Dr. Gari D. Clifford, University Lecturer & Associate Director,

1. The Electrocardiogram: Etiology, Acquisition, Transmission and Storage Lab 1 – Acquiring your own ECGGari Clifford, PhD Dr. Gari D. Clifford, University Lecturer & Associate Director, Centre for Doctoral Training in Healthcare Innovation Institute of Biomedical Engineering, University of Oxford

2. The surface ECG How do we record it? mV potential difference changes across torso Place electrodes on skin with good impedance matching … And amplify the difference

3. Recording the surface ECG (Defib Protect) Isolate Filter Amplify Anti-alias Digitize

4. Static defibrillation protection For use in medical situations, the ECG must be able to recover from a 5kV, 100A impulse (defibrillation) Use large inductors and diodes

5. Isolation Opto-isolators DC-DC converters

6. RF Shielding and Emissions Electromagnetic compatibility (EMC) the ability of a device to function (a) properly in its intended electromagnetic environment, and (b) without introducing excessive EM energy that may interfere with other devices Electromagnetic disturbance (EMD) any EM phenomenon that may degrade the performance of equipment, such as medical devices or any electronic equipment. Examples include power line voltage dips and interruptions, electrical fast transients (EFTs), electromagnetic fields (radiated emissions), electrostatic discharges, and conducted emissions Electromagnetic interference (EMI) degradation of the performance of a piece of equipment, transmission channel, or system (such as medical devices) caused by an electromagnetic disturbance Electrostatic discharge (ESD) the rapid transfer of electrostatic charge between bodies of different electrostatic potential, either in proximity in air (air discharge) or through direct contact (contact discharge) Emissions electromagnetic energy emanating from a device generally falling into two categories: conducted and radiated. Both categories of emission may occur simultaneously, depending on the configuration of the device

7. RF testing

8. Transmission and storage Speed? 15 leads, @ 1kHz, 16 bits = 30 kb/s Data formats – headers, checksums Open/ proprietary? Protocols (HL7) Synchronization between devices, clock drift, network timing, daylight savings Annotations, meta-data Encryption Storage, backup, remote access

9. Choosing electrode placement ... Recall the dipole model: The dipole field due to current flow in a myocardial cell at the advancing front of depolarization. Vm is the transmembrane potential.

10. The Idealized Spherical Torso with the Centrally Located Cardiac Source (Simple dipole model)

11. Excitation of the Heart

12. Excitation of the Heart

13. Clinical Lead Placement Einthoven Limb Leads:

14. Precordial leads

15. 12 Lead ECG

17. The temporal pattern of the heart vector combined with the geometry of the standard frontal plane limb leads.

18. Choosing a lead set Ischemia – at least 5 precordial leads Holter 3 lead VCG EASI Mason-Likar 12 lead diagnostic Derived ECGs -the Dower transform …

19. And now … the lab Record your own ECG – just 2 bipolar leads Examine time domain properties This afternoon (2.30-4.00): Examine spectral properties Filter it Tomorrow afternoon (1-5pm): Build a VF detector (wed & thurs) Build a QRS detector Extract respiration Compare it to the pulse ox

20. And now … the lab Break into 4 groups of 5 (~ per placements) Choose a corner of the room. Connect equipment to each machine in each corner Follow instructions on handout: Turn on the equipment, connect it and make sure it is working – make a noise recording (square wave) Load it into Matlab and check! Choose a (first) volunteer from your group Prep the electrode areas Attach and look for characteristic pattern Follow questions and make notes!

21. Skin preparation Shave off hair Abrade skin (to remove dead skin and improve conductivity) Clean with alcohol Wait for alcohol to evaporate Place electrode patches on clinical locations

22. Connecting yourself up Lead I = ch 1 : brown +ve (Left Arm ), red -ve (Right Arm),  Lead II = ch 2 : black +ve (Left Leg) , white (Right Arm) -veCommon = Earth : green (Right Leg) - just above right hip Standard 5 lead connection box

23. Questions? http://www.robots.ox.ac.uk/~gari/cdt/teaching

24. References Physiology:Reisner A., Clifford G.D. and Mark, R.G. The Physiological Basis of the Electrocardiogram Ch1 in: Clifford G.D., Azuaje, F., McSharry P.E. (Eds): Advanced Methods and Tools for ECG Analysis. Artech House Publishing, October 2006. Online at: http://www.mit.edu/~gari/ecgbook/ch1.pdf Hardware: Clifford G.D. and Oefinger M.B. ECG acquisition, storage, transmission and representation. Ch2 in: Clifford G.D., Azuaje, F., McSharry P.E. (Eds): Advanced Methods and Tools for ECG Analysis. Artech House Publishing, October 2006. Online at - http://www.mit.edu/~gari/ecgbook/ch2.pdf ECG lead systems: Jaakko Malmivuo & Robert Plonsey: Bioelectromagnetism - Principles and Applications of Bioelectric and Biomagnetic Fields, Oxford University Press, New York, 1995. Ch15 and Ch16. Online at http://www.bem.fi/book/15/15.htmhttp://www.bem.fi/book/16/16.htm Regulations FDA, 21 CFR Part 11, "Electronic Records; Electronic Signatures; Final Rule." Federal Register Vol. 62, No. 54, 13429, March 20, 1997. FDA, Compliance Program Guidance Manual, "Compliance Program 7348.810 – Bioresearch Monitoring - Sponsors, Contract Research Organizations and Monitors," February 21, 2001. FDA, Compliance Program Guidance Manual, "Compliance Program 7348.811 - Bioresearch Monitoring - Clinical Investigators," September 30, 2000. FDA, Good Clinical Practice VICH GL9. FDA, Guideline for the Monitoring of Clinical Investigations. FDA, Information Sheets for Institutional Review Boards and Clinical Investigators. http://www.fda.gov/ic/ohrt/irbs/default.htm FDA, E6 Good Clinical Practice: Consolidated Guidance. http://www.fda.gov/cder/guidance/959fnl.pdf. FDA, Part 11, Electronic Records; Electronic Signatures — Scope and Application, 2003. FDA, General Principles of Software Validation; Guidance for Industry and FDA Staff.

25. Understanding the ECG: A Cautionary Note Basic cell electrophysiology, wavefront propagation model, dipole model: Powerful, but incomplete There will always be electrophysiologic phenomena which will not conform with these explanatory models Near-field effects Examples: Localised ischemia metabolic disturbances anti-arrhythmic medications need for 12-lead ECG to record a 3-D phenomenon (spatially over-sample)

26. Normal features of the electrocardiogram.