EKG Practice Test
This is a free 15-question sampler on EKG interpretation, written by the StudyPDF team. It covers the conduction pathway, what each wave and interval measures, normal values, lead placement, artifact, electrolyte changes and the ischemia to infarction progression, mixing multiple choice, select all that apply and fill in the blank. Answer all 15 questions, then check your score and read the explanation for every question.
Which structure normally sets the rate of the heart?
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All 15 questions at a glance
Prefer to read before you play? Every question in the sampler is listed below. Answers and explanations stay collapsed until you open them.
1. Which structure normally sets the rate of the heart?
- A. The AV node
- B. The SA node
- C. The bundle of His
- D. The Purkinje fibers
Show answer and explanation
Answer: B. The SA node
The SA node sits in the upper right atrium and fires about 60 to 100 times a minute, which is faster than any other pacemaker site, so it sets the pace. If it fails, a slower site takes over: the AV junction at about 40 to 60 and the ventricles at about 20 to 40.
2. The P wave on an EKG represents:
- A. Depolarization of the atria
- B. Repolarization of the atria
- C. Depolarization of the ventricles
- D. Repolarization of the ventricles
Show answer and explanation
Answer: A. Depolarization of the atria
The P wave is the electrical spread across the atria, and atrial contraction follows it. Atrial repolarization does happen, but it is buried inside the much larger QRS complex, so you never see it as its own wave.
3. Complete the sentence.
In a healthy adult, the PR interval measures _____ seconds.
Options for blank 1: 0.04 to 0.10, 0.12 to 0.20, 0.20 to 0.28, 0.30 to 0.40
Show answer and explanation
Answer: 0.12 to 0.20
The PR interval runs from the start of the P wave to the start of the QRS, so it measures everything from atrial depolarization through the delay at the AV node. A constant PR interval longer than 0.20 seconds with every P wave still conducted is first degree AV block.
4. After the AV node, in what order does the impulse travel to reach the ventricular muscle?
- A. Bundle of His, then the bundle branches, then the Purkinje fibers
- B. Purkinje fibers, then the bundle of His, then the bundle branches
- C. Bundle branches, then the bundle of His, then the Purkinje fibers
- D. Bundle of His, then the Purkinje fibers, then the bundle branches
Show answer and explanation
Answer: A. Bundle of His, then the bundle branches, then the Purkinje fibers
The full pathway is SA node, atria, AV node, bundle of His, right and left bundle branches, Purkinje fibers, then ventricular muscle. The AV node holds the impulse for about a tenth of a second so the atria can finish emptying into the ventricles, and that pause is most of what the PR interval measures.
5. The T wave represents:
- A. Repolarization of the ventricles
- B. Depolarization of the ventricles
- C. Repolarization of the atria
- D. The delay at the AV node
Show answer and explanation
Answer: A. Repolarization of the ventricles
The T wave is the ventricles resetting electrically so they can be stimulated again. Part of that reset is the relative refractory period, which is why a beat landing on the T wave is dangerous and can trigger ventricular tachycardia or fibrillation.
6. Complete the sentence.
On standard paper running at 25 mm per second, one large box is 0.20 seconds. A regular rhythm with 5 large boxes between one R wave and the next has a rate of about _____ beats per minute.
Options for blank 1: 50, 60, 75, 100
Show answer and explanation
Answer: 60
Five large boxes is one second, so one beat per second is 60 beats per minute. The shortcut is to divide 300 by the number of large boxes between R waves, since 300 large boxes go by in a minute, and it only works when the rhythm is regular.
7. A monitor shows a regular rhythm at 35 beats per minute, no visible P waves, and a QRS measuring 0.16 seconds. Where is this rhythm most likely coming from?
- A. The SA node
- B. The atria, outside the SA node
- C. The AV junction
- D. The ventricles
Show answer and explanation
Answer: D. The ventricles
A normal QRS is under 0.12 seconds, which is under three small boxes, because the His and Purkinje network spreads the impulse through both ventricles almost at once. A QRS this wide means the impulse is crawling muscle to muscle instead, and combined with no P waves and a rate in the 20 to 40 range it points to a ventricular escape rhythm. A junctional escape rhythm would be faster, around 40 to 60, and narrow.
