Rhythm Interpretation Practice Questions

31 multiple-choice questions on Rhythm interpretation for paramedic and EMT students, from Chapter 18 (Cardiovascular Emergencies). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

31 practice questions

1. A strip shows a regular rhythm at 76/min, an upright P wave before every QRS, a constant PR interval of 0.16 seconds, and a QRS of 0.08 seconds. What is the rhythm?

   1. A. Sinus arrhythmia
   2. B. Junctional rhythm
   3. C. First-degree AV block
   4. D. Normal sinus rhythm
   Show answer

   Answer: D. Normal sinus rhythm

   A regular rate of 60 to 100 with a normal P before each QRS, a PR of 0.12 to 0.20 seconds, and a narrow QRS is normal sinus rhythm.

2. A strip shows a regular rhythm at 46/min with upright P waves before each QRS, a PR interval of 0.18 seconds, and a QRS of 0.08 seconds. What is the rhythm?

   1. A. Junctional escape rhythm
   2. B. Sinus bradycardia
   3. C. Idioventricular rhythm
   4. D. Second-degree AV block
   Show answer

   Answer: B. Sinus bradycardia

   All sinus criteria are met but the rate is below 60, so this is sinus bradycardia. A junctional rhythm would have absent or inverted P waves or a short PR.

3. A febrile 40-year-old has a regular rhythm at 132/min, an upright P wave before each QRS, a PR interval of 0.14 seconds, and a QRS of 0.08 seconds. What is the rhythm?

   1. A. Sinus tachycardia
   2. B. Supraventricular tachycardia
   3. C. Atrial flutter with 2:1 block
   4. D. Accelerated junctional rhythm
   Show answer

   Answer: A. Sinus tachycardia

   Normal P waves before every QRS at a rate above 100 indicate sinus tachycardia, which here is a response to fever. Treat the cause rather than the rate.

4. A strip shows an irregularly irregular rhythm at about 120/min, no identifiable P waves, a wavy baseline, and a QRS of 0.08 seconds. What is the rhythm?

   1. A. Atrial flutter with variable block
   2. B. Multifocal atrial tachycardia
   3. C. Atrial fibrillation
   4. D. Sinus arrhythmia
   Show answer

   Answer: C. Atrial fibrillation

   An irregularly irregular narrow-complex rhythm with no discernible P waves and a fibrillatory baseline is atrial fibrillation. Flutter shows organized sawtooth waves, and MAT shows distinct P waves of varying shape.

5. A strip shows regular sawtooth-shaped atrial waves at about 300/min, a regular ventricular rate of 150/min, and a QRS of 0.08 seconds. What is the rhythm?

   1. A. Atrial flutter with 2:1 conduction
   2. B. Sinus tachycardia with peaked P waves
   3. C. Atrial fibrillation with rapid response
   4. D. Supraventricular tachycardia with aberrancy
   Show answer

   Answer: A. Atrial flutter with 2:1 conduction

   Sawtooth flutter waves at about 300/min with every second wave conducted give a ventricular rate near 150. A regular narrow rhythm at exactly 150 should always raise suspicion for flutter.

6. A 28-year-old with sudden palpitations has a regular narrow-complex rhythm at 190/min. P waves are not visible and the QRS is 0.08 seconds. What is the most likely rhythm?

   1. A. Sinus tachycardia
   2. B. Ventricular tachycardia
   3. C. Atrial fibrillation
   4. D. Supraventricular tachycardia
   Show answer

   Answer: D. Supraventricular tachycardia

   A regular narrow-complex tachycardia this fast with abrupt onset and no visible P waves is typical of reentrant SVT. Sinus tachycardia rarely exceeds about 150 at rest and has visible P waves.

7. A strip shows the PR interval getting progressively longer with each beat until a P wave is not followed by a QRS, after which the cycle repeats. QRS is 0.08 seconds. What is the rhythm?

   1. A. Second-degree AV block type II
   2. B. Third-degree AV block
   3. C. Second-degree AV block type I
   4. D. First-degree AV block
   Show answer

   Answer: C. Second-degree AV block type I

   Progressive PR lengthening ending in a dropped QRS is second-degree type I (Wenckebach), usually at the level of the AV node and often benign.

8. A strip shows a constant PR interval of 0.18 seconds, but every few beats a P wave is not followed by a QRS. The QRS is 0.14 seconds. What is the rhythm?

