Relias Dysrhythmia Basic A Exam V2.0: Advanced Clinical Mastery Edition (2025/2026 Update)
A Comprehensive 150-Question Practice Test Bank with In-Depth Clinical Rationales, Complex Scenario-Based Questions, and Advanced ECG
Interpretation for Healthcare Professionals
Table of Contents
Section Topic Area Questions
I Advanced ECG Principles & Waveform Analysis 1–12
II Sinus Rhythm Complexities & Variants 13–20
III Atrial Dysrhythmias: Advanced Concepts 21–35
IV Junctional Rhythms & Complex Conduction 36–45
V Ventricular Dysrhythmias: High-Risk Scenarios 46–60
VI Advanced AV Blocks & Conduction Disorders 61–75
VII Pacemaker Technology & Troubleshooting 76–85
VIII Antiarrhythmic Pharmacology: Mechanism-Based 86–95
IX Emergency Interventions & ACLS Updates 96–110
X Clinical Scenarios: Diagnostic Challenges 111–125
XI Mixed Rhythm Interpretation: Complex Strips 126–140
XII High-Yield Review & Board-Style Questions 141–150
Section I: Advanced ECG Principles & Waveform Analysis
🟢 1. A 12-lead ECG demonstrates a QRS axis of -30 degrees with a dominant R wave in lead aVL and a deep S wave in lead III. The R-wave progression in
the precordial leads is reversed (transition occurs before V1). This pattern is most consistent with:
🟢 A) Left ventricular hypertrophy
🟢 B) Right bundle branch block
🔴🔴 C) Left anterior fascicular block (LAFB)
🟢 D) Inferior wall myocardial infarction
Rationale: Left anterior fascicular block (LAFB) produces left-axis deviation (-30 to -90 degrees), a small q wave in lead I and aVL, deep S wave in inferior
leads (II, III, aVF), and delayed R-wave progression with transition before V1. This blocks the anterior-superior division of the left bundle, altering
depolarization sequence. The axis deviation and R/S ratio distinguish LAFB from left ventricular hypertrophy (which has voltage criteria) and right bundle
branch block (which has wide QRS, rsR' pattern).
🟢 2. A patient's ECG shows ST-segment elevation of 2 mm in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Additionally, there is
first-degree AV block (PR interval 0.28 seconds). The patient is experiencing bradycardia at 48 bpm. This clinical picture is most consistent with which
vascular territory involvement?
🟢 A) Anterior wall MI (LAD occlusion)
🟢 B) Lateral wall MI (LCx occlusion)
🔴🔴 C) Inferior wall MI with right ventricular (RV) involvement
🟢 D) Posterior wall MI
Rationale: Inferior wall MI (right coronary artery or dominant left circumflex) commonly presents with ST elevation in leads II, III, aVF, reciprocal depression
in I and aVL, and is frequently complicated by AV conduction abnormalities (first-degree AV block, Mobitz I), sinus bradycardia, and right ventricular
,involvement. Inferior MI increases vagal tone, causing bradycardia and AV blocks. RV involvement is suspected with ST elevation in V4R and is associated
with hypotension requiring volume resuscitation.
🟢 3. A 55-year-old patient's ECG demonstrates a QRS duration of 0.14 seconds with a broad, notched R wave in lead V6 and a broad, deep S wave in lead
V1. The T wave is discordant to the QRS in the lateral leads. This pattern is most consistent with:
🟢 A) Left bundle branch block (LBBB)
🔴🔴 B) Left bundle branch block with secondary ST-T wave changes
🟢 C) Right bundle branch block
🟢 D) Nonspecific intraventricular conduction delay
Rationale: LBBB is characterized by QRS >0.12 seconds, broad notched or slurred R wave in leads I, aVL, V5, V6 (lateral leads), and deep S waves in V1-V2.
