23 Cardiology & Resuscitation Practice Questions & Answers

1. 1. A 72-year-old patient complains of palpitations. The monitor shows a narrow-complex rhythm at about 110/min that is irregularly irregular, with no discernible P waves and a chaotic, wavering baseline. What is the rhythm?

   • A.Sinus tachycardia with frequent PACs
   • B.Second-degree AV block, Mobitz type I
   • C.Atrial fibrillation with rapid ventricular response✓ Answer
   • D.Atrial flutter with variable conduction

   Atrial fibrillation is defined by the combination of an irregularly irregular ventricular response and the absence of organized P waves, because the atria depolarize chaotically rather than as a single wavefront. Atrial flutter shows organized sawtooth flutter waves, and sinus tachycardia with PACs still shows underlying P waves with only intermittent irregularity.

   Source: NREMT Paramedic Test Plan (eff. 7/1/2024), Cardiology & Resuscitation — ECG rhythm interpretation; standard ECG criteria for atrial fibrillation (AHA ECC reference)Report a problem with this question

2. 2. On a rhythm strip you note grouped beating: the PR interval lengthens progressively over three beats until a P wave is not followed by a QRS, and then the cycle repeats. The QRS complexes are narrow. What is the rhythm?

   • A.Second-degree AV block, Mobitz type II
   • B.First-degree AV block
   • C.Third-degree (complete) AV block
   • D.Second-degree AV block, Mobitz type I (Wenckebach)✓ Answer

   Progressive PR prolongation ending in a dropped QRS is the hallmark of Mobitz type I, because the block sits in the AV node and conduction fatigues gradually. Mobitz type II shows a fixed PR with sudden non-conducted beats, third-degree block shows complete P-QRS dissociation, and first-degree block never drops a beat.

   Source: NREMT Paramedic Test Plan, Cardiology & Resuscitation — ECG interpretation; standard AV block criteria (AHA ACLS bradycardia reference)Report a problem with this question

3. 3. A 68-year-old is pale and confused with BP 74/40. The monitor shows a ventricular rate of 36/min with wide QRS complexes, and P waves that march through the strip with no fixed relationship to the QRS. What is the most appropriate next intervention?

   • A.Give adenosine 6 mg rapid IV push
   • B.Begin transcutaneous pacing✓ Answer
   • C.Give atropine 1 mg IV and reassess before any other therapy
   • D.Perform synchronized cardioversion

   This is third-degree AV block with a wide-complex ventricular escape, meaning the block is below the AV node; atropine works by increasing AV nodal conduction and is unlikely to help (and should not delay pacing) in infranodal block. An unstable patient with high-grade block needs immediate transcutaneous pacing, with a chronotropic infusion as an alternative.

   Source: AHA ACLS Adult Bradycardia Algorithm — atropine ineffective in infranodal (Mobitz II / third-degree wide-complex) block; proceed to pacingReport a problem with this question

4. 4. A 60-year-old with crushing chest pain has 2 mm ST elevation in leads II, III, and aVF with reciprocal depression in aVL. BP is 102/68. Before administering nitroglycerin, what should the paramedic do?

   • A.Apply CPAP to improve oxygenation
   • B.Give a 2 L normal saline bolus prophylactically
   • C.Administer a beta-blocker to reduce myocardial oxygen demand
   • D.Obtain a right-sided lead (V4R) to evaluate for right ventricular infarction✓ Answer

   Inferior STEMI (ST elevation in II, III, aVF) frequently involves the right ventricle, and an RV infarct makes the patient preload-dependent — nitroglycerin can cause profound hypotension by dropping preload. Recording V4R identifies RV involvement before venodilators are given; if V4R shows ST elevation, nitrates are withheld and hypotension is treated with fluid.

   Source: AHA ACS guidance — inferior STEMI: obtain V4R; nitrates cautioned/contraindicated in RV infarction (preload dependence)Report a problem with this question

5. 5. A 55-year-old with a history of prior MI has a regular, monomorphic wide-complex tachycardia at 180/min. He is alert with BP 118/70. You cannot determine whether the rhythm is VT or SVT with aberrancy. How should you manage this rhythm?

   • A.Treat it as SVT and give diltiazem
   • B.Treat it as ventricular tachycardia✓ Answer
   • C.Perform immediate defibrillation
   • D.Assume it is benign and transport with monitoring only

   A wide-complex tachycardia of uncertain origin is treated as VT because that assumption is the safest: VT therapies (amiodarone, procainamide, cardioversion) will not seriously harm an SVT patient, whereas AV-nodal blockers such as diltiazem or verapamil given to true VT can cause hemodynamic collapse. A prior MI also makes VT statistically far more likely.

