An investigator investigates the effects of two different medications on the heart rate of patients suffering from persistent atrial fibrillation. After several days of receiving therapeutic doses of medication, participants' heart rates are measured for 24 hours at rest and during 10 minutes of moderate exercise. The results are compared to placebo and are depicted in the graphs below. Which of the following medications is the red line most likely to represent? (drug 1)?

Question

Quizplus · Accepted Answer

Eductional Objective: Digoxin increases parasympathetic tone, which slows atrioventricular node conduction. This mechanism is effective at controlling ventricular rate in atrial fibrillation at rest, but it performs poorly during exercise, when parasympathetic output is low in comparison to high levels of sympathetic tone.

An Investigator Investigates the Effects of Two Different Medications on the Heart