EKG Practice Test with Answers
EKG practice test for independent study: review 78 original ECG interpretation questions, each answered from and quoted from a StatPearls chapter on the National Library of Medicine's NCBI Bookshelf. These are text questions; no rhythm-strip images are shown.
EKG practice questions: ECG paper and rate calculation, waves and intervals, AV blocks, bundle branch blocks, axis, ST changes, QT and electrolyte clues, atrial fibrillation, SVT, WPW, ventricular tachycardia and the prehospital 12-lead, cited to StatPearls chapters on NCBI Bookshelf (National Library of Medicine). Every answer is grounded in a quoted source line.
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01At standard paper speed, how fast does ECG paper move? A. 10 mm per second. B. 25 mm per second. C. 50 mm per second. D. 100 mm per second.
B. 25 mm per second. Standard speed is 25 mm/sec, which sets the time value of every box on the grid.
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“The electrocardiograph moves at a speed of 25 mm/sec.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗02On standard ECG paper, how much time does one small box represent? A. 0.04 seconds. B. 0.02 seconds. C. 0.12 seconds. D. 0.20 seconds.
A. 0.04 seconds. Each large box (0.2 s) is split into five small boxes of 0.04 s each.
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“Each large square is further divided into five small squares of 0.04 sec each.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗03How many large boxes span one second on a standard-speed ECG strip? A. Three. B. Ten. C. Twenty-five. D. Five.
D. Five. One second is five large boxes, each worth 0.2 seconds.
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“1 second is divided into five large squares, each representing 0.2 sec.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗04With standard calibration, how far should a 1 mV signal move the stylus? A. 1 mm (1 small box). B. 5 mm (1 large box). C. 1 cm (10 small boxes). D. 2 cm (4 large boxes).
C. 1 cm (10 small boxes). Standard calibration is 10 mm per mV, so a 1 mV signal moves the stylus 1 cm.
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“an increase of voltage by one mVolt should move the stylus by 1 cm”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗05A regular rhythm has 4 large boxes between consecutive R waves. What is the approximate heart rate? A. About 60 beats per minute. B. About 75 beats per minute. C. About 100 beats per minute. D. About 150 beats per minute.
B. About 75 beats per minute. For a regular rhythm, divide 300 by the number of large boxes between R waves: 300 / 4 = 75.
VERIFIED AGAINST THE SOURCE
“dividing 300 by the number of big squares or 1500 by the number of small squares between two R waves”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗06A regular rhythm has 15 small boxes between consecutive R waves. What is the approximate heart rate? A. About 100 beats per minute. B. About 50 beats per minute. C. About 150 beats per minute. D. About 200 beats per minute.
A. About 100 beats per minute. Divide 1500 by the number of small boxes between R waves: 1500 / 15 = 100.
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“dividing 300 by the number of big squares or 1500 by the number of small squares between two R waves”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗07What is the quickest way to estimate the rate of an irregular rhythm? A. Divide 300 by the number of large boxes between any two R waves. B. Count the P waves on a 3-second strip and multiply by 10. C. Divide 1500 by the shortest R-R interval in small boxes. D. Count the QRS complexes on a 10-second strip and multiply by 6.
D. Count the QRS complexes on a 10-second strip and multiply by 6. Box-counting methods assume a regular rhythm; for an irregular one, count beats over 10 seconds and multiply by 6.
VERIFIED AGAINST THE SOURCE
“For an irregular rhythm, count the number of beats in a 10-second strip and multiply it by 6.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗08Below what heart rate is a rhythm described as bradycardia? A. 50 beats per minute. B. 70 beats per minute. C. 60 beats per minute. D. 40 beats per minute.
C. 60 beats per minute. A rate under 60 is called bradycardia.
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“If it is less than 60, it is called bradycardia”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗09What does the P wave represent? A. Ventricular repolarization. B. Atrial depolarization, right atrium first and then left. C. Depolarization of the interventricular septum. D. Conduction delay in the AV node.
B. Atrial depolarization, right atrium first and then left. The first half of the P wave reflects right atrial depolarization and the second half left atrial depolarization.
