2.2 Electrocardiogram Rhythm Interpretation Flashcards
EKG
- Graphical display of electrical heart rhythm
- Shows polarization and depolarization of cardiac muscle
Only shows electrical system, not the pump system
- EKG’s can help determine damage/strain to the heart and where it is occurring (12-Lead)
General Knowledge
SA Node - Found in the right atrium of the heart. It is the natural pacemaker of the heart.
AV Node - Found within the border of the right atrium and ventricle. It is the “gatekeeper” of the heart. It decides what impulses to let through.
The impulse goes from AV node to bundle of his (left and right bundle branches) to the purkinje fibers.
INHERENT RATES OF CARDIAC CELLS
SA Node - 60-100 BPM
AV Node - 40-60 BPM
Bundle of His - 40-60 BPM
Left/Right Bundle Branches - 20-40 BPM
Purkinje Fibers - 20-40 BPM
EKG
P Wave - Atrial Depolarization (The 2 atrium’s are contracting)
QRS Complex - Ventricular Depolarization (Ventricles of the heart are contracting)
T Wave - Ventricular Repolarization (Ventricles are relaxing)
“Atrial Repolarization is found in the QRS complex”
EKG Interpretation
Each small box = 0.04 seconds
Each big box = 0.20 seconds
6 Steps
1. Identify the P Wave
(Normally present and upright. Inversion can mean dysrhythmias)
2. Measure PR Interval
(Distance between beginning of p-wave and beginning of QRS complex. Count the boxes and multiply it by 0.04 seconds. The value should be between 0.12 - 0.20 seconds. Anything longer could indicate dysrhythmias)
3. Measure the QRS Complex
(Measure small boxes between the QRS complex. It should equal 0.06-0.12 seconds. Anything more can indicate dysrhythmias)
4. Identify the Rhythm
(Measure distance between R’s. Distance should be the same between each R wave)
5. Determine the heart rate
(You will see 3 lines at the top of the screen. 3 of those lines equals 60 seconds. Count the number of R’s between the 3 lines and multiply by 10 to get heart rate)
(You can use big-box method. Count how many big boxes there are between R’s and do 300 divided by that number. That will tell you the HR)
6. Interpret the strip
Reciprocal Changes
- ST-Segment depression occurring on an ECG which also has ST-segment elevation in at least 2 leads in a single anatomic segment
EKG 12-Lead
Leads are placed on right and left arms as well as right and left legs.
- The one we look at most is the left leg (Does not have to be on left leg, can be on lower left chest)
LEAD 1 - Compares left arm with right arm
LEAD 2 - Reads from negative in the right arm to positive in the left leg
(Follows the normal conduction of impulse from the SA node)
LEAD 3 - Reads from negative in the left arm to positive in the left leg.
EKG Paper
- Horizontal axis records time
- Vertical axis records amplitude (of impulse)
- At the top of the paper there is little black marks. Between each black mark there is 3 seconds.
- Each large grid box is 0.20 seconds
- Each small grid box is 0.04 seconds
Parts of EKG
P wave - Atrial depolarization
P-R Interval - Travel time from SA node to AV node (From beginning of P to Beginning of Q)
(0.12-0.20 seconds)
QRS Complex (Less than 0.12 seconds)
Large Q wave indicates previous damage to the heart (Silent MI will have residual enlarged Q waves)
R Wave - Ventricular depolarization (Feeling patients pulse is reflection of R wave)
ST Segment
- Looking to make sure it returns to isoelectric line
T-Wave
- Ventricular Re-polarization (heart gets ready for next depolarization)
U-Wave (Small wave after T-Wave)
- Recovery of purkinje fibers (many people do not have observable U-waves)
- Atrial Repolarization is somewhere in the QRS
Q-T Interval (Beginning of Q to End of T wave) (Less than 0.56 seconds)
- This is when ventricles are repolarizing so they are vulnerable (refractory period) which means cells cannot depolarize again until repolarization has occurred.
- Absolute refractory period - ABSOLUTELY CANNOT DEPOLARIZE AGAIN UNTIL REPOLARIZATION
- Relative refractory period - Risk of an impulse striking too early and hitting on the T wave to trigger an early depolarization again. (Can cause Lethal Dysrhythmia)
How to Interpret ECG Rhythm
- What is the rate
- Regular/Irregular?
- Is there a P after every QRS
- Is there a QRS after every P
- What is the PR Interval
- What is the QRS time
- What is the QT interval
- Is the ST Isoelectric
How to Measure Rate?
- Look at 6 seconds, count the number of P waves, and multiply by 10
(Used for quick estimates or irregular rhythms)
Regular Rhythms
1500 method
- Count number of small boxes between QRS complexes and divide 1500 by that number
- Most accurate for regular rhythms
300 method
- Count number of large boxes between 2 QRS complexes and divide 300 by that number
12-Lead ECG Nursing Tips
- When attaching ECG leads to a patient with a lot of chest hair, get the patients permission to clip their chest hair to improve adhesion of the leads.
Intervals
PR Interval - Start of P to Start of Q
- Time taken for electrical activity to move from atria to ventricles
PR Segment - Flat line between end of P to start of Q
- Time delay between atrial and ventricular activation
QRS Complex - Beginning of Q to end of S
- Depolarization of Ventricles
QT Interval - Beginning of Q to end of T
- Represents time taken for ventricles to depolarize and then repolarize
ST Segment - End of S to Beginning of T
- Isometric Line
- Represents time between depolarization and repolarization of ventricles (ventricular contraction)
P wave - Atrial depolarization
Normal Sinus Rhythm
- Truly normal rhythm
- Initiated by SA node
NORMAL
- Regular
- 60-100 bpm
- P for every QRS
- QRS for every P
- PR Interval - 0.12-0.20 seconds
- QRS - Less than 0.12 seconds
- QT Interval - Less than 0.56
- ST Line should be Isometric
Respiratory Sinus Arrhythmia - HR increases with inhalation and HR decreases with exhalation
(More common in pediatrics than adults)
Premature Atrial Complex - Individual complex occurs earlier than expected
(Typically is benign. Can be caused by pain, fever, anxiety, fear unless it increases in frequency)
Sinus Bradycardia
- Less than 60 bpm but everything else is normal
Associated with
- Hypothyroidism, Increased Intracranial Pressure, Inferior Wall MI, Athletes
Treatment (Typically does not require treatments)
- Assess patient for symptoms
- Atropine to increase rate
- Pacemaker
Sinus Tachycardia
- Rate above 100 bpm but everything else is normal
Associated with
- Exercise, pain, hypovolemia, MI, HF, fever, Anxiety, Stress, Hyperthyroidism
Treatment (Based on underlying cause)
- Hypovolemia - Fluid
- Fever - Antipyretics
- Exercise - Rest
- Pain - Analgesics
- MI/HF - Beta-Blockers and other Antidysrhythmic
