SA node AV node Bundle of His & Rt & Lt BB Purkinje fibers Depolarization is the fundamental electrical event of the heart. This wave of depolarization represents a flow of electricity detected by electrodes on the surface of the body. Repolarization can also be detected
Waveforms
Duration Amplitude Configurationrefers to shape & appearance
EKG paper
light linesdark lines1mm by 1mm small boxes
5mm by 5mm large boxes horizontal axis measures time
1 sm box = 0.04 seconds 1 lg box = 0.20 seconds 5 consecutive lg boxes = 1 second vertical axis measures voltage vertical slash marks
from 1 to next is 15 lg boxes = 3 seconds
calculate HR
look at 2 consecutive 3 sec. intervals - count beats X 10 count number of sm boxes between R-R divide by 1500
Normal EKG
our focus is on the electrcal event that produces basic waves and lines of the EKG
Pacer or P-wave
the SA node fires spontaneously as the depolarization spreads thru the atria a P-wave is recorded upright and rounded shape
AV conduction
conduction slows to a crawl at the AV node after 0.10 sec, depolarizing wave is released from the AV node & races to the bundle of His
QRS complex
vent depolarization is marked by the QRS complex Q wave - 1st downward deflection R wave - 1st upward deflection S wave - 1st downward deflection after an upward deflection
T wave
ventricular repolarization occurs creating a T wave upright & rounded but follows the QRS complex
Isoelectric lines
PR intervalincludes the P-wave & the straight line connecting it to the QRS measures time from onset of atrial depol to the onset of vent depol
ST segment
straight line connecting the end of the QRS & the beginning of the T wave measures time form end of vent depol until vent repol
QT interval
includes the QRS complex, ST segment, & T wave measures from beginning of vent depol to end of vent repol.
Electrodes and 12 Lead EKGs
The 12 lead EKG consists of 12 recordings of electrical impulse each form a unique angle. 12 lead EKG & cardiac monitoring are different
Vocabulary
tachycardia bradycardia dysrhythmia arrhythmia
Vocabulary
artifact ectopy aberrancy
Measuring waves & intervals
calculating HR PR intervalQRS complexbeginning of the P wave to the beginning of QRS normal = 0.12 - 0.20 sec
beginning of the R to the end of the S wave normal = 0.04 - 0.11 sec rhythm
measure R-R interval if the distance is the same = regular rhythm
Steps for Interpretation
1. Rate2. Rhythmwhat is the vent rate?
measure R-R interval regular vs. irreg
Steps for Interpretation
3. P waveare P waves present? are there P waves in front of each QRS? configuration - is it same or different? is each P wave followed by a QRS? rate rhythm (use P-P interval)
Steps for Interpretation
4. PR intervalmeasure for each complex determine the length & is it normal? are all PR intervals the same?
Steps for Interpretation
5. QRS complexmeasure each complex determine length & is it normal? are all QRS complexes the same length? are all the same shape? is each QRS preceded by a P wave?
Steps for Interpretation
6. InterpretationAll rhythms are compared to normal sinus rhythm. Questions regarding interpretation???match the data to the criteria is the rhythm normal or abnormal? if abnormal, then it is the result of ectopic focus or blockage of impulse. interpretation will determine the need to call the doctor, initiate treatment, etc.