Wattle Pharmacy Prep

Cardiovascular physiology and pathophysiology
Practice questions with explanations

Cardiovascular physiology and pathophysiology belongs to Biomedical sciences, which makes up about 20% of the Overseas Pharmacist Readiness Assessment (OPRA®). Answer each question yourself before opening the explanation.

1. Which physiological factor increases the risk of thrombosis in an immobilised patient?

  1. Increased venous flow velocity
  2. Venous stasis from the loss of the calf muscle pump, one element of Virchow's triad
  3. Reduced clotting factor concentrations
  4. Increased fibrinolytic activity
Show answer

B. Venous stasis from the loss of the calf muscle pump, one element of Virchow's triad

The calf muscles act as a pump that returns venous blood against gravity, and immobility removes it. Combined with the hypercoagulability of surgery, malignancy or pregnancy and any endothelial injury, this completes the triad. Prophylaxis therefore combines mechanical measures such as early mobilisation and compression with pharmacological anticoagulation.

2. Which phase of the cardiac action potential in ventricular myocytes is maintained mainly by inward calcium current balancing outward potassium current?

  1. Phase 3, repolarisation
  2. Phase 2, the plateau
  3. Phase 4, the resting potential
  4. Phase 0, rapid depolarisation
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B. Phase 2, the plateau

The plateau of phase 2 is the balance between calcium entering through L-type channels and potassium leaving through delayed rectifier channels, and it is what makes cardiac contraction long enough to eject blood. Phase 0 is the fast sodium current, phase 3 is repolarisation as potassium efflux outlasts the fading calcium current, and phase 4 is the resting potential maintained by inward rectifier potassium channels.

3. Which statement about the coronary circulation is correct?

  1. Coronary arteries dilate in response to rising oxygen tension
  2. The left ventricle is perfused mainly during diastole, so tachycardia reduces its perfusion time
  3. Coronary flow is highest during systole in the left ventricle
  4. The myocardium extracts about 25% of the oxygen delivered at rest
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B. The left ventricle is perfused mainly during diastole, so tachycardia reduces its perfusion time

During systole the contracting left ventricular wall compresses its own intramural vessels, so most of its perfusion occurs in diastole. Tachycardia shortens diastole disproportionately and cuts perfusion time exactly when demand is highest, which is why rate control relieves angina. The myocardium already extracts about 70 to 80% of delivered oxygen at rest, so extra demand can only be met by increased flow, and coronary vessels dilate in response to hypoxia and adenosine.

These are 3 of the 40 questions on cardiovascular physiology and pathophysiology in the app.

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