8. Which of the following chest electrode positions for a 12 lead EKG are correct?
Select all that apply.
- A. V1 in the fourth intercostal space at the right sternal border
- B. V2 in the fourth intercostal space at the left sternal border
- C. V4 in the fifth intercostal space at the midclavicular line
- D. V3 directly below the right clavicle
- E. V6 in the second intercostal space at the anterior axillary line
Show answer and explanation
Answer: A. V1 in the fourth intercostal space at the right sternal border, B. V2 in the fourth intercostal space at the left sternal border, C. V4 in the fifth intercostal space at the midclavicular line
V1 and V2 sit either side of the sternum in the fourth intercostal space, V4 goes in the fifth intercostal space at the midclavicular line, and V3 goes midway between V2 and V4. V5 and V6 stay on the same horizontal line as V4, at the anterior axillary and midaxillary lines, and placing any chest electrode too high is a common reason a tracing shows changes the heart does not have.
9. Which group of leads looks at the inferior wall of the heart?
- A. I, aVL, V5 and V6
- B. II, III and aVF
- C. V1 and V2
- D. V3 and V4
Show answer and explanation
Answer: B. II, III and aVF
Leads II, III and aVF all look up from below, so together they view the inferior wall, which is usually supplied by the right coronary artery. The other groups are septal at V1 and V2, anterior at V3 and V4, and lateral at I, aVL, V5 and V6, and changes have to show up in at least two neighboring leads to count.
10. In the progression from ischemia to injury to infarction, which finding indicates acute myocardial injury?
- A. T wave inversion
- B. ST segment depression
- C. ST segment elevation
- D. A pathologic Q wave
Show answer and explanation
Answer: C. ST segment elevation
Ischemia, which is muscle that is short of oxygen but still alive, shows up as T wave inversion or ST depression. Injury raises the ST segment, and completed infarction leaves a pathologic Q wave that usually stays for life, so ST elevation in two neighboring leads is the finding that makes the situation time critical.
11. Which EKG changes are associated with a rising serum potassium level?
Select all that apply.
- A. Tall, narrow, peaked T waves
- B. Progressive widening of the QRS complex
- C. Flattening and eventual loss of the P wave
- D. A prominent U wave after the T wave
- E. A shortened PR interval with a delta wave
Show answer and explanation
Answer: A. Tall, narrow, peaked T waves, B. Progressive widening of the QRS complex, C. Flattening and eventual loss of the P wave
Hyperkalemia usually peaks the T waves first, then flattens the P waves and widens the QRS, and at extreme levels the QRS and T merge into a sine wave pattern. U waves belong to low potassium, and a short PR with a delta wave is preexcitation, not an electrolyte problem.
12. Complete the sentence.
A low serum potassium level classically flattens the T waves and produces a prominent _____ just after the T wave.
Options for blank 1: P wave, U wave, J wave, delta wave
Show answer and explanation
Answer: U wave
The U wave is a small extra deflection after the T wave, seen best in V2 and V3 and at slower rates. Hypokalemia also flattens the T wave and depresses the ST segment, and it lengthens repolarization enough to raise the risk of a dangerous ventricular rhythm.
13. Which of the following can produce artifact on an EKG tracing?
Select all that apply.
- A. Shivering or muscle tremor
- B. Dried out or loosely attached electrodes
- C. The patient moving or the chest rising with each breath
- D. A heart rate at the top of the normal range
- E. Fresh electrodes applied to clean, dry skin
Show answer and explanation
Answer: A. Shivering or muscle tremor, B. Dried out or loosely attached electrodes, C. The patient moving or the chest rising with each breath
Artifact is electrical noise that did not come from the heart, and the usual sources are muscle activity, poor electrode contact, movement and nearby electrical equipment. Before you treat an alarming looking tracing, look at the patient: if they are awake and comfortable, check the leads and the skin prep first.