The T wave is discordant (opposite direction) to the QRS, representing secondary repolarization changes. The broad S wave in V1 and the notched R wave
in V6 are hallmark findings. Secondary ST-T wave changes are normal in bundle branch block and do not represent ischemia, but acute MI can be masked
by LBBB (Sgarbossa criteria required).
🟢 4. A 68-year-old patient presents with chest pain. The ECG shows LBBB with ST elevation of 5 mm in lead V2, 4 mm in lead V3, and 3 mm in lead V4
(Sgarbossa criteria). Which of the following interpretations is correct?
🟢 A) The ST elevation is due to normal secondary changes in LBBB
🟢 B) The ECG is nondiagnostic because LBBB masks ischemia
🔴🔴 C) This meets Sgarbossa criteria for acute MI and requires immediate reperfusion
🟢 D) The patient requires stress testing before intervention
Rationale: Sgarbossa criteria are used to diagnose acute myocardial infarction in the presence of LBBB. The modified Sgarbossa criteria include: 1)
Concordant ST elevation ≥1 mm (most specific, as seen here >3 mm); 2) Concordant ST depression ≥1 mm in V1-V3; 3) Discordant ST elevation ≥5 mm (or
≥25% of QRS depth). This patient meets criterion 1 with ST elevation >3 mm, indicating acute MI requiring immediate reperfusion. ST elevation due to
LBBB alone is typically <1 mm.
🟢 5. A patient's ECG demonstrates a prolonged QTc interval of 520 ms. Which of the following medications is LEAST likely to exacerbate this finding?
🟢 A) Amiodarone
🟢 B) Sotalol
🟢 C) Haloperidol
🔴🔴 D) Metoprolol
Rationale: Metoprolol (a beta-blocker) does NOT significantly prolong the QT interval and is actually the treatment of choice for long QT syndrome.
Amiodarone, sotalol (Class III antiarrhythmics), and haloperidol (antipsychotic) are all associated with QT prolongation and risk of Torsades de pointes.
Other QT-prolonging drugs include macrolide antibiotics, fluoroquinolones, and certain antihistamines.
🟢 6. A 12-lead ECG shows a prominent U wave of 0.3 mV in lead V3 with a flattened T wave. The patient has a history of heart failure and is on furosemide
therapy. Which electrolyte imbalance is most likely responsible?
🟢 A) Hyperkalemia
🔴🔴 B) Hypokalemia
🟢 C) Hypermagnesemia
🟢 D) Hypercalcemia
Rationale: Hypokalemia (serum K+ <3.5 mEq/L) causes prominent U waves (most prominent in leads V2-V4), flattened or inverted T waves, and subtle ST
depression. This is commonly seen in patients on loop diuretics (furosemide). The U wave is a small deflection following the T wave, typically best seen in
the precordial leads. Hyperkalemia presents with tall peaked T waves. Hypocalcemia prolongs the QT interval. Hypermagnesemia is rare but can cause
bradycardia and hypotension.
🟢 7. A patient's ECG demonstrates a QRS axis of +100 degrees with a small R wave in lead I and a deep S wave in lead aVF. The QRS is narrow (0.08
seconds). This axis deviation is most consistent with:
🟢 A) Left ventricular hypertrophy
🔴🔴 B) Right axis deviation (normal variant or RVH)
🟢 C) Left anterior fascicular block
🟢 D) Inferior MI
,Rationale: Normal QRS axis is -30 to +90 degrees. Right axis deviation (>+90 degrees) can be a normal variant in thin, tall individuals, or indicate right
ventricular hypertrophy (RVH), acute pulmonary embolism, or chronic lung disease. The small R wave in lead I and deep S wave in aVF indicate electrical
forces directed rightward. Left axis deviation (<-30 degrees) would have a deep S in lead III and small R in lead aVF.
