Pathophysiology
Which mechanism best explains hypoxaemia in acute pulmonary embolism?
A. Alveolar hypoventilation
B. Diffusion limitation
C. Right-to-left intracardiac shunt
D. Ventilation–perfusion mismatch
E. Reduced haemoglobin concentration
D. Ventilation–perfusion mismatch
What type of respiratory failure is most typical of acute PE?
A. Type 1 hypoxaemic
B. Type 2 hypercapnic
C. Mixed type
D. Neuromuscular
E. Ventilatory pump failure
A. Type 1 hypoxaemic
Which factor is part of Virchow’s triad?
A. Hypertension
B. Platelet activation
C. Hypercoagulability
D. Atherosclerosis
E. Vasodilation
C. Hypercoagulability
Which drug is first-line treatment for acute PE?
A. Aspirin
B. Warfarin
C. Low molecular weight heparin
D. Clopidogrel
E. Alteplase
C. Low molecular weight heparin
A large PE causes acute right ventricular failure primarily due to:
A. Reduced myocardial oxygen supply
B. Increased pulmonary vascular resistance
C. Reduced left ventricular preload
D. Pulmonary oedema
E. Hypoxic pulmonary vasoconstriction
B. Increased pulmonary vascular resistance
Which ABG pattern is most consistent with early PE?
A. ↓ PaO₂, ↑ PaCO₂, ↓ pH
B. ↓ PaO₂, ↓ PaCO₂, ↑ pH
C. Normal PaO₂, ↑ PaCO₂
D. ↑ PaO₂, ↓ PaCO₂
E. ↓ PaO₂, normal pH
B. ↓ PaO₂, ↓ PaCO₂, ↑ pH
Which clinical feature most strongly suggests PE over pneumonia?
A. Fever
B. Productive cough
C. Sudden-onset dyspnoea
D. Crackles on auscultation
E. Raised CRP
C. Sudden-onset dyspnoea
Which patient with PE requires thrombolysis?
A. Small subsegmental PE
B. Stable oxygen saturations
C. Mild tachycardia
D. Hypotension and shock
E. Raised D-dimer only
D. Hypotension and shock
Why is PaCO₂ often low in early pulmonary embolism?
A. Reduced CO₂ production
B. Increased dead space ventilation
C. Reduced diffusion capacity
D. Hypoventilation
E. Respiratory muscle fatigue
B. Increased dead space ventilation
Which ABG finding suggests a massive pulmonary embolism?
A. Respiratory alkalosis
B. Normal pH
C. Metabolic alkalosis
D. Respiratory acidosis
E. Isolated hypoxaemia
D. Respiratory acidosis
Which investigation is most appropriate for a haemodynamically stable patient with suspected PE?
A. Chest X-ray
B. ECG
C. D-dimer only
D. CT pulmonary angiography
E. Ventilation–perfusion scan
D. CT pulmonary angiography
What is the main mechanism of action of heparin?
A. Inhibition of platelet aggregation
B. Direct thrombin inhibition
C. Activation of antithrombin III
D. Vitamin K antagonism
E. Factor VII inhibition
C. Activation of antithrombin III
Why may hypoxaemia in PE not fully correct with supplemental oxygen?
A. CO₂ retention
B. Alveolar collapse
C. Shunt physiology
D. Reduced cardiac output
E. Reduced haemoglobin
C. Shunt physiology
Which physiological parameter is most likely to be increased in PE?
A. Alveolar ventilation
B. Pulmonary capillary blood flow
C. Diffusion capacity
D. Shunt fraction
E. Dead space ventilation
E. Dead space ventilation
Which ECG finding is classically (but uncommonly) associated with PE?
A. ST elevation in V1–V4
B. S1Q3T3 pattern
C. Left bundle branch block
D. ST depression in II, III, aVF
E. Pathological Q waves
B. S1Q3T3 pattern
Which complication is most associated with long-term untreated PE?
A. Pulmonary oedema
B. Left ventricular hypertrophy
C. Chronic thromboembolic pulmonary hypertension
D. Pulmonary fibrosis
E. Recurrent pneumonia
C. Chronic thromboembolic pulmonary hypertension