ECG Cardiac Pharmacology 4

Question 1

Flecainide is contraindicated in patients with structural heart disease primarily because it can cause which dangerous arrhythmia?

Accepted Answer

Proarrhythmia including fatal ventricular tachycardia

Answer

The CAST trial demonstrated that Class IC drugs like flecainide can paradoxically increase mortality in post-MI patients by triggering lethal ventricular arrhythmias.

Question 2

A patient's ECG shows a rate of 42 bpm with a narrow QRS and no P waves. After atropine fails to increase the rate, which drug class would be next?

Accepted Answer

Catecholamine (dopamine or epinephrine infusion)

Answer

When atropine fails in symptomatic bradycardia, a chronotropic catecholamine infusion (dopamine or epinephrine) is used as a bridge to transcutaneous pacing.

Question 3

Which drug's antiarrhythmic mechanism involves activation of acetylcholine-sensitive potassium current (IKACh) in the atria?

Accepted Answer

Adenosine

Answer

Adenosine activates GIRK channels (IKACh) by binding to A1 receptors, hyperpolarizing atrial and AV nodal cells to terminate reentrant SVT.

Question 4

Dronedarone differs from amiodarone primarily in that it:

Accepted Answer

Lacks iodine moieties, reducing thyroid and pulmonary toxicity

Answer

Dronedarone was developed without iodine to reduce amiodarone's thyroid and pulmonary toxicity while retaining multi-channel blocking antiarrhythmic properties.

Question 5

Digoxin increases vagal tone and inhibits the Na+/K+-ATPase pump. What is the net effect on the ventricular rate in atrial fibrillation?

Accepted Answer

Rate slows due to increased AV nodal refractoriness

Answer

Digoxin slows ventricular rate in AF primarily through enhanced vagal tone at the AV node, increasing AV nodal refractoriness and reducing conduction.

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ECG Certification Practice Test

ECG Cardiac Pharmacology 4