   1. A. Second-degree AV block type I
   2. B. Third-degree AV block
   3. C. Blocked premature atrial complexes
   4. D. Second-degree AV block type II
   Show answer

   Answer: D. Second-degree AV block type II

   A constant PR with intermittently nonconducted P waves is second-degree type II (Mobitz II). It is usually below the AV node, often has a wide QRS, and can progress to complete heart block.

9. A strip shows regular P waves at 80/min and a regular wide QRS at 36/min, with PR intervals that vary completely because P waves and QRS complexes have no relationship. What is the rhythm?

   1. A. Third-degree AV block
   2. B. Second-degree AV block type II
   3. C. Second-degree AV block type I
   4. D. Idioventricular rhythm
   Show answer

   Answer: A. Third-degree AV block

   Atria and ventricles beating independently with no relationship (AV dissociation) is complete heart block. The slow wide escape here suggests a ventricular origin.

10. A strip shows a regular rhythm at 72/min, a P wave before every QRS, a constant PR interval of 0.28 seconds, and a QRS of 0.08 seconds. What is the rhythm?

    1. A. Second-degree AV block type I
    2. B. Sinus rhythm with first-degree AV block
    3. C. Junctional rhythm with long PR
    4. D. Second-degree AV block type II
    Show answer

    Answer: B. Sinus rhythm with first-degree AV block

    Every P wave is conducted, but the PR interval is constantly longer than 0.20 seconds. That defines first-degree AV block, which itself usually needs no treatment.

11. A strip shows a regular wide-complex rhythm at 170/min, no visible P waves, and a QRS of 0.16 seconds with uniform complexes. What is the rhythm?

    1. A. Polymorphic ventricular tachycardia
    2. B. Monomorphic ventricular tachycardia
    3. C. Sinus tachycardia with bundle branch
    4. D. Accelerated idioventricular rhythm
    Show answer

    Answer: B. Monomorphic ventricular tachycardia

    A regular wide-complex tachycardia with identical QRS complexes and no visible P waves should be treated as monomorphic VT until proven otherwise.

12. A patient with a prolonged QT interval suddenly develops a wide-complex rhythm at 250/min in which the QRS amplitude waxes and wanes, appearing to twist around the baseline. What is the rhythm?

    1. A. Ventricular fibrillation
    2. B. Monomorphic VT
    3. C. Torsades de pointes
    4. D. Atrial fibrillation
    Show answer

    Answer: C. Torsades de pointes

    Polymorphic VT with twisting QRS amplitude in a setting of prolonged QT is torsades de pointes. Magnesium sulfate is the drug commonly used for it.

13. A pulseless patient's monitor shows chaotic, irregular deflections of varying shape and size with no identifiable P waves, QRS complexes, or T waves. What is the rhythm?

    1. A. Ventricular fibrillation
    2. B. Polymorphic ventricular tachycardia
    3. C. Coarse atrial fibrillation
    4. D. Pulseless electrical activity
    Show answer

    Answer: A. Ventricular fibrillation

    Disorganized chaotic activity with no recognizable complexes in a pulseless patient is VF. It is a shockable rhythm requiring immediate defibrillation.

14. A strip shows a regular rhythm at 34/min, no P waves, and wide bizarre QRS complexes of 0.16 seconds. What is the rhythm?

    1. A. Junctional escape rhythm
    2. B. Sinus bradycardia
    3. C. Idioventricular rhythm
    4. D. Atrial fibrillation
    Show answer

    Answer: C. Idioventricular rhythm

    A slow (20 to 40/min) wide-complex rhythm without P waves arises from ventricular pacemaker cells. Junctional escape rhythms are narrow and usually 40 to 60/min.

15. A strip shows two P waves for every QRS, with a constant PR interval in the conducted beats and a QRS of 0.14 seconds. Which statement is most accurate?

    1. A. This proves the block is Wenckebach (type I)
    2. B. This is third-degree block with a junctional escape
    3. C. This is a benign rhythm needing no monitoring
    4. D. Type I and type II cannot be told apart for sure
    Show answer

    Answer: D. Type I and type II cannot be told apart for sure

    With 2:1 conduction there are never two conducted beats in a row, so you cannot see whether the PR lengthens; the level of block cannot be proved from the strip alone. A wide QRS makes block below the AV node (type II behavior) more likely, so prepare to pace if the patient becomes unstable. The constant PR in conducted beats rules out complete block, and the rhythm is not benign.

16. A strip shows a regular rhythm at 50/min, a narrow QRS of 0.08 seconds, and inverted P waves immediately before each QRS with a PR of 0.08 seconds. What is the rhythm?

    1. A. Junctional escape rhythm
    2. B. Sinus bradycardia
    3. C. Idioventricular rhythm
    4. D. First-degree AV block
    Show answer

    Answer: A. Junctional escape rhythm

    Inverted P waves with a short PR (or P waves that are absent or follow the QRS) and a narrow QRS at 40 to 60/min indicate a junctional escape rhythm.

17. A strip shows a regular narrow-complex rhythm at 84/min with no visible P waves. The QRS is 0.08 seconds. Which rhythm best fits?

    1. A. Junctional escape rhythm
    2. B. Normal sinus rhythm
    3. C. Atrial flutter
    4. D. Accelerated junctional rhythm
    Show answer

    Answer: D. Accelerated junctional rhythm

    A junctional rhythm faster than its intrinsic rate of 40 to 60, but at or below 100, is an accelerated junctional rhythm. Above 100 it would be junctional tachycardia.

18. In an otherwise normal sinus rhythm, one beat occurs early with a wide, bizarre QRS, no preceding P wave, a T wave opposite to the QRS, and a full compensatory pause. What is this beat?

    1. A. Premature atrial complex
    2. B. Premature junctional complex
    3. C. Premature ventricular complex
    4. D. Ventricular escape beat
    Show answer

    Answer: C. Premature ventricular complex

    An early, wide, bizarre complex without a P wave followed by a full compensatory pause is a PVC. An escape beat comes late, after a pause, not early.

19. A strip shows a sinus beat followed by a premature wide bizarre complex, repeating in that pattern throughout. What is this called?

    1. A. Ventricular trigeminy
    2. B. Ventricular couplets
    3. C. Ventricular bigeminy
    4. D. Run of ventricular tachycardia
    Show answer

    Answer: C. Ventricular bigeminy

    Every other beat being a PVC is bigeminy; every third beat is trigeminy. Two PVCs in a row are a couplet, and three or more in a row form a run of VT.

20. In a sinus rhythm, one beat comes early with a narrow QRS and a P wave that looks different from the other P waves. What is this beat?

    1. A. Premature ventricular complex
    2. B. Junctional escape beat
    3. C. Premature atrial complex
    4. D. Sinus pause
    Show answer

    Answer: C. Premature atrial complex

    An early beat with an abnormally shaped P wave and a narrow QRS originates in the atria outside the SA node. PVCs are wide and lack a preceding P wave.

21. A healthy 20-year-old's strip shows normal P waves, PR, and QRS, but the R-R interval shortens with inspiration and lengthens with expiration. What is the rhythm?

    1. A. Atrial fibrillation
    2. B. Sinus arrhythmia
    3. C. Sinus exit block type II
    4. D. Wandering pacemaker
    Show answer

    Answer: B. Sinus arrhythmia

    Rate variation with breathing and otherwise normal sinus features is sinus arrhythmia, a normal finding especially in young people.

22. Your cardiac arrest patient's monitor shows a flat line. Before treating it as asystole, what should you do?

    1. A. Deliver one shock in case of fine VF
    2. B. Increase the paper speed to 50 mm/sec
    3. C. Give atropine to stimulate the heart
    4. D. Confirm in another lead and check the leads
    Show answer

    Answer: D. Confirm in another lead and check the leads

    A flat line can result from a loose lead, low gain, or fine VF in one lead. Confirm asystole by checking connections and viewing a second lead; atropine is not recommended for asystole.

23. A patient without a pulse shows a regular narrow-complex rhythm at 70/min on the monitor. What is the rhythm called?

    1. A. Pulseless electrical activity
    2. B. Normal sinus rhythm
    3. C. Agonal idioventricular rhythm
    4. D. Pulseless ventricular tachycardia
    Show answer

    Answer: A. Pulseless electrical activity

    Any organized electrical rhythm other than VF or VT without a palpable pulse is PEA. Treatment is CPR, epinephrine, and searching for reversible causes, not defibrillation.

24. A COPD patient's strip shows an irregular rhythm at 118/min with at least three different P wave shapes, varying PR intervals, and narrow QRS complexes. What is the rhythm?

    1. A. Atrial fibrillation with RVR
    2. B. Sinus tachycardia with PACs
    3. C. Atrial flutter with variable block
    4. D. Multifocal atrial tachycardia
    Show answer

    Answer: D. Multifocal atrial tachycardia

    Three or more P wave morphologies with an irregular rate above 100 is MAT, commonly seen with chronic lung disease. It differs from AF because distinct P waves are present.

