A 37-year-old man with no significant medical history visits the office complaining of palpitations. He leads a healthy lifestyle, exercises on a daily basis, and does not use tobacco, alcohol, or illegal drugs. The ECG demonstrates atrial fibrillation with a rapid ventricular response. An echocardiogram reveals normal heart function and no evidence of valvular disease. The patient is put on an antiarrhythmic medication that has been shown to be effective in both atrial and ventricular arrhythmias. This medication causes QRS prolongation with only a minor increase in QT interval duration on ECG. Which of the following action potential curve regions is most affected by this drug?

Question

Quizplus · Accepted Answer

Eductional Objective: Flecainide, a class 1C antiarrhythmic agent, blocks the fast sodium channels responsible for ventricular depolarization (phase 0), extending the QRS duration while having little effect on the QT interval. The most QT prolongation is caused by class 1A and class III agents.

A 37-Year-Old Man with No Significant Medical History Visits the Office