Week 09 ECG Lab

Question 1

What does the tangential of an electric field line indicate?

What does the density of a field lines indicate?

Answer 1

tangential indicates direction of field at that point

density indicates strength of the field

Question 2

What are the 6 main events whose electrical vectors show up on an ECG and what direction/magnitude are their vectors?

Which important event is electrically overshadowed by another, larger simultaneous event?

Answer 2

• see image below
• atrial repolarization is overshadowed by ventricular depolarization

Question 3

The direction of the vector of a certain ECG wave must be flipped.

Which one and why?

Answer 3

• the **T wave **vector’s direction is upward and to the left, corresponding with the apex > base movement of the ventricular polarization
• this vector must be flipped downward and to the right, because it is a repolarization (or movement of negative, rather than positive, charge)

Question 4

What are the important parts of an ECG wave and what physiological events do they correspond to?

Answer 4

• P Wave - atrial depolarization
• QRS Complex - ventricular depolarization
  
  • Q Wave - septal depolarization
  • R Wave - major “downward” ventricular depol.
  • S Wave - slight “upward” vent. margin depol.​
• T Wave - ventricular repolarization

Question 5

What is an active electrode?

Answer 5

an electrode whose potential **changes continuously **during the cardiac cycle

Question 6

What is an inactive electrode?

Answer 6

an electrode in contact with the body whose potential is practically constant

Question 7

What is a unipolar lead?

Answer 7

reads potential difference between active and inactive electrodes

Question 8

What is a bipolar lead?

Answer 8

records potential difference between two active electrodes

Question 9

What do the verteces of an einthoven triangle represent?

The sides?

Answer 9

verteces - limb electrodes

sides - limb leads I - III

(base is I, left is II, right is III)

Question 10

What is an integral vector?

Answer 10

the spatial dipole vector representing the electric field of the heart

(often used to refer to the frontal projection of the vector seen in einthoven’s triangle)

Question 11

What is the electrical axis of the heart?

Answer 11

the integral vector constructed from the largest deflection of the R wave

Question 12

What are the leads in einthovens triangle?

What do they connect?

Answer 12

bipolar leads in the frontal plane

I - right arm to left arm

II - left foot to right arm

III - left foot to left arm

Question 13

What are Wilson’s chest leads?

Answer 13

V1 - V6

six unipolar leads in the horizontal plane which use electrodes placed along the chest from the sternum leftward

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Question 14

What are Goldberger’s leads?

Answer 14

**unipolar **leads located in the frontal plane

• electrodes labeled aVR, aVL, aVF for right, left, and foot

Question 15

What is vectorcardiography?

Answer 15

recording of the change of the integral vector in 3D space