A House investigation is casting a wider net into whether artificial-heart pioneer Robert Jarvik improperly endorsed a cholesterol-reducing medication in a number of advertisements.

House Energy and Commerce Committee Chairman John Dingell, D-Mich., and committee member Rep. Bart Stupak, D-Mich., sent a letter Tuesday to FDA Commissioner Andrew von Eschenbach demanding to see records housed in the FDA's Division of Drug Marketing, Advertising and Communications office regarding recent advertisements for the cholesterol-decreasing drug Lipitor.

Dingell and Stupak asked for all records relating to print, radio, TV or Internet advertisements for Lipitor featuring Jarvik, setting a Feb. 5 deadline. The letter follows a Jan. 7 letter to Pfizer Inc. — which markets Lipitor — also seeking records regarding the advertisement.

In the widely seen advertisements, Jarvik endorses Lipitor, which is the top-selling drug worldwide and accounts for about one-third of Pfizer's sales, according to Bloomberg News. Jarvik helped develop the first fully artificial heart and is known worldwide as an innovator in the field.

The lawmakers are concerned that Jarvik is blurring the lines between his professional experience and his endorsement of the product, said a committee spokeswoman who asked that her name not be published.

"There are concerns his role is potentially misleading to consumers. ... He seems to be dispensing some professional or medical advice in these commercials," the spokeswoman said.

An FDA spokeswoman did not immediately return a message seeking comment.

The House panel's spokeswoman said the letter to the FDA is not considered a hostile one, and the lawmakers are not assuming that FDA has done anything wrong.

"There are questions that we would like to have answered," she said. She also said she was not aware of any specific statutes that were being applied in the investigation, but they likely will develop as the probe moves along.

As evidence highlighting the committee's concerns, she pointed to a recent interview Jarvik gave on the ABC network in which he said he does have a medical degree and is a research scientist, but he does not have a license to practice medicine or dispense medication.

Jarvik also admitted he did not take the drug until after he began working on the commercials, and began taking the drug about one month after beginning the ads.

Asked in the interview how much he is being paid for the ad campaign, Jarvik did not cite a specific dollar amount, but said "I'm paid an amount that I think for a celebrity ad would be considered a lot for most people. ... If you're talking about the amount of money that say professional athletes make for dealing with these things, I don't think it's comparable to that. I think it's a lower scale than that."

Click here to see the interview on ABC's "Good Morning America."

In one ad available on the Internet, Jarvik begins: "Just because I'm a doctor doesn't mean I don't worry about my cholesterol." He is followed by a narrator who describes Jarvik as "inventor of the Jarvik Artificial Heart, Doctor Robert Jarvik."

Click here to see the 60-second ad in its entirety.

Jarvik goes on in the ad to describe the effects of Lipitor in reducing cholesterol and cites its FDA approval.

"Lipitor is one of the most researched medicines. You don't have to be a doctor to appreciate that. ... Lowering cholesterol is important, but could you be doing more with Lipitor? Ask your doctor. Don't wait."

Messages left seeking comment from Jarvik Heart Inc., where Jarvik is president and CEO, and Pfizer, were not immediately returned Wednesday.

A statement from Jarvik on Jarvik Heart's Web site discussing his relationship with Pfizer says that while he does not practice clinical medicine or treat patients, his career in medical science gives him the training and expertise to advocate Lipitor.

Click here to read Jarvik's full statement.

"I have the training, experience and the medical knowledge to understand the conclusions of the extensive clinical trials that have been conducted to study the safety and effectiveness of Lipitor," Jarvik wrote.

He added: "I accepted the role of spokesman for Lipitor because I am dedicated to the battle against heart disease, which killed my father at age 62 and motivated me to become a medical doctor." He has been a spokesman for Lipitor for two years.

Pfizer was first to be targeted by the committee investigation, receiving a letter from Dingell and Stupak on Jan. 7 seeking records related to the advertising campaign, contractual relationships with Jarvik, financial records and documents regarding the truth of Jarvik's claims and his professional qualifications.

At the time, Pfizer spokesman Chris Loder said: "Dr. Jarvik is a respected health care professional and heart expert who knows how imperative it is for patients to do everything they can to keep their heart working well," according to The Associated Press.