<prompt> A 60-year-old man with rheumatic mitral stenosis and atrial fibrillation is on therapy for a fast ventricular rate. While on treatment he develops a regular pulse of 64 beatsmin. Which of the following is the probable drug that the patient is receiving?VerapamilDigoxinCarvedilolPropranolol  <response>: Ans. B DigoxinRef: KDT 8the p561Digitalis is used to control ventricular rate in atrial fibrillation. It increases the refractoriness of AV node and decreases the conduction through AV node. 