[1] Univ Hosp Maastricht, Cardiovasc Res Inst Maastricht, Dept Cardiol, NL-6202 AZ Maastricht, Netherlands
[2] Tufts Univ, Sch Med, Boston, MA 02111 USA
[3] Univ Bonn, Inst Physiol, Med Clin, D-5300 Bonn, Germany
[4] Interuniv Cardiol Inst Netherlands, Maastricht, Netherlands