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“the first half of the P wave represents right atrial depolarization and the second half shows left atrial depolarization”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗10In normal sinus rhythm, in which lead is the P wave consistently negative? A. aVR. B. Lead II. C. Lead I. D. aVF.
A. aVR. The sinus P wave is upright in leads I and II and negative in aVR.
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“It is always positive in the lead I and II and consistently negative in lead aVR in normal sinus rhythm.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗11What is the normal range for the PR interval? A. 40 to 80 ms (1 to 2 small boxes). B. 200 to 280 ms (5 to 7 small boxes). C. 360 to 440 ms (9 to 11 small boxes). D. 120 to 200 ms (3 to 5 small boxes).
D. 120 to 200 ms (3 to 5 small boxes). A normal PR interval is 3 to 5 small boxes, or 120 to 200 ms.
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“The average interval is 3 to 5 small squares (120 to 200 ms).”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗12What is the normal duration of the QRS complex? A. 120 to 200 ms. B. Under 40 ms. C. Under 120 ms, usually 60 to 100 ms. D. 200 to 240 ms.
C. Under 120 ms, usually 60 to 100 ms. A standard QRS is narrower than three small boxes.
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“A standard QRS complex has a duration of less than three small squares (under 120 ms, usually 60 to 100 ms).”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗13A widened QRS complex should raise concern for which pair of causes? A. Hypothermia or sinus arrhythmia. B. Hyperkalemia or a bundle branch block. C. Hypercalcemia or first-degree AV block. D. Pericarditis or atrial flutter.
B. Hyperkalemia or a bundle branch block. A prolonged QRS may point to hyperkalemia or a bundle branch block.
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“A prolonged QRS may indicate hyperkalemia or bundle branch block”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗14How wide must a Q wave be to count as pathologic? A. Wider than 40 ms (one small box). B. Wider than 10 ms. C. Wider than 120 ms (three small boxes). D. Wider than 200 ms (one large box).
A. Wider than 40 ms (one small box). A Q wave lasting more than 40 ms, one small box, is considered pathologic.
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“A Q-wave duration greater than 40 milliseconds (one small box)”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗15With normal R-wave progression across the chest leads, which lead shows the smallest R wave? A. V3. B. V5. C. V6. D. V1.
D. V1. The R wave is smallest in V1 and grows to its largest around V5.
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“Lead V1 has the smallest R wave, and lead V5 has the largest”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗16What electrical event does the T wave represent? A. Atrial depolarization. B. Atrial repolarization. C. Ventricular repolarization. D. Conduction through the bundle of His.
C. Ventricular repolarization. The T wave reflects ventricular repolarization.
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“The normal T wave represents vectors of electrical activity associated with ventricular repolarization.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗17A small wave that follows the T wave is most often linked to which electrolyte problem? A. Hyperkalemia. B. Hypokalemia. C. Hypercalcemia. D. Hypernatremia.
B. Hypokalemia. This is the U wave, which is commonly associated with hypokalemia.
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“It is a small wave that follows the T wave. It represents the delayed repolarization of the papillary muscles or Purkinje fibers. It is commonly associated with hypokalemia.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗18Tall, peaked T waves should make you think of which electrolyte disorder? A. Hyperkalemia. B. Hypokalemia. C. Hypomagnesemia. D. Hyponatremia.
A. Hyperkalemia. Peaked T waves go with hyperkalemia and can precede arrhythmias and cardiac arrest.
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“Peaked T waves associated with hyperkalemia may precipitate arrhythmias and cardiac arrest.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗19An Osborn (J) wave on the ECG is a clue to which condition? A. Hyperthyroidism. B. Digoxin toxicity. C. Acute pericarditis. D. Hypothermia.
D. Hypothermia. The Osborn wave is an abnormal ECG finding in hypothermia.
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“Also known as the Osborn wave, it is an abnormal ECG finding in hypothermia.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗20How much ST elevation is considered significant? A. Any elevation in a single lead. B. At least 0.5 mm in any lead. C. At least 1 mm in a limb lead or 2 mm in a precordial lead. D. At least 5 mm in a limb lead.
C. At least 1 mm in a limb lead or 2 mm in a precordial lead. ST elevation counts when it reaches at least 1 mm in a limb lead or 2 mm in a precordial lead.
