Fig. 1

Protocol outline. Schematic timeline of the study protocol. The black arrows represent the time points at which atrial myocardial biopsies were taken. Aox: aortic cross clamp. CPB: cardiopulmonary bypass. a Helium preconditioning group. Helium was administered in three cycles for 5 min, followed by 5 min inhalation of oxygen enriched air (30 % oxygen). b Helium postconditioning group, helium administration started at the end of aortic cross clamping for 15 min and was continued for 5 min after begin of reperfusion. c Helium pre-and postconditioning group. Helium was administered both as preconditioning stimulus before cardiopulmonary bypass and as postconditioning stimulus at the end of aortic cross clamping. d Anesthetic preconditioning group in which sevoflurane was administered in three cycles of 5 min. e Untreated controls