Cardiac Monitors

Question 1

Order of the electrical system of the heart

Answer 1

SA node
Internodal Tracts
AV node
Bundle of His
Bundle Branches
Purkinje fibers

Question 2

List the Internodal Tracts that travel from the SA node to the AV node

Answer 2

Anterior internodal tract
Middle internodal tract (Wenckebach tract)
Posterior internodal tract (Thorel tract)

Question 3

What is the conduction velocity?

Answer 3

Quantifies how fast an electrochemical impulse propagates along a neural pathway

Question 4

What is the conduction velocity of the SA and AV nodes?

Answer 4

0.02-0.1 m/sec (slow conduction)

Question 5

What is the conduction velocity of myocardial muscle cells?

Answer 5

0.3-1 m/sec (intermediate conduction)

Question 6

What is the conduction velocity of His bundle, bundle branches, and Purkinje fibers?

Answer 6

1-4 m/sec (fast conduction)

Question 7

Conduction velocity is a function of:

Answer 7

1. Resting membrane potential
2. Amplitude of the action potential
3. Rate of change in membrane potential during phase 0

Question 7

Conduction velocity is affected by:

Answer 7

ANS tone
Hyperkalemia induced closure of fast Na channels
ischemia
acidosis
antiarrhythmic drugs

Question 8

The AV node is the only _____

Answer 8

electrical pathway between the cardiac chambers
Think of the AV node as the “gatekeeper” of electrical transmission between the atria and the ventricles

Question 9

James fiber is an ____ and connects ____

Answer 9

Accessory pathway
Connects atrium to AV node

Question 10

Atrio-hisian fiber is an ____ and connects ____

Answer 10

Accessory pathway
Connects atrium to His bundle

Question 11

Kent’s bundle is an ____ and connects ____

Answer 11

Accessory pathway
Connects atrium to ventricle

Question 12

Mahaim bundle is an ____ and connects ____

Answer 12

Accessory pathway
Connects AV node to ventricle

Question 13

List the conduction velocities of the cardiac conduction pathway from slowest to fastest.

Answer 13

AV node, SA node, myocardial muscle cells, His Bundle, Bundle branches, Purkinje fibers

Question 14

Phase 0

Answer 14

Event: Depolarization
Ion Movement: Na moves in
Key EKG Events: QRS

Question 15

Phase 1

Answer 15

Event: Initial Repolarization
Ion Movement: Chloride in and Potassium out
Key EKG Events: QRS

Question 16

Phase 2

Answer 16

Event: Plateau
Ion Movement: Calcium moves in and Potassium moves out
Key EKG Events: ST segment

Question 17

Phase 3

Answer 17

Event: Final Repolarization
Ion Movement: Potassium moves out
Key EKG Events: T wave

Question 18

Phase 4

Answer 18

Event: Resting phase
Ion Movement: Potassium leak
Key EKG Events: End of T wave to next QRS

Question 19

The absolute refractory period means ___

Answer 19

that no stimulus (no matter how strong) can depolarize the myocyte

Question 20

The relative refractory period means ____

Answer 20

that a larger than normal stimulus is required to depolarize the myocyte

Question 21

P wave (electrical event)

Answer 21

depolarization begins in the atria

Question 22

PR interval (electrical event)

Answer 22

depolarization complete in the atria

Question 23

QRS (electrical event)

Answer 23

repolarization of atria
depolarization begins in the ventricle

Question 24

ST segment (electrical event)

Answer 24

Depolarization is complete in the ventricle

Question 25

T wave (electrical event)

Answer 25

Repolarization begins in the ventricle

Question 26

After the T wave (electrical event)

Answer 26

Repolarization is complete in the ventricle

Question 27

Biphasic P waves (lead II) suggest ___

Answer 27

LA enlargement (think mitral stenosis)

Question 28

Tall P waves suggest ___

Answer 28

RA enlargement (think about cor pulmonale)

Question 29

the PR interval would be prolonged with ___

Answer 29

1st degree heart block

Question 30

PR interval depression suggests ___

Answer 30

viral pericarditis atrial infarction

Question 31

P wave and PR internal duration

Answer 31

P wave: 0.08-0.12 second PR internal: 0.12-0.2 second

Question 32

Q wave and QRS complex duration

Answer 32

Q wave: <0.04 second QRS complex: <0.1 second

Question 33

What abnormality in the Q wave would make you think about an MI?

Answer 33

If the amplitude is greater than a third of the R wave If the duration is greater than 0.04 seconds If the depth is greater than 1mm

Question 34

If the QRS complex is increased, consider:

Answer 34

LCH, bundle branch block, ectopic beat, WPW

Question 35

Normal QTc interval

Answer 35

In women: < 0.47 seconds In men: < 0.45 seconds

Question 36

If the ST segment elevation or depression is greater than 1 mm, consider:

Answer 36

1) MI but can also be caused by hyperkalemia or endocarditis

Question 37

Usually, the T wave points ______

Answer 37

in the same direction as the QRS complex

Question 38

The T wave points in the opposite direction of the QRS if ________

Answer 38

repolarization is prolonged by: - myocardial ischemia - bundle branch block

Question 39

Peaked T waves are caused by ___

Answer 39

myocardial ischemia, LVH, or an intracranial bleed

Question 40

The U wave is _____

Answer 40

Usually absent. If it is > 1.5 mm, then consider hypokalemia

Question 41

The Osborn wave is ___

Answer 41

Usually absent. It is a small positive deflection immediately after the QRS complex (At the beginning of the ST segment) and may occur with hypothermia.

Question 42

Where do you measure ST changes from?

Answer 42

The PR segment because it is an isoelectric line *As a general rule, changes greater than +1 or -1 are significant

Question 43

The J point is ____

Answer 43

where the QRS complex ends and the ST segment begins

Question 44

List the EKG changes seen with hyperkalemia (in order of early to late)

Answer 44

Narrow and peaked T waves Short QT Wide QRS Low P amplitude Wide PR Nodal Block Sine wave fusion of QRS and T which leads to VF or asystole

Question 45

EKG changes with hypokalemia

Answer 45

U wave ST depression Flat T wave Long QT interval

Question 46

EKG changes with hypercalcemia

Answer 46

Short QT

Question 47

EKG changes with hypocalcemia

Answer 47

Long QT

Question 48

EKG changes with hypermagnesemia

Answer 48

Not significant unless VERY HIGH: heart block or cardiac arrest

Question 49

EKG changes with hypomagnesemia

Answer 49

Not significant unless very low: Long QT

Question 50

A positive deflection occurs when ___

Answer 50

the vector of depolarization travels toward the positive electrode

Question 51

A negative deflection occurs when ___

Answer 51

the vector of depolarization travels away from the positive electrode

Question 52

A biphasic deflection occurs when ____

Answer 52

the vector of depolarization travels perpendicular to the positive electrode