[1] STATE UNIV LEIDEN HOSP, DEPT EXPTL CARDIOL, 2333 AA LEIDEN, NETHERLANDS
[2] UNIV LONDON UNIV COLL, DEPT PHYSIOL, LONDON WC1E 6BT, ENGLAND
[3] UNIV PAVIA, INST HUMAN PHYSIOL, I-27100 PAVIA, ITALY
[4] KING EDWARD VII HOSP, MIDHURST, W SUSSEX, ENGLAND