🟢 8. A patient's ECG shows a prolonged PR interval of 0.32 seconds with a normal QRS duration. The P waves are biphasic in lead V1 (positive component
> negative component). This finding suggests:
🟢 A) Normal variant first-degree AV block
🟢 B) Hyperkalemia with AV conduction delay
🔴🔴 C) Left atrial enlargement with first-degree AV block
🟢 D) Right atrial enlargement
Rationale: Biphasic P waves in V1 with a prominent negative component (P-terminal force) indicate left atrial enlargement (LAE). The prolonged PR interval
(>0.20 sec) indicates first-degree AV block. LAE is commonly associated with mitral valve disease, hypertension, and left ventricular hypertrophy. The
combination suggests underlying cardiac pathology affecting both atrial structure and AV conduction. Right atrial enlargement presents with tall peaked P
waves in lead II (P pulmonale).
🟢 9. A patient's ECG demonstrates a QRS alternans pattern (alternating QRS amplitude) at a rate of 180 bpm with a narrow QRS. This finding is most
concerning for:
🟢 A) Atrial fibrillation with rapid ventricular response
🟢 B) Sinus tachycardia with dehydration
🔴🔴 C) Electrical alternans due to pericardial effusion or tachycardia
🟢 D) Ventricular tachycardia
Rationale: Electrical alternans (alternating amplitude of QRS complexes) is a classic sign of pericardial effusion with cardiac tamponade, especially when
associated with tachycardia. The mechanism involves the heart swinging within the fluid-filled pericardial sac, causing varying electrical axis. However, it can
also be seen in rapid tachycardia (rate-related). In this patient with narrow complex tachycardia, the alternans pattern raises concern for pericardial effusion
or underlying structural disease. Ventricular tachycardia would have wide QRS >0.12 seconds.
🟢 10. A patient's ECG demonstrates ST depression of 2 mm in leads V1-V4 with tall R waves in V1-V2 and upright T waves in V1-V2. This pattern is most
consistent with:
🟢 A) Anterior wall MI
🟢 B) Lateral wall MI
🔴🔴 C) Posterior wall MI (reciprocal changes)
🟢 D) Pulmonary embolism
Rationale: Posterior wall MI (posterior descending artery occlusion) presents with reciprocal changes in the anterior precordial leads: ST depression in V1-
V4, tall R waves (>0.04 sec or R/S >1), and upright T waves. True posterior infarction is diagnosed by placing posterior leads (V7-V9), which show ST
elevation. This is often missed because standard 12-lead ECG shows only reciprocal ST depression. Anterior MI presents with ST elevation in V1-V4.
Pulmonary embolism typically has sinus tachycardia, right axis deviation, and S1Q3T3 pattern.
🟢 11. A patient's ECG demonstrates a well-defined J wave (Osborn wave) at the R-ST junction in leads II, V4, and V6. The patient is a 45-year-old with a
history of alcohol use disorder found unresponsive in a cold environment. What is the most likely diagnosis?
🟢 A) Hyperkalemia
🟢 B) Acute myocardial infarction
🟢 C) Pulmonary embolism
🔴🔴 D) Hypothermia
Rationale: Osborn waves (J waves) are characteristic of hypothermia (core temperature <32°C). They appear as a positive deflection at the J point (junction
of QRS and ST segment). They are most prominent in the inferior (II, III, aVF) and left precordial (V4-V6) leads. Hypothermia also causes bradycardia,
prolonged PR/QRS/QTc intervals, and shivering artifact. Treatment is rewarming. Other causes of J waves include hypercalcemia, early repolarization, and
neurological injury.
🟢 12. A patient's 12-lead ECG demonstrates ST elevation of 1.5 mm in leads V1-V2 with a slow upsloping ST segment. There is no reciprocal ST
depression. The patient is a 25-year-old asymptomatic athlete. This ECG finding is most consistent with:
🟢 A) Brugada syndrome
🟢 B) Anterior MI
, 🔴🔴 C) Early repolarization (benign)
🟢 D) Pericarditis
Rationale: Early repolarization is a benign ECG variant commonly seen in young, healthy individuals (especially athletes). It is characterized by ST elevation
(usually <2 mm) in the precordial leads (V2-V4) with a notched QRS, upward concave ST segment, and no reciprocal changes. Unlike ischemia, early
repolarization has no reciprocal ST depression and is associated with prominent T waves. It is a normal variant and requires no treatment. Brugada
syndrome would show coved-type ST elevation in V1-V3 with inverted T waves. Pericarditis would have diffuse ST elevation and PR depression.
