IMPROVED PROTECTION OF THE HYPERTROPHIED LEFT-VENTRICLE BY HISTIDINE-CONTAINING CARDIOPLEGIA

Background Myocardial hypertrophy has been shown to lead to increased susceptibility to ischemia with accelerated loss of high-energy nucleo tides, greater accumulation of Hi and lactate, and earlier onset of co ntracture. Methods and Results To determine whether promoting anaerobi c glycolysis during ischemia by buffering H+ results in improved prese rvation of the hypertrophied heart, we studied the effect of a histidi ne-containing solution (HBS) on recovery of contractile function and e nergetic state. Hypertrophied rabbit hearts (aortic banding at 10 days ) were subjected to 40 minutes of 37 degrees C ischemia and reperfusio n in an isolated Langendorff model. This group was compared with; grou ps receiving St Thomas solution and high-potassium Krebs buffer soluti on (KCl). Although both phosphocreatine (PCr) and ATP were lower in hy pertrophied hearts by end-ischemia compared with nonhypertrophied age- matched controls, there was significantly higher PCr, ATP, and intrace llular pH in the HBS group compared with the St Thomas and KCI groups. Recovery of left ventricular developed pressure was best in the HBS g roup (91% of preischemic values) as was enddiastolic pressure after 30 minutes of reperfusion. Lactate production was also significantly gre ater in the HBS group, suggesting augmentation of anaerobic glycolysis . Conclusions We concluded that administration of histidine-containing cardioplegia promotes anaerobic glycolysis and improves recovery of h igh-energy phosphates and contractile function in hypertrophied myocar dium.