree) Timing irregularity in PR interval  Bundle branch block Long QRS interval  Arrhythmia Heart rate too fast or slow ( 100 BPM)  Myocardial Ischemia Depressed ST segment Clinically, the electrocardiogram is a powerful tool in diagnosing certain types of heart disease.

Muscle Contraction Software Development  Moving median filter (n=fs) 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 2 nd order lowpass (f l =15 Hz) to remove high frequency noise Signal Conditioning

Q P, noise R Q, P, noise T S Software Development  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 ECG Analysis  Peak-detector algorithm locates peaks/valleys in the ECG along with their amplitudes and derivatives

Software Development  User is given feedback consisting of: Type Subtype Risk Weight Heart Block1 st degree92%2% 1 st degree heart block is caused by…It results in…It is usually treated by… 2 nd degree10%5% 2 nd degree heart block… 3 rd degree0.2%40% 3 rd degree heart block… … TOTAL RISK11% 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 1 st degree heart block is diagnosed when the PR interval is greater than 0.2 seconds

Criteria for Success  Design of on-chest ECG hardware  Ability to detect peak-to-peak time intervals programmatically Completing:

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

Future Work  Finish computer program  Design and implement flash memory storage  Create a working prototype

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

Questions?