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“at least 1 mm in a limb lead or 2 mm in a precordial lead”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗21Why do you look for ST elevation in two or more contiguous leads? A. A single lead is too fast to measure. B. Elevation in contiguous leads is highly specific for infarction. C. Contiguous leads cancel out artifact. D. Only contiguous leads can show PR depression.
B. Elevation in contiguous leads is highly specific for infarction. ST elevation is highly specific when present in two or more contiguous leads.
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“ST-elevation is highly specific if present in two or more contiguous leads”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗22Diffuse ST elevation with PR depression most suggests which diagnosis? A. Acute pericarditis. B. Inferior STEMI. C. Hypokalemia. D. Wolff-Parkinson-White pattern.
A. Acute pericarditis. In acute pericarditis the ST elevations are diffuse and come with PR depression.
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“ST-elevations are diffuse in acute pericarditis and associated with PR-depression”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗23An inferior wall STEMI typically produces reciprocal ST depression in which leads? A. II and aVF. B. V1 and V2. C. V5 and V6 only. D. I and aVL.
D. I and aVL. Inferior STEMI causes reciprocal ST depression in leads I and aVL.
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“inferior wall STEMI produces reciprocal ST depression in leads I and aVL”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗24Which coronary artery usually supplies the inferior wall of the heart? A. The left anterior descending artery. B. The circumflex artery. C. The right coronary artery. D. The left main coronary artery.
C. The right coronary artery. The inferior wall is usually supplied by the right coronary artery; the anteroseptal wall by the left anterior descending artery.
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“Inferior Wall - Right coronary artery - Anteroseptal - Left anterior descending artery”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗25Hyperacute T waves early in a myocardial infarction appear where? A. Only in lead aVR. B. In the leads corresponding to the affected coronary artery. C. In every lead equally. D. Only in the limb leads.
B. In the leads corresponding to the affected coronary artery. Hyperacute T waves show up in the leads that map to the blocked artery.
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“Hyperacute T waves representing myocardial infarction are seen in the leads corresponding to the affected coronary artery.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗26Large, symmetric T-wave inversions in the anterior chest leads can signal which dangerous lesion? A. Severe narrowing of the proximal left anterior descending artery (Wellens syndrome). B. Right coronary artery spasm. C. An accessory pathway. D. Hypercalcemia.
A. Severe narrowing of the proximal left anterior descending artery (Wellens syndrome). Type A Wellens syndrome reflects critical proximal LAD narrowing.
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“severe narrowing of the proximal left anterior descending artery causes large, symmetrically inverted T waves in the anterior precordial leads”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗27Which non-ischemic causes can produce ST depression? A. Hypercalcemia only. B. First-degree AV block. C. Sinus arrhythmia. D. Digoxin toxicity, hypokalemia, hypothermia and tachycardia.
D. Digoxin toxicity, hypokalemia, hypothermia and tachycardia. ST depression is not always ischemia; digoxin, low potassium, hypothermia and tachycardia can cause it.
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“ST depressions are also associated with non-ischemic causes, including digoxin toxicity, hypokalemia, hypothermia, and tachycardia.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗28How does the QT interval change as the heart rate increases? A. It lengthens. B. It stays the same. C. It shortens. D. It becomes irregular.
C. It shortens. The QT interval has an inverse relation to heart rate, which is why it is corrected (QTc).
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“A QT interval has an inverse relation to the heart rate.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗29A prolonged QT interval puts the patient at risk for which arrhythmia? A. Sinus arrhythmia. B. Torsades de pointes. C. First-degree AV block. D. Atrial flutter with 2:1 block.
B. Torsades de pointes. A long QT carries an imminent risk of serious ventricular arrhythmias, including torsades de pointes.
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“A prolonged QT interval presents an imminent risk for serious ventricular arrhythmias, including Torsades de Pointes”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗30Above what QTc value does the risk of torsades de pointes clearly rise? A. 500 ms. B. 350 ms. C. 400 ms. D. 300 ms.
