EKG Technician Certification 2026/2027 Study Guide | EKG Technician
Certification Exam Prep | NHA Certified EKG Technician (CET) Practice
Questions & Answers, Detailed Rationales, ECG Interpretation, Cardiac
Rhythms, 12-Lead EKG, Lead Placement, Patient Preparation &
Comprehensive Certification Review
Question 1: What is the primary electrical function of the Sinoatrial (SA) node
in a healthy heart?
A. To slow down the electrical impulse before it reaches the ventricles
B. To act as the primary pacemaker by initiating the electrical impulse
C. To conduct the impulse from the atria to the ventricles
D. To serve as a backup pacemaker if the primary pacemaker fails
CORRECT ANSWER: B. To act as the primary pacemaker by initiating the
electrical impulse
Rationale: The SA node, located in the right atrium, possesses the highest rate of
automaticity and normally fires at a rate of 60-100 beats per minute, initiating each
cardiac cycle. Its function is to generate the electrical impulse that spreads across the
atria, leading to atrial depolarization.
Question 2: Which lead placement is correct for the V1 electrode during a
standard 12-lead EKG?
A. Fourth intercostal space, left sternal border
B. Fourth intercostal space, right sternal border
C. Fifth intercostal space, midclavicular line
D. Fifth intercostal space, anterior axillary line
CORRECT ANSWER: B. Fourth intercostal space, right sternal border
Rationale: V1 is placed at the fourth intercostal space to the right of the sternum. V2 is
placed at the fourth intercostal space to the left. V3 is placed midway between V2 and
V4, V4 at the fifth intercostal space midclavicular line, V5 at the anterior axillary line,
and V6 at the midaxillary line.
Question 3: On the EKG paper, what does the horizontal axis represent, and
what is the standard paper speed?
A. Amplitude; 10 mm/mV
B. Time; 25 mm/s
C. Voltage; 50 mm/s
D. Heart rate; 50 mm/s
CORRECT ANSWER: B. Time; 25 mm/s
Rationale: The horizontal axis on EKG paper measures time. At the standard speed of 25
mm/s, each small square (1 mm) equals 0.04 seconds, and each large square (5 mm)
equals 0.20 seconds. The vertical axis measures amplitude or voltage.
Question 4: The P wave on a normal EKG represents which cardiac event?
,A. Ventricular repolarization
B. Ventricular depolarization
C. Atrial depolarization
D. Atrial repolarization
CORRECT ANSWER: C. Atrial depolarization
Rationale: The P wave is the first positive deflection and represents the electrical
depolarization of the atria, initiated by the SA node, leading to atrial contraction.
Ventricular depolarization is represented by the QRS complex, and ventricular
repolarization by the T wave.
Question 5: What is the standard duration of the PR interval (measured from
the beginning of the P wave to the beginning of the QRS complex) in a normal
EKG?
A. 0.20 to 0.40 seconds
B. 0.12 to 0.20 seconds
C. Less than 0.12 seconds
D. 0.08 to 0.12 seconds
CORRECT ANSWER: B. 0.12 to 0.20 seconds
Rationale: The PR interval measures the time from the onset of atrial depolarization to
the onset of ventricular depolarization, representing conduction through the AV node,
bundle of His, and bundle branches. A normal PR interval ranges from 120 to 200 ms
(0.12 to 0.20 seconds).
Question 6: The QRS complex on a standard EKG typically has a duration of:
A. 0.20 to 0.40 seconds
B. 0.12 to 0.20 seconds
C. Less than 0.12 seconds
D. 0.04 to 0.08 seconds
CORRECT ANSWER: C. Less than 0.12 seconds
Rationale: The QRS complex represents rapid ventricular depolarization. In a healthy
individual, the QRS duration should be narrow, typically between 0.06 and 0.10 seconds
(1.5 to 2.5 small squares), and certainly less than 0.12 seconds. A wide QRS (>0.12s)
indicates a conduction delay.
Question 7: If the R-R interval is constant and the heart rate is 60 beats per
minute, what is the R-R interval in seconds?