Section II: Sinus Rhythm Complexities & Variants
🟢 13. A patient's ECG shows a sinus rhythm at 88 bpm with intermittent prolongation of the PR interval from 0.18 to 0.28 seconds that is not cycle-
dependent. The P waves are normal. What is the most likely diagnosis?
🟢 A) Wenckebach block (Mobitz I)
🟢 B) Fixed first-degree AV block
🔴🔴 C) Variable first-degree AV block (due to vagal fluctuation or drugs)
🟢 D) Atrial bigeminy
Rationale: Variable PR interval prolongation without a progressive pattern (not cycle-dependent) suggests variation in vagal tone, drug effect (digoxin,
beta-blockers, calcium channel blockers), or intrinsic AV nodal disease. Unlike Wenckebach, there is no progressive prolongation and no dropped beats.
The normal P waves indicate sinus origin. This is a form of first-degree AV block with variability, often exacerbated by vagal tone changes or medications.
🟢 14. A patient with known sick sinus syndrome presents with intermittent episodes of sinus bradycardia (40 bpm) alternating with sinus tachycardia (120
bpm) without precipitants. The term for this clinical entity is:
🟢 A) Sinus arrhythmia
🟢 B) Sinus node reentry
🔴🔴 C) Tachycardia-bradycardia syndrome (sick sinus syndrome variant)
🟢 D) Atrial fibrillation
Rationale: Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome characterized by alternating episodes of sinus bradycardia and
supraventricular tachycardia (often atrial fibrillation or flutter). The bradycardia may occur spontaneously or after termination of the tachycardia. This
causes symptoms of syncope, palpitations, and fatigue. Treatment typically requires pacemaker placement for bradycardia and rate-control/antiarrhythmic
drugs for tachycardia, but the antiarrhythmics may worsen bradycardia.
🟢 15. A patient's Holter monitor demonstrates sinus pauses of 3.5 seconds that occur during sleep. The patient is asymptomatic. What is the appropriate
management?
🟢 A) Pacemaker placement
🟢 B) Atropine 0.5 mg IV push
🔴🔴 C) Clinical correlation and routine follow-up
🟢 D) Adenosine challenge test
Rationale: Sinus pauses up to 3 seconds are considered normal during sleep in healthy individuals, especially young people and athletes. Pauses >3
seconds that occur in awake state or cause symptoms (syncope, dizziness) may require pacemaker placement. This asymptomatic patient with nocturnal
pauses requires correlation with symptoms. Pacemaker placement is indicated only if symptoms correlate with the pauses or if pauses exceed 5 seconds.
🟢 16. A 72-year-old patient with hypertension has an ECG that shows sinus rhythm with a PR interval of 0.26 seconds and a heart rate of 62 bpm. The QRS
is narrow. Which of the following is the most appropriate initial management?
🟢 A) Start metoprolol for rate control
🟢 B) Consider pacemaker placement
🔴🔴 C) Monitor and evaluate for reversible causes (medication review, thyroid, electrolytes)
🟢 D) Administer atropine 0.5 mg IV push
Rationale: First-degree AV block (PR >0.20 sec) in an asymptomatic patient requires no treatment but does warrant evaluation for reversible causes:
medications (beta-blockers, calcium channel blockers, digoxin), electrolyte disturbances, ischemic heart disease, and structural heart disease. Pacemaker
placement is not indicated for asymptomatic first-degree AV block. Atropine is for symptomatic bradycardia. This patient is asymptomatic with a normal
heart rate, so monitoring and evaluation are appropriate.
