Two US senators have asked the non-profit Cardiovascular Research Foundation and Columbia University to clarify their financial relations with manufacturers of cardiac devices such as stents.

Chuck Grassley, senior Republican member of the Senate Committee on Finance, and Herb Kohl, chairman of the Senate Special Committee on Aging, have been investigating links between the medical drug and device industry and influential doctors for several years (BMJ 2008;336:1268, 7 Jun, doi:10.1136/bmj.39598.476250.DB; 2008;336:1327, 14 Jun, doi:10.1136/bmj.39609.364688.DB; 2008;337:a929, 21 Jul, doi:10.1136/bmj.a929; 2008;337:a2088, 16 Oct, doi:10.1136/bmj.a2088; 2008;337:a2200, 21 Oct, doi:10.1136/bmj.a2200).

The senators sent letters to Lee Bollinger, president of Columbia University, and Gregg Stone, chairman of the Cardiovascular Research Foundation, who is also a professor at Columbia. They asked for information by 30 October.

The senators asked Mr Bollinger for information about payments to 22 …