Cardiology MCQs for Third-Year Medical Students
Question 1: ECG Interpretation - Left Bundle Branch Block
A 68-year-old man presents with chest pain. His ECG shows QRS duration of 140 ms, broad monophasic R waves in leads I, aVL, V5, and V6, and absent Q waves in lateral leads. What is the diagnosis?
A) Right bundle branch block
B) Left anterior fascicular block
C) Complete left bundle branch block
D) Wolff-Parkinson-White syndrome
E) Normal variant
Correct Answer: C
Explanation for Correct Answer: Complete left bundle branch block (LBBB) is characterized by QRS duration ≥120 ms, broad monophasic R waves in lateral leads (I, aVL, V5-V6), and absence of septal Q waves in these leads 1. The QRS duration of 140 ms exceeds the threshold, and the morphology matches LBBB criteria. This pattern reflects delayed left ventricular activation, causing the entire QRS complex to be prolonged and the characteristic broad R waves in lateral leads.
Why Other Answers Are Incorrect:
A) Right bundle branch block - RBBB shows QRS ≥120 ms but with a different pattern: rSR' (rabbit ears) in V1-V2 and wide S waves in lateral leads (I, V5-V6), not broad R waves 2, 1.
B) Left anterior fascicular block - This produces left axis deviation (typically -45° to -90°) with small Q waves in I and aVL, and small R waves with deep S waves in inferior leads. QRS duration is typically <120 ms 1.
D) Wolff-Parkinson-White syndrome - WPW shows a short PR interval (<120 ms), delta wave (slurred upstroke of QRS), and wide QRS, representing pre-excitation via an accessory pathway 2, 1. The question describes normal PR interval characteristics of LBBB.
E) Normal variant - A QRS duration of 140 ms is pathological and cannot be normal. Normal QRS duration is <120 ms 1.
Question 2: Echocardiography Indications
A 45-year-old woman presents with bilateral ankle edema but has normal jugular venous pressure and no other signs of heart disease. Which statement about echocardiography is correct?
A) Echocardiography is mandatory to rule out heart failure
B) Echocardiography is not recommended in this scenario
C) Transesophageal echocardiography should be performed first
D) Stress echocardiography is the test of choice
E) Cardiac MRI should precede echocardiography
Correct Answer: B
Explanation for Correct Answer: Echocardiography is not recommended when peripheral edema occurs without elevated central venous pressure and no evidence of heart disease 3. The guideline explicitly states that "in the absence of an elevation in central venous pressure, a cardiac or pericardial reason for peripheral edema is usually not present, and echocardiography is not recommended." This patient's edema is likely from non-cardiac causes (venous insufficiency, lymphatic obstruction, medication side effects, renal disease, or hepatic disease).
Why Other Answers Are Incorrect:
A) Echocardiography is mandatory to rule out heart failure - This contradicts ACC/AHA guidelines 3. Echocardiography should be reserved for patients with clinical signs suggesting cardiac disease or elevated central venous pressure.
C) Transesophageal echocardiography should be performed first - TEE is invasive and indicated only when transthoracic echo is non-diagnostic in appropriate clinical scenarios 3. It has no role in screening patients without cardiac signs.
D) Stress echocardiography is the test of choice - Stress echo is used to evaluate ischemia, valvular disease under stress, or diastolic dysfunction during exercise 4. It has no indication for isolated peripheral edema without cardiac symptoms.
E) Cardiac MRI should precede echocardiography - Advanced imaging is not indicated without clinical evidence of cardiac disease. The stepwise approach begins with clinical assessment, not imaging 3.
Question 3: Atrial Fibrillation Recognition
A 72-year-old man's telemetry shows an irregularly irregular rhythm with no discernible P waves and a ventricular rate of 110 bpm. What is the rhythm?
A) Multifocal atrial tachycardia
B) Atrial flutter with variable block
C) Atrial fibrillation
D) Wandering atrial pacemaker
E) Sinus arrhythmia
Correct Answer: C
Explanation for Correct Answer: Atrial fibrillation is characterized by an irregularly irregular ventricular rhythm with absent P waves, replaced by fibrillatory waves 1. The complete absence of organized atrial activity distinguishes AF from other atrial arrhythmias. The irregular ventricular response results from random AV nodal conduction of the chaotic atrial electrical activity.
Why Other Answers Are Incorrect:
A) Multifocal atrial tachycardia - MAT shows at least three different P wave morphologies with varying PR intervals and an irregular rhythm 1. Crucially, P waves are present and identifiable, unlike in AF. MAT typically occurs in patients with severe pulmonary disease.
