Skip to content
Free NREMT practice questionsFree Paramedic practice questions · Cardiology & Resuscitation

10 free Paramedic practice questions: 12-Lead ECG Interpretation and STEMI Recognition

These are real questions from the same bank the app draws from. Each one is written to the NREMT Paramedic content specifications and kept inside the Paramedic scope of practice. Pick an answer and you get the full rationale, including why the other three options are wrong.

Work through all 10, then move on to the next topic. When you want the full picture, the free Paramedic diagnostic covers every topic in one sitting. No account needed for any of it.

Question 1 of 10

A 62-year-old patient reports chest tightness that began an hour ago. The 12-lead ECG shows 1 mm of ST elevation in V2 and 1 mm in V3, measured at the J point, with no reciprocal depression. The vital signs are BP 142/86, P 92, R 20, and SpO₂ 96% on room air. How should this tracing be read?

Show the answer and rationale

Correct answer · V2 and V3 carry a higher threshold, so this is under the bar

The elevation is 1 mm in V2 and 1 mm in V3, measured at the J point. V2 and V3 have a higher STEMI threshold than the other leads. These two chest leads sit closer to the ventricle, so they normally show more ST elevation at baseline. In V2 and V3, the elevation has to be larger, roughly 2 mm, to tell ischemia apart from normal early repolarization. A 1 mm rise in only these two leads is under that bar. This tracing does not meet STEMI criteria. Keep this patient on the acute coronary syndrome pathway, treat the symptoms, and repeat 12-leads. Do not activate the cath lab on this ECG alone.

Why the others are wrong

Absent reciprocal depression rules out an acute occlusion here: Reciprocal depression makes a STEMI call stronger when you see it. Many real infarctions never show reciprocal depression, so a tracing without it proves nothing. The real problem here is height, because 1 mm in V2 and V3 is short of the 2 mm those leads need.

These leads are not contiguous, so the thresholds do not apply: V2 and V3 sit right next to each other on the chest wall, so they are contiguous. The label changes from septal to anterior between them, and they still count as neighboring leads. This tracing fails on height, not on which leads are grouped together.

This meets criteria, so activate the catheterization team now: ST elevation in two neighboring leads does look like a STEMI. Activating fast is the right move when the tracing meets criteria. V2 and V3 need roughly 2 mm at the J point before they count. With only 1 mm, activating now sends a team in before the tracing reaches the threshold.

Question 2 of 10

A 66-year-old patient with 40 minutes of chest pressure has a 12-lead ECG showing 2 mm of horizontal ST depression in V1, V2, and V3 with unusually tall R waves in those leads. The vital signs are BP 136/82, P 88, R 18, and SpO₂ 97% on room air. What is the most appropriate next step with the ECG?

Show the answer and rationale

Correct answer · Read it as a posterior STEMI and activate the cath lab

This is a posterior STEMI. The 12-lead shows ST depression in V1, V2, and V3, with tall R waves in those same leads. No standard lead sits over the back of the heart. V1 through V3 look at the back wall from the front of the chest, so the changes show up flipped. ST elevation on the back wall shows up as ST depression in V1 through V3. The Q wave shows up as a tall R wave. A posterior STEMI is still a STEMI, so it gets the same response. Activate the cath lab on this tracing.

Why the others are wrong

Repeat the same tracing in 10 minutes and compare: Repeating the 12-lead in 10 minutes makes sense when the first tracing does not tell you enough. This tracing already shows a posterior STEMI. Waiting 10 minutes only delays the cath lab.

Add V4R to look for right ventricular involvement: V4R looks for a right ventricular infarction. You add V4R when II, III, and aVF show ST elevation. This tracing has no ST elevation in II, III, or aVF, and all of the changes are in V1 through V3.

Treat the depression as subendocardial ischemia only: ST depression by itself can be subendocardial ischemia. Tall R waves in the same leads as the depression are what make this a posterior STEMI. If you call it ischemia only, the cath lab never gets activated.

