CRAT STUDY GUIDE 2026/2027 QUESTIONS AND
SOLUTIONS RATED A+
✔✔The EGC waveform - ✔✔the recorded electrical activity produced during
depolarization and repolarization
✔✔isoelectric line - ✔✔period of no electrical activity, also known as the baseline
✔✔P-wave - ✔✔represents atrial depolarization with the resulting atrial contraction. SA
node. ATRIAL DEPOLARIZATION Normal=less than .10 Anything to do with p-waves is
atrium
✔✔PR Segment - ✔✔Delay at AV node
✔✔PR interval - ✔✔represents time from when electrical impulse is initiated until the
ventricles are simulated (another words, how long it was held in AV node) Normal=.12-
.20, measure by counting small boxes from beginning of p wave to beginning of QRS
and multiple this number by .04
✔✔QRS - ✔✔represents ventricular depolarization with the resulting ventricular
contraction, the time it takes the electrical impulse to travel through AV node down the
bundle branches to the purkinje fibers. this is the heart beat you feel or hear.
VENTRICULAR DEPOLARIZATION Normal=.04-.10
✔✔Q-wave - ✔✔if there it is the first negative deflection before R wave. Normal q wave
is 1/4 height of R-wave. Pathologic Q waves (deeper) are a sign of previous myocardial
infarction
✔✔R-wave - ✔✔first positive wave, represents conduction of electrical activity to left
ventricle. Area of heart=bundle branches bicuspid and tricuspid valve closes. ventricular
excitement complete, Purkinje fibers
✔✔S-wave - ✔✔first negative deflection after R wave, represents electrical conduction
thru both ventricles
✔✔ST segment - ✔✔measured from end of s wave to beginning of T wave. Normal is
on the isoelectric line. if elevated or depressed it could reflect ischemia
✔✔Ischemia - ✔✔lack of blood supply to an area of tissue due to blockage in circulation
to the area
✔✔T-wave - ✔✔represents ventricular repolarization, ventricles relax and semilunar
valve close. (Aortic and pulmonary valves)
, ✔✔U-wave - ✔✔represents VENTRICULAR REPOLARIZATION having a U wave could
mean low potassium
✔✔J point - ✔✔junction of QRS and ST interval
✔✔Atrial repolarization - ✔✔hidden in QRS do not se on ECG
✔✔one small box= - ✔✔.04 seconds or 40 milliseconds
✔✔one large box= - ✔✔.20 seconds or 200 milliseconds
✔✔five large boxes= - ✔✔1.0 second or 1000 miliseconds
✔✔15 large boxes= - ✔✔3 seconds, there are marks every three seconds on bottom of
pink ECG paper
✔✔3 common ways to measure heart rate - ✔✔R-R (300) method (semi accurate), 6
second method (generic), and the 1500 method (most accurate)
✔✔measuring heart rate with small boxes formula (1500 method) - ✔✔1500 divided by
number of small boxes between one QRS or p-wave to the next
✔✔measuring heart rate quick method (6 second method) - ✔✔count number of QRS in
six second strip and times by ten
✔✔Measuring heart rate with big box formula (300 method) - ✔✔count large boxes and
divide the total into 300
✔✔Calculating heart rate with measurement of the R-R Interval - ✔✔1 box
between=300bpm & .2 seconds between beats
2 box between=150bpm & .4 seconds between beats
3 box between=100bpm & .6 seconds between beats
4 box between=75bpm & .8 seconds between beats
5 box between=60bpm & 1.0 seconds between beats
6 box between=50bpm & 1.2 seconds between beats
✔✔measuring pauses - ✔✔count number of small boxes between 2 QRS and times by
.04
✔✔Precordial leads - ✔✔The chest leads, located in front of heart (pre-in front, cordial-
heart) Each chest lead begins with letter V (V1, V2, V3,V4, V5, V6) And record activity
between 6 points in the heart. unipolar leads because they measure in one direction
only
SOLUTIONS RATED A+
✔✔The EGC waveform - ✔✔the recorded electrical activity produced during
depolarization and repolarization
✔✔isoelectric line - ✔✔period of no electrical activity, also known as the baseline
✔✔P-wave - ✔✔represents atrial depolarization with the resulting atrial contraction. SA
node. ATRIAL DEPOLARIZATION Normal=less than .10 Anything to do with p-waves is
atrium
✔✔PR Segment - ✔✔Delay at AV node
✔✔PR interval - ✔✔represents time from when electrical impulse is initiated until the
ventricles are simulated (another words, how long it was held in AV node) Normal=.12-
.20, measure by counting small boxes from beginning of p wave to beginning of QRS
and multiple this number by .04
✔✔QRS - ✔✔represents ventricular depolarization with the resulting ventricular
contraction, the time it takes the electrical impulse to travel through AV node down the
bundle branches to the purkinje fibers. this is the heart beat you feel or hear.