B) Atrial flutter with variable block - Flutter shows characteristic sawtooth flutter waves (F waves) at 250-350 bpm, typically in inferior leads (II, III, aVF) 2, 1. Even with variable block, flutter waves remain visible, unlike the absent P waves in this case.
D) Wandering atrial pacemaker - This shows at least three different P wave morphologies with varying PR intervals but at a rate <100 bpm 1. P waves are present and the rhythm is typically irregular but not as chaotically irregular as AF.
E) Sinus arrhythmia - This shows normal P waves with phasic variation in PP intervals related to respiration 1. P waves are present and have consistent morphology, and the rhythm variation is regular and predictable.
Question 4: Dilated Cardiomyopathy Assessment
A 52-year-old man with dilated cardiomyopathy undergoes echocardiography. Which finding is MOST characteristic?
A) Increased wall thickness with small ventricular cavity
B) Dilated ventricular chambers with normal wall thickness
C) Normal ventricular size with atrial enlargement
D) Asymmetric septal hypertrophy
E) Intense stippled appearance of myocardium
Correct Answer: B
Explanation for Correct Answer: Dilated cardiomyopathy characteristically shows dilated ventricular chambers with normal wall thickness and varying degrees of depressed systolic function 3. This distinguishes DCM from hypertrophic conditions. Doppler techniques reveal associated valvular regurgitation (particularly mitral regurgitation from annular dilatation), allow estimation of pulmonary artery pressures, and assess diastolic function. The normal wall thickness despite chamber dilatation is a key diagnostic feature.
Why Other Answers Are Incorrect:
A) Increased wall thickness with small ventricular cavity - This describes hypertrophic cardiomyopathy, not dilated cardiomyopathy 3. HCM shows increased wall thickness (≥15 mm) with preserved or reduced cavity size.
C) Normal ventricular size with atrial enlargement - This pattern is characteristic of restrictive cardiomyopathy 3. Restrictive CM shows normal ventricular size and systolic function with biatrial enlargement and characteristic Doppler inflow patterns indicating impaired ventricular filling.
D) Asymmetric septal hypertrophy - This is the hallmark of hypertrophic cardiomyopathy, particularly the obstructive form 3. The septum is disproportionately thickened compared to the posterior wall (ratio ≥1.3:1).
E) Intense stippled appearance of myocardium - This characteristic "sparkling" or granular appearance is seen in cardiac amyloidosis, a form of restrictive cardiomyopathy 3. It results from amyloid protein infiltration of the myocardium.
Question 5: Ventricular Tachycardia Classification
A patient's telemetry shows a wide complex tachycardia at 180 bpm with uniform QRS morphology lasting 45 seconds. What is the classification?
A) Nonsustained monomorphic ventricular tachycardia
B) Sustained monomorphic ventricular tachycardia
C) Polymorphic ventricular tachycardia
D) Accelerated idioventricular rhythm
E) Ventricular flutter
Correct Answer: B
Explanation for Correct Answer: Sustained monomorphic ventricular tachycardia is defined as VT lasting >30 seconds or requiring termination due to hemodynamic compromise 1. The uniform (monomorphic) QRS morphology indicates a single ventricular focus or reentrant circuit. The 45-second duration exceeds the 30-second threshold for "sustained" classification. This distinction is clinically critical as sustained VT carries higher risk and typically requires immediate intervention and long-term management strategies including ICD consideration.
Why Other Answers Are Incorrect:
A) Nonsustained monomorphic ventricular tachycardia - NSVT is defined as VT lasting <30 seconds 1. This episode lasted 45 seconds, exceeding the threshold. While the morphology is correctly identified as monomorphic, the duration classification is wrong.
C) Polymorphic ventricular tachycardia - Polymorphic VT shows varying QRS morphology, indicating multiple ventricular foci or a shifting reentrant circuit 2, 1. This case describes uniform morphology. Torsades de pointes is a specific form of polymorphic VT with characteristic twisting QRS axis.
D) Accelerated idioventricular rhythm - AIVR has a rate of 50-110 bpm, slower than VT 1. It's commonly seen after reperfusion in myocardial infarction and is generally benign. The rate of 180 bpm far exceeds AIVR criteria.
E) Ventricular flutter - This shows a sinusoidal pattern at 250-350 bpm without distinct QRS complexes and T waves 1. It represents a transition between VT and ventricular fibrillation and is immediately life-threatening.
Question 6: Pericardial Effusion Detection
Which imaging modality is considered the BEST technique for detecting and evaluating pericardial effusion?