Question 3 of 10

A 59-year-old patient has 30 minutes of chest pressure and a 12-lead ECG showing 2 mm of ST elevation in II, III, and aVF with reciprocal depression in I and aVL. The lungs are clear and the neck veins are distended. The vital signs are BP 92/58, P 62, R 18, and SpO₂ 96% on room air. Aspirin has been given. What additional tracing should be obtained before any preload reducing medication?

Show the answer and rationale

Correct answer · A right sided tracing that includes V4R

This patient has an inferior STEMI, with 2 mm of ST elevation in II, III, and aVF and reciprocal depression in I and aVL. The lungs are clear, the neck veins are distended, and the blood pressure is 92/58. Those findings with an inferior infarction point to right ventricular infarction until proven otherwise. Every inferior STEMI gets a right sided tracing with V4R. The right ventricle depends on preload, the blood filling it. Nitroglycerin lowers preload and can drop the blood pressure. Confirm with V4R before you give nitroglycerin. If V4R shows ST elevation, withhold nitroglycerin and give fluid instead.

Why the others are wrong

A repeat 12-lead recorded after 10 minutes: Repeat 12-leads matter on a long transport. Repeating the same 12 leads tells you nothing about the right ventricle. Waiting 10 minutes delays the V4R answer while the blood pressure is already 92/58.

A 30 second rhythm strip recorded in lead II: A rhythm strip in lead II shows you rate and regularity. The question here is which chamber is infarcted. Lead II cannot see the right ventricle.

A repeat 12-lead after a 250 mL fluid bolus: Fluid may well be where this patient's care is headed. A repeat 12-lead after the bolus still shows the same 12 views, and none of them look at the right ventricle. The nitroglycerin decision depends on the right ventricle, so the right sided lead comes first.

Question 4 of 10

A 49-year-old patient reports an ache across the chest that started while carrying groceries in from the car and has not let up. The 12-lead ECG shows 2 mm of ST elevation in aVL, with no ST change in I, V5, V6, or any other lead. The vital signs are BP 154/92, P 76, R 18, and SpO₂ 98% on room air. Which reading of this tracing is correct?

Show the answer and rationale

Correct answer · Not an injury pattern, because one lead alone never meets the criteria

This tracing is not an injury pattern. Only aVL shows ST elevation. Lead I, V5, and V6 are flat, and no other lead is elevated. STEMI criteria need new ST elevation in two or more contiguous leads. Contiguous leads look at the same wall or the wall next to it. Injured heart muscle covers a region, so its current shows up in more than one lead. A single elevated lead with flat neighbors is more likely a misplaced electrode, artifact, or a normal variant. Activation depends on contiguous leads, not on how many millimeters one lead rises. The chest pain has not let up, and a tracing that misses the criteria does not prove the patient is safe. Repeat the 12-lead and keep checking serial tracings instead of activating the cath lab.

Why the others are wrong

High lateral injury, because aVL watches the high lateral wall: Lead aVL does look at the high lateral wall, and high lateral injury is a real pattern. High lateral injury needs lead I to elevate too. Lead I is flat here, so the lone elevated lead in aVL cannot stand for the whole wall.

Inferior injury, because aVL sits electrically opposite the inferior wall: Lead aVL sits opposite the inferior leads, II, III, and aVF. Real inferior injury does cause reciprocal ST depression in aVL. This tracing has no inferior elevation at all, and aVL is elevated, not depressed. Option C reads that relationship backward.

Not an injury pattern, because aVL needs 2.5 mm before it counts: A higher threshold of 2.5 mm does exist in 12-lead criteria. The 2.5 mm threshold is for V2 and V3 in certain age and sex groups, not for aVL. Even a taller elevation in aVL would still fail, because one lead is not two contiguous leads.