A Comprehensive 150-Question Practice Test Bank with In-Depth Clinical Rationales, Complex Scenario-Based Questions, and Advanced ECG
Interpretation for Healthcare Professionals
Table of Contents
Section Topic Area Questions
I Advanced ECG Principles & Waveform Analysis 1–12
II Sinus Rhythm Complexities & Variants 13–20
III Atrial Dysrhythmias: Advanced Concepts 21–35
IV Junctional Rhythms & Complex Conduction 36–45
V Ventricular Dysrhythmias: High-Risk Scenarios 46–60
VI Advanced AV Blocks & Conduction Disorders 61–75
VII Pacemaker Technology & Troubleshooting 76–85
VIII Antiarrhythmic Pharmacology: Mechanism-Based 86–95
IX Emergency Interventions & ACLS Updates 96–110
X Clinical Scenarios: Diagnostic Challenges 111–125
XI Mixed Rhythm Interpretation: Complex Strips 126–140
XII High-Yield Review & Board-Style Questions 141–150
Section I: Advanced ECG Principles & Waveform Analysis
🟢 1. A 12-lead ECG demonstrates a QRS axis of -30 degrees with a dominant R wave in lead aVL and a deep S wave in lead III. The R-wave progression in
the precordial leads is reversed (transition occurs before V1). This pattern is most consistent with:
🟢 A) Left ventricular hypertrophy
🟢 B) Right bundle branch block
🔴🔴 C) Left anterior fascicular block (LAFB)
🟢 D) Inferior wall myocardial infarction
Rationale: Left anterior fascicular block (LAFB) produces left-axis deviation (-30 to -90 degrees), a small q wave in lead I and aVL, deep S wave in inferior
leads (II, III, aVF), and delayed R-wave progression with transition before V1. This blocks the anterior-superior division of the left bundle, altering
depolarization sequence. The axis deviation and R/S ratio distinguish LAFB from left ventricular hypertrophy (which has voltage criteria) and right bundle
branch block (which has wide QRS, rsR' pattern).
🟢 2. A patient's ECG shows ST-segment elevation of 2 mm in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Additionally, there is
first-degree AV block (PR interval 0.28 seconds). The patient is experiencing bradycardia at 48 bpm. This clinical picture is most consistent with which
vascular territory involvement?
🟢 A) Anterior wall MI (LAD occlusion)
🟢 B) Lateral wall MI (LCx occlusion)
🔴🔴 C) Inferior wall MI with right ventricular (RV) involvement
🟢 D) Posterior wall MI
Rationale: Inferior wall MI (right coronary artery or dominant left circumflex) commonly presents with ST elevation in leads II, III, aVF, reciprocal depression
in I and aVL, and is frequently complicated by AV conduction abnormalities (first-degree AV block, Mobitz I), sinus bradycardia, and right ventricular
,involvement. Inferior MI increases vagal tone, causing bradycardia and AV blocks. RV involvement is suspected with ST elevation in V4R and is associated
with hypotension requiring volume resuscitation.
🟢 3. A 55-year-old patient's ECG demonstrates a QRS duration of 0.14 seconds with a broad, notched R wave in lead V6 and a broad, deep S wave in lead
V1. The T wave is discordant to the QRS in the lateral leads. This pattern is most consistent with:
🟢 A) Left bundle branch block (LBBB)
🔴🔴 B) Left bundle branch block with secondary ST-T wave changes
🟢 C) Right bundle branch block
🟢 D) Nonspecific intraventricular conduction delay
Rationale: LBBB is characterized by QRS >0.12 seconds, broad notched or slurred R wave in leads I, aVL, V5, V6 (lateral leads), and deep S waves in V1-V2.
The T wave is discordant (opposite direction) to the QRS, representing secondary repolarization changes. The broad S wave in V1 and the notched R wave
in V6 are hallmark findings. Secondary ST-T wave changes are normal in bundle branch block and do not represent ischemia, but acute MI can be masked
by LBBB (Sgarbossa criteria required).
