10 USMLE Cardiology Questions with Answers and Explanations (Set 1)

These 10 USMLE cardiology practice questions cover topics that come up again and again on Step 1 and Step 2 CK: arrhythmias, heart blocks, valve murmurs, congenital heart disease, acute coronary syndrome, aortic dissection and heart failure. Each question includes the correct answer and an explanation.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. A 37-year-old previously healthy man is brought to the emergency room for dizziness, chest pain and palpitations. Cardiac chemistry panel is normal. ECG shows a sloping upstroke of the QRS complex. What is the treatment of choice of this condition?

A- Atropine
B- Digoxin
C- Metoprolol
D- Procainamide
E- Verapamil

According to ECG findings, this is a case of Wolff-Parkinson-White syndrome. The treatment of choice of this case is procainamide.
The correct answer is D

 

Question 2. A 76-year-old woman comes to your office for a consultation. Yesterday, she had left hemiparesis for 30 minutes. She thought it was a stroke but now she is completely asymptomatic. She has a history of atrial fibrillation, angina and hypertension. She takes aspirin 81 mg and propranolol 80 mg. What is your appropriate initial management for this patient?

A- Schedule another appointment whenever she has symptoms
B- Schedule transesophageal echocardiography
C- Schedule carotid duplex ultrasonography
D- Schedule MRI to the brain
E- Obtain CT scan of the head

This is most likely a case of transient ischemic attack (TIA). It is also known as “mini-strokes”. It occurs when blood supply of the brain is temporarily blocked. It lasts for a few minutes up to an hour and leaves no permanent damage. The most common cause of TIA is carotid artery stenosis which is mainly caused by atherosclerosis. CT scan of the head is the first step of action to exclude cerebral hemorrhage or stroke. Carotid duplex ultrasonography is scheduled if it TIA occurs again or in suspected patients.
The correct answer is E

 

Question 3. A 38-year-old man is brought to the emergency room because of palpitation and shortness of breath for 4 hours. He travelled to Brazil two years ago on a business trip. He was bitten there by a fly and was treated by analgesics for a few weeks due to fever and headaches. On examination, heart rate is 150 with a shifting of the apex to the left. Imaging studies and further investigations show cardiomyopathy. What is the organism most likely responsible for this condition?

A- Staphylococcus aureus
B- Streptococcus pyogenes
C- Ascaris lumbricoides
D- Trypanosoma cruzi
E- Trichophyton rubrum

This is a case of Chagas disease caused by Trypanosoma cruzi and also called American trypanosomiasis. It is spread to human through insects called Triatominae and also known as kissing bug. It lives in Central and South America. Infection with this microorganism causes severe myocarditis and leads to cardiomyopathy.
The correct answer is D

 

Question 4. Congenital heart diseases are defects of the heart and/or great arteries that are present at birth. They may be manifested at birth or hidden until later in life. Cyanosis is an important sign to diagnose and differentiate between types of congenital heart disease. What is the most common congenital heart disease?

A- Atrial septal defect
B- Ventricular septal defect
C- Patent ductus arteriosus
D- Transposition of the great arteries
E- Tetralogy of Fallot

Ventricular septal defect is the most common congenital heart disease. In most cases it is undiagnosed at birth but manifests 3-4 weeks after birth. It is acyanotic but if untreated, it can lead to severe complications such as Eisenmenger’s syndrome.
The correct answer is B

 

Question 5. A 64-year-old woman complains of continuous chest pain for 20 minutes. It started suddenly during a stressful meeting. Her pain is dull, aching in nature, and 9/10 in severity. She had several episodes of chest pain in the past that started after exertion and resolved by rest. She was diagnosed with type 2 diabetes and hypertension 8 years ago. Her pulse is 98/min., regular, and blood pressure is 160/100. ECG shows T inversion in leads II, III, and AVF. Cardiac enzymes are negative. Echocardiography shows no wall motion abnormalities and an ejection fraction of 65%. Which of the following is the most appropriate immediate treatment for this patient?

A- Ibuprofen
B- Tissue plasminogen activator (tPA)
C- Enoxaparin
D- Coronary angioplasty
E- Cardiac catheterization

This is a case of unstable angina or NSTEMI confirmed by ECG changes, negative cardiac enzymes and echocardiography. The main course of treatment is anticoagulation such as enoxaparin and should be administered as soon as possible. Ibuprofen and other NSAIDs are contraindicated in this case as they increase mortality and morbidity. Thrombolysis as tPA are indicated in elevated ST myocardial infarction. Coronary angioplasty and cardiac catheterization are invasive procedures that not recommended at this time.
The correct answer is C

 

Question 6. A 43-year-old man presents to the ER with an excruciating chest pain radiating to his jaw and left shoulder. The patient is in moderate distress. Examination reveals a small nodule in his right Achilles tendon. Family history indicates that his father died of a heart attack in the age of 45. His laboratory tests reveal elevated levels of CK-MB, troponin T, and very high cholesterol (670 mg/dL). A diagnosis of myocardial infarction and familial hypercholesterolemia is made in this patient. The patient is admitted to the intensive care unit (ICU) for urgent treatment. The patient has improved in the following week and is discharged. A list of medications has been prescribed for this patient. Which one of these medications acts through inhibition of the enzyme HMG-CoA reductase?

