EDAIC Cardiovascular Physiology and Pharmacology 2 — Questions and Answers
Question 1: Which of the following best describes the Frank-Starling mechanism?
- Increased heart rate improves contractility
- Stroke volume increases with increased ventricular end-diastolic volume (Correct answer)
- Afterload reduction increases cardiac output
- Sympathetic stimulation increases preload
Correct answer: Stroke volume increases with increased ventricular end-diastolic volume
The Frank-Starling mechanism states that stroke volume increases as ventricular end-diastolic volume (preload) increases, due to optimal actin-myosin overlap.
Question 2: The velocity of conduction is SLOWEST through which cardiac structure?
- Bundle of His
- Purkinje fibers
- AV node (Correct answer)
- Ventricular myocardium
Correct answer: AV node
The AV node has the slowest conduction velocity (~0.05 m/s), creating the essential delay between atrial and ventricular contraction.
Question 3: A patient receives a drug that selectively blocks I_f (funny current) channels. What is the primary effect?
- Decreased automaticity of the SA node (Correct answer)
- Prolonged QT interval
- Reduced ventricular contractility
- Increased AV nodal conduction
Correct answer: Decreased automaticity of the SA node
I_f channels carry mixed Na+/K+ inward current responsible for pacemaker depolarization; blocking them (e.g., ivabradine) reduces SA node automaticity and heart rate.
Question 4: Which parameter is MOST directly measured by thermodilution pulmonary artery catheter?
- Systemic vascular resistance
- Cardiac output (Correct answer)
- Left ventricular end-diastolic pressure
- Mixed venous oxygen saturation
Correct answer: Cardiac output
Thermodilution measures cardiac output directly by detecting temperature change in the pulmonary artery after cold saline injection into the right atrium.
Question 5: Levosimendan improves cardiac contractility primarily by:
- Inhibiting phosphodiesterase III
- Sensitizing troponin C to calcium (Correct answer)
- Activating beta-1 adrenoceptors
- Blocking potassium channels
Correct answer: Sensitizing troponin C to calcium
Levosimendan binds to troponin C and stabilizes the calcium-troponin C complex, increasing myofilament calcium sensitivity without raising intracellular calcium.
Question 6: During a hypertensive crisis, sodium nitroprusside acts primarily by:
- Blocking alpha-1 adrenoceptors
- Releasing nitric oxide causing smooth muscle relaxation (Correct answer)
- Inhibiting ACE
- Blocking calcium entry in vascular smooth muscle
Correct answer: Releasing nitric oxide causing smooth muscle relaxation
Sodium nitroprusside spontaneously releases nitric oxide, which activates guanylate cyclase in vascular smooth muscle, increasing cGMP and causing vasodilation.
Question 7: Which of the following best describes pulsus paradoxus?
- A fall in systolic BP >10 mmHg during expiration
- An exaggerated fall in systolic BP >10 mmHg during inspiration (Correct answer)
- A rise in diastolic BP during inspiration
- Pulse pressure widening during Valsalva
Correct answer: An exaggerated fall in systolic BP >10 mmHg during inspiration
Pulsus paradoxus is an exaggerated inspiratory decrease in systolic BP >10 mmHg, classically seen in cardiac tamponade and severe asthma.
EDAIC Cardiovascular Physiology and Pharmacology 2
Which of the following best describes the Frank-Starling mechanism?