A. 0.80 seconds
B. 1.00 second
C. 1.20 seconds
D. 0.60 seconds
CORRECT ANSWER: B. 1.00 second
,Rationale: Heart rate is calculated as 60 divided by the R-R interval (in seconds). If HR =
60 bpm, then 60 / R-R = 60, so R-R = 1.0 second. This is equivalent to 5 large squares
(25 mm) at standard paper speed of 25 mm/s.
Question 8: Which of the following leads are considered "limb leads" in a
standard 12-lead EKG?
A. V1, V2, V3
B. aVR, aVL, aVF
C. I, II, III
D. V4, V5, V6
CORRECT ANSWER: C. I, II, III
Rationale: The standard 12-lead EKG consists of 6 limb leads (I, II, III, aVR, aVL, aVF)
and 6 precordial leads (V1-V6). Leads I, II, and III are the bipolar limb leads and form
Einthoven's triangle. The augmented leads (aVR, aVL, aVF) are unipolar limb leads.
Question 9: What is the physiological effect of the parasympathetic nervous
system on the heart rate?
A. It increases the heart rate via the release of norepinephrine
B. It decreases the heart rate via the release of acetylcholine
C. It has no effect on the heart rate
D. It increases the contractility of the ventricles
CORRECT ANSWER: B. It decreases the heart rate via the release of
acetylcholine
Rationale: The parasympathetic nervous system, via the vagus nerve, releases
acetylcholine at the SA node, which hyperpolarizes the pacemaker cells, slowing the rate
of depolarization and decreasing the heart rate. The sympathetic system increases heart
rate and contractility via norepinephrine.
Question 10: What is the most common cause of a wandering baseline artifact
on an EKG tracing?
A. Loose or poor electrode contact with the skin
B. Somatic tremor from muscle movement
C. Alternating current (AC) interference
D. Improper grounding of the EKG machine
CORRECT ANSWER: A. Loose or poor electrode contact with the skin
Rationale: Wandering baseline (also called baseline drift) is often caused by poor
electrode contact, dried out gel, or movement of the electrodes due to skin tension. It
manifests as a slow, undulating shift of the isoelectric line. AC interference appears as a
thin, regular oscillation (50 or 60 Hz), and somatic tremor appears as irregular high-
frequency noise.
, Question 11: On an EKG tracing, the ST segment represents which phase of the
cardiac cycle?
A. The period between ventricular depolarization and repolarization
B. The period of rapid ventricular depolarization
C. The period of atrial depolarization
D. The period of ventricular repolarization
CORRECT ANSWER: A. The period between ventricular depolarization and
repolarization
Rationale: The ST segment connects the QRS complex (ventricular depolarization) with
the T wave (ventricular repolarization). It represents the plateau phase (phase 2) of the
ventricular action potential, where the myocardial cells are depolarized. Elevation or
depression of the ST segment can indicate myocardial ischemia or injury.
Question 12: In which of the following conditions would you expect to see
prominent U waves on an EKG?
A. Hypercalcemia
B. Hypokalemia
C. Hyperkalemia
D. Myocardial infarction
CORRECT ANSWER: B. Hypokalemia
Rationale: U waves are small, late deflections following the T wave and are best seen in
leads V2-V4. They are often associated with hypokalemia, bradycardia, or left
ventricular hypertrophy. Hyperkalemia is associated with peaked T waves, and
hypercalcemia shortens the QT interval.
Question 13: To measure the heart rate using the "300" method, you count the
number of large squares between two consecutive R waves. If there are 3 large
squares, what is the approximate heart rate?
A. 150 bpm
B. 100 bpm
C. 75 bpm
D. 60 bpm
CORRECT ANSWER: B. 100 bpm
Rationale: The "300" method is used for regular rhythms. 300 divided by the number of
large squares between R waves gives the heart rate. = 100 bpm. 1 large square =
0.2 sec, so an R-R interval of 0.6 sec corresponds to 100 bpm.
Question 14: When applying precordial electrodes, where should the V4
electrode be placed?
