Successful transplantation after long-term preservation of dog hearts.

Nucleoside transport inhibition is a new approach to long-term preservation of donor hearts. To evaluate its effectiveness, the following were tested: 1) the effect of nucleoside transport inhibition on high-energy phosphate content after cardioplegic arrest and during long-term cold storage (group I: cardioplegia, control ]n = 18]; group II: cardioplegia plus nucleoside transport inhibitor [n = 18]); 2) the effect of nucleoside transport inhibition on high-energy phosphates and hemodynamic recovery in a modified blood-perfused Langendorff system (group III: 24-h cold storage followed by reperfusion [n = 6]; group IV: addition of nucleoside transport inhibition to cardioplegia but not during reperfusion [n = 6]; group V: addition of nucleoside transport inhibition during reperfusion [n = 6]; group VI: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 6]); and 3) the effect of nucleoside transport inhibition added to cardioplegia and during reperfusion on high-energy phosphate content and outcome after heart transplantation (group VII: no nucleoside transport inhibitor in cardioplegia and during reperfusion [n = 8]; group VIII: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 8]). The following results were obtained: 1) addