12/8/2014 Medical Physiology Cardiac Electrophysiology II Eric Olson

Question 1

A positive and negative electrode pair constitutes:

Answer 1

A single lead. A single lead measures the voltage difference between two electrodes.

Question 2

In physiology, the flow of what ions is considered a positive current?

Answer 2

Positive ions

Question 3

Te first part of the EKG is called:

Answer 3

the P wave

Question 4

The P wave is produced by:

Answer 4

the depolarization of the atria.

Question 5

When the atrial depolarization reached the AV node, the AV node depolarizes slowly. Is this event represented on the EKG?

Answer 5

Yes, by a pause before the QRS complex.

Question 6

What actions in the heartbeat make up the QRS complex?

Answer 6

Depolarization of the bundle of His to the left and right bundle branches and Purkinje fibers (ventricular contraction)

Question 7

The repolarization of the ventricles produces what on the EKG?

Answer 7

T wave

Question 8

What extra wave is produced in about 50% of people?

Answer 8

The U wave

Question 9

In EKG, 5 mm along the time axis = how long?

Answer 9

0.2s

Question 10

In EKG 5 mm along the voltage axis = ?

Answer 10

0.5 mV

Question 11

What is the QT interval?

Answer 11

The period from the beginning of the QRS complex to the end of the T wave.

Question 12

T/F: The T wave is a positive deflection on the EKG.

Answer 12

True, despite that it’s the repolarization event.

Question 13

What pathology can invert the T wave?

Answer 13

Ischemia

Question 14

What pathology can disrupt the T wave?

Answer 14

Potassium channel blockade

Question 15

T/F: Depending on the placement of the leads, the QRS complex will be the different for the same heartbeat.

Answer 15

True

Question 16

What placement of the electrodes would produce an isoelectric QRS wave?

Answer 16

Electrode is orthagonal to wave travel (depolarization passes from left to right)

Question 17

What does orthagonal mean w/r/t EKG and lead placement?

Answer 17

“At a right angle to” meaning that isolelectric EKG traces

Question 18

A depolarization wave traveling in the direction of the lead towards the positive end produces a _____ signal on the EKG.

Answer 18

positive

Question 19

What does aVR stand for?

Answer 19

Augmented voltage right

Question 20

aVL is what lead?

Answer 20

Augmented voltage left

Question 21

aVF is what lead?

Answer 21

Augmented voltage foot

Question 22

The aV leads are sometimes called:

Answer 22

unipolar leads

Question 23

The largest QRS complex is normally detected between what degrees?

Answer 23

-30 and 0

Question 24

Between 0 and 90 degrees is called:

Answer 24

the primary axis

Question 25

If both aVF and lead I show a positive QRS complex, then the axis is:

Answer 25

Normal

Question 26

A QRS axis that shows lead I is positive, but aVF is negative, what pathology is suggested?

Answer 26

LV hypertrophy

Left anterior fascicular block

Question 27

A QRS axis that shows a negative aVF and negative lead I are seen when?

Answer 27

Never, this is “no man’s land.”

Question 28

A QRS axis that shows a negative lead I and positive aVF suggest what pathology?

Answer 28

RV hypertrophy

Left posterior fascicular block

Question 29

What are the six chest leads on the EKG?

Answer 29

V1-V6