🟢 4. A 68-year-old patient presents with chest pain. The ECG shows LBBB with ST elevation of 5 mm in lead V2, 4 mm in lead V3, and 3 mm in lead V4
(Sgarbossa criteria). Which of the following interpretations is correct?
🟢 A) The ST elevation is due to normal secondary changes in LBBB
🟢 B) The ECG is nondiagnostic because LBBB masks ischemia
🔴🔴 C) This meets Sgarbossa criteria for acute MI and requires immediate reperfusion
🟢 D) The patient requires stress testing before intervention
Rationale: Sgarbossa criteria are used to diagnose acute myocardial infarction in the presence of LBBB. The modified Sgarbossa criteria include: 1)
Concordant ST elevation ≥1 mm (most specific, as seen here >3 mm); 2) Concordant ST depression ≥1 mm in V1-V3; 3) Discordant ST elevation ≥5 mm (or
≥25% of QRS depth). This patient meets criterion 1 with ST elevation >3 mm, indicating acute MI requiring immediate reperfusion. ST elevation due to
LBBB alone is typically <1 mm.
🟢 5. A patient's ECG demonstrates a prolonged QTc interval of 520 ms. Which of the following medications is LEAST likely to exacerbate this finding?
🟢 A) Amiodarone
🟢 B) Sotalol
🟢 C) Haloperidol
🔴🔴 D) Metoprolol
Rationale: Metoprolol (a beta-blocker) does NOT significantly prolong the QT interval and is actually the treatment of choice for long QT syndrome.
Amiodarone, sotalol (Class III antiarrhythmics), and haloperidol (antipsychotic) are all associated with QT prolongation and risk of Torsades de pointes.
Other QT-prolonging drugs include macrolide antibiotics, fluoroquinolones, and certain antihistamines.
🟢 6. A 12-lead ECG shows a prominent U wave of 0.3 mV in lead V3 with a flattened T wave. The patient has a history of heart failure and is on furosemide
therapy. Which electrolyte imbalance is most likely responsible?
🟢 A) Hyperkalemia
🔴🔴 B) Hypokalemia
🟢 C) Hypermagnesemia
🟢 D) Hypercalcemia
Rationale: Hypokalemia (serum K+ <3.5 mEq/L) causes prominent U waves (most prominent in leads V2-V4), flattened or inverted T waves, and subtle ST
depression. This is commonly seen in patients on loop diuretics (furosemide). The U wave is a small deflection following the T wave, typically best seen in
the precordial leads. Hyperkalemia presents with tall peaked T waves. Hypocalcemia prolongs the QT interval. Hypermagnesemia is rare but can cause
bradycardia and hypotension.
🟢 7. A patient's ECG demonstrates a QRS axis of +100 degrees with a small R wave in lead I and a deep S wave in lead aVF. The QRS is narrow (0.08
seconds). This axis deviation is most consistent with:
🟢 A) Left ventricular hypertrophy
🔴🔴 B) Right axis deviation (normal variant or RVH)
🟢 C) Left anterior fascicular block
🟢 D) Inferior MI
,Rationale: Normal QRS axis is -30 to +90 degrees. Right axis deviation (>+90 degrees) can be a normal variant in thin, tall individuals, or indicate right
ventricular hypertrophy (RVH), acute pulmonary embolism, or chronic lung disease. The small R wave in lead I and deep S wave in aVF indicate electrical
forces directed rightward. Left axis deviation (<-30 degrees) would have a deep S in lead III and small R in lead aVF.