VENTRICULAR DEPOLARIZATION Normal=.04-.10
✔✔Q-wave - ✔✔if there it is the first negative deflection before R wave. Normal q wave
is 1/4 height of R-wave. Pathologic Q waves (deeper) are a sign of previous myocardial
infarction
✔✔R-wave - ✔✔first positive wave, represents conduction of electrical activity to left
ventricle. Area of heart=bundle branches bicuspid and tricuspid valve closes. ventricular
excitement complete, Purkinje fibers
✔✔S-wave - ✔✔first negative deflection after R wave, represents electrical conduction
thru both ventricles
✔✔ST segment - ✔✔measured from end of s wave to beginning of T wave. Normal is
on the isoelectric line. if elevated or depressed it could reflect ischemia
✔✔Ischemia - ✔✔lack of blood supply to an area of tissue due to blockage in circulation
to the area
✔✔T-wave - ✔✔represents ventricular repolarization, ventricles relax and semilunar
valve close. (Aortic and pulmonary valves)
, ✔✔U-wave - ✔✔represents VENTRICULAR REPOLARIZATION having a U wave could
mean low potassium
✔✔J point - ✔✔junction of QRS and ST interval
✔✔Atrial repolarization - ✔✔hidden in QRS do not se on ECG
✔✔one small box= - ✔✔.04 seconds or 40 milliseconds
✔✔one large box= - ✔✔.20 seconds or 200 milliseconds
✔✔five large boxes= - ✔✔1.0 second or 1000 miliseconds
✔✔15 large boxes= - ✔✔3 seconds, there are marks every three seconds on bottom of
pink ECG paper
✔✔3 common ways to measure heart rate - ✔✔R-R (300) method (semi accurate), 6
second method (generic), and the 1500 method (most accurate)
✔✔measuring heart rate with small boxes formula (1500 method) - ✔✔1500 divided by
number of small boxes between one QRS or p-wave to the next
✔✔measuring heart rate quick method (6 second method) - ✔✔count number of QRS in
six second strip and times by ten
✔✔Measuring heart rate with big box formula (300 method) - ✔✔count large boxes and
divide the total into 300
✔✔Calculating heart rate with measurement of the R-R Interval - ✔✔1 box
between=300bpm & .2 seconds between beats
2 box between=150bpm & .4 seconds between beats
3 box between=100bpm & .6 seconds between beats
4 box between=75bpm & .8 seconds between beats
5 box between=60bpm & 1.0 seconds between beats
6 box between=50bpm & 1.2 seconds between beats
✔✔measuring pauses - ✔✔count number of small boxes between 2 QRS and times by
.04
✔✔Precordial leads - ✔✔The chest leads, located in front of heart (pre-in front, cordial-
heart) Each chest lead begins with letter V (V1, V2, V3,V4, V5, V6) And record activity
between 6 points in the heart. unipolar leads because they measure in one direction
only