   Source: AHA ACLS Adult Tachycardia (with pulse) Algorithm — wide-complex tachycardia of uncertain type is managed as VT; avoid AV-nodal blockersReport a problem with this question

6. 6. During transport, a patient's rhythm degenerates into a polymorphic ventricular tachycardia in which the QRS complexes appear to twist around the baseline. The pre-event 12-lead showed a markedly prolonged QT interval. Which medication specifically targets this rhythm?

   • A.Magnesium sulfate✓ Answer
   • B.Adenosine
   • C.Diltiazem
   • D.Atropine

   The rhythm described is torsades de pointes, a polymorphic VT associated with QT prolongation. Magnesium sulfate is the specific pharmacologic therapy because magnesium stabilizes myocardial cell membranes and suppresses the early afterdepolarizations that trigger torsades; if the patient is pulseless or deteriorates, unsynchronized defibrillation is required.

   Source: AHA ACLS — magnesium sulfate 1-2 g IV for torsades de pointes associated with prolonged QTReport a problem with this question

7. 7. A 28-year-old has sharp chest pain that worsens when lying flat and improves when leaning forward. The 12-lead shows ST elevation in nearly all leads with PR-segment depression, and no reciprocal ST depression. Which condition best explains these findings?

   • A.Anterior STEMI
   • B.Prinzmetal angina
   • C.Left bundle branch block
   • D.Acute pericarditis✓ Answer

   Pericarditis produces diffuse ST elevation because the entire inflamed pericardium injures the epicardial surface globally, not in one coronary territory — hence no reciprocal depression — and PR depression plus positional/pleuritic pain are characteristic. A STEMI elevates ST segments only in the contiguous leads of the occluded artery's territory with reciprocal changes opposite them.

   Source: 12-lead STEMI mimics — pericarditis: diffuse ST elevation with PR depression, no reciprocal changes (NREMT Cardiology & Resuscitation ECG content; AHA ECC reference)Report a problem with this question

8. 8. An adult in cardiac arrest remains in ventricular fibrillation after the second defibrillation attempt, and CPR has resumed. According to the ACLS cardiac arrest algorithm, which medication is given at this point?

   • A.Atropine 1 mg IV
   • B.Epinephrine 1 mg IV✓ Answer
   • C.Lidocaine 1.5 mg/kg IV
   • D.Amiodarone 300 mg IV

   In the shockable-rhythm arm of the ACLS algorithm, epinephrine 1 mg IV/IO is given after the second shock (then every 3-5 minutes) because its alpha-adrenergic effect raises aortic diastolic pressure and coronary perfusion pressure during CPR. Antiarrhythmics such as amiodarone or lidocaine are reserved for VF/pVT that persists after the third shock, and atropine has no role in cardiac arrest.

   Source: AHA ACLS Adult Cardiac Arrest Algorithm — epinephrine after 2nd shock in VF/pVT; antiarrhythmic after 3rd shockReport a problem with this question

9. 9. A dialysis patient who missed two sessions is in cardiac arrest with PEA. The pre-arrest ECG showed tall, peaked T waves and a widening QRS. In addition to CPR and epinephrine, which intervention directly targets the suspected cause?

   • A.Defibrillation at maximum energy
   • B.Magnesium sulfate 2 g IV
   • C.Atropine 1 mg IV
   • D.IV calcium (calcium chloride or gluconate)✓ Answer

   Missed dialysis with peaked T waves and QRS widening points to hyperkalemia, one of the reversible Hs and Ts of PEA arrest. IV calcium is given first because it directly stabilizes the myocardial cell membrane against the depolarizing effect of potassium, buying time while sodium bicarbonate and albuterol shift potassium into cells; defibrillation does not treat PEA.

   Source: AHA ACLS — reversible causes (Hs & Ts): hyperkalemia; calcium as first-line membrane stabilizerReport a problem with this question

10. 10. A 4-year-old child (16 kg) is in cardiac arrest and the monitor shows ventricular fibrillation. What is the recommended energy dose for the first defibrillation attempt?

    • A.4 J/kg (64 J)
    • B.10 J/kg (160 J)
    • C.2 J/kg (32 J)✓ Answer
    • D.0.5 J/kg (8 J)

    The pediatric defibrillation sequence starts at 2 J/kg for the first shock and escalates to 4 J/kg for subsequent shocks (subsequent doses at least 4 J/kg, not to exceed 10 J/kg or the adult dose). Starting lower than adults reflects the smaller pediatric myocardial mass, while escalation addresses refractory VF.