🟢 8. A patient's ECG shows a prolonged PR interval of 0.32 seconds with a normal QRS duration. The P waves are biphasic in lead V1 (positive component
> negative component). This finding suggests:
🟢 A) Normal variant first-degree AV block
🟢 B) Hyperkalemia with AV conduction delay
🔴🔴 C) Left atrial enlargement with first-degree AV block
🟢 D) Right atrial enlargement
Rationale: Biphasic P waves in V1 with a prominent negative component (P-terminal force) indicate left atrial enlargement (LAE). The prolonged PR interval
(>0.20 sec) indicates first-degree AV block. LAE is commonly associated with mitral valve disease, hypertension, and left ventricular hypertrophy. The
combination suggests underlying cardiac pathology affecting both atrial structure and AV conduction. Right atrial enlargement presents with tall peaked P
waves in lead II (P pulmonale).
🟢 9. A patient's ECG demonstrates a QRS alternans pattern (alternating QRS amplitude) at a rate of 180 bpm with a narrow QRS. This finding is most
concerning for:
🟢 A) Atrial fibrillation with rapid ventricular response
🟢 B) Sinus tachycardia with dehydration
🔴🔴 C) Electrical alternans due to pericardial effusion or tachycardia
🟢 D) Ventricular tachycardia
Rationale: Electrical alternans (alternating amplitude of QRS complexes) is a classic sign of pericardial effusion with cardiac tamponade, especially when
associated with tachycardia. The mechanism involves the heart swinging within the fluid-filled pericardial sac, causing varying electrical axis. However, it can
also be seen in rapid tachycardia (rate-related). In this patient with narrow complex tachycardia, the alternans pattern raises concern for pericardial effusion
or underlying structural disease. Ventricular tachycardia would have wide QRS >0.12 seconds.
🟢 10. A patient's ECG demonstrates ST depression of 2 mm in leads V1-V4 with tall R waves in V1-V2 and upright T waves in V1-V2. This pattern is most
consistent with:
🟢 A) Anterior wall MI
🟢 B) Lateral wall MI
🔴🔴 C) Posterior wall MI (reciprocal changes)
🟢 D) Pulmonary embolism
Rationale: Posterior wall MI (posterior descending artery occlusion) presents with reciprocal changes in the anterior precordial leads: ST depression in V1-
V4, tall R waves (>0.04 sec or R/S >1), and upright T waves. True posterior infarction is diagnosed by placing posterior leads (V7-V9), which show ST
elevation. This is often missed because standard 12-lead ECG shows only reciprocal ST depression. Anterior MI presents with ST elevation in V1-V4.
Pulmonary embolism typically has sinus tachycardia, right axis deviation, and S1Q3T3 pattern.
🟢 11. A patient's ECG demonstrates a well-defined J wave (Osborn wave) at the R-ST junction in leads II, V4, and V6. The patient is a 45-year-old with a
history of alcohol use disorder found unresponsive in a cold environment. What is the most likely diagnosis?
🟢 A) Hyperkalemia
🟢 B) Acute myocardial infarction
🟢 C) Pulmonary embolism
🔴🔴 D) Hypothermia
Rationale: Osborn waves (J waves) are characteristic of hypothermia (core temperature <32°C). They appear as a positive deflection at the J point (junction
of QRS and ST segment). They are most prominent in the inferior (II, III, aVF) and left precordial (V4-V6) leads. Hypothermia also causes bradycardia,
prolonged PR/QRS/QTc intervals, and shivering artifact. Treatment is rewarming. Other causes of J waves include hypercalcemia, early repolarization, and
neurological injury.
🟢 12. A patient's 12-lead ECG demonstrates ST elevation of 1.5 mm in leads V1-V2 with a slow upsloping ST segment. There is no reciprocal ST
depression. The patient is a 25-year-old asymptomatic athlete. This ECG finding is most consistent with:
🟢 A) Brugada syndrome
🟢 B) Anterior MI
, 🔴🔴 C) Early repolarization (benign)
🟢 D) Pericarditis
Rationale: Early repolarization is a benign ECG variant commonly seen in young, healthy individuals (especially athletes). It is characterized by ST elevation
(usually <2 mm) in the precordial leads (V2-V4) with a notched QRS, upward concave ST segment, and no reciprocal changes. Unlike ischemia, early
repolarization has no reciprocal ST depression and is associated with prominent T waves. It is a normal variant and requires no treatment. Brugada
syndrome would show coved-type ST elevation in V1-V3 with inverted T waves. Pericarditis would have diffuse ST elevation and PR depression.
