A low myocardial content of α-ketoglutarate during heart surgery might aggravate ischaemic injury. 24 men undergoing coronary surgery participated in a randomised controlled study. 28 g α-ketoglutarate was added to blood cardioplegia for intermittent antegrade intracoronary perfusion in 13 cases. α-ketoglutarate reduced the appearance in blood of the ischaemic markers creatine kinase MB and troponin T (at 4 h after release of aortic cross-clamp; median [95% Cl] 49 [37-60] μg/L in controls vs 32 [27-37] μg/L for creatine kinase MB, 2·0 [1·2-2·8] vs 1·1 [0·8-1·4] μg/L for troponin T). These findings signify attenuated ischaemic injury, possibly secondary to enhanced myocardial oxidative capacity.