The effect of amino acid L-glutamate on the extended preservation ex vivo of the heart for transplantation

The present study was undertaken to assess the effect of L-glutamate on the extended preservation of the heart ex vivo added to a hypothermic preservative solution. Ten sheep hearts were removed after application of cold crystalloid potassium cardioplegia. The hearts were immersed in iced normal saline and right ventricular and left ventricular intraventricular balloons were connected to transducers to measure compliance. Thermistor probes were placed in the interventricular septum. The heart was mounted on a retrograde perfusion apparatus via the cannula in the brachiocephalic trunk and placed in an isolated glass cylinder. The perfusion apparatus consisted of a roller pump, a heat exchanger, and a pediatric membrane oxygenator. Control determinations and those after 8 hr of preservation were made while the hearts were perfused with enriched autologous blood. Right and left ventricular compliance, left ventricular systolic and diastolic pressures, right ventricular systolic and diastolic pressures, left ventricular dP/dt, coronary arteriovenous oxygen consumption, lactate production, and heart weight were measured. Results showed significantly improved left and right ventricular systolic function with L-glutamate preservation. Whole heart oxygen consumption in the L-glutamate group showed a 4% increase, while the placebo group showed a significant decrease in oxygen consumption after 8 hr of preservation as compared with a 81% increase in the placebo group. After 8 hr of perfusion there was 67% increase in the heart weight of the control and a 42% increase in the L-glutamate group. The addition of L-glutamate to the preservation solution resulted in significantly better systolic global left and right ventricular function after 8 hr of preservation ex vivo and suggests that this amino acid may be effective in hypothermic preservation of hearts for transplantation.