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Heart Activity Measurements

Heart Activity Measurements Edit Varga Heart Activity Measurements Pulse rate ECG/EKG – electrocardiogram Impedance cardiogram, IKG -- impedance cardiography EchoKG – echocardiogram Magnetocardiography (MCG) Artery’s pulsation Heart Activity Measurements Pulse rate

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Heart Activity Measurements

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  1. Heart Activity Measurements Edit Varga

  2. Heart Activity Measurements • Pulse rate • ECG/EKG – electrocardiogram • Impedance cardiogram, IKG -- impedance cardiography • EchoKG – echocardiogram • Magnetocardiography (MCG) Heart Activity Measurements

  3. Artery’s pulsation

  4. Heart Activity Measurements • Pulse rate • ECG/EKG – electrocardiogram • Impedance cardiogram, IKG -- impedance cardiography • EchoKG – echocardiogram • Magnetocardiography (MCG) Heart Activity Measurements

  5. EKG/ECG -- electrocardiogram Williem Einthoven: in 1924 Nobel prize ECK -- electrocardiogram

  6. ECK -- electrocardiogram

  7. ATRIUM VENTRICLE ECK -- electrocardiogram

  8. The conduction system of the heart. ECK -- electrocardiogram

  9. Animation of a normal EKG wave ECK -- electrocardiogram

  10. Different waveforms for each of the specialized cells found in the heart ECK -- electrocardiogram

  11. Information from EKG • If the electric or muscular function of the heart is disturbed for some reason, it will affect how the electric signals spread through the heart muscle. ECK -- electrocardiogram

  12. The heart's electrical axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane. Lead I. Lead III. Lead II. ECK -- electrocardiogram

  13. EKG • These three bipolar limb leads roughly form an equilateral triangle (with the heart at the center) that is called Einthoven's triangle in honor of Willem Einthoven who developed the electrocardiogram in 1901. ECK -- electrocardiogram

  14. Different directions during the EKG measurement Negative electrode on the right arm and the positive electrode on the left arm Negative electrode on the right arm and the positive electrode on the left leg. Negative electrode on the left arm and the positive electrode on the left leg. Maximal positive deflection is obtained in lead III when the depolarization wave travels parallel to the axis between the left arm and left leg. ECK -- electrocardiogram

  15. ECK -- electrocardiogram

  16. The realtively small P wave is produced by electrical currents generated just before contraction of the atria EKG Accoustic QRS complex is caused by currents generated in the ventricles during depolarization just prior to venticular contraction. R is the most prominent component of this wave complex. ECK -- electrocardiogram

  17. 160 ms 300 ms 370 ms ECK -- electrocardiogram 830 ms

  18. positive deflection on the ECG negative deflection on the ECG equiphasic complex deflection on the ECG External snap Snap coated with Ag/AgCl Gel soaked sponge Adhesive layer ECK -- electrocardiogram

  19. ECK -- electrocardiogram

  20. The ECG system Instrumentation amplifier, which has a very high CMRR (90dB) (common-mode rejection ratio) and high gain (1000), with power supply +9V and -9V. An opto-coupler to isolate the In-Amp and Output. A transducer AgCl electrode, which convert ECG into electrical voltage. The voltage is in the range of 1 mV ~ 5 mV Bandpass filter of 0.04 Hz to 150 Hz filter. It’s implemented by cascading a low-pass filter and a high pass filter ECK -- electrocardiogram

  21. Heart Activity Measurements • Pulse rate • ECG/EKG – electrocardiogram • Impedance cardiogram, IKG -- impedance cardiography • EchoKG – echocardiogram • Magnetocardiography (MCG) Heart Activity Measurements

  22. Impedance cardiogram Impedance changes Differentiatior Amplifier dZ/dt Z0 value is the total impedance between the two inner leads High-frequency = 40-100 KHz Constant current = 4 mA Impedance cardiogram

  23. Impedance cardiogram R-Z is the time interval from the R wave of the ECG to maximum ejection as indicated by the peak of dZ/dt ventricular ejection time Impedance cardiogram

  24. Part of automated external defibrillator • Investigate circulatory system problems: valve defects, right-left shunting, congestive failure • Impedance of the thorax can be considered to be divided into two parts: • the impedance of both tissue and fluids • the amount and distribution of blood The amount of blood in the thorax changes as a function of the heart cycle. The changes in the distribution of blood in the thorax as a function of the heart cycle can be determined by measuring the impedance changes of the thorax. Band electrodes ECK -- electrocardiogram

  25. Heart Activity Measurements • Pulse rate • ECG/EKG – electrocardiogram • Impedance cardiogram, IKG -- impedance cardiography • EchoKG – echocardiogram • Magnetocardiography (MCG) Heart Activity Measurements