A. Fourth intercostal space, right sternal border
B. Fifth intercostal space, midclavicular line
Certification Exam Prep | NHA Certified EKG Technician (CET) Practice
Questions & Answers, Detailed Rationales, ECG Interpretation, Cardiac
Rhythms, 12-Lead EKG, Lead Placement, Patient Preparation &
Comprehensive Certification Review
Question 1: What is the primary electrical function of the Sinoatrial (SA) node
in a healthy heart?
A. To slow down the electrical impulse before it reaches the ventricles
B. To act as the primary pacemaker by initiating the electrical impulse
C. To conduct the impulse from the atria to the ventricles
D. To serve as a backup pacemaker if the primary pacemaker fails
CORRECT ANSWER: B. To act as the primary pacemaker by initiating the
electrical impulse
Rationale: The SA node, located in the right atrium, possesses the highest rate of
automaticity and normally fires at a rate of 60-100 beats per minute, initiating each
cardiac cycle. Its function is to generate the electrical impulse that spreads across the
atria, leading to atrial depolarization.
Question 2: Which lead placement is correct for the V1 electrode during a
standard 12-lead EKG?
A. Fourth intercostal space, left sternal border
B. Fourth intercostal space, right sternal border
C. Fifth intercostal space, midclavicular line
D. Fifth intercostal space, anterior axillary line
CORRECT ANSWER: B. Fourth intercostal space, right sternal border
Rationale: V1 is placed at the fourth intercostal space to the right of the sternum. V2 is
placed at the fourth intercostal space to the left. V3 is placed midway between V2 and
V4, V4 at the fifth intercostal space midclavicular line, V5 at the anterior axillary line,
and V6 at the midaxillary line.
Question 3: On the EKG paper, what does the horizontal axis represent, and
what is the standard paper speed?
A. Amplitude; 10 mm/mV
B. Time; 25 mm/s
C. Voltage; 50 mm/s
D. Heart rate; 50 mm/s
CORRECT ANSWER: B. Time; 25 mm/s
Rationale: The horizontal axis on EKG paper measures time. At the standard speed of 25
mm/s, each small square (1 mm) equals 0.04 seconds, and each large square (5 mm)
equals 0.20 seconds. The vertical axis measures amplitude or voltage.
Question 4: The P wave on a normal EKG represents which cardiac event?
,A. Ventricular repolarization
B. Ventricular depolarization
C. Atrial depolarization
D. Atrial repolarization
CORRECT ANSWER: C. Atrial depolarization
Rationale: The P wave is the first positive deflection and represents the electrical
depolarization of the atria, initiated by the SA node, leading to atrial contraction.
Ventricular depolarization is represented by the QRS complex, and ventricular
repolarization by the T wave.
Question 5: What is the standard duration of the PR interval (measured from
the beginning of the P wave to the beginning of the QRS complex) in a normal
EKG?
A. 0.20 to 0.40 seconds
B. 0.12 to 0.20 seconds
C. Less than 0.12 seconds
D. 0.08 to 0.12 seconds
CORRECT ANSWER: B. 0.12 to 0.20 seconds
Rationale: The PR interval measures the time from the onset of atrial depolarization to
the onset of ventricular depolarization, representing conduction through the AV node,
bundle of His, and bundle branches. A normal PR interval ranges from 120 to 200 ms
(0.12 to 0.20 seconds).
Question 6: The QRS complex on a standard EKG typically has a duration of:
A. 0.20 to 0.40 seconds
B. 0.12 to 0.20 seconds
C. Less than 0.12 seconds
D. 0.04 to 0.08 seconds
CORRECT ANSWER: C. Less than 0.12 seconds
Rationale: The QRS complex represents rapid ventricular depolarization. In a healthy
individual, the QRS duration should be narrow, typically between 0.06 and 0.10 seconds
(1.5 to 2.5 small squares), and certainly less than 0.12 seconds. A wide QRS (>0.12s)
indicates a conduction delay.
Question 7: If the R-R interval is constant and the heart rate is 60 beats per
minute, what is the R-R interval in seconds?
