The EKG

Animation – Listen Carefully

• http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_electrical.html

ELECTROCARDIOGRAMEKG (ECG)

Remember: The heart has its own electrical

system.

Do you the know the 4 parts involved?

What is an EKG?

• What is an Electrocardiogram?– A measurement of the electrical activity in the

heart.

• What 4 parts of the heart are used in electrical signal?– Sinoatrial node, atrioventricular node, Bundle

of His, Purkinje Fibers

1. SA - Sinoatrial Node

1.initiates an electrical sequence

2. AV - Atrioventricular Node

3.Purkinje Fibers

4.Bundle of His

ECG• ECG = measurement of electrical activity over time• Measured using electrodes

– Electrical contacts on the skin– Electrodes measure voltage between the electrodes

over time• Can be used to measure abnormal heart rhythms of the

heart– Such as damaged muscle tissue during a myocardial

infraction– Can diagnose irregular heart beat, irregular speed of

contractions, angina (tissue damage), or even tissue death (myocardial infarction).

Electrodes

• Can be placed in different areas to achieve different results/measurements

• Detect the electrical impulse being produced by the heart – detecting the difference between the charges in the

areas where the electrodes are attached– The greater the intensity of the impulse, the greater

the difference in the charges, and the larger the upward or downward peak will appear on the EKG

Can You Label All of the EKG Parts?

http://upload.wikimedia.org/wikipedia/commons/9/9e/SinusRhythmLabels.svg

What Does an EKG Look Like?

R

Q

P = P Wave- Just before atrial contraction

QRS Complex- Impulse causing ventricle

contraction

T= T Wave – Ventricles relax

p

S

T

P Through T = Systolic Pressure

T Through P = Diastolic

Direction of impulse

Table 2

 

Standard Resting Electrocardiogram Interval Times

 

P–R interval 0.12 to 0.20 s

QRS interval less than 0.12 s 

Q–T interval 0.30 to 0.40 s

How is it Measured?

• Heart generates electrical current• At rest…

– Heart muscle is polarized (more positively charged ions on the outside of the heart cells

– More negatively charged ions are inside• Then the positive ions move to the inside of cells and negatively

charged ions move to the outside– The flow of electrons into the cells cause an electrical current– This is called depolarization

• Then the positive ions move back to the outside of the cells and negatively charged ions move back to inside– This is called repolzarization

Current passes through body to skin.

Current can be measured with an electrocardiogram. (EKG,ECG)

Vernier.com

Depolarization and Repolarization

• At rest…– Heart muscle is polarized (more positively charged ions on the

outside of the heart cells– More negatively charged ions are inside

• Then the positive ions move to the inside of cells and negatively charged ions move to the outside– The flow of electrons out of the cells cause an electrical current– This is called depolarization

• Then the positive ions move back to the outside of the cells and negatively charged ions move back to inside– This is called repolarization

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--

-

+

+

+

+

+

Depolarization

+

+

+

+

+

-

-

-

-

-

Heart Cells Cause Muscle Contraction

Repolarization

Common Issues

• P Wave Absent– Lack of normal depolarization of the atria

• QRS Complex Absent– indicates the electrical impulse was blocked

before it reached the ventricles• Abnormally shaped complexes

– abnormal spread of the impulse through the muscle tissue, such as in myocardial infarction• pulse cannot follow its normal pathway because

of tissue death or injury

What does all of this mean?• P wave

– Atrium contract/depolarize– Blood flows through atrium into ventricles– SA node sends signal to AV node

• Q– Atrium relax/repolarize

• R– Left Ventricle contract/depolarize– AV node sends signal to Purkinje fibers

• S– Right Ventricle contract/depolarize– AV nodes sends signal to Purkinje fibers

• T wave– Ventricles relax/repolarize

Excel Results for EKG

  Time (seconds)  

Test Subject P Wave (start) Q R S T Wave (end) P-R Interval QRS Complex Q-T Complex Heart Rate (BPM)

Walters 1                  

Walters 2                  

Walters 3                  

Myocardial Infarction

EKG in LabView

Quiz Question 1

• What is the main item that neutrophils attack in the body?a) Bacteria

b) Viruses

c) Allergies

d) Cancer

Quiz Question 2

• The white blood cell count in the body is normally _____.a) 1,000 to 2,000

b) 4,000 to 10,000

c) 15,000 to 20,000

d) 95,000 to 100,000

Quiz Question 3

• The systolic phase of an EKG begins at _____.a) P

b) Q

c) R

d) S

e) T

Quiz Question 4

• The R point corresponds with ______.a) Atrium contraction

b) Left Ventricle contraction

c) Right Ventricle contraction

d) Ventricular relaxation

Quiz Question 5

• The T wave corresponds with ______.a) Atrium contraction

b) Left Ventricle contraction

c) Right Ventricle contraction

d) Ventricular relaxation