The Electrocardiogram
What is the difference between an electrocardiogram and electrocardiograph?
Electrocardiogram - The actual EKG strip print out
Electrocardiograph - The EKG machine
How many seconds is one large box?
How many seconds is one small box?
One large box - 0.20 seconds
One small box - 0.04 seconds
What does the QRS complex on a cardiac cycle represent?
Represent Atrial Repolarization (Relaxation) & Ventricular Depolarization (Contraction)
What classifies a rhythm as irregular?
When there is a difference of more than 2 small boxes between any r-to-r interval on an EKG strip.
When performing an EKG, what is being viewed?
The electrical activity of the heart
In one cardiac cycle which waveforms represent positive and negative deflections?
Negative - Q, S
What does the T wave represent?
Represent Ventricular Repolarization (Relaxation) & Potassium levels
When looking at step 3, p waves, what are the three things you should be looking for?
1. Are they present?
2. Are they upright and rounded?
3. Is there a P wave for every QRS complex?
What is the placement for each chest lead for a 12-lead EKG?
V1 - 4th intercostal space right
V2 - 4th intercostal space left
V3 - 5th intercostal space between V2 & V4
V4 - 5th intercostal space Mid-clavicular line
V5 - 5th intercostal space Anterior Axillary line
V6 - 5th intercostal Mid-Axillary line
What does the P wave represent?
What is the normal length of a P wave?
Represents - Atrial Depolarization (Contraction)
Normal length - 0.10 seconds
What are the 5 steps to interpreting an EKG strip?
Step 1: Heart Rate
Step 2: Heart Rhythm
Step 3: P waves
Step 4: PR Interval
Step 5: QRS Complex
For steps 3 and 4, PR Interval and QRS complex, what are we measuring and what are there normal values?
PR Interval - From the beginning of the P wave to the beginning of the QRS complex (Q wave); Normal Value - 0.12 - 0.20 seconds
QRS Complex - From the beginning of the Q wave to the end of the S wave; Normal Value - 0.12 seconds or less
What is the color for each chest lead on a 12-lead EKG?
V1 - Red
V2 - Yellow
V3 - Green
V4 - Blue
V5 - Brown or Orange
V6 - Black or Purple
How is the PR interval measured?
What is the length of a normal PR Interval?
PR Interval is measured from the beginning of the P wave to the beginning of the Q wave (QRS complex)
Normal PR Interval: 0.12 - 0.20 seconds
- 6 Second Strip
- R-to-R Method
- Sequence Method
How is the ST Segment measured?
From the end of the QRS complex (S wave) to the beginning of the T wave
Which limbs leads are used to form Einthoven's Triangle, and which lead is used as a ground electrode?
Right arm, Left arm, Left Leg
Ground Electrode - Right leg
What is the length of a normal QRS complex?
QRS complex is measured from the beginning of the Q wave to the end of the S wave
Normal QRS complex - 0.12 seconds or less
Explain how to use each of the three methods for calculating a patient's heart rate.
- 6 second method: count the number of QRS complexes within a 6 second strop and multiply that number by 10
- R-to-R method: Find a QRS complex that falls on a heavy line (large box), count the number of large boxes from that R wave to the next R wave, then divide that number into 300
-Sequence method: Count the number of small boxes between any R-to-R interval and divide that number into 1500
What are the 4 causes of artifacts?
1. Patient Movement
2. Loose or defective electrode
3. 60 cycle interference
4. Faulty EKG Equipment