A. 0.80 seconds
B. 1.00 second
C. 1.20 seconds
D. 0.60 seconds
CORRECT ANSWER: B. 1.00 second
,Rationale: Heart rate is calculated as 60 divided by the R-R interval (in seconds). If HR =
60 bpm, then 60 / R-R = 60, so R-R = 1.0 second. This is equivalent to 5 large squares
(25 mm) at standard paper speed of 25 mm/s.
Question 8: Which of the following leads are considered "limb leads" in a
standard 12-lead EKG?
A. V1, V2, V3
B. aVR, aVL, aVF
C. I, II, III
D. V4, V5, V6
CORRECT ANSWER: C. I, II, III
Rationale: The standard 12-lead EKG consists of 6 limb leads (I, II, III, aVR, aVL, aVF)
and 6 precordial leads (V1-V6). Leads I, II, and III are the bipolar limb leads and form
Einthoven's triangle. The augmented leads (aVR, aVL, aVF) are unipolar limb leads.
Question 9: What is the physiological effect of the parasympathetic nervous
system on the heart rate?
A. It increases the heart rate via the release of norepinephrine
B. It decreases the heart rate via the release of acetylcholine
C. It has no effect on the heart rate
D. It increases the contractility of the ventricles
CORRECT ANSWER: B. It decreases the heart rate via the release of
acetylcholine
Rationale: The parasympathetic nervous system, via the vagus nerve, releases
acetylcholine at the SA node, which hyperpolarizes the pacemaker cells, slowing the rate
of depolarization and decreasing the heart rate. The sympathetic system increases heart
rate and contractility via norepinephrine.
Question 10: What is the most common cause of a wandering baseline artifact
on an EKG tracing?
A. Loose or poor electrode contact with the skin
B. Somatic tremor from muscle movement
C. Alternating current (AC) interference
D. Improper grounding of the EKG machine
CORRECT ANSWER: A. Loose or poor electrode contact with the skin
Rationale: Wandering baseline (also called baseline drift) is often caused by poor
electrode contact, dried out gel, or movement of the electrodes due to skin tension. It
manifests as a slow, undulating shift of the isoelectric line. AC interference appears as a
thin, regular oscillation (50 or 60 Hz), and somatic tremor appears as irregular high-
frequency noise.
, Question 11: On an EKG tracing, the ST segment represents which phase of the
cardiac cycle?
A. The period between ventricular depolarization and repolarization
B. The period of rapid ventricular depolarization
C. The period of atrial depolarization
D. The period of ventricular repolarization
CORRECT ANSWER: A. The period between ventricular depolarization and
repolarization
Rationale: The ST segment connects the QRS complex (ventricular depolarization) with
the T wave (ventricular repolarization). It represents the plateau phase (phase 2) of the
ventricular action potential, where the myocardial cells are depolarized. Elevation or
depression of the ST segment can indicate myocardial ischemia or injury.
Question 12: In which of the following conditions would you expect to see
prominent U waves on an EKG?
A. Hypercalcemia
B. Hypokalemia
C. Hyperkalemia
D. Myocardial infarction
CORRECT ANSWER: B. Hypokalemia
Rationale: U waves are small, late deflections following the T wave and are best seen in
leads V2-V4. They are often associated with hypokalemia, bradycardia, or left
ventricular hypertrophy. Hyperkalemia is associated with peaked T waves, and
hypercalcemia shortens the QT interval.
Question 13: To measure the heart rate using the "300" method, you count the
number of large squares between two consecutive R waves. If there are 3 large
squares, what is the approximate heart rate?
A. 150 bpm
B. 100 bpm
C. 75 bpm
D. 60 bpm
CORRECT ANSWER: B. 100 bpm
Rationale: The "300" method is used for regular rhythms. 300 divided by the number of
large squares between R waves gives the heart rate. = 100 bpm. 1 large square =
0.2 sec, so an R-R interval of 0.6 sec corresponds to 100 bpm.
Question 14: When applying precordial electrodes, where should the V4
electrode be placed?
A. Fourth intercostal space, right sternal border
B. Fifth intercostal space, midclavicular line
