<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 52-year-old man comes to the physician because of a 3-day history of intermittent chest tightness that worsens with exercise. He has chronic atrial fibrillation treated with a drug that prolongs the QT interval. During cardiac stress testing, an ECG shows progressive shortening of the QT interval as the heart rate increases. Which of the following drugs is this patient most likely taking?? A: Diltiazem, B: Lidocaine, C: Flecainide, D: Dofetilide, E: Carvedilol,  <response>: This is a clinical vignette about a 52-year-old man with chest tightness that worsens with exercise. He has atrial fibrillation and is on a medication that prolongs the QT interval. During cardiac stress testing, his ECG showed shortening of the QT interval as his heart rate increased. The question is asking which medication he is most likely taking that can prolong the QT interval. Of the choices, diltiazem is a calcium channel blocker used for hypertension and angina - it does not prolong QT. Lidocaine is an antiarrhythmic that shortens QT. Flecainide is an antiarrhythmic that can prolong QT. Dofetilide is an antiarrhythmic specifically used for atrial fibrillation that prolongs QT. Carvedilol is a beta blocker used for hypertension and heart failure - it does not prolong QT.Based on the information provided, the patient is most likely taking an antiarrhythmic medication used for atrial fibrillation that prolongs the QT interval. Of the choices, dofetilide is the most likely answer.D: Dofetilide 