Question 5 of 10

A 71-year-old patient reports crushing chest pain for 25 minutes. The 12-lead ECG shows 3 mm of ST elevation in II, III, and aVF with reciprocal depression in I and aVL. The lungs are clear in all fields. The vital signs are BP 84/56, P 46, R 20, and SpO₂ 95% on room air. What is the most appropriate treatment for this patient?

Show the answer and rationale

Correct answer · Withhold nitroglycerin and treat the pressure with fluid titrated to perfusion

This is a right ventricular infarct until a right-sided tracing proves otherwise. The 3 mm of ST elevation in II, III, and aVF is an inferior pattern. The blood pressure is 84/56, and the lungs are clear. The right coronary artery feeds the inferior wall and the right ventricle, so one blockage explains both. A damaged right ventricle is preload dependent. The right ventricle needs blood coming in before it can push anything forward. Any drug that lowers preload can drop the blood pressure in a way you cannot fix in the field. Get the right-sided tracing before you give anything that lowers preload. Withhold the nitroglycerin. Give fluid titrated to perfusion. Listen to the lung sounds between boluses so you hear right away if the left side stops keeping up.

Why the others are wrong

Start vasoactive support now, since fluid has nowhere to go at this pressure: Vasoactive support is a real option in this patient. It comes after fluid, not instead of it. A right ventricle that is short on volume needs fluid first, and a vasopressor does not add volume.

Give nitroglycerin for the ischemia and recheck the pressure after each dose: Nitroglycerin is the usual drug for ischemic chest pain. In a preload dependent right ventricle, nitroglycerin lowers preload and the blood pressure drops fast. Rechecking the pressure after the dose is too late to help.

Treat the rate with atropine and hold every other decision until it rises: Atropine is the first drug for a symptomatic bradycardia, and a rate of 46 with a pressure of 84/56 is symptomatic. The same artery that feeds the inferior wall usually supplies the nodes that set the rate. Atropine can go in alongside the fluid. Option C does not work because it holds every other decision until the rate rises. Fluid for the low pressure, the right-sided tracing, and withholding nitroglycerin all happen now, not after the rate comes up.

Question 6 of 10

A 13-year-old patient has had a stabbing pain under the breastbone since waking, a week after a fever and sore throat, and the pain sharpens with every deep breath. The 12-lead ECG shows concave ST elevation in II, III, aVF, I, aVL, V4, V5, and V6, the PR segment is depressed, and nothing on the tracing mirrors the elevation from the opposite side. The vital signs are BP 104/62, P 112, R 24, and SpO₂ 97% on room air. Which condition does this pattern identify?

Show the answer and rationale

Correct answer · Acute pericarditis inflaming the whole pericardial sac

This is acute pericarditis. The whole pericardial sac is inflamed, so the ST elevation shows up everywhere at once. This tracing has concave elevation in the inferior, lateral, and anterior leads at the same time. The PR segment is depressed, and no leads show reciprocal ST depression. A true occlusion is territorial. It elevates the leads over one wall and depresses the leads on the opposite wall. The history fits pericarditis too. Pericarditis often follows a viral illness, and the pain is pleuritic, so it sharpens with every deep breath. Pericarditis is an inflammation the hospital manages. It does not need the emergent reperfusion an infarction needs.

Why the others are wrong

Left main occlusion producing change across every territory: A left main occlusion can change nearly every lead. Its picture is ST depression across most of the leads with elevation in aVR. This tracing shows elevation in nearly every lead, the reverse of the left main picture.

Benign early repolarization, which is common at this age: Benign early repolarization is another STEMI mimic, and it also gives concave elevation. The rest of this patient points to pericarditis. PR depression and pleuritic pain a week after a fever and sore throat are what pericarditis looks like.

An inferior infarction that has spread into the lateral and anterior walls: An inferior infarction that spreads is still one blocked artery. A single occluded vessel almost always produces reciprocal depression in the leads opposite the injury. This tracing has elevation over the inferior, lateral, and anterior walls with no reciprocal depression anywhere.