A. 500 ms. A QTc greater than 500 ms is associated with an increased risk of torsades.
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“A QTc greater than 500 is associated with an increased risk of torsade de pointes.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗31Which formula is most commonly used to correct the QT interval for heart rate? A. The Cockcroft-Gault formula. B. The Parkland formula. C. The Friedewald formula. D. The Bazett formula (QT divided by the square root of RR).
D. The Bazett formula (QT divided by the square root of RR). Bazett is the most widely used QT correction, though it over- and under-corrects at extremes of rate.
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“the Bazett formula (QTC = QT / √ RR) is the most commonly used”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗32When the QTc is prolonged, which blood levels should be checked? A. Sodium and chloride only. B. Glucose and lactate. C. Potassium, calcium and magnesium. D. Troponin only.
C. Potassium, calcium and magnesium. Low potassium, calcium and magnesium can each prolong the QT.
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“Serum potassium, calcium, and magnesium levels should be checked, as low serum of each can cause QT prolongation.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗33What is the first-line drug treatment for torsades de pointes? A. Adenosine. B. Magnesium sulfate. C. Digoxin. D. Verapamil.
B. Magnesium sulfate. Magnesium sulfate is first line, and it helps regardless of the serum magnesium level.
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“Also, the first-line treatment is magnesium sulfate, and the benefit is independent of serum magnesium level.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗34A patient in torsades de pointes becomes hemodynamically unstable. What is indicated? A. Non-synchronized electrical defibrillation. B. Synchronized cardioversion at low energy. C. Adenosine rapid IV push. D. Vagal maneuvers.
A. Non-synchronized electrical defibrillation. An unstable patient in torsades should be defibrillated (non-synchronized).
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“A hemodynamically unstable patient should receive non-synchronized electrical defibrillation.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗35A short QT interval (under 360 ms) may be associated with which electrolyte abnormality? A. Hypocalcemia. B. Hypokalemia. C. Hypomagnesemia. D. Hypercalcemia.
D. Hypercalcemia. A short QT can be a clue to a high calcium level.
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“A short QT interval ( less than 360 milliseconds) may be associated with hypercalcemia”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗36What PR interval defines first-degree AV block? A. A PR interval that lengthens until a beat drops. B. A PR interval shorter than 120 ms. C. A constant PR interval longer than 200 ms with every P wave conducted. D. P waves unrelated to the QRS complexes.
C. A constant PR interval longer than 200 ms with every P wave conducted. First-degree block keeps 1:1 conduction with a constant PR over 200 ms; no P waves are blocked.
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“First-degree AV block is a 1:1 association between P waves and QRS (1:1 AV conduction) and a constant PR interval of >200 ms.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗37The PR interval gets longer with each beat until a P wave is not followed by a QRS. What rhythm is this? A. Second-degree AV block, Mobitz type II. B. Second-degree AV block, Mobitz type I (Wenckebach). C. Third-degree AV block. D. First-degree AV block.
B. Second-degree AV block, Mobitz type I (Wenckebach). Progressive PR prolongation ending in a dropped beat is Mobitz type I.
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“progressive prolongation of the PR interval, and then suddenly, a P wave is not followed by the QRS complex”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗38In Mobitz type II block, how do the PR intervals of the conducted beats behave? A. They stay constant, with single P waves dropped at unpredictable intervals. B. They lengthen progressively before each dropped beat. C. They vary randomly because the atria and ventricles are dissociated. D. They are shorter than 120 ms with a delta wave.
A. They stay constant, with single P waves dropped at unpredictable intervals. Mobitz II shows constant PR intervals with sudden, unpredictable non-conducted P waves.
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“both before and after the non-conducted P wave, and exhibit consistent PR intervals”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗39Which type of AV block usually produces no symptoms? A. Mobitz type II block. B. Third-degree block with a slow ventricular escape. C. Complete heart block after a large infarction. D. First-degree and Mobitz type I second-degree block.
D. First-degree and Mobitz type I second-degree block. First-degree and Mobitz I blocks are usually asymptomatic and often found incidentally.
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“Patients with first and Mobitz type I, second-degree AV blocks are usually asymptomatic”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗40A rare symptomatic, unstable patient with Mobitz type I block may need which emergency treatment? A. Adenosine. B. Magnesium sulfate. C. Atropine or cardiac pacing. D. Synchronized cardioversion.
