NAC OSCE Diagnostic Investigations & Data Interpretation 2 — Questions and Answers
Question 1: A 62-year-old man with acute chest pain has an ECG showing ST elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Which coronary artery is most likely occluded?
- Left anterior descending artery
- Left circumflex artery
- Right coronary artery (Correct answer)
- Left main coronary artery
Correct answer: Right coronary artery
ST elevation in the inferior leads (II, III, aVF) with reciprocal changes in the lateral leads (I, aVL) indicates an inferior STEMI, most commonly due to right coronary artery occlusion.
Question 2: A 70-year-old woman presents with palpitations. ECG shows an irregularly irregular rhythm, no identifiable discrete P waves, and a ventricular rate of 118 bpm. What is the diagnosis?
- Atrial flutter with variable block
- Atrial fibrillation (Correct answer)
- Ventricular tachycardia
- Multifocal atrial tachycardia
Correct answer: Atrial fibrillation
Atrial fibrillation is characterized by an irregularly irregular ventricular rhythm with absent distinct P waves, reflecting chaotic atrial electrical activity.
Question 3: A 55-year-old man's ECG shows a PR interval of 240 ms with every P wave followed by a QRS complex and no dropped beats. What is the correct interpretation?
- First-degree AV block (Correct answer)
- Mobitz Type I (Wenckebach) second-degree AV block
- Mobitz Type II second-degree AV block
- Complete (third-degree) AV block
Correct answer: First-degree AV block
First-degree AV block is defined by a PR interval >200 ms (0.20 s) with 1:1 conduction of all P waves — prolonged conduction but no dropped beats.
Question 4: A 30-year-old man presents with sudden onset dyspnea and right-sided pleuritic chest pain. CXR shows a hyperlucent right hemithorax with absent lung markings and tracheal deviation to the left. What is the most appropriate immediate intervention?
- CT chest to confirm diagnosis
- Needle decompression at the right 2nd intercostal space, midclavicular line (Correct answer)
- Chest tube at 5th intercostal space, midaxillary line
- High-flow oxygen and observation
Correct answer: Needle decompression at the right 2nd intercostal space, midclavicular line
The CXR and clinical features indicate tension pneumothorax, a life-threatening emergency requiring immediate needle decompression without delay for imaging confirmation.
Question 5: A 65-year-old woman with dyspnea has a CXR showing bilateral perihilar infiltrates in a 'bat-wing' pattern, Kerley B lines, and cardiomegaly. What is the most likely diagnosis?
- Community-acquired pneumonia
- Cardiogenic pulmonary edema (Correct answer)
- ARDS
- Pulmonary sarcoidosis
Correct answer: Cardiogenic pulmonary edema
Bilateral perihilar ('bat-wing') infiltrates, Kerley B lines (interstitial edema), and cardiomegaly on CXR are classic radiographic signs of cardiogenic pulmonary edema.
Question 6: A 70-year-old woman with hip pain undergoes X-ray showing loss of joint space, subchondral sclerosis, osteophyte formation, and subchondral cysts of the right hip. What is the most likely diagnosis?
- Rheumatoid arthritis
- Osteoarthritis (Correct answer)
- Septic arthritis
- Avascular necrosis
Correct answer: Osteoarthritis
The radiographic triad of joint space narrowing, subchondral sclerosis, and osteophyte formation are pathognomonic for osteoarthritis.
Question 7: A chest X-ray shows complete opacification (white-out) of the right hemithorax with tracheal deviation to the left and no air bronchograms. What is the most likely diagnosis?
- Tension pneumothorax
- Massive pleural effusion (Correct answer)
- Lobar consolidation
- Right-sided hemothorax with consolidation
Correct answer: Massive pleural effusion
A massive pleural effusion produces complete opacification of the affected hemithorax and pushes the trachea and mediastinum away (contralateral deviation), unlike consolidation where the trachea deviates toward the lesion.
NAC OSCE Diagnostic Investigations & Data Interpretation 2
A 62-year-old man with acute chest pain has an ECG showing ST elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL.
Which coronary artery is most likely occluded?