Concepts of Cardiac Monitoring

Question 1

Cardiac Cycle

Electrical

Answer 1

Depolarization
Repolarization

Question 2

Depolarization

Answer 2

electrical activation of cell caused by influx of sodiuminto cell while potassium exits cell

Question 3

Repolarization

Answer 3

return of cell to resting state caused by re-entry of potassium into cell while sodium exits

Question 4

Refractory Periods

Answer 4

Effective refractory period: phase in which cells are incapable of depolarizing
Relative refractory period: phase in which cells require stronger-than-norm stim to depolarize

Question 5

Normal Conduction System

SA node

Answer 5

Primary pacemaker
Location: near superior vena cava in R. Atrium
Adults: Impulse formation at a rate of 60-100

childs vary with age

Question 6

AV node

Answer 6

Slows the electrical impulse in atrial
Allow time for atria to ctxs and fill the ventricles before ventricles ctxs
Gatekeeper: prevents excess number of impulse from reaching the vent.
Can generate impulse at a rate of 40-60/ min if the SA node fails

Question 7

contin

Answer 7

• The impulse travels rapidly through the Bundle of His (just beneath the AV node)
• To the right and left bundle branches (the main highways to the ventricles)
• Then the impulse is propelled through the Purkinje fibers located in the ventricular muscle
• Left divides into anterior & posterior branches
• Purkinje fibers can generate impulses if higher pacemakers fail (20-40/minute)
• Finally, the impulse arrives at the ventricle itself, causing it to depolarize

Question 8

Electrophysiology

Answer 8

Electrical activity of the heart

Question 9

What is a Lead?

Answer 9

View of the heart, not a physical wire

record activity in the frontal plane

• Leads can be either unipolar or bipolar.
• Chest leads are unipolar, meaning they have one positive electrode looking at the heart
• Limb leads are bipolar, meaning that they have both a negative and positive electrode, either three or five electrode cables are needed for a bipolar system.
• Standard leads are the limb leads

Question 10

Standard Limb Leads

Answer 10

Lead I, II, III
Bipolar leads
positive + and neg - pole

Question 11

Augmented Limbs Leads

Answer 11

Unipolar
(aVR), (aVL), (aVF)
* A means augmented; leads produce small complexes that must be augmented or enlarged
* V means voltage
* R=Right arm, L=Left arm,** F**= Left foot where the (+) electrode is placed

Question 12

Precordial Leads (6)

Answer 12

Positioned on the chest wall directly over the heart
V1, V2, V3, V4, V5, V6
View of heart from horizontal plane vs frontal plane
Unipolar leads
Positioning is cruical accurate dx

Question 13

Cable Connections and Locations

Answer 13

White (R.arm)
Black (L.arm)
Red (L.leg)
Green (R.leg)
Brown (Chest)

Question 14

12 Lead EGC?

Answer 14

Look at more views of the heart