Section II: Sinus Rhythm Complexities & Variants
🟢 13. A patient's ECG shows a sinus rhythm at 88 bpm with intermittent prolongation of the PR interval from 0.18 to 0.28 seconds that is not cycle-
dependent. The P waves are normal. What is the most likely diagnosis?
🟢 A) Wenckebach block (Mobitz I)
🟢 B) Fixed first-degree AV block
🔴🔴 C) Variable first-degree AV block (due to vagal fluctuation or drugs)
🟢 D) Atrial bigeminy
Rationale: Variable PR interval prolongation without a progressive pattern (not cycle-dependent) suggests variation in vagal tone, drug effect (digoxin,
beta-blockers, calcium channel blockers), or intrinsic AV nodal disease. Unlike Wenckebach, there is no progressive prolongation and no dropped beats.
The normal P waves indicate sinus origin. This is a form of first-degree AV block with variability, often exacerbated by vagal tone changes or medications.
🟢 14. A patient with known sick sinus syndrome presents with intermittent episodes of sinus bradycardia (40 bpm) alternating with sinus tachycardia (120
bpm) without precipitants. The term for this clinical entity is:
🟢 A) Sinus arrhythmia
🟢 B) Sinus node reentry
🔴🔴 C) Tachycardia-bradycardia syndrome (sick sinus syndrome variant)
🟢 D) Atrial fibrillation
Rationale: Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome characterized by alternating episodes of sinus bradycardia and
supraventricular tachycardia (often atrial fibrillation or flutter). The bradycardia may occur spontaneously or after termination of the tachycardia. This
causes symptoms of syncope, palpitations, and fatigue. Treatment typically requires pacemaker placement for bradycardia and rate-control/antiarrhythmic
drugs for tachycardia, but the antiarrhythmics may worsen bradycardia.
🟢 15. A patient's Holter monitor demonstrates sinus pauses of 3.5 seconds that occur during sleep. The patient is asymptomatic. What is the appropriate
management?
🟢 A) Pacemaker placement
🟢 B) Atropine 0.5 mg IV push
🔴🔴 C) Clinical correlation and routine follow-up
🟢 D) Adenosine challenge test
Rationale: Sinus pauses up to 3 seconds are considered normal during sleep in healthy individuals, especially young people and athletes. Pauses >3
seconds that occur in awake state or cause symptoms (syncope, dizziness) may require pacemaker placement. This asymptomatic patient with nocturnal
pauses requires correlation with symptoms. Pacemaker placement is indicated only if symptoms correlate with the pauses or if pauses exceed 5 seconds.
🟢 16. A 72-year-old patient with hypertension has an ECG that shows sinus rhythm with a PR interval of 0.26 seconds and a heart rate of 62 bpm. The QRS
is narrow. Which of the following is the most appropriate initial management?
🟢 A) Start metoprolol for rate control
🟢 B) Consider pacemaker placement
🔴🔴 C) Monitor and evaluate for reversible causes (medication review, thyroid, electrolytes)
🟢 D) Administer atropine 0.5 mg IV push
Rationale: First-degree AV block (PR >0.20 sec) in an asymptomatic patient requires no treatment but does warrant evaluation for reversible causes:
medications (beta-blockers, calcium channel blockers, digoxin), electrolyte disturbances, ischemic heart disease, and structural heart disease. Pacemaker
placement is not indicated for asymptomatic first-degree AV block. Atropine is for symptomatic bradycardia. This patient is asymptomatic with a normal
heart rate, so monitoring and evaluation are appropriate.
