I&M #2 exam review

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I&M #2 exam review
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2013-03-29 10:04:07
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I&M review #2
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  1. What are three common solutions to prevent baseline offset of ECG caused by the halfcell potential created between an electrode and skin?
    1. Use a differential input dc amplifier so that the effects of two halfcell potentials (one from each electrode) are canceled out.

    2. Use an ac coupled amplifier so that the DC voltage is blocked.
  2. With an ECG, what is the most common cause of artifact signal?  How can this be prevented?
    • electrode slippage
    • use a rough surface electrode (like BIS)
  3. Differential amplifier
  4. diff amp- AC COUPLED
  5. Explain this graph
    Transmembrane potential occurs  slightly before muscle contraction
  6. The INTERFERENCE THEORY states that the ECG is the result of _________ and _________ summation of electrical activity of the _____ as seen by the electrode placed external to the _________ cells of the ______________.
    • temporal
    • spatial
    • heart
    • depolarizing
    • myocardium
  7. Explain the dipole theory (ECG)
    separation of charge creates moving current?  depolarization can be seen as a dipole
  8. Equipotential lines:  True or false: current and potential lines do not exist the limbs? 
    The limbs act as a ___________.
    • TRUE
    • Resistor
  9. Myocardial electrical activity: 
    1) Vector length is the ________ of the gradient.
    2) Vector __________ indicates anatomic pathway.
    • magnitude
    • direction
  10. ID structure (all names) and charges
    triaxial reference system (einthoven's triangle rearranged)
  11. ID part of contraction including wave and area for all 3 leads
    • Atrial Depol
    • I- P
    • II- P
    • III- P
  12. ID part of contraction including wave and area for all 3 leads
    • Septal Depol
    • I- Q
    • II- Q
    • III- R
  13. ID part of contraction including wave and area for all 3 leads
    • Apical Depolarization
    • I- R
    • II- R
    • II- R
  14. ID part of contraction including wave and area for all 3 leads
    • L Ventricular Depolarization
    • I- R
    • II- R
    • III- S
  15. ID part of contraction including wave and area for all 3 leads
    • Late L ventricular depolarization
    • I- R
    • II - R
    • III- S
  16. ID part of contraction including wave and area for all 3 leads
    Complete depol or repol (looks same for both)
  17. ID part of contraction including wave and area for all 3 leads
    • Ventricular repolarization
    • I- T
    • II- T
    • III- T
  18. What is the acquisition axis?
    leads 1,2,3
  19. When making a diagnosis, ECG leads should ______ the heart, to get a proper reading.
    Encase
  20. Define Einthoven's Law, explain reasoning.
    • II = I + III
    • potential of any wave in lead II equals sum of I and III.
    • This comes from Kirchhoff's law, voltages around loop must equal zero.
  21. Augmented vector leads are also called ___________ leads.  They show a ___% increase in voltage (over vector leads).  This is accomplished but using the sum of the vector leads, and another electrode.
    • UNIPOLAR
    • 50%
    • This is accomplished but using the sum of the vector leads, and another electrode.
  22. AVR vector points toward ____
    AVL vector points toward ____
    AVF vector points toward ______
    • RA
    • LA
    • Feet
  23. The reference system that includes the vector leads (triaxial) plus augmented leads is the:
    Hexaxial system
  24. The precordial leads are also called the _________ leads.  They form a vector on the ________ plane.
    • Unipolar
    • Transverse
  25. Name the proper placements of the following leads: V1
    V1- 4th intercostal, right of sternal margin
  26. Name the proper placements of the following leads: V2
    V2- 4th intercostal, left of sternal margin
  27. Name the proper placements of the following leads: V3
    V3- btw  V2 and V4
  28. Name the proper placements of the following leads: V4
    V4- 5th intercostal space @ midclavicular line
  29. Name the proper placements of the following leads: V5
    V5- fifth intercostal space @ anterior axillary line
  30. Name the proper placements of the following leads: V6
    V6- 5th intercostal space, midaxillary line
  31. Modified bipolar limb leads, select lead ___ on screen.
    I
  32. Name the modified limb leads:
    • CS5- LA in V5, RA Central Subclavian
    • modifications:  Ra at Central Manubrium (CM5), Central Back (CB5), Central Chest (CC5).
    • MCL- choose lead III, LA central subclavian, RA r sternal margin.
  33. What it is the EASI electrode system.
    Set placement, algorithms create 12 lead ECG readings
  34. the cardiac vector is the _______ ___ complex.
    mean QRS
  35. Normal wave falls within -30 to ___ degrees on axis.  Name other deviations:
  36. Name the time of normal segements and complexes.
  37. name the following waves
    • 1- Q
    • 2- R
    • 3- S
    • 4- QS
  38. The normal range of the electric axis lies between ____ and ____ in the frontal plane

    between ____ and _____ in the transverse plane.
    • -30° and +90°
    • +30° and -30°
  39. the square form at the beginning of ECG graph is the _________ ________.
    calibration signal
  40. Differential amp output equation
    a(B-A)
  41. What is a Common Mode Signal?
    • A signal that is present everywhere on the body that the differential amplifier
    • will see at both input terminals simultaneously.

    E.G. 60 hz signal from power
  42. Common mode rejection:
    • common mode rejection ratio CMRR (the
    • higher the better).
  43. Why is there a Right Leg Electrode?
    • Reference for amplifier
    • reject common mode
  44. amplitude of ECG waveform
    1 mv
  45. AHA recommends what range for ECG writing
    .05 - 150 Hz (250 for infants)
  46. ST segment monitoring ranges
    .05 - 60 hz
  47. Low Pass filters:
    • permit only low frequencies to pass through.
    • imp for retaining ST segment info, rejects high f interference
  48. High pass filters:
    • reject low f, permit high f to pass
    • remove baseline wandering and half-cell potentials
  49. notch filters
    reject specific signals
  50. if you increase low cutoff frequency this will effect
    ST segment
  51. if you decrease high cutoff frequency this will effect
    R wave amplitude
  52. Ischemia causes inversion of __ wave.  This is due to altered ____________.
    • T
    • repolarization
  53. Sinus Dysrhythmia is ____. explain cause
    Benign, changes slightly with breathing
  54. J point
    point at with electrical signal zero, after QRS

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