Free SCFHS Cardiothoracic Surgery mock test

Cardiothoracic Surgery sample questions with answers

10 more original exam-style Cardiothoracic Surgery questions, worked in full. They are not real or recalled exam questions, and none of them is in the mock above or on the bank page, so sit the mock first if you have not.

1. Question 1 · Arrhythmias and Conduction Defects

   After aortic valve replacement a patient in sinus rhythm develops complete heart block. Which temporary pacing mode best maintains cardiac output?

   1. ADual-chamber pacing (DDD)
   2. BVentricular pacing at a fixed rate (VVI)
   3. CAtrial-only pacing (AAI)
   4. DAsynchronous ventricular pacing (VOO)
   Show answer and explanation

   Correct answer: A. Dual-chamber pacing (DDD)

   Atrioventricular synchrony adds about 20 to 30% to output, so DDD pacing is best when the sinus node works. VVI loses atrial kick. AAI cannot pace through heart block. VOO risks competition with intrinsic beats.

   Reference: 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay

2. Question 2 · Cardiac and Pulmonary Physiology

   At which lung volume is pulmonary vascular resistance lowest?

   1. AFunctional residual capacity
   2. BResidual volume
   3. CTotal lung capacity
   4. DClosing capacity
   Show answer and explanation

   Correct answer: A. Functional residual capacity

   Pulmonary vascular resistance is lowest at FRC, where extra-alveolar vessels are held open by traction and alveolar vessels are not yet compressed. At low volumes extra-alveolar vessels narrow. At high volumes, such as total lung capacity, alveolar vessels are stretched and compressed by distended alveoli, so resistance rises on both sides of FRC.

   Reference: Hall, Guyton and Hall Textbook of Medical Physiology, 14th ed. (2020)

3. Question 3 · Cardiac and Pulmonary Physiology

   A man with severe aortic stenosis develops angina during rapid atrial fibrillation. What is the main mechanism of the ischaemia?

   1. ASystolic compression of the coronaries by the stenotic valve
   2. BReduced preload from loss of atrial kick causing low cardiac output
   3. CCoronary vasospasm from raised sympathetic tone
   4. DShortened diastole reduces coronary perfusion while demand rises
   Show answer and explanation

   Correct answer: D. Shortened diastole reduces coronary perfusion while demand rises

   The left ventricle is perfused mainly in diastole, and perfusion pressure is aortic diastolic pressure minus LVEDP. In aortic stenosis the hypertrophied ventricle has high demand and high LVEDP, and tachycardia shortens diastole further. Loss of atrial kick adds to symptoms but is not the main cause of angina. Vasospasm and systolic compression are not the mechanism.

   Reference: Hall, Guyton and Hall Textbook of Medical Physiology, 14th ed. (2020)

4. Question 4 · Cardiovascular and Pulmonary Pharmacology

   A patient on stable warfarin is started on amiodarone for postoperative atrial fibrillation, and the INR rises from 2.5 to 4.5 within a week. What explains this?

   1. AAmiodarone displaces warfarin from albumin and increases its renal clearance
   2. BAmiodarone induces hepatic enzymes and increases vitamin K synthesis
   3. CAmiodarone blocks platelet aggregation and prolongs the INR directly
   4. DAmiodarone inhibits CYP2C9 and reduces warfarin metabolism
   Show answer and explanation

   Correct answer: D. Amiodarone inhibits CYP2C9 and reduces warfarin metabolism

   Amiodarone inhibits CYP2C9 and CYP3A4, so warfarin clearance falls and the INR rises; the warfarin dose usually needs a cut of 30 to 50%. Enzyme induction would lower the INR. Amiodarone does not alter renal clearance of warfarin, and platelet effects do not change the INR.

   Reference: Bojar, Manual of Perioperative Care in Adult Cardiac Surgery, 6th ed. (2021)

5. Question 5 · Ischemic Heart Disease

   On the arterial trace of an intra-aortic balloon pump, when should the balloon inflate?

   1. AAt the peak of systole
   2. BDuring isovolumetric contraction
   3. CAt the dicrotic notch, at the start of diastole
   4. DAt end diastole, with the R wave
   Show answer and explanation

   Correct answer: C. At the dicrotic notch, at the start of diastole

   Inflation at the dicrotic notch, when the aortic valve closes, raises diastolic pressure and coronary perfusion. Deflation just before systole lowers afterload. Inflating in systole raises afterload, and inflating at end diastole would make the balloon oppose ventricular ejection.

