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When cells are in a ____ state they are polarized and carry a ___ net charge
when cells are in a resting state, they are polarized and have net (+) charge
the shift in electrolyte concentration reverses the charge on the cell membrane
Electrical depolarization occurs before ...
cardiac muscle contraction
once depolarization occurs, what's next?
the return back to a resting state is called repolarization
explain getting a charge
- all cell membranes are charged ... meaning that they have electrical potentials
- when cells are in resting (polarized) state, they carry (+) charge
- the shift in electrolyte concentrations reverses the charge on the cell membranes (depolarization)
- after depolarization the return back to resting state is called repolarization
what produces the various waves on EKG?
depolarization and repolarization of the myocardial cells
the patient is linked directly to a cardiac monitor through a cable
usually seen in ICUs and ERs
limits the patients mobility
Telemetry monitoring system
- electrodes are connected to the patient and a short cable connects to a battery transmitter that the patient can out in their pocket and carry
- EKG tracing are more difficult to obtain because the patient is up moving around
Bedside monitoring system
- has 3 leads +, -, and ground
- goes with pt as they are being transported
depending on how the leads are placed on the chest, the resulting monitor picture will resemble leads I,II and III
As long as the leads are placed correctly on the skin and has ......
good contact and seal and the EKG is able to detect those polarity changes you will see quality EKG tracings
standard limb leads are ...
- Leads I,II, and III
- they record frontal plane activity and are bipolar which means that each lead has 2 electrodes which record the electrical potential of the heart flowing toward 2 extremities
Augmented and precordial leads do what
determine where the irregularity is.
describe the leads
- 3 leads
- lead I, the QRS is +
- lead II, the QRS is +
- lead III, the QRS is partly + and partly -
Lead placement is based on.....
which lead is most commonly used for tracings?
lead II is most commonly used because it is a clear upright image
What Must Be Done?
- Stable site
- shave excess hair
- clean site with alcohol to remove oils and debris
- Avoid boney prominences, joint, and skn folds
- Apply electrode firmly, hold down to form seal with skin
- Change every 2-3 days (every day is better)
- Watch skin for irritation
Must have good contact to get good reading!!
What should monitor alarms be set on?
you should always set alarms or normal limits and assess your patient
NEVER ignore the alarm!!!
Describe the conduction system.
Electrical Conduction through the Heart
- Sinoatrial Node (SA Node)
- Intraatrial Pathway
- Internodal Pathways
- Atrioventricular Junction (AV Junction)
- Bundle of HIS
- Left bundle branches (2 divisons)
- Right Bundle Branch
- Purkinjie Fibers
As Ventricular depolarization/activation occurs, what happens?
it produced QRS complex on the EKG
After each depolarization, what happens?
the muscle rests while the ventricle fill with blood
Each Cardiac cycle consists of ...
depolarization and repolarization.
what influences the SA Node?
the sympathetic and parasympathetic nervous system.
The one with the fastest pacemaker ALWAYS controls the heart rate. So it fluctuates with nervous stimulation
- a flat baseline
- anything above is +
- anything below is -
what represents atrial depolarization (Diastole)?
P Wave represents atrial depolarization (diastole) in which the cardiac muscle fibers lengthen, the heart dilates, and cavities fill with blood.
what produces the P-Wave?
Atrial excitation spreads through the right and left atria which produces the P-Wave
Generally what does the P-Wave look like?
P-Waves are generally small, upright, and rounded (and all look the same)
beat after beat after beat the P-wave should all look the same.
the period of time for atrial depolarization and atrial repolarization to occur.
the straight line after the P-Wave
- ventricular depolarization
- Q-, R+, S-
- not all QRS complexes have 3 components, sometimes the S Wave will not be there
what comes after QRS complex?
ST Segment (straight line between the S Wave and the T wave) represents the early phase of ventricular muscle recovery (REPOLARIZATION)
What represents ventricular repolarization?
T Wave represents ventricular repolarization
What does the QT Segment represent?
the period of time between ventricular depolarization to ventricular repolarization
QT varies with heart rae
what is U Wave?
- U Wave represents an electrolyte abnormality, usually potassium.
- U Wave is not normally present on Normal EKG
When the cell responds to an electrical stimulus it is ________. the surface of the stimulates portion becomes electrically ____.
When the cell responds to an electrical stimulus it is DEPOLARIZED, the surface of the stimulated portion becomes electrically NEGATIVE
The cell is ___ when the electric charges return to their original locations in the resting state
The cell is repolarized when the electric charges return to their original locations in the resting state
explain home cells respond to electrical stimulus
- When the cell responds to an electrical stimulus it is DEPOLARIZED, the surface of the stimulated portion becomes electrically NEGATIVE
- The cell is repolarized when the electric charges return to their original locations in the resting state
each small box is
each large box equals
- .20 seconds
- 1 large box is equal to 5 small boxes
calculating Heart Rate what do the boxes and markings on the paper mean?
- small box = .04 seconds
- large box = .20 seconds
- there are 5 small boxes in each large box
- the marks across the top of the paper = 3 seconds
- there are 15 large boxes in 3 seconds
- only use if regular rhythm
what is the 1 x 10 method?
count the number of complexes in a 6 second time interval and multiply by 10 to get heart rate
what are the 5 steps to assess rhythm strip
- determine if rhythm is regular
- determine the heart rate
- look at atrial activity (P-wave)
- look at ventricular activity (QRS Complexes)
- Determine relationship between atrial and ventricular activity
Step 1 for assessing Rhythm Strip
Determine if rhythm is regular, if it is not then what makes it irregular
step 2 assessing rhythm strip
Determine Heart RAte.
Is the atrial Heart Rate and the Ventricular heart rate the same? count and make sure you have the same number of P waves and QRS Complexes
step 3 of assessing rhythm strip
look at atrial activity
does every P-Wave look the same, small, round and upright
step 4 of assessing rhythm strip
look at ventricles
Do all of the QRS complexes look the same, NARROW
Step 5 Assessing Rhythm Strip
Determine relationship between atrial and ventricular activity
do all QRS Complexes follow P-waves?
measuring/calculating EKG, what is measured horizontal and what is measured vertically?
- Horizontal = time
- Vertical = voltage
- each small box is 1mm voltage
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