A) Chest X-ray
B) Cardiac CT
C) Echocardiography
D) Cardiac MRI
E) Nuclear imaging
Correct Answer: C
Explanation for Correct Answer: Echocardiography remains the best technique for evaluating pericardial effusion 3. This was one of the earliest clinical applications of echocardiography and remains the gold standard. Echo can detect even small effusions (as little as 20 mL), assess hemodynamic significance (tamponade physiology), guide pericardiocentesis, and evaluate for associated cardiac abnormalities. It's readily available, non-invasive, portable, and provides real-time assessment without radiation exposure.
Why Other Answers Are Incorrect:
A) Chest X-ray - While chest X-ray may show cardiomegaly with a "water bottle" heart configuration when effusion exceeds 250 mL, it cannot detect small effusions and provides no information about hemodynamic significance or precise loculation 3. It's insensitive and non-specific.
B) Cardiac CT - CT can visualize pericardial effusion and measure pericardial thickness but involves radiation exposure and cannot assess real-time hemodynamics 4. It's useful for evaluating pericardial masses or calcification but not the first-line test for effusion.
C) Cardiac MRI - MRI provides excellent tissue characterization and can distinguish hemorrhagic from serous effusions 4. However, it's expensive, time-consuming, not portable, and unavailable in emergencies. It's not the best initial test despite excellent anatomic detail.
E) Nuclear imaging - Nuclear studies have no role in detecting or evaluating pericardial effusion 3. They assess myocardial perfusion and viability, not pericardial disease.
Question 7: AV Nodal Reentrant Tachycardia
A 28-year-old woman presents with sudden-onset palpitations. ECG shows narrow complex tachycardia at 180 bpm with no visible P waves. What is the most likely diagnosis?
A) Sinus tachycardia
B) Atrial flutter
C) AV nodal reentrant tachycardia
D) Atrial fibrillation
E) Ventricular tachycardia with aberrancy
Correct Answer: C
Explanation for Correct Answer: AV nodal reentrant tachycardia (AVNRT) typically presents as narrow complex tachycardia with absent or pseudo-R' waves (retrograde P waves buried in QRS) 1. AVNRT is the most common paroxysmal supraventricular tachycardia, accounting for 60% of cases. The reentrant circuit involves dual AV nodal pathways (fast and slow). The sudden onset and termination ("paroxysmal") is characteristic. P waves are typically not visible because atrial and ventricular activation occur simultaneously.
Why Other Answers Are Incorrect:
A) Sinus tachycardia - Sinus tachycardia shows normal P waves preceding each QRS with gradual onset and termination 1. The rate rarely exceeds 150-160 bpm in adults at rest. The sudden onset and absent P waves exclude this diagnosis.
B) Atrial flutter - Flutter shows characteristic sawtooth flutter waves at 250-350 bpm, typically with 2:1 AV conduction resulting in ventricular rate of 150 bpm 2, 1. Flutter waves would be visible, particularly in inferior leads.
D) Atrial fibrillation - AF shows irregularly irregular rhythm 1. This case describes regular tachycardia at 180 bpm, excluding AF. AF also lacks organized atrial activity.
E) Ventricular tachycardia with aberrancy - VT shows wide QRS complexes (>120 ms) 1. The question specifies narrow complex tachycardia, excluding VT. Aberrancy refers to abnormal conduction of supraventricular impulses, not VT.
Question 8: Right Ventricular Hypertrophy Criteria
Which ECG finding is MOST specific for right ventricular hypertrophy?
A) Right axis deviation alone
B) Tall R wave in V1 with right axis deviation
C) Deep S waves in V5-V6
D) P pulmonale
E) Incomplete RBBB
Correct Answer: B
Explanation for Correct Answer: The combination of tall R wave in V1 (R wave >7 mm or R/S ratio >1) with right axis deviation is highly specific for RVH 1. While individual criteria have varying sensitivity and specificity, the combination significantly increases diagnostic accuracy. RVH criteria include: R wave in V1 >7 mm, R/S ratio in V1 >1, right axis deviation (>+90°), and ST-T wave changes in right precordial leads. The presence of multiple criteria increases specificity.
Why Other Answers Are Incorrect:
A) Right axis deviation alone - While right axis deviation (>+90°) suggests RVH, it can occur in other conditions including left posterior fascicular block, lateral MI, normal variant in thin individuals, and chronic lung disease 2, 1. Sensitivity and specificity are insufficient when used alone.