A- Atenolol
B- Fenofibrate
C- Lovastatin
D- Niacin
E- Orlistat

Statins lower LDL by inhibiting HMG-CoA reductase, the rate-limiting step in cholesterol production. Statins dramatically reduce the mortality of patients with hypercholesterolemia. Atenolol is a beta blocker and has no role in reducing cholesterol. Fenofibrate and niacin have different mechanism of action. They mainly lower triglycerides and increase HDL. Orlistat lowers rate of absorption of fat from diet by inhibition of pancreatic lipase.
The correct answer is C
Read this Pharmacology MCQs Book

 

Question 7. A 35-year-old man with a history of Marfan syndrome presents to the emergency room complaining of chest pain radiating to his upper back between shoulder blades. His blood pressure is 170/90 mmHg in his right arm and 90/60 in left arm. His pulse is 98/min. Cardiac examination reveals regular rhythm with diastolic murmur on the left lower sternal border. Lung examination reveals clear bilateral breath sounds. An echocardiogram shows dissection of the thoracic aorta involving the left subclavian artery. Which of these is the recommended immediate drug of choice?

A- Clopidogrel
B- Heparin
C- Sodium nitroprusside
D- Calcium gluconate
E- Labetalol

This is a typical presentation of aortic dissection. Labetalol is an alpha and beta adrenergic antagonist. It is the recommended drug of choice in this case. Sodium nitroprusside is contraindicated as its mechanism of action is dilation of blood vessels which could worsens the case.
The correct answer is E

 

Question 8. A 54 year old man presents to the emergency room complaining of progressive shortness of breath for 3 weeks. He has a long history of left sided heart failure treated by enalapril. Chest x-ray reveals bilateral pulmonary edema. After receiving the appropriate treatment, he is hospitalized for further investigations. Which of these findings is most likely revealed after further investigations?

A- Normal arterial O2 partial pressure
B- Normal arterial CO2 partial pressure
C- Normal respiratory function tests
D- Decreased pulmonary artery pressure
E- Increased pulmonary venous pressure

Decreased left ventricular contractility due to left ventricular heart failure leads to increased end-diastolic pressure in the left ventricle which leads to increased pulmonary venous pressure. It also leads to increased pulmonary artery pressure. Arterial O2 and Co2 partial pressure should be affected due to lung edema and defective inflation. Respiratory function tests are affected for the same reason.
The correct answer is E

 

Question 9. A 65 year-old woman presents to the emergency room for transient loss of consciousness. While she was walking with her husband today, she felt lightheaded and lost her consciousness for a few minutes then, she made a full recovery. On examination, her pulse is 86/min. and her blood pressure is 148/82. On auscultation, there is a systolic ejection murmur heard at the 2nd right intercostal space and radiates to the carotids. Lungs are clear bilaterally. What is the most likely diagnosis?

A- Mitral stenosis
B- Mitral regurgitation
C- Aortic stenosis
D- Aortic insufficiency
E- Pulmonic stenosis

This is a typical presentation of aortic stenosis with the typical murmur, mid systolic crescendo-decrescendo ejection murmur heard loudest at the second right intercostal space. Aortic stenosis causes low blood ejected to the carotids and eventually less blood to the brain, which causes transient loss of consciousness.
The correct answer is C

 

Question 10. A 68-year-old man presents to the emergency room complaining of multiple episodes of fainting since he woke up today. His fainting mainly occurs when he stands up. He has a history of coronary artery disease, diabetes, high cholesterol and hypertension. He takes atenolol, metformin, lovastatin and lisinopril. On physical examination, his blood pressure is 120/75, pulse is 55/min. and irregular, heart sounds are normal and lungs are clear on auscultation. ECG shows dropped beat after progressive lengthening of the PR interval. What is the most likely initial diagnosis?

A- Atrial flutter
B- Atrial fibrillation
C- Mobitz type I (Wenckebach) second degree AV block
D- Mobitz type II second degree AV block
E- Third degree atrioventricular block

ECG finding is compatible with type 1 second degree A-V block (Mobitz 1). It is characterized by progressive prolongation of P-R intervals followed by a dropped beat. In atrial flutter, ECG shows the characteristic sawtooth pattern. Atrial fibrillation shows no P waves and irregular irregularity. In the other 2 types of BBB, there is no P-R prolongation. ECG shows two or more P waves for every normal or slightly abnormal QRS complex.
The correct answer is C

 

High-yield points from this set

  • A slurred upstroke of the QRS (delta wave) = Wolff-Parkinson-White syndrome; avoid AV-node blockers such as digoxin and verapamil.
  • Transient focal weakness that fully resolves = TIA; the first step is a non-contrast CT of the head.
  • Cardiomyopathy after travel to Central or South America suggests Chagas disease (Trypanosoma cruzi).
  • Ventricular septal defect is the most common congenital heart disease.
  • Unstable angina/NSTEMI is treated urgently with anticoagulation (e.g., enoxaparin), not thrombolytics.
  • Statins inhibit HMG-CoA reductase, the rate-limiting step of cholesterol synthesis.
  • Aortic dissection: lower heart rate and blood pressure first with an IV beta-blocker such as labetalol.
  • Left heart failure raises pulmonary venous pressure and causes pulmonary edema.
  • Exertional syncope with a crescendo-decrescendo murmur at the right upper sternal border radiating to the carotids = aortic stenosis.
  • Progressive PR lengthening followed by a dropped beat = Mobitz type I (Wenckebach).

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