An 83-year-old male who was on the telemetry unit for a hear…
An 83-year-old male who was on the telemetry unit for a heart failure exacerbation has been transferred to the intensive care unit due to new onset atrial fibrillation with a rapid ventricular response. He was given a diltiazem bolus followed by a continuous diltiazem infusion without successful rate control. It has been less than 48 hours and direct current cardioversion is being considered. The success of electrical cardioversion is inversely proportional to which of the following?