ECG Cardiac Pharmacology 2

Question 1

Which antiarrhythmic drug class works by blocking sodium channels and slowing phase 0 depolarization?

Accepted Answer

Class I

Answer

Class I antiarrhythmics block sodium channels, reducing the rate of rise of phase 0 of the cardiac action potential.

Question 2

A patient receives IV adenosine for SVT. Which ECG change would you expect immediately after administration?

Accepted Answer

Transient AV block

Answer

Adenosine causes transient AV block by hyperpolarizing AV nodal cells, which terminates reentrant SVT.

Question 3

Digoxin toxicity on an ECG most commonly presents as which rhythm?

Accepted Answer

PVCs with bigeminy

Answer

Digoxin toxicity classically causes increased automaticity and AV block, manifesting as PVCs and bigeminy on the ECG.

Question 4

Which drug used to treat atrial fibrillation primarily works by blocking IKr potassium channels to prolong the action potential?

Accepted Answer

Dofetilide

Answer

Dofetilide is a pure Class III agent that selectively blocks IKr potassium channels, prolonging repolarization and the QT interval.

Question 5

A patient on amiodarone should be monitored for which ECG manifestation as a sign of toxicity?

Accepted Answer

Markedly prolonged QT interval

Answer

Amiodarone prolongs the QT interval as a pharmacologic effect, and excessive prolongation increases the risk of torsades de pointes.

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