   Reference: Braunwald's Heart Disease, 12th ed. (2022)

6. Question 6 · Congenital Heart Diseases

   A 10-year-old has high blood pressure in the arms, weak femoral pulses and notching of the lower rib margins on chest radiography. What is the diagnosis and the cause of the rib changes?

   1. APatent ductus arteriosus, with raised pulmonary flow
   2. BCoarctation, from enlarged intercostal collaterals
   3. CAortic stenosis, with a dilated ascending aorta
   4. DTakayasu arteritis of the carotid arteries, with pleural scarring
   Show answer and explanation

   Correct answer: B. Coarctation, from enlarged intercostal collaterals

   Coarctation causes upper limb hypertension and delayed or weak femoral pulses. Rib notching comes from enlarged intercostal arteries that carry collateral flow around the narrowing. A ductus gives a continuous murmur and bounding pulses, and aortic stenosis does not cause leg pulse delay.

   Reference: Park's Pediatric Cardiology for Practitioners, 6th ed. (2014)

7. Question 7 · Radiology of Thorax

   On a lateral chest radiograph a mass fills the retrosternal clear space. Which mediastinal compartment is it in?

   1. AThe anterior mediastinum, where thymoma and teratoma arise
   2. BThe posterior mediastinum, where the neurogenic tumours usually arise
   3. CThe middle mediastinum, around the carina
   4. DThe superior sulcus, at the lung apex
   Show answer and explanation

   Correct answer: A. The anterior mediastinum, where thymoma and teratoma arise

   The retrosternal clear space lies in front of the heart and ascending aorta, which is the anterior mediastinum. Thymoma, teratoma, thyroid masses and lymphoma are found there. Neurogenic tumours sit in the posterior compartment. Middle mediastinal masses are central and a sulcus mass is at the apex.

   Reference: Shields' General Thoracic Surgery, 8th ed. (2018)

8. Question 8 · Monitoring of Cardiac Patient

   A patient's arterial line shows a systolic pressure of 95 mmHg on the monitor, but the cuff reads 120 mmHg, and the waveform has a slow upstroke and no dicrotic notch. What is the most likely cause?

   1. AAn underdamped system, with ringing and overshoot on the trace
   2. BAn overdamped system, for example from a bubble in the line
   3. CA patient with real hypotension
   4. DA transducer positioned below the heart level
   Show answer and explanation

   Correct answer: B. An overdamped system, for example from a bubble in the line

   An overdamped trace loses the notch and under-reads the systolic pressure, and bubbles, clots and kinks are the usual causes. An underdamped line over-reads systolic pressure with spikes. Real hypotension would match the cuff. A transducer set too low raises all readings.

   Reference: Miller's Anesthesia, 9th ed. (2019)

9. Question 9 · Cardio-pulmonary Resuscitation

   A patient being paced through epicardial wires has a pulseless electrical activity arrest after cardiac surgery. What should be done early in the resuscitation?

   1. AIncrease the pacing rate to 120 beats per minute
   2. BGive 1 mg of epinephrine at once
   3. CConvert the pacing to an asynchronous mode at maximum output
   4. DPause the pacing to see whether ventricular fibrillation is hidden underneath
   Show answer and explanation

   Correct answer: D. Pause the pacing to see whether ventricular fibrillation is hidden underneath

   Pacing spikes can mask underlying ventricular fibrillation, which should be shocked. The STS consensus advises pausing the pacemaker in PEA to look. A faster rate or asynchronous maximum output does not address this. Routine epinephrine is avoided after cardiac surgery.

   Reference: Society of Thoracic Surgeons Expert Consensus for the Resuscitation of Patients Who Arrest After Cardiac Surgery (2017)

10. Question 10 · Arrhythmias and Conduction Defects

    A patient with rapid atrial fibrillation on day 2 after surgery becomes cold and confused, with a blood pressure of 70/40 mmHg. What is the treatment?

    1. AIntravenous amiodarone infusion alone, with cardioversion deferred
    2. BAn intravenous diltiazem bolus
    3. CSynchronised direct current cardioversion
    4. DAn intravenous digoxin loading dose
    Show answer and explanation

    Correct answer: C. Synchronised direct current cardioversion

    Atrial fibrillation with haemodynamic instability needs immediate synchronised cardioversion. Drugs act too slowly and diltiazem would drop the pressure further. Amiodarone is used after cardioversion to help hold sinus rhythm.

    Reference: 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation