EKG

P Wave

○ Movement of the electrical

activity through the upper

heart chambers (atria)

○ Atrial depolarization

○ Leads to atrial contraction

QRS Complex

Movement of electrical impulses

through the lower chambers of

the heart (ventricles)

○ Ventricular depolarization

○ Results in ventricular

contraction

○ Atrial repolarization occurs but it

is not seen

T Wave

Small, upward sloping

curve

○ Period when ventricles are

relaxing electrically and

preparing for next contraction

○ Ventricular repolarization

U Wave

Small, upward curve

● Repolarization of the

Bundle of His and Purkinje

fibers

● Not always seen

PR interval

○ P wave and baseline prior to

QRS complex

● Beginning of atrial

depolarization to beginning of

ventricular depolarization

● PR interval is 0.12 to 0.20

seconds

QT Interval

Includes the QRS complex, the

ST segment, and the T wave

● Period of time from start of

ventricular depolarization to

the end of ventricular

repolarization

● 0.4 to 0.44 seconds

ST Segment

Straight, level line from end of

QRS complex to the beginning

of the T wave

● Time between ventricular

depolarization and the

beginning of ventricular

repolarization

○ Elevated/lowered may mean

muscle damage or ischemia

Alternating Current (AC) Interference

○ Tracing line jagged, series of uniform, small spikes

○ Causes by interference from electrical equipment

Somatic Interference

○ Muscle movement

○ May need to move electrodes closer (thighs/shoulders) to reduce

interference

Flatline

○ Loose or disconnected wire

○ Lead wires may be switched

○ Is the pt in cardiac arrest????

Wandering baseline

○ Shift in the baseline from the center

position for that lead

○ Causes

■ Inadequately warmed stylus

■ Electrodes too loose or

incorrectly placed

■ Tension on electrodes

■ Inadequate electrolyte

■ Presence of creams/lotion on skin

Artifact

Causes

○ Improper technique

○ Poor conduction

○ Outside interference

○ Improper handling of the

tracing

V1

4 th intercostal, Right of sternum

○ This guides all other electrodes

● V2

4 th intercostal, Left of sternum

V4

5 th intercostal, Midclavicular line

V3

5 th intercostal, Place halfway between

V2,V4

V6

5 th intercostal, Midaxillary line

V5

5 th intercostal, Halfway between V4,V6

(anterior axillary line

Unipolar leads

aVR, aVL, aVF

Bipolar Leads

I, II, III

Ground

RL Lead

What is the standard speed for adults

25 mm/sec

10 times method

Count # QRS complex in 6

sec (30 large boxes) and

multiply by 10

1500 method

Count the # of small boxes

between 2 R-R intervals

○ Divide this number into

1500

These 10 electrodes evaluate 12

different pathways of the heart’s

electrical activity

True

A resting cardiac cell is

polarized - Meaning the cell has a negative

charge on the inside and a positive

charge on the outside

Depolarization

When the cardiac cell loses its

polarity

○ Electrical impulse that initiates a

chain reaction(action potential)

resulting in contraction

Repolarizatio

A period of electrical recovery when

polarity is restored

○ The heart returns to a resting,

polarized state

Electrical impulse flows from SA

node to ventricles

Detected by electrodes

○ Detects disruptions or disturbances

in heart’s rhythm

Alert Clinician Immediately

Ventricular Fibrillation

 Ventricular Tachycardia

 Supraventricular Tachycardia

 Myocardial infarction

 Asystole

Exercise Electrocardiography

Stress Test

Ambulatory Electrocardiography 1

Holter Monitoring 1

Holter Monitor

Electrocardiography device

worn for a 24-hour period of

normal activity

30 Day event monito

Pt wears for 30 days

■ EKG constantly records

■ Pt logs activities performed

and any sxs experienced

■ Pt pushes button on

machine to mark EKG when

sxs occur

Electrocardiography

Graphic pattern created from

the electrical impulses

generated within the heart as

it pumps

● A “picture” of how the

electrical system is working

why

Evaluate symptoms of heart disease

○ Detect abnormal heart rhythms

○ Evaluate pt’s heart after MI

○ Assess effectiveness or side effects of

certain meds