    Source: AHA PALS Pediatric Cardiac Arrest Algorithm — first shock 2 J/kg, subsequent shocks 4 J/kgReport a problem with this question

11. 11. During CPR with continuous waveform capnography, the ETCO2 abruptly rises from 14 mmHg to 42 mmHg. What does this change most likely indicate?

    • A.The patient is developing severe acidosis
    • B.The compressor is fatiguing and needs relief
    • C.The endotracheal tube has become dislodged
    • D.Return of spontaneous circulation (ROSC)✓ Answer

    ETCO2 during CPR is a direct proxy for pulmonary blood flow, so a sudden sustained jump toward normal values means the heart has resumed pumping and is delivering far more CO2 to the lungs — the earliest sign of ROSC. Tube dislodgement or compressor fatigue would drop the ETCO2, not raise it.

    Source: AHA ACLS — waveform capnography during CPR: abrupt sustained ETCO2 increase indicates ROSC; <10 mmHg prompts improving compressionsReport a problem with this question

12. 12. A 70-year-old is diaphoretic and lightheaded with BP 78/50. The monitor shows sinus bradycardia at 38/min with narrow QRS complexes. IV access is established. What is the first-line pharmacologic intervention?

    • A.Dopamine infusion at 5-20 mcg/kg/min
    • B.Epinephrine infusion at 2-10 mcg/min
    • C.Immediate transcutaneous pacing before any medication
    • D.Atropine 1 mg IV✓ Answer

    For unstable bradycardia with a narrow-complex (nodal-level) rhythm, atropine 1 mg IV is first line because its anticholinergic effect blocks vagal tone at the SA and AV nodes, and it can be repeated every 3-5 minutes to a total of 3 mg. Pacing and chronotropic infusions (dopamine or epinephrine) are the next step when atropine fails — they are not first line when IV atropine is immediately available for a nodal bradycardia.

    Source: AHA ACLS Adult Bradycardia Algorithm — atropine 1 mg first line; pacing/dopamine/epinephrine if ineffectiveReport a problem with this question

13. 13. An 8-month-old infant is limp and mottled with a heart rate of 50/min. You have already provided effective bag-mask ventilation with 100% oxygen for 30 seconds, but the heart rate remains 50 with poor perfusion. What should you do next?

    • A.Continue ventilation only and reassess in 2 minutes
    • B.Begin chest compressions✓ Answer
    • C.Apply transcutaneous pacing immediately
    • D.Give atropine before any other intervention

    In pediatric patients, a heart rate below 60/min with signs of poor perfusion despite adequate oxygenation and ventilation is treated as impending arrest: begin CPR, because pediatric cardiac output is heavily rate-dependent and bradycardia this profound cannot sustain perfusion. Epinephrine is the first-line drug in this pathway; atropine is reserved for suspected increased vagal tone or primary AV block.

    Source: AHA PALS Bradycardia with a Pulse Algorithm — CPR if HR <60/min with poor perfusion despite oxygenation/ventilation; epinephrine before atropineReport a problem with this question

14. 14. A 30-year-old has sudden palpitations. The monitor shows a regular narrow-complex tachycardia at 190/min with no visible P waves. She is alert, BP 124/78, with no chest pain or dyspnea. What is the most appropriate first intervention?

    • A.Adenosine 12 mg rapid IV push
    • B.Synchronized cardioversion at 100 J
    • C.Attempt vagal maneuvers✓ Answer
    • D.Amiodarone 150 mg over 10 minutes

    This is stable SVT, so the least invasive therapy comes first: vagal maneuvers (such as a modified Valsalva) increase parasympathetic tone at the AV node and terminate up to about a quarter of SVT episodes without drugs. If vagal maneuvers fail, adenosine is given starting at 6 mg — not 12 mg — and cardioversion is reserved for unstable patients.

    Source: AHA ACLS Adult Tachycardia Algorithm — stable regular narrow-complex: vagal maneuvers first, then adenosine 6 mg, then 12 mgReport a problem with this question

15. 15. A 66-year-old is confused and hypotensive (BP 76/44) with cool, mottled skin. The monitor shows an irregularly irregular narrow-complex tachycardia at 168/min. What is the most appropriate immediate treatment?

