EKG 4

Question 1

Effect of AP conduction on waveforms

Answer 1

___

Question 2

Effect of AP duration on waveforms

Answer 2

. Purkinje fibers have very long duration APs
. Endocardial APs have longer duration than epicardial APs
. ____

Question 3

A wave of depolarization towards the + electrode of a lead will cause ___ deflection

Answer 3

Positive upward

Question 4

Wave of depolarization moving away from + electrode of a lead will cause a __ deflection

Answer 4

Neg. downward

Question 5

A wave of repolarization moving towards + electrode of a lead Weill cause ____ deflection

Answer 5

Negative downward

Question 6

A wave of repolarization moving away from the + electrode of a lead will cause a ___ deflection

Answer 6

. Positive upward

Question 7

A wave of depolarization or repolarization moving perpendicular to a lead will cause __ deflection

Answer 7

. No net deflection

Question 8

Measured potential at a given location is proportional to ____

Answer 8

((E)(Cos angle))/r^2
. E = potential at the source
. Angle is btw the axis of the dipole and the axis of the lead
.r is distance btw dipole and the measurement site
. Cos 0 degrees = 1
. Cos 90 degrees = 0
. Cos 180 degrees = -1

Question 9

Sum of ____ leads to waveforms we record as an EKG

Answer 9

Instantaneous vectors

Question 10

Vector loops

Answer 10

. Series of vectors that are continuously changing direction and magnitude
. Made up on infinite number of instantaneous vectors

Question 11

Vectors in Einthoven’s Triangle are looking at vectors in what plane?

Answer 11

Frontal plane

Question 12

Net vector

Answer 12

. Vector corresponding to the sum of positive and neg. deflections of the waveform
.

Question 13

Factors for why EKG looks the way it does

Answer 13

. cellular electrical events (APs) which occur at different times in different regions of the heart
. Recording of these events from different angles (vector analysis)