C) Deep S waves in V5-V6 - Deep S waves in lateral leads can suggest RVH but also occur in RBBB, left anterior fascicular block, and normal variants 1. This finding lacks specificity without additional criteria.
D) P pulmonale - P pulmonale (tall peaked P waves >2.5 mm in inferior leads) indicates right atrial abnormality, not RVH 1. While often associated with RVH (both occurring in pulmonary hypertension), it reflects atrial rather than ventricular pathology.
E) Incomplete RBBB - Incomplete RBBB (rsR' pattern in V1 with QRS 100-119 ms) is a conduction abnormality, not a hypertrophy pattern 1. It can be a normal variant or occur with RVH but is not specific for RVH.
Question 9: Diastolic Dysfunction vs Systolic Dysfunction
A 65-year-old woman with heart failure symptoms has an ejection fraction of 55%. What is the most likely diagnosis?
A) Dilated cardiomyopathy
B) Heart failure with preserved ejection fraction (diastolic dysfunction)
C) Acute myocardial infarction
D) Hypovolemia
E) Normal heart function
Correct Answer: B
Explanation for Correct Answer: Heart failure with preserved ejection fraction (HFpEF), also called diastolic dysfunction, is diagnosed when heart failure symptoms occur with LVEF >40-50% 3. The guideline states that "diastolic dysfunction is thought to be present when a patient with heart failure has an LV ejection fraction >40%." This patient's EF of 55% is normal (normal EF ≥50%), yet she has heart failure symptoms, indicating impaired ventricular filling rather than impaired contraction. Treatment and prognosis differ from systolic heart failure, making proper diagnosis critical.
Why Other Answers Are Incorrect:
A) Dilated cardiomyopathy - DCM characteristically shows reduced ejection fraction (<40%), dilated chambers, and depressed systolic function 3. This patient has preserved EF of 55%, excluding DCM.
C) Acute myocardial infarction - While MI can present with heart failure, the preserved EF suggests this is not acute extensive MI 3. Acute MI typically causes regional wall motion abnormalities and reduced EF if causing heart failure symptoms.
D) Hypovolemia - Hypovolemia causes symptoms of low cardiac output (hypotension, tachycardia, poor perfusion) but not heart failure with pulmonary congestion 3. The EF would typically be normal or hyperdynamic with hypovolemia.
E) Normal heart function - Despite normal EF, the patient has heart failure symptoms 3. Normal EF does not equal normal cardiac function; diastolic dysfunction impairs ventricular filling despite preserved contractility.
Question 10: Third-Degree AV Block
A patient's ECG shows P waves marching through at 80 bpm and QRS complexes at 35 bpm with no relationship between them. What is the diagnosis?
A) Second-degree AV block Mobitz I
B) Second-degree AV block Mobitz II
C) Third-degree (complete) AV block
D) AV dissociation due to accelerated junctional rhythm
E) 2:1 AV block
Correct Answer: C
Explanation for Correct Answer: Third-degree (complete) AV block shows complete absence of AV conduction with independent atrial and ventricular rhythms 2, 1. No P waves conduct to the ventricles; the atria and ventricles beat independently. The ventricular rate of 35 bpm indicates a ventricular escape rhythm (rate <40 bpm), which is slower and less reliable than junctional escape (40-60 bpm). This is a medical emergency requiring temporary pacing, as the escape rhythm may fail, causing asystole.
Why Other Answers Are Incorrect:
A) Second-degree AV block Mobitz I (Wenckebach) - Mobitz I shows progressive PR interval prolongation until a P wave fails to conduct, then the cycle repeats 1. Some P waves do conduct, unlike complete heart block where none conduct.
B) Second-degree AV block Mobitz II - Mobitz II shows intermittent non-conducted P waves without progressive PR prolongation 2, 1. The PR interval is constant for conducted beats. Some P waves conduct, unlike this case where none conduct.
D) AV dissociation due to accelerated junctional rhythm - AV dissociation can occur when a junctional or ventricular pacemaker accelerates beyond the sinus rate 1. However, the ventricular rate of 35 bpm is too slow for an accelerated rhythm. Additionally, occasional capture or fusion beats may occur, unlike complete heart block.
E) 2:1 AV block - In 2:1 block, every other P wave conducts 1. The ventricular rate would be exactly half the atrial rate (40 bpm if atrial rate is 80 bpm). This case shows no mathematical relationship between rates, indicating complete block.
Question 11: Torsades de Pointes
A patient on antiarrhythmic therapy develops polymorphic VT with a characteristic twisting QRS axis around the baseline. What is this rhythm?