    • A.Synchronized cardioversion✓ Answer
    • B.Vagal maneuvers followed by adenosine
    • C.Unsynchronized defibrillation at 200 J
    • D.Diltiazem IV for rate control

    Hypotension and altered mental status make this an unstable tachyarrhythmia (rapid atrial fibrillation), and any unstable tachycardia with a pulse gets immediate synchronized cardioversion — the shock is synchronized to the R wave to avoid delivering energy during the vulnerable T wave, which could induce VF. Diltiazem would worsen hypotension, and adenosine does not convert atrial fibrillation.

    Source: AHA ACLS Adult Tachycardia Algorithm — unstable tachycardia with a pulse: immediate synchronized cardioversionReport a problem with this question

16. 16. A 24-year-old with known Wolff-Parkinson-White syndrome presents with an irregular wide-complex tachycardia at rates varying up to 250/min, consistent with pre-excited atrial fibrillation. He is currently maintaining adequate perfusion. Which medication is most appropriate?

    • A.Diltiazem
    • B.Adenosine
    • C.Procainamide✓ Answer
    • D.Metoprolol

    In pre-excited atrial fibrillation, AV-nodal blocking agents (adenosine, calcium-channel blockers, beta-blockers) are contraindicated because blocking the AV node shunts all atrial impulses down the accessory pathway, which can accelerate the ventricular rate into VF. Procainamide slows conduction in the accessory pathway itself, making it the appropriate drug; if the patient becomes unstable, synchronized cardioversion is used.

    Source: AHA ACLS/ECC guidance — avoid AV-nodal blockers in pre-excited (WPW) atrial fibrillation; procainamide or cardioversion preferredReport a problem with this question

17. 17. A 58-year-old with substernal chest pressure is suspected of having an acute coronary syndrome. He has no allergies and no signs of active bleeding. Which prehospital medication has the greatest effect on reducing mortality in ACS?

    • A.Aspirin 162-325 mg chewed✓ Answer
    • B.Nitroglycerin 0.4 mg sublingual
    • C.Fentanyl for analgesia
    • D.High-flow oxygen by non-rebreather

    Aspirin irreversibly inhibits platelet cyclooxygenase, blocking thromboxane A2-mediated platelet aggregation on the ruptured plaque — directly limiting the clot that is causing the infarction — and it is the prehospital ACS drug with proven mortality benefit. Nitroglycerin and fentanyl relieve symptoms without improving survival, and supplemental oxygen is indicated only when SpO2 is below 90%.

    Source: AHA ACS guidelines — early aspirin reduces mortality; oxygen only if SpO2 <90%Report a problem with this question

18. 18. A 62-year-old man with chest pain has BP 142/88 and HR 92. During your SAMPLE history he mentions taking sildenafil the previous evening. Which of these findings contraindicates nitroglycerin administration?

    • A.Blood pressure of 142/88
    • B.Heart rate of 92/min
    • C.Sildenafil use within the past 24-48 hours✓ Answer
    • D.History of a previous myocardial infarction

    Nitroglycerin donates nitric oxide, which raises cGMP to dilate vessels; PDE-5 inhibitors like sildenafil block the enzyme that breaks cGMP down, so combining the two produces unopposed, potentially refractory hypotension. Recent PDE-5 inhibitor use (roughly 24 hours for sildenafil, up to 48 hours for tadalafil) therefore contraindicates nitrates, while his vital signs and MI history do not.

    Source: AHA ACS guidance — nitroglycerin contraindicated with recent PDE-5 inhibitor use (sildenafil/tadalafil, 24-48 h)Report a problem with this question

19. 19. A 74-year-old woman awoke severely dyspneic. She has diffuse crackles, pink frothy sputum, SpO2 84%, and BP 186/104. Which treatment combination is most appropriate?

    • A.Normal saline bolus and supine positioning
    • B.Albuterol nebulizer and epinephrine IM
    • C.CPAP with nitroglycerin✓ Answer
    • D.Rapid sequence intubation as the first intervention

    This is hypertensive acute cardiogenic pulmonary edema: CPAP splints alveoli open and raises intrathoracic pressure to reduce preload, while nitroglycerin dilates the venous (and at higher doses arterial) system to cut the preload and afterload that are flooding the lungs. Fluids and supine positioning would worsen the edema, and noninvasive support usually averts the need for intubation.

    Source: Prehospital acute pulmonary edema standard of care — CPAP plus nitroglycerin for preload/afterload reduction (NREMT Cardiology & Resuscitation — heart failure management)Report a problem with this question

20. 20. A 45-year-old stabbing victim is hypotensive with distended neck veins and muffled heart tones. The monitor shows sinus tachycardia with QRS complexes that alternate in amplitude beat to beat. Which condition do these findings indicate?