C. Atropine or cardiac pacing. Atropine (emergently) or pacing is used for the uncommon unstable Mobitz I patient.
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“may require treatment with either atropine (emergently) or cardiac pacing”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗41P waves and QRS complexes march along with no relationship to each other. What is the rhythm? A. Mobitz type I block. B. Third-degree (complete) heart block. C. First-degree AV block. D. Sinus arrhythmia.
B. Third-degree (complete) heart block. In complete heart block there is no AV conduction, so P waves never relate to the QRS complexes.
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“AV conduction is absent in third-degree or complete heart block, and the P waves are never related to the QRS complexes.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗42In complete heart block, what keeps the ventricles beating? A. A junctional or ventricular escape rhythm. B. Conducted sinus impulses. C. An accessory pathway. D. Retrograde atrial activation.
A. A junctional or ventricular escape rhythm. With no AV conduction, a junctional or ventricular escape rhythm drives the ventricles.
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“Instead, if ventricular conduction occurs, it is maintained by a junctional or ventricular escape rhythm.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗43Which AV blocks tend to reflect severe damage to the conduction system? A. First-degree block only. B. Mobitz type I only. C. Sinus arrhythmia. D. Mobitz type II and third-degree block.
D. Mobitz type II and third-degree block. Higher-degree blocks (Mobitz II and third-degree) usually mean severe conduction-system damage.
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“patients with higher degrees of an AV block (Mobitz type 2 AV block, 3rd degree) tend to have severe damage to the conduction system”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗44What is the mainstay of treatment for irreversible complete heart block? A. Long-term atropine. B. Catheter ablation of the AV node. C. A permanent pacemaker. D. Beta-blockers.
C. A permanent pacemaker. Permanent complete heart block is treated with a permanent pacemaker.
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“In the case of irreversible or permanent complete heart block, a permanent pacemaker remains the mainstay of the treatment.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗45Which tick-borne infection can cause complete heart block that may reverse with antibiotics? A. Influenza. B. Lyme disease. C. Hepatitis A. D. Strep throat.
B. Lyme disease. Lyme carditis can cause complete heart block that is potentially reversible with antibiotic therapy.
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“Lyme disease may be associated with a complete heart block and is potentially reversible with antibiotic therapy.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗46A QRS wider than 0.12 seconds with an RSR' pattern in V1 and V2 indicates what? A. Right bundle branch block. B. Left bundle branch block. C. Left ventricular hypertrophy. D. Wolff-Parkinson-White pattern.
A. Right bundle branch block. RBBB shows a wide QRS with an RSR' pattern in V1 and V2.
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“widened QRS complex greater than 0.12 seconds, along with an RSR pattern in V1 and V2”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗47In left bundle branch block, where are the broad or notched R waves found? A. Leads V1 and V2 only. B. Leads II, III and aVF. C. Lead aVR only. D. Leads I, aVL, V5 and V6.
D. Leads I, aVL, V5 and V6. LBBB widens the QRS beyond 0.12 s with broad or notched R waves in the lateral leads.
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“The left bundle branch block is represented on the ECG by a widened QRS complex greater than 0.12 seconds, broad or notched R wave with prolonged upstroke in the leads V5, V6, I, and aVL”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗48How many lead wires does a conventional 12-lead ECG use? A. Twelve. B. Six. C. Ten. D. Four.
C. Ten. The 12 leads (six limb and six precordial) are recorded through ten wires.
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“The conventional 12-lead ECG consisting of six limbs and six precordial leads is organized into ten wires.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗49Where is the V4 electrode placed? A. Fourth intercostal space, right sternal border. B. Fifth intercostal space, midclavicular line. C. Fifth intercostal space, midaxillary line. D. Second intercostal space, midclavicular line.
B. Fifth intercostal space, midclavicular line. V4 sits in the fifth intercostal space at the midclavicular line.
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“V4 is placed at the level of the fifth intercostal space in the mid-clavicular line”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗50Where is the V6 electrode placed? A. Fifth intercostal space, midaxillary line. B. Fifth intercostal space, midclavicular line. C. Fourth intercostal space, left sternal border. D. Sixth intercostal space, posterior axillary line.
