A 45-year-old man who has recently begun treatment for paroxysmal atrial fibrillation is subjected to stress ECG testing. The patient exercises for 9 minutes on a treadmill and achieves 98 percent of the age-predicted maximal heart rate without experiencing chest pain or ST-segment changes. His pre-test resting QRS complex duration is 95 milliseconds (normal: 80-120 milliseconds) and his corrected QT (QTc) interval duration is 410 milliseconds (normal: 440 milliseconds). His ECG findings at his maximum heart rate show a QRS complex duration of 125 msec and a QTc interval duration of 400 msec. Based on the patient's test results, which of the following medications is most likely being used to treat his atrial fibrillation?

Question

Quizplus · Accepted Answer

Eductional Objective: Class 1C antiarrhythmics, such as flecainide, are strong sodium channel blockers with a greater effect at higher heart rates (use-dependence). This makes them more effective at treating tachyarrhythmias, but at higher heart rates, it can also cause prolonged QRS duration (a proarrhythmic effect).

A 45-Year-Old Man Who Has Recently Begun Treatment for Paroxysmal