14. For continuous cardiac monitoring in a hospital bed, where are the limb electrodes placed?
- A. On the wrists and ankles, as in a resting 12 lead
- B. On the torso, near the shoulders and over the lower ribcage or hips
- C. All four together on the left side of the chest
- D. Anywhere convenient, as long as they stay stuck down
Show answer and explanation
Answer: B. On the torso, near the shoulders and over the lower ribcage or hips
For continuous monitoring the limb electrodes are moved onto the torso and placed over bone rather than muscle, so arm and leg movement does not fill the screen with artifact. That shift changes the recorded shapes slightly, which is why a monitor strip should not replace a standard 12 lead when you are judging ST segments.
15. A rhythm is irregularly irregular, has no identifiable P waves, and shows a wavy baseline between the QRS complexes. This is:
- A. Sinus arrhythmia
- B. Atrial flutter
- C. Atrial fibrillation
- D. Junctional rhythm
Show answer and explanation
Answer: C. Atrial fibrillation
In atrial fibrillation the atria fire chaotically from many sites at once, so there is no organized P wave and the AV node passes impulses through at unpredictable intervals. The atria quiver instead of contracting, which costs the ventricles their final filling boost and lets blood pool, and that pooling is the reason clot risk drives treatment.
What an EKG test actually asks you
There is no single national EKG exam. The phrase covers several different tests: the dysrhythmia or EKG competency test inside a nursing or paramedic program, the rhythm exam a hospital gives before it lets you work on a telemetry floor, and certification exams for EKG technicians and rhythm analysis offered by organizations such as the NHA. The number of questions, the time limit, the passing score and how many attempts you get are set by whoever gives the test, so the only reliable numbers are the ones in your own candidate handbook or course syllabus.
What those tests have in common is the content. Almost all of them expect you to know the conduction pathway, what each wave and interval represents, the normal measurements, how to calculate a rate, how to identify the common rhythms, and where the electrodes go for both a 12 lead and continuous monitoring. Many also ask about artifact, electrolyte effects and the ischemia, injury and infarction pattern, because a technician who cannot tell a loose electrode from a real change is a safety problem.
One detail that varies more than people expect is how much strip reading is required. Some exams are almost entirely rhythm identification from printed strips. Others are mostly knowledge questions with only a handful of strips. Find out which kind you are sitting before you decide how to split your study time, because the two need different practice.
How to use this sampler
These 15 questions lean on the why rather than the naming. They ask what the PR interval is actually measuring, why a wide QRS matters, which leads look at which wall, and what potassium does to the tracing. That is the knowledge that makes strip reading fast later, because a rhythm you can reason about is one you do not have to memorize.
Take it in one sitting without notes, then read the explanation for every question, including the ones you got right. Treat a wrong answer as a topic rather than a fact. If you missed the chest lead question and the inferior wall question, review lead placement and lead groups together, since they are the same idea seen from two directions.
Pair this with strip practice. Knowledge questions and strip identification are different skills, and passing one does not predict the other. The two sibling quizzes linked below are the strip side of the same material, so run all three and compare where you drop points.
How StudyPDF builds full practice tests from your own materials
Fifteen questions can show you where you are shaky. They cannot get you ready on their own, and a generic bank rarely matches the emphasis of your own instructor or your hospital's rhythm policy.
StudyPDF works from your material instead. You upload your EKG textbook, lecture slides or the dysrhythmia packet your program handed out, and Bo, the study agent, builds full-length practice tests from those exact pages. Every question is grounded in your material, and every explanation cites where the answer comes from, so you can go straight to the source when something looks off. You can regenerate fresh tests as often as you like, narrow them to one area such as AV blocks or 12 lead interpretation, and track which concepts you keep missing.
You do not have to upload anything to start. If you have no file at hand, name a topic instead, for example heart blocks or electrolyte changes on the EKG, and Bo writes a practice test from that. Starting is free.
Written by the StudyPDF team. Last updated 2026-08-19.