A. Fifth intercostal space, midaxillary line. V6 sits in the fifth intercostal space at the midaxillary line.
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“V6 is placed at the level of the fifth intercostal space in the mid-axillary line”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗51Where are V1 and V2 placed relative to the sternum? A. Both on the left midclavicular line. B. V1 left of the sternum and V2 right of it. C. Both directly over the sternum. D. V1 just right of the sternal border and V2 just left of it.
D. V1 just right of the sternal border and V2 just left of it. V1 goes to the right of the sternal border and V2 to the left of the sternal edge.
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“V1 is placed to the right of the sternal border, and V2 is situated to the left of the sternal edge.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗52Which leads are the augmented unipolar limb leads? A. I, II and III. B. V1, V2 and V3. C. aVR, aVL and aVF. D. V4, V5 and V6.
C. aVR, aVL and aVF. Leads I, II and III are the bipolar limb leads; aVR, aVL and aVF are the augmented unipolar leads.
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“standard bipolar limb leads (I, II, and III) and augmented unipolar leads (aVL, aVF, and aVR)”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗53In which plane do the precordial (chest) leads record the heart's electrical activity? A. The vertical (frontal) plane. B. The horizontal plane. C. The sagittal plane only. D. They record no plane; they measure rate only.
B. The horizontal plane. Limb leads view the vertical plane; precordial leads view the horizontal plane.
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“The limb leads view the heart in a vertical plane, and the precordial leads record the heart's electrical activity in the horizontal plane.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗54The QRS is positive in both lead I and aVF. What is the axis? A. Normal axis. B. Left axis deviation. C. Right axis deviation. D. Extreme (northwest) axis.
A. Normal axis. A positive QRS in leads I and aVF indicates a normal axis.
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“normal axis when the QRS complex is positive in leads I and aVF”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗55The QRS is negative in lead I and positive in aVF. What does this suggest? A. Left axis deviation. B. Normal axis. C. Low voltage. D. Right axis deviation.
D. Right axis deviation. Negative in lead I with positive in aVF points to right axis deviation.
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“The combination of a negative QRS deflection in lead I and a positive QRS deflection in lead aVF suggests right axis deviation.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗56Are there absolute contraindications to recording a 12-lead ECG? A. Yes, a pacemaker. B. Yes, pregnancy. C. No, there are none. D. Yes, recent chest surgery.
C. No, there are none. There are no absolute contraindications for an electrocardiogram.
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“There are no absolute contraindications for an electrocardiogram.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗57What are the classic ECG features of atrial fibrillation? A. A regular narrow rhythm with sawtooth flutter waves. B. An irregularly irregular rhythm with no discrete P waves and a fibrillatory baseline. C. A short PR interval with a delta wave. D. Progressive PR lengthening with dropped beats.
B. An irregularly irregular rhythm with no discrete P waves and a fibrillatory baseline. AF shows an irregularly irregular ventricular rhythm, absent discrete P waves and variable fibrillatory activity.
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“A typical ECG demonstrates an irregularly irregular ventricular rhythm with absent discrete P waves and variable fibrillatory activity.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗58What is the most common sustained cardiac arrhythmia? A. Atrial fibrillation. B. Ventricular tachycardia. C. Atrial flutter. D. Third-degree AV block.
A. Atrial fibrillation. Atrial fibrillation is the most common sustained arrhythmia.
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“Atrial fibrillation is the most common sustained cardiac arrhythmia”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗59In the CHA2DS2-VASc stroke-risk score for atrial fibrillation, how many points does a prior stroke or TIA add? A. 1 point. B. 3 points. C. 0 points. D. 2 points.
D. 2 points. Prior stroke or transient ischemic attack scores 2 points.
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“Stroke or transient ischemic attack: 2 points”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗60Can aspirin replace anticoagulation for stroke prevention in atrial fibrillation? A. Yes, aspirin is equivalent. B. Yes, if combined with clopidogrel. C. No; aspirin alone or with clopidogrel is not recommended as an alternative. D. Yes, for any patient over 65.
