MYOCARDIAL-METABOLISM STUDIED DURING WARM BLOOD ANTERO-RETROGRADE REPERFUSION IN ISCHEMIC HUMAN HEARTS

We propose modified warm blood antegrade-retrograde reperfusion (WBARR ) of arrested hearts as a metabolic model with which to study substrat e exchange and energy metabolism during the recovery phase after 90 mi n of ischaemia in man. Eleven anaesthetized patients undergoing aorto- coronary bypass were studied during WBARR. The protocol was designed a s follows: period 1, a warm blood reperfusion with potassium (3 min); period 2, a warm blood reperfusion without potassium (2 min). The perf usion flow rate averaged 250+/-2 ml/min at the beginning of period 1 a nd 218+/-19 ml/min at the beginning and at the end of period 2; the pe rfusion was performed antegradely and retrogradely in the arrested hea rts. Samples were simultaneously taken from the coronary venous sinus (CVS) and from the aortic root needle (AR). At the beginning of WBARR lactate release was 85+/-44 mu mol/min and at the end it had significa ntly decreased to 21+/-99 mu mol/min (P<0.03). Simultaneously, non-est erified fatty acids (NEFA) and beta-hydroxy-butyrate were initially re leased (71+/-66 and 22+/-66 mu mol/min, respectively), while at the en d of the WBARR there was an uptake of both NEFA (20+/-22 mu mol/min; P <0.01) and beta-hydroxy-butyrate (12+/-35 mu mol/min; P=0.290). Alanin e, glycerol and branched chain amino acid balance across the heart did not significantly change. In summary after 90 min of ischaemia the he art energy metabolism is mainly anaerobic and based on glucose consump tion, with lactate, NEFA and amino acids, which are mainly released. A fter 5 min of WBARR (recovery from ischaemia), lactate release is sign ificantly reduced and NEFA becomes the energy supply of the heart. In conclusion, (1) WBARR is a valuable method with which to study myocard ial metabolism in anaesthetized humans and may be combined with the us e of tracers; (2) the study of myocardial metabolism in arrested heart s eliminates the imprecisions arising from the noncontinuous coronary blood flow; (3) NEFA become an important source of energy utilized by human hearts in the recovery phase from ischaemia.