Dr. Robert Jarvik is best known for the artificial heart he pioneered more than a quarter-century ago. Since then he had toiled in relative obscurity  until he began appearing in television ads two years ago for the Pfizer cholesterol drug Lipitor.

The ads have depicted him, among other outdoorsy pursuits, rowing a one-man racing shell swiftly across a mountain lake. “When diet and exercise aren’t enough, adding Lipitor significantly lowers cholesterol,” Dr. Jarvik says in the ad.

Celebrity advertising endorsements are nothing new, of course. But the Lipitor campaign is a rare instance of a well-known doctor’s endorsing a drug in advertising  and it has helped rekindle a smoldering debate over whether it is appropriate to aim ads for prescription drugs directly at consumers.

A Congressional committee, concerned that the Lipitor ads could be misleading, has said it wants to interview Dr. Jarvik about his role as the drug’s pitchman.