ECG Cardiac Pharmacology 3 — Questions and Answers
Question 1: Atropine is administered to a patient in symptomatic bradycardia. What is its mechanism of action on the heart?
- Blocks muscarinic receptors, increasing heart rate (Correct answer)
- Stimulates beta-1 receptors, increasing contractility
- Blocks alpha receptors, reducing afterload
- Inhibits sodium channels, stabilizing membranes
Correct answer: Blocks muscarinic receptors, increasing heart rate
Atropine competitively blocks muscarinic (M2) receptors, removing vagal tone and allowing the SA node to increase its firing rate.
Question 2: Which medication used in ACLS for ventricular fibrillation works by blocking both sodium and potassium channels?
- Amiodarone (Correct answer)
- Epinephrine
- Magnesium sulfate
- Vasopressin
Correct answer: Amiodarone
Amiodarone is a Class III agent with Class I, II, and IV properties that blocks sodium, potassium, and calcium channels and is a first-line antiarrhythmic in VF/pVT.
Question 3: A patient in torsades de pointes should receive which treatment to stabilize cardiac membranes?
- IV magnesium sulfate (Correct answer)
- Amiodarone infusion
- Digoxin loading dose
- Oral flecainide
Correct answer: IV magnesium sulfate
Magnesium sulfate is the treatment of choice for torsades de pointes because it stabilizes cardiac membranes and suppresses early afterdepolarizations.
Question 4: Propranolol's cardiac effects are primarily due to blockade of which receptor?
- Beta-1 adrenergic receptors (Correct answer)
- Alpha-1 adrenergic receptors
- Muscarinic M2 receptors
- Dopamine D1 receptors
Correct answer: Beta-1 adrenergic receptors
Propranolol is a non-selective beta-blocker that blocks beta-1 receptors in the heart, reducing heart rate, contractility, and conduction velocity.
Question 5: Which drug is given during CPR primarily to increase systemic vascular resistance and improve coronary perfusion pressure?
- Epinephrine (Correct answer)
- Amiodarone
- Lidocaine
- Atropine
Correct answer: Epinephrine
Epinephrine stimulates alpha-1 receptors to cause vasoconstriction, increasing aortic diastolic pressure and coronary perfusion pressure during CPR.
Question 6: Procainamide belongs to which antiarrhythmic class and produces which metabolite that also has antiarrhythmic properties?
- Class IA; N-acetylprocainamide (NAPA) (Correct answer)
- Class IB; lidocaine metabolite
- Class IC; moricizine
- Class III; dofetilide metabolite
Correct answer: Class IA; N-acetylprocainamide (NAPA)
Procainamide is a Class IA sodium channel blocker metabolized to NAPA (N-acetylprocainamide), which has Class III potassium channel blocking properties.
Question 7: Which ECG finding would indicate that a patient's beta-blocker is producing therapeutic effects?
- Decreased resting heart rate and prolonged PR interval (Correct answer)
- Shortened QTc and narrow QRS
- ST segment elevation
- Development of delta waves
Correct answer: Decreased resting heart rate and prolonged PR interval
Beta-blockers slow SA node automaticity (reducing heart rate) and slow AV nodal conduction (prolonging the PR interval) as expected therapeutic effects.
ECG Cardiac Pharmacology 3
Atropine is administered to a patient in symptomatic bradycardia.
What is its mechanism of action on the heart?