A) Monomorphic ventricular tachycardia
B) Ventricular fibrillation
C) Torsades de pointes
D) Ventricular flutter
E) Bidirectional ventricular tachycardia
Correct Answer: C
Explanation for Correct Answer: Torsades de pointes is a specific form of polymorphic VT characterized by QRS complexes that appear to twist around the isoelectric baseline 1. The name means "twisting of the points" in French. It occurs in the setting of prolonged QT interval (congenital or acquired) and is triggered by early afterdepolarizations. Common causes include antiarrhythmic drugs (Class IA and III), electrolyte abnormalities (hypokalemia, hypomagnesemia), and bradycardia. Treatment differs from other VT: magnesium sulfate, correction of electrolytes, and increasing heart rate (pacing or isoproterenol), NOT standard antiarrhythmics which may worsen it.
Why Other Answers Are Incorrect:
A) Monomorphic ventricular tachycardia - Monomorphic VT shows uniform QRS morphology indicating a single focus or circuit 2, 1. The question describes polymorphic VT with changing morphology, excluding monomorphic VT.
B) Ventricular fibrillation - VF shows chaotic, disorganized electrical activity without identifiable QRS complexes 1. While torsades can degenerate into VF, the described twisting pattern indicates organized polymorphic VT, not VF.
D) Ventricular flutter - Flutter shows regular sinusoidal oscillations at 250-350 bpm without distinct QRS-T complexes 1. It lacks the characteristic twisting pattern of torsades and represents a transition between VT and VF.
E) Bidirectional ventricular tachycardia - Bidirectional VT shows alternating QRS axis (beat-to-beat alternation) 1. It's classically associated with digitalis toxicity or catecholaminergic polymorphic VT. The pattern is alternating, not twisting.
Question 12: Left Atrial Abnormality
Which ECG finding is MOST consistent with left atrial abnormality?
A) Tall peaked P waves in lead II
B) Biphasic P wave in V1 with prominent negative terminal deflection
C) P wave duration <80 ms
D) Absent P waves
E) P pulmonale pattern
Correct Answer: B
Explanation for Correct Answer: Left atrial abnormality is characterized by a biphasic P wave in V1 with a prominent negative terminal deflection (≥1 mm deep and ≥40 ms duration) 1. This is called the "P terminal force" and reflects delayed left atrial activation. Additional criteria include P wave duration ≥120 ms in lead II (P mitrale - notched P wave with two humps) and increased P wave area. Left atrial abnormality commonly occurs with mitral valve disease, left ventricular dysfunction, and hypertension.
Why Other Answers Are Incorrect:
A) Tall peaked P waves in lead II - Tall peaked P waves (>2.5 mm) in inferior leads indicate right atrial abnormality (P pulmonale) 2, 1. This occurs with pulmonary hypertension, chronic lung disease, or tricuspid valve disease.
C) P wave duration <80 ms - Normal P wave duration is 80-120 ms 1. Left atrial abnormality causes prolonged P wave duration (≥120 ms) due to delayed left atrial activation. Short P wave duration is normal or suggests intra-atrial conduction acceleration.
D) Absent P waves - Absent P waves indicate atrial fibrillation, junctional rhythm, or ventricular rhythm 1. While AF commonly results from left atrial disease, absent P waves don't indicate left atrial abnormality on ECG.
E) P pulmonale pattern - P pulmonale (tall peaked P waves) indicates right atrial abnormality, not left 1. The term comes from its association with pulmonary disease causing right atrial enlargement.
Question 13: Wolff-Parkinson-White Syndrome
A 22-year-old man's ECG shows PR interval of 90 ms, slurred upstroke of the QRS complex, and QRS duration of 130 ms. What is the diagnosis?
A) First-degree AV block
B) Left bundle branch block
C) Wolff-Parkinson-White syndrome
D) Hyperkalemia
E) Acute myocardial infarction
Correct Answer: C
Explanation for Correct Answer: Wolff-Parkinson-White syndrome shows the classic triad: short PR interval (<120 ms), delta wave (slurred upstroke of QRS), and wide QRS complex 1. This represents ventricular pre-excitation via an accessory pathway (bundle of Kent) that bypasses the AV node. The delta wave is the hallmark finding, representing early ventricular activation through the accessory pathway. WPW patients are at risk for AVRT (AV reentrant tachycardia) and, rarely, sudden death if AF conducts rapidly through the accessory pathway. The PR interval of 90 ms is short, and the slurred upstroke is the delta wave.