C. No; aspirin alone or with clopidogrel is not recommended as an alternative. Antiplatelet therapy is not an acceptable substitute for anticoagulation.
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“Aspirin alone or in combination with clopidogrel is not recommended as an alternative to anticoagulation”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗61How is ventricular tachycardia defined? A. Any single premature ventricular beat. B. Three or more consecutive wide-complex beats at a rate over 100 per minute. C. A narrow-complex rhythm over 150 per minute. D. Two wide beats in a row at any rate.
B. Three or more consecutive wide-complex beats at a rate over 100 per minute. VT is a wide complex tachycardia of 3 or more consecutive beats faster than 100/min.
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“Ventricular tachycardia is defined as a wide complex tachycardia (WCT) consisting of 3 or more consecutive beats at a rate exceeding 100 per minute.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗62Ventricular tachycardia is sorted into monomorphic and polymorphic types based on what? A. QRS morphology. B. The PR interval. C. P-wave shape. D. The patient's age.
A. QRS morphology. VT is classified by whether the QRS shape stays the same or changes.
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“Ventricular tachycardia is classified as monomorphic or polymorphic based on QRS morphology.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗63What is "VT storm"? A. VT lasting longer than 30 seconds. B. VT that converts to atrial fibrillation. C. VT that occurs during exercise. D. Three or more episodes of sustained VT within 24 hours.
D. Three or more episodes of sustained VT within 24 hours. Electrical storm is 3 or more sustained VT episodes in 24 hours.
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“3 or more episodes of sustained ventricular tachycardia within 24 hours”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗64Is adenosine reliable for terminating ventricular tachycardia? A. Yes; it is first line for VT. B. Yes, but only for polymorphic VT. C. No; it is typically ineffective in VT. D. Yes, if given intramuscularly.
C. No; it is typically ineffective in VT. Adenosine is typically ineffective for terminating VT.
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“In addition, adenosine is typically ineffective in terminating ventricular tachycardia.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗65What QRS width and heart rate characterize supraventricular tachycardia (SVT)? A. Wide QRS with a rate of 60 to 100. B. Narrow QRS (under 120 ms) with a rate over 100, typically 150 to 220. C. Narrow QRS with a rate under 60. D. Wide QRS with a rate over 250 only.
B. Narrow QRS (under 120 ms) with a rate over 100, typically 150 to 220. SVT originates at or above the AV node and is usually narrow-complex at 150 to 220 bpm.
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“characterized by a narrow QRS complex (<120 ms) with a heart rate exceeding 100 bpm, typically ranging from 150 to 220 bpm”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗66Which medication is first line for acute SVT, especially when the AV node is involved? A. Adenosine. B. Amiodarone. C. Magnesium sulfate. D. Atropine.
A. Adenosine. Adenosine is first line for acute SVT.
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“Adenosine is the first-line medication for acute supraventricular tachycardia, especially if atrioventricular node involvement is suspected.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗67How should adenosine be given? A. As a slow IV infusion over 30 minutes. B. Intramuscularly. C. By mouth. D. As a rapid IV push, preferably through a large peripheral vein.
D. As a rapid IV push, preferably through a large peripheral vein. Adenosine is metabolized rapidly, so it must be pushed fast.
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“Adenosine is rapidly metabolized in the body and should be administered as a rapid intravenous push, preferably through a large peripheral vein.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗68A patient in SVT is hypotensive with altered mental status. What should be considered? A. Oral beta-blocker and recheck in an hour. B. Non-synchronized defibrillation at the lowest energy. C. Immediate synchronized cardioversion. D. Observation only.
C. Immediate synchronized cardioversion. Unstable SVT calls for immediate synchronized cardioversion.
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“Indicators such as respiratory distress, hypotension, altered mental status, or chest pain should be assessed.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗69What is a delta wave? A. A notch at the end of the T wave. B. A slurred upstroke at the start of the QRS complex. C. An extra P wave before each QRS. D. A deep Q wave in lead III.
B. A slurred upstroke at the start of the QRS complex. The delta wave is the slurred upstroke of preexcitation through an accessory pathway.