Question 7 of 10

A 65-year-old patient has had a squeezing pressure across the chest and nausea since finishing dinner about 30 minutes ago. The 12-lead ECG shows 2 mm of ST elevation in II, III, and aVF, and Q waves wider than 0.04 seconds in V3 and V4. The vital signs are BP 138/86, P 94, R 20, and SpO₂ 96% on room air. What do these two findings represent?

Show the answer and rationale

Correct answer · A new inferior occlusion alongside an older anterior infarction

This tracing shows a new inferior STEMI and an older anterior infarction. The two findings come from two different times. Put each finding on a wall first. The ST elevation is in II, III, and aVF. Those leads look at the inferior wall, which the right coronary artery supplies. The Q waves are in V3 and V4. Those leads look at the anterior wall, which the left anterior descending artery supplies. Two walls fed by two different arteries cannot both come from one event. ST elevation means heart muscle is being injured right now, and ST elevation is what activates the cath lab. A Q wave wider than 0.04 seconds means necrosis, heart muscle that has already died. A Q wave tells you how old the damage is, not how urgent it is. The anterior wall was damaged at some point in the past. The inferior wall is infarcting in front of you, and the inferior wall is the one you act on.

Why the others are wrong

A single inferior occlusion whose changes reached the anterior wall: Infarctions do extend and grow. An extension stays inside one artery's territory. II, III, and aVF belong to the right coronary artery, and V3 and V4 belong to the left anterior descending. An inferior occlusion shows up in other leads as reciprocal ST depression in I and aVL. An inferior occlusion does not create Q waves across the chest.

An old anterior infarction only, since Q waves date this tracing: The Q waves really are the older finding on this tracing. A Q wave only tells you about the wall it sits in. The Q waves in V3 and V4 cannot date the ST elevation in II, III, and aVF, and that elevation decides where this patient goes.

A new inferior occlusion that the Q waves time at several hours: The new inferior occlusion in D is correct, and a Q wave does tell you about age. These Q waves sit in the anterior leads, not the inferior leads, so they say nothing about the inferior event. Nothing on this tracing tells you how long the inferior occlusion has been going on.

Question 8 of 10

A paramedic is measuring the amount of ST deviation on the 12-lead ECG of a 58-year-old patient with chest pain. The vital signs are BP 140/86, P 90, R 18, and SpO₂ 97% on room air. Where on the complex is that measurement taken, and against what reference?

Show the answer and rationale

Correct answer · At the J point where the QRS ends, against the TP or PR baseline

ST deviation is measured at the J point, against the TP or PR baseline. The J point is the spot where the QRS ends and the ST segment begins. That spot is where you measure how far the ST segment has lifted or dropped. You compare the J point to the baseline, which is the flat stretch of the TP segment or the PR segment. The baseline shows where that lead sits when nothing is happening. ST deviation only means something compared to that baseline. Measuring anywhere else makes the number too big or hides it. Getting this measurement right matters most in V2 and V3. In those leads, the ST segment sits higher off the baseline even in a healthy heart. That's why V2 and V3 need more elevation than the other leads to count. Group the leads by wall first, then measure at the J point.

Why the others are wrong

At the end of the P wave, against the segment that follows the P wave: The PR segment does play a part here as one of the baselines you compare against. The measurement itself is taken at the J point, not at the end of the P wave.

At the midpoint of the ST segment, against the top of the R wave: The middle of the ST segment is often where the elevation looks biggest. The measurement is standardized at the J point. The top of the R wave is not a baseline, so you cannot measure deviation against the R wave.

At the peak of the T wave, against the flat line that follows the T wave: The T wave is part of repolarization, and watching the T wave is useful. ST deviation is measured where the ST segment starts, not at the peak of the T wave that follows the ST segment.