Why Other Answers Are Incorrect:
A) First-degree AV block - First-degree AV block shows prolonged PR interval (>200 ms), not shortened 2, 1. The PR interval of 90 ms is abnormally short, opposite of first-degree block. There would be no delta wave in first-degree block.
B) Left bundle branch block - LBBB shows QRS ≥120 ms with broad R waves in lateral leads and absent septal Q waves 1. The PR interval is normal (120-200 ms), and there's no delta wave. The slurred upstroke in WPW is at the beginning of the QRS (delta wave), not throughout.
D) Hyperkalemia - Hyperkalemia causes peaked T waves, widened QRS, and eventually sine wave pattern 1. The PR interval may prolong, not shorten. There's no delta wave in hyperkalemia.
E) Acute myocardial infarction - MI shows ST elevation or depression, T wave changes, and possibly Q waves 2, 1. The PR interval is normal, and there's no delta wave. WPW can mimic MI with pseudo-infarction patterns, but the short PR and delta wave are diagnostic.
Question 14: Restrictive Cardiomyopathy
A 58-year-old man with dyspnea undergoes echocardiography showing normal ventricular size, normal systolic function, and marked biatrial enlargement. What is the most likely diagnosis?
A) Dilated cardiomyopathy
B) Hypertrophic cardiomyopathy
C) Restrictive cardiomyopathy
D) Constrictive pericarditis
E) Normal heart
Correct Answer: C
Explanation for Correct Answer: Restrictive cardiomyopathy characteristically shows normal ventricular size and systolic function with atrial enlargement 3. The guideline states: "Echocardiography usually reveals normal ventricular size and systolic function with atrial enlargement in patients with restricted cardiomyopathy." Doppler studies demonstrate characteristic inflow velocity profiles with rapid early filling and shortened deceleration time. The marked biatrial enlargement results from impaired ventricular filling due to stiff, non-compliant ventricles. Causes include amyloidosis (which may show stippled myocardial appearance), sarcoidosis, hemochromatosis, and endomyocardial fibrosis.
Why Other Answers Are Incorrect:
A) Dilated cardiomyopathy - DCM shows dilated ventricular chambers with normal wall thickness and reduced systolic function 3. This patient has normal ventricular size and normal systolic function, excluding DCM.
B) Hypertrophic cardiomyopathy - HCM shows increased wall thickness (≥15 mm), often with asymmetric septal hypertrophy 3. This patient has normal ventricular size without mention of increased wall thickness.
C) Constrictive pericarditis - Constrictive pericarditis can mimic restrictive cardiomyopathy with similar hemodynamics 3. However, echo typically shows thickened pericardium, ventricular interdependence, and respiratory variation in mitral inflow. The question describes myocardial disease, not pericardial disease.
E) Normal heart - A normal heart would not have marked biatrial enlargement or dyspnea 3. The combination of symptoms and biatrial enlargement indicates pathology despite normal ventricular size and function.
Question 15: Electrical Alternans
A patient with pericardial effusion shows beat-to-beat variation in QRS amplitude on ECG. What is this finding called?
A) Pulsus paradoxus
B) Electrical alternans
C) Ventricular bigeminy
D) Artifact
E) Atrial fibrillation
Correct Answer: B
Explanation for Correct Answer: Electrical alternans is beat-to-beat variation in QRS amplitude (and sometimes P wave and T wave amplitude) 1. It's classically associated with large pericardial effusion and cardiac tamponade, though it can occur with other conditions. The mechanism involves the heart swinging within the pericardial fluid, changing the electrical axis with each beat. When seen with tachycardia and low voltage, it's highly suggestive of tamponade. Total electrical alternans (P, QRS, and T waves) is more specific for pericardial effusion than QRS alternans alone.
Why Other Answers Are Incorrect:
A) Pulsus paradoxus - Pulsus paradoxus is a physical examination finding (>10 mmHg drop in systolic BP with inspiration), not an ECG finding 3. It occurs with tamponade but is detected by blood pressure measurement, not ECG.
C) Ventricular bigeminy - Bigeminy shows alternating normal and premature ventricular complexes 2, 1. The PVCs have different morphology (wide, bizarre), not just different amplitude. The rhythm is also irregular with compensatory pauses.
D) Artifact - While artifact can cause amplitude variation, the clinical context of pericardial effusion and consistent beat-to-beat pattern indicates true electrical alternans 1. Artifact is typically irregular and associated with patient movement or loose electrodes.