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“identified by a delta wave (a slurred upstroke to the QRS complex)”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗70Which PR interval is typical of the Wolff-Parkinson-White pattern? A. Short, under 120 ms. B. Normal, 120 to 200 ms. C. Long, over 200 ms. D. Progressively lengthening.
A. Short, under 120 ms. WPW preexcitation shows a short PR interval with a delta wave.
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“The ECG will show a short PR interval (<120 ms)”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗71Why are AV nodal blocking drugs such as adenosine dangerous in WPW with atrial fibrillation? A. They cause severe hypokalemia. B. They convert the rhythm to sinus bradycardia. C. They lengthen the QT interval. D. They allow unopposed conduction down the accessory pathway, which can lead to ventricular fibrillation.
D. They allow unopposed conduction down the accessory pathway, which can lead to ventricular fibrillation. Blocking the AV node leaves the accessory pathway unopposed and can trigger VF.
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“allowing unopposed antegrade conduction through the accessory pathway, which may lead to ventricular fibrillation”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗72What R-R variation defines sinus arrhythmia? A. Absent P waves with an irregular rhythm. B. R-R variation under 0.04 seconds. C. R-R variation greater than 0.12 seconds with normal sinus P waves. D. Dropped QRS complexes.
C. R-R variation greater than 0.12 seconds with normal sinus P waves. Sinus arrhythmia is an irregular sinus rhythm with R-R variation over 0.12 s and uniform sinus P waves.
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“Sinus arrhythmia characteristically presents with an irregular rate in which the variation in the R-R interval is greater than 0.12 seconds.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗73What usually causes the rate to vary in respiratory sinus arrhythmia? A. An accessory pathway. B. Vagal stimulation that changes with breathing. C. Degeneration of the AV node. D. Low potassium.
B. Vagal stimulation that changes with breathing. Respiration produces vagal stimuli that vary the R-R interval; it is common in children and young adults.
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“Respirations lead to vagal stimuli, resulting in R-R interval variations.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗74What is the main goal of a prehospital 12-lead ECG? A. Identify STEMI sooner so reperfusion happens faster. B. Measure the QT interval for billing. C. Replace the hospital ECG. D. Diagnose sinus arrhythmia.
A. Identify STEMI sooner so reperfusion happens faster. The prehospital ECG speeds STEMI recognition and timely intervention.
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“The main goal of the prehospital ECG is to identify STEMI more quickly, leading to timelier intervention in appropriate candidates.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗75For a STEMI patient taken to a PCI-capable center, what is the goal first-medical-contact-to-device time? A. 3 hours or less. B. 6 hours or less. C. 12 hours or less. D. 90 minutes or less.
D. 90 minutes or less. The goal FMC-to-device time is 90 minutes or less, even if that means bypassing a closer non-PCI hospital.
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“with a goal of FMC-to-device time of 90 min or less”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗76How should a new-onset left bundle branch block be treated in a patient with a fitting clinical picture of acute coronary syndrome? A. As a benign incidental finding. B. As proof of hyperkalemia. C. As an ST-segment elevation equivalent. D. As a reason to give adenosine.
C. As an ST-segment elevation equivalent. New-onset LBBB in the right clinical context is handled as a STEMI equivalent.
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“New-onset LBBB in the appropriate clinical context is considered an ST-segment elevation equivalent.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗77What QRS duration fits an incomplete right bundle branch block? A. 60 to 80 milliseconds. B. 100 to 119 milliseconds. C. 120 to 160 milliseconds. D. Over 200 milliseconds.
B. 100 to 119 milliseconds. Incomplete RBBB has the same RBBB features with a QRS of 100 to 119 ms.
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“Incomplete right bundle branch block has similar electrocardiographic features with a QRS duration of 100 to 119 milliseconds.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗78An isolated right bundle branch block is found in an asymptomatic patient. How is it generally regarded? A. As benign. B. As a STEMI equivalent. C. As an indication for immediate pacing. D. As diagnostic of pulmonary embolism.
A. As benign. In isolation and without symptoms, RBBB is benign.
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“In isolation and in an asymptomatic patient, RBBB is benign.”
— StatPearls (StatPearls Publishing), NCBI Bookshelf, National Library of Medicine ↗Know questions we're missing?
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