    • A.Cardiac tamponade✓ Answer
    • B.Tension pneumothorax
    • C.Massive pulmonary embolism
    • D.Cardiogenic shock from ventricular failure

    Hypotension, JVD, and muffled heart tones form Beck's triad, and electrical alternans (alternating QRS amplitude) occurs because the heart swings within the fluid-filled pericardial sac. The accumulating pericardial blood compresses the ventricles and prevents diastolic filling; prehospital care is fluid to support preload and rapid transport, since tamponade is also a reversible cause of PEA arrest.

    Source: Cardiac tamponade — Beck triad and electrical alternans; reversible cause (T) in the Hs & Ts (AHA ACLS reference)Report a problem with this question

21. 21. You achieve ROSC in a 59-year-old after a VF arrest. He remains unresponsive with a supraglottic airway in place, SpO2 99% on 100% oxygen, and ETCO2 30 mmHg. How should ventilation and oxygenation be managed?

    • A.Ventilate about 10 breaths/min, target ETCO2 35-45 mmHg, and titrate oxygen to SpO2 92-98%✓ Answer
    • B.Continue 100% oxygen and increase the rate until ETCO2 falls below 25 mmHg
    • C.Hyperventilate at 24 breaths/min to protect the brain from swelling
    • D.Stop ventilating since SpO2 is already 99%

    Post-ROSC care targets normal physiology: hyperventilation causes cerebral vasoconstriction and raises intrathoracic pressure, reducing both cerebral perfusion and venous return, while prolonged hyperoxia may worsen reperfusion injury. Ventilating about 10/min to an ETCO2 of 35-45 mmHg and titrating oxygen to SpO2 92-98% avoids both extremes in the comatose post-arrest patient.

    Source: AHA ACLS Post-Cardiac Arrest Care Algorithm — 10 breaths/min, ETCO2 35-45 mmHg, SpO2 92-98%, avoid hyperventilation and hyperoxiaReport a problem with this question

22. 22. A patient's ECG shows a regular narrow-complex rhythm at 45/min with absent or inverted P waves immediately before or after each QRS. Which pacemaker site is most likely driving this rhythm, based on intrinsic rates?

    • A.An ectopic atrial focus firing at its usual rate
    • B.The AV junction✓ Answer
    • C.The SA node
    • D.Ventricular Purkinje fibers

    A junctional escape rhythm arises from the AV junction, whose intrinsic rate is 40-60/min; the QRS stays narrow because conduction still travels down the normal His-Purkinje system, and P waves are absent or inverted because the atria are depolarized retrogradely. A ventricular pacemaker would fire at 20-40/min with wide complexes, and the SA node's intrinsic rate is 60-100/min with upright P waves.

    Source: Cardiac conduction system intrinsic rates — SA node 60-100, AV junction 40-60, ventricles 20-40 (NREMT Cardiology & Resuscitation — anatomy/physiology foundations)Report a problem with this question

23. 23. A 12-lead ECG on a 57-year-old with chest pain shows 3 mm ST elevation in leads V1 through V4. Which coronary artery is most likely occluded, and which wall is infarcting?

    • A.Left anterior descending artery — anterior wall✓ Answer
    • B.Right coronary artery — inferior wall
    • C.Circumflex artery — lateral wall
    • D.Right coronary artery — posterior wall

    Leads V1-V4 sit over the anterior surface of the left ventricle, which is supplied by the left anterior descending (LAD) artery, so contiguous ST elevation there localizes an anterior STEMI to an LAD occlusion. Inferior infarcts show in II, III, and aVF (usually RCA), and lateral infarcts show in I, aVL, V5, and V6 (usually circumflex); anterior MIs carry high risk of pump failure because of the large territory involved.

    Source: 12-lead infarct localization — V1-V4 anterior (LAD); II/III/aVF inferior (RCA); I/aVL/V5-V6 lateral (circumflex) (NREMT Cardiology & Resuscitation ECG content)Report a problem with this question

Practice questions modeled on the NREMT paramedic examination specifications and the National EMS Education Standards. Drug doses, device settings, and other figures that national guidelines revise are deliberately not tested — always follow your medical director, current guidelines, and local protocols. Not medical advice, and not affiliated with or endorsed by the National Registry of Emergency Medical Technicians (NREMT) or NHTSA. Study the official materials at nremt.org. Official NREMT →