Cardiovascular drugs: class IC antiarrhythmics: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Cardiovascular drugs: class IC antiarrhythmics

Sample item

A 62-year-old man with a previous myocardial infarction and an ejection fraction of 35% has frequent ventricular premature beats. A colleague proposes flecainide to suppress them. Why is this inappropriate?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Use-dependent sodium channel block in structural heart disease increases proarrhythmic mortality

In the Cardiac Arrhythmia Suppression Trial, encainide and flecainide suppressed ventricular ectopy after infarction but increased mortality. Class IC drugs markedly slow conduction and can provoke fatal re-entrant ventricular arrhythmias in scarred myocardium. They are used only in patients without structural heart disease, for example for atrial fibrillation or supraventricular tachycardia.

Option by option

  • A. It prolongs the QT interval through IKr block and causes torsades

    Flecainide acts chiefly by widening the QRS through sodium channel block; torsades from marked QT prolongation is the typical hazard of class IA and III agents.

  • B. Use-dependent sodium channel block in structural heart disease increases proarrhythmic mortality (correct)

    Correct. Slowed conduction in scar tissue favours lethal re-entry.

  • C. It causes severe bradycardia through beta-adrenergic blockade

    Flecainide has no important beta-blocking action.

  • D. It causes pulmonary fibrosis with long-term use

    Pulmonary fibrosis is characteristic of amiodarone.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Use-dependent sodium channel block in structural heart disease increases proarrhythmic mortality. In the Cardiac Arrhythmia Suppression Trial, encainide and flecainide suppressed ventricular ectopy after infarction but increased mortality.

Why is "It prolongs the QT interval through IKr block and causes torsades" not the answer?

Flecainide acts chiefly by widening the QRS through sodium channel block; torsades from marked QT prolongation is the typical hazard of class IA and III agents.

Why is "It causes severe bradycardia through beta-adrenergic blockade" not the answer?

Flecainide has no important beta-blocking action.

Why is "It causes pulmonary fibrosis with long-term use" not the answer?

Pulmonary fibrosis is characteristic of amiodarone.

What concept does this question test?

It tests Cardiovascular drugs: class IC antiarrhythmics in Pharmacology. Class IC drugs markedly slow conduction and can provoke fatal re-entrant ventricular arrhythmias in scarred myocardium. They are used only in patients without structural heart disease, for example for atrial fibrillation or supraventricular tachycardia.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular drugs: class IC antiarrhythmics?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.