E) Atrial fibrillation - AF shows irregularly irregular rhythm with absent P waves 1. While QRS amplitude may vary in AF due to varying ventricular filling, this is not called electrical alternans and doesn't show the regular beat-to-beat alternation seen with pericardial effusion.
Question 16: Exercise Testing Indications
According to training guidelines, what is the MINIMUM number of exercise tests a Level 1 cardiology trainee should perform?
A) 25 tests
B) 50 tests
C) 100 tests
D) 150 tests
E) 200 tests
Correct Answer: C
Explanation for Correct Answer: Level 1 trainees must gain proficiency in standard exercise testing with a minimum experience of 100 tests 2. The guideline states: "Level 1 trainees will gain proficiency in the standard exercise test and interpretation (minimal experience 100 tests)." This includes performing tests under supervision, interpreting results, and understanding indications, contraindications, and complications. The trainee should perform at least 50 tests during 1-2 months of active participation in an exercise laboratory, with the remaining tests performed throughout the training period 1.
Why Other Answers Are Incorrect:
A) 25 tests - This number is insufficient for Level 1 competency 1. It represents only one-quarter of the required minimum and would not provide adequate experience for independent interpretation.
B) 50 tests - While 50 tests is mentioned as the minimum during the dedicated exercise laboratory rotation 2, the total minimum for Level 1 competency is 100 tests. Level 2 training requires an additional 50 tests beyond Level 1.
D) 150 tests - This exceeds Level 1 requirements 1. Level 1 requires 100 tests; Level 2 requires an additional 50 tests (total 150). This would represent Level 2 training.
E) 200 tests - This far exceeds the requirements for Level 1 training 1. Even Level 2 training (advanced exercise testing) requires only 150 total tests. This number has no basis in the guidelines.
Question 17: Myocardial Infarction ECG Changes
A patient presents 6 hours after chest pain onset. ECG shows ST elevation in leads II, III, and aVF. Where is the infarction located?
A) Anterior wall
B) Lateral wall
C) Inferior wall
D) Posterior wall
E) Septal region
Correct Answer: C
Explanation for Correct Answer: ST elevation in leads II, III, and aVF indicates inferior wall myocardial infarction 2. These leads view the inferior surface of the left ventricle, supplied by the right coronary artery (80-90% of cases) or left circumflex artery (10-20%). The time course shows ST elevation within hours of onset, followed by T wave inversion and Q wave development over days to weeks 2. Inferior MI may be associated with right ventricular infarction (check right-sided leads) and AV blocks (due to RCA supplying the AV node).
Why Other Answers Are Incorrect:
A) Anterior wall - Anterior MI shows ST elevation in precordial leads V1-V4 2. It results from left anterior descending artery occlusion and typically causes larger infarcts with worse prognosis than inferior MI.
B) Lateral wall - Lateral MI shows ST elevation in leads I, aVL, V5, and V6 2. It results from left circumflex or diagonal branch occlusion. The question shows changes in inferior leads, not lateral leads.
C) Posterior wall - Posterior MI shows ST depression in V1-V3 (reciprocal changes) and tall R waves in V1-V2 2. True posterior leads (V7-V9) would show ST elevation. The question describes ST elevation in inferior leads, not posterior changes.
E) Septal region - Septal MI shows ST elevation in V1-V2 2. It results from proximal LAD occlusion affecting septal perforators. The question shows changes in inferior leads, not septal leads.
Question 18: Cardiotoxic Drug Monitoring
A patient is receiving doxorubicin chemotherapy. Which test is most valuable for monitoring cardiac function?
A) Serial ECGs
B) Serial echocardiography
C) Exercise stress testing
D) Cardiac biomarkers
E) Chest X-ray
Correct Answer: B
Explanation for Correct Answer: Echocardiography is valuable in following therapy with drugs known to depress LV function, such as doxorubicin 3. The guideline specifically mentions this indication for serial echocardiography. Doxorubicin causes dose-dependent cardiotoxicity leading to dilated cardiomyopathy. Serial echo monitoring allows detection of subclinical LV dysfunction before symptomatic heart failure develops, enabling dose adjustment or discontinuation. Current guidelines recommend baseline echo and monitoring at cumulative doses of 240 mg/m², 400 mg/m², and after completion of therapy. Strain imaging may detect early changes before EF declines 4.
Why Other Answers Are Incorrect:
A) Serial ECGs - While ECG may show nonspecific changes with doxorubicin cardiotoxicity (decreased voltage, ST-T changes), it's insensitive for detecting early LV dysfunction 1. ECG cannot quantify ejection fraction or detect subclinical dysfunction.