Question 9 of 10

A 72-year-old patient is hypotensive and anxious with distended neck veins and heart sounds that are hard to hear. Breath sounds are present and equal in all fields. The monitor shows the height of the complexes alternating from beat to beat, and the 12-lead ECG shows no ST elevation in any lead. The vital signs are BP 82/60, P 128, R 26, and SpO₂ 94% on room air. Which condition fits this picture?

Show the answer and rationale

Correct answer · Pericardial tamponade compressing the heart from outside

This is pericardial tamponade. Fluid fills the sac around the heart faster than the sac can stretch. The fluid squeezes the heart from the outside, so the heart cannot fill. That gives you a low blood pressure of 82/60, distended neck veins, and heart sounds that are hard to hear. The heart sounds are muffled because the fluid sits between the heart and your stethoscope. The complexes alternate in height from beat to beat because the heart is swinging in the fluid. The breath sounds are present and equal, and that's what tells you this is not a tension pneumothorax. Field care is support: IV access, oxygen, and fast transport. Draining the fluid is done at the hospital.

Why the others are wrong

Tension pneumothorax, since venous return is being obstructed: A tension pneumothorax also blocks blood from getting back to the heart. A tension pneumothorax distends the neck veins and drops the pressure too, but it takes away the breath sounds on the affected side. This patient's breath sounds are present and equal in all fields.

Right ventricular infarction, since the neck veins are distended: A right ventricular infarction can give you distended neck veins with a low pressure. A right ventricular infarction comes with ST elevation in the inferior leads. This 12-lead shows no ST elevation in any lead.

Cardiogenic shock, since the pressure has fallen with a fast rate: Cardiogenic shock does cause a low pressure with a fast rate. Cardiogenic shock comes from the heart muscle failing, and it usually brings crackles in the lungs. This heart is being squeezed from the outside, and the lungs are clear.

Question 10 of 10

A paramedic obtains a 12-lead ECG on a patient with chest discomfort and notes new ST elevation in lead III only, with no changes in any other lead, including II and aVF. What is the most appropriate interpretation of this finding?

Show the answer and rationale

Correct answer · This is a nondiagnostic finding; reassess and continue monitoring

ST elevation in a single lead is a nondiagnostic finding. STEMI criteria need elevation in two or more leads that look at the same wall. Lead III looks at the inferior wall along with leads II and aVF. This question tells you II and aVF have no changes. One elevated lead with the rest of its wall quiet usually means artifact, a misplaced electrode, or a baseline shift that is not from ischemia. This tracing does not meet STEMI criteria. Nondiagnostic does not mean the patient is fine. The patient still has chest discomfort. Keep monitoring and repeat the 12-lead. If an infarct is developing, the elevation will show up in II and aVF on a later tracing.

Why the others are wrong

Activate the cath lab as a STEMI alert: A STEMI alert is the right call once elevation shows up in neighboring leads. That means II, III, and aVF together, or V2 through V4 together. The clock on reperfusion starts with your radio call. Here only lead III is elevated, and II and aVF are normal. Activating on one lead can send a cath team after artifact. Repeat the tracing before you call it.

This is a diagnostic lateral wall STEMI: The lateral leads are I, aVL, V5, and V6. Those electrodes sit on the left side and look in at the side of the heart. Lead III is not a lateral lead, because it belongs to the inferior group with II and aVF. Even if one elevated lead counted, it would point to the inferior wall, and it would still need a partner.

This is a posterior wall MI seen as a mirror image: A posterior wall MI shows up as ST depression with tall R waves in V1 through V3. That depression is a mirror image of elevation on the back wall. This tracing shows elevation in lead III and no depression in the anterior leads. Nothing here points to a posterior MI.

Find out which Paramedic topics are costing you points

Ten questions on one topic tell you about that topic. The free diagnostic covers every Paramedic topic and breaks your results down by topic, so you know what to drill next. No card, no signup to try it.

Take the free Paramedic diagnostic

More free Paramedic practice questions by topic