  26. EchoKG Echocardiogram Ultrasound waves: 2.5–18 MHz EchoKG -- Echocardiogram

  27. ECK -- electrocardiogram

  28. EchoKG -- Echocardiogram EchoKG -- Echocardiogram

  29. Transducer EchoKG -- Echocardiogram

  30. 40 kHz Ultrasound receiver A X100 transistor amplifier is followed by a zero cross detector circuit, using a voltage comparator. The output is a TTL logic signal, corresponding to the received 40KHz signal. ECK -- electrocardiogram

  31. Medium Power 40KHz Ultrasound Transducer Driver This crystal controlled circuit drives a 40KHz piezoelectric transducer with a 30v peak to peak signal. ECK -- electrocardiogram

  32. Heart Activity Measurements • Pulse rate • ECG/EKG – electrocardiogram • Impedance cardiogram, IKG -- impedance cardiography • EchoKG – echocardiogram • Magnetocardiography (MCG) Heart Activity Measurements

  33. dc SQUIDs Scanning electron micrograph of the SQUID ring with step-edge Josephson junctions. • Magnetometers based on dc SQUIDs are currently the most sensitive sensors for magnetic fields, achieving a magnetic field resolution which is about a billion times below the earth's magnetic field. • A dc SQUID basically consists of a superconducting ring interrupted by two weak links called Josephson junctions. • SQUID can be viewed as a flux-to-voltage converter. ECK -- electrocardiogram

  34. Noise spectrum of the magnetic field noise in an industrial environment, measured with an unshielded multiloop magnetometer The magnetometer's intrinsic noise level is several orders of magnitude lower. ECK -- electrocardiogram

  35. dc SQUIDs A multiloop SQUID magnetometer. The diameter of this device is 8.5 mm. • The SQUID ring itself is enlarged and it consists of several identical pickup loops, which are connected in parallel to reduce the inductance. The 16 loops are arranged to the cart-wheel like shape of the device. A multilayer technology is needed for the preparation. ECK -- electrocardiogram

  36. Block diagram of a SQUID magnetometer transform the applied flux into a room temperature voltage output senses changes in the external magnetic field and transforms them into an electrical current acquiring, storing analyzing data transforms the resulting current into a magnetic flux in the SQUID sensor ECK -- electrocardiogram

  37. 68-channel dc-SQUID system SQUID maps the axial (BZ) component ECK -- electrocardiogram

  38. Real-time magnetocardiogram recorded with a multiloop magnetometer. ECK -- electrocardiogram

  39. Magnetocardiography (MCG) • Magnetic field: x, y, z component • Grid measurement • Similar sensitivity to EKG • Higher SNR than EKG Magnetocardiography (MCG)

  40. magnode Solenoid coil Ir = reciprocal current ΦLM = reciprocal magnetic scalar potential field HLM = reciprocal magnetic field BLM = reciprocal magnetic induction field ELM = reciprocal electric field JLM = lead field   VLM = voltage in the lead due to the volume source i in the volume conductor   Magnetocardiography (MCG)

  41. Measurement of the x-component of the magnetic heart vector The general construction of the measurement system Baule-McFee lead system Measurement of the z-component of the magnetic heart vector Measurement of the y-component of the magnetic heart vector Magnetocardiography (MCG)

  42. Unipolar & Bipolar measurement locations on the anterior and posterior sides ECK -- electrocardiogram

  43. Schematic illustration of the generation of the x component of the MCG signal. ECK -- electrocardiogram

  44. Advantages • Insulating barriers such as the skull, varying layers of tissue, anatomical open spaces, do not attenuate or distort magnetic fields. The magnetic permeability of the tissue = free space. Therefore the sensitivity of the MCG is not affected by the high electric resistivity of lung tissue. • different sensitivity distribution with EKG • the magnetic detector is not in contact with the subject • SQUID magnetometer is readily capable of measuring DC signals. Such signals can be obtained electrically only with great difficulty. Magnetocardiography (MCG)

  45. Disadvantages • ECG is easier to use • Technologically more complicated, requires complex and expensive equipment: SQUID magnetometer, liquid helium, and a low-noise environment • Because of the development of the SQUID technology, a shielded room is no longer needed in magnetocardiography. • Future: at the liquid nitrogen temperature which decreases the operational costs Magnetocardiography (MCG)

  46. References • MCG: • http://butler.cc.tut.fi/~malmivuo/bem/bembook/20/20.htm • http://www.kreynet.de/asc/squids.html • EchoKG: • http://www.heartsite.com/html/echocardiogram.html#what_US • http://www.discovercircuits.com/DJ-Circuits/ultra40khzxtr1.htm • EKG • http://en.wikipedia.org/wiki/Electrocardiogram • http://www.ecglibrary.com/ • http://www.americanheart.org/presenter.jhtml?identifier=3005172 • http://www.medmovie.com/mmdatabase/MediaPlayer.aspx?ClientID=68&TopicID=600 • John L. Andreassi: Psychophysiology • http://www.cisl.columbia.edu/kinget_group/student_projects/ECG%20Report/E6001%20ECG%20final%20report.htm

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