C) Exercise stress testing - Stress testing may reveal exercise-induced dysfunction but is less sensitive than resting echo for detecting doxorubicin cardiotoxicity 1. It's also impractical for serial monitoring in cancer patients who may be debilitated.
D) Cardiac biomarkers - While troponin and BNP may elevate with cardiotoxicity, they're not routinely used for monitoring 3. They lack the specificity and ability to quantify ventricular function that echo provides.
E) Chest X-ray - Chest X-ray is insensitive for detecting early cardiotoxicity 3. Cardiomegaly appears only with advanced dysfunction and significant chamber dilatation. It cannot quantify ejection fraction or detect subclinical changes.
Question 19: Mobitz Type I vs Type II
A patient's ECG shows progressive PR interval prolongation from 160 ms to 240 ms over three beats, then a dropped QRS, followed by a PR interval of 160 ms. What is the diagnosis?
A) First-degree AV block
B) Mobitz type I (Wenckebach) second-degree AV block
C) Mobitz type II second-degree AV block
D) Third-degree AV block
E) 2:1 AV block
Correct Answer: B
Explanation for Correct Answer: Mobitz type I (Wenckebach) shows progressive PR interval prolongation until a P wave fails to conduct, then the cycle repeats 1, 2, 1. The PR interval is shortest after the dropped beat and progressively lengthens. This pattern reflects progressive AV nodal refractoriness. Mobitz I typically occurs at the AV node level, has a narrow QRS (unless pre-existing bundle branch block), and has a better prognosis than Mobitz II. It may be seen in athletes, during sleep, or with inferior MI. Treatment is usually not required unless symptomatic.
Why Other Answers Are Incorrect:
A) First-degree AV block - First-degree block shows constant PR prolongation (>200 ms) with all P waves conducted 1. There are no dropped beats. This patient has dropped beats, excluding first-degree block.
C) Mobitz type II second-degree AV block - Mobitz II shows constant PR intervals with sudden dropped beats without progressive prolongation 2, 1. It occurs below the AV node (His-Purkinje system), typically has wide QRS, and carries worse prognosis requiring pacemaker. The progressive PR prolongation excludes Mobitz II.
D) Third-degree AV block - Complete heart block shows no AV conduction with independent atrial and ventricular rhythms 1. This patient has intermittent conduction (some P waves conduct), excluding third-degree block.
E) 2:1 AV block - In 2:1 block, every other P wave conducts with constant PR intervals for conducted beats 1. This patient shows 3:2 conduction (three P waves, two QRS complexes) with progressive PR prolongation, not 2:1 block.
Question 20: Dyspnea Evaluation with Echocardiography
A 55-year-old man presents with dyspnea and clinical signs of heart disease. What is the appropriate use of echocardiography?
A) Echocardiography is not indicated
B) Echocardiography is indicated to identify cardiac causes
C) Only stress echocardiography is appropriate
D) Cardiac CT should be performed first
E) Echocardiography only if chest X-ray is abnormal
Correct Answer: B
Explanation for Correct Answer: Echocardiography is indicated for dyspnea with clinical signs of heart disease 3. The guideline explicitly lists "Dyspnea with clinical signs of heart disease" as an indication for echocardiography. Dyspnea is a cardinal symptom of heart failure, often related to elevated pulmonary venous pressure. While dyspnea can have non-cardiac causes (pulmonary disease, anemia, neuromuscular disease), the presence of clinical signs of heart disease makes echo appropriate. Echo can identify valvular, coronary, myocardial, or pericardial disease causing dyspnea and guide management.
Why Other Answers Are Incorrect:
A) Echocardiography is not indicated - This contradicts ACC/AHA guidelines 3. When clinical signs of heart disease accompany dyspnea, echo is clearly indicated to identify the cardiac cause and assess severity.
C) Only stress echocardiography is appropriate - Resting transthoracic echo is the initial test 3, 4. Stress echo is reserved for specific indications like evaluating ischemia or valvular disease during exercise. Initial evaluation requires resting echo.
D) Cardiac CT should be performed first - CT is not the first-line test for evaluating dyspnea with heart disease signs 4. Echocardiography is more appropriate, providing functional and hemodynamic information. CT may be useful for specific indications like coronary anatomy or pulmonary embolism.
E) Echocardiography only if chest X-ray is abnormal - Clinical signs of heart disease are sufficient indication for echo 3. Waiting for chest X-ray results delays diagnosis and is not required. Chest X-ray and echo provide complementary information; neither is prerequisite for the other.