25. A strip shows a regular rhythm in which a vertical spike precedes each wide QRS complex at a rate of 70/min. What is the rhythm?

    1. A. Ventricular paced rhythm
    2. B. Atrial paced rhythm
    3. C. Accelerated idioventricular
    4. D. Right bundle branch block
    Show answer

    Answer: A. Ventricular paced rhythm

    A pacemaker spike followed by a wide QRS indicates ventricular pacing. With atrial pacing, the spike precedes the P wave instead.

26. On a transcutaneous pacing strip, pacer spikes appear at the set rate, but some spikes are not followed by a wide QRS and T wave. This finding is:

    1. A. Failure to sense
    2. B. Failure to capture
    3. C. Failure to pace
    4. D. Normal demand mode
    Show answer

    Answer: B. Failure to capture

    Spikes without a following depolarization mean the current is not capturing the myocardium; increase the milliamps per protocol. Confirm mechanical capture with a palpable pulse.

27. A strip shows a short PR interval of 0.10 seconds, a slurred upstroke at the start of the QRS, and a QRS of 0.12 seconds. What pattern is this?

    1. A. Lown-Ganong-Levine
    2. B. Wolff-Parkinson-White
    3. C. Left bundle branch block
    4. D. Accelerated junctional
    Show answer

    Answer: B. Wolff-Parkinson-White

    A short PR, a delta wave (slurred QRS upstroke), and a widened QRS indicate preexcitation through an accessory pathway, the WPW pattern.

28. During a regular wide-complex tachycardia at 160/min, you see an occasional narrow beat that looks like the patient's normal QRS. What does this finding indicate?

    1. A. Ventricular tachycardia with capture beats
    2. B. SVT with a rate-related bundle branch block
    3. C. Atrial flutter with variable conduction
    4. D. Sinus tachycardia with frequent PVCs
    Show answer

    Answer: A. Ventricular tachycardia with capture beats

    An occasional narrow beat (a capture beat) or a hybrid-looking beat (a fusion beat) occurs when a sinus impulse briefly reaches the ventricles during VT; both point to AV dissociation and strongly support VT. SVT with aberrancy (a rate-related bundle branch block) would keep the same wide shape throughout, flutter shows sawtooth waves, and sinus tachycardia with PVCs would be mostly narrow.

29. A 68-year-old with a prior MI has a stable, regular wide-complex tachycardia at 150/min. How should you interpret it?

    1. A. Treat it as SVT because he is stable
    2. B. Treat it as VT until proven otherwise
    3. C. Assume aberrancy because the rate is 150
    4. D. Ignore it until the hospital reads it
    Show answer

    Answer: B. Treat it as VT until proven otherwise

    Most regular wide-complex tachycardias in older patients with structural heart disease, especially a prior MI, are VT, and being stable does not make it SVT. Giving drugs meant for SVT, such as diltiazem, to a patient in VT can cause collapse. A rate of 150 does not prove aberrancy, and an untreated wide-complex tachycardia should not be ignored.

30. A patient on digoxin for atrial fibrillation now has a slow, perfectly regular ventricular rate of 40/min with fibrillatory waves still visible. What does this suggest?

    1. A. Complete heart block with an escape rhythm
    2. B. Successful conversion to sinus rhythm
    3. C. Ideal rate control of the atrial fibrillation
    4. D. Atrial flutter with 4:1 conduction
    Show answer

    Answer: A. Complete heart block with an escape rhythm

    AF normally conducts irregularly, so a regular slow ventricular rhythm in AF means the atrial impulses are no longer getting through and a junctional or ventricular escape has taken over, which is a classic sign of digoxin toxicity. Sinus rhythm would have P waves, ideal rate control would still be irregular, and flutter would show sawtooth waves.

31. During sinus rhythm at 70/min, the monitor shows a sudden 3.5-second pause with no P wave, after which sinus beats resume. The pause is not a multiple of the P-P interval. What is this?

    1. A. Sinus arrhythmia
    2. B. First-degree AV block
    3. C. Second-degree AV block type II
    4. D. Sinus arrest
    Show answer

    Answer: D. Sinus arrest

    In sinus arrest the SA node fails to fire, so there is no P wave and the pause is not an exact multiple of the normal P-P interval (an exact multiple suggests sinus exit block). Sinus arrhythmia varies gradually with breathing, first-degree block only prolongs the PR, and in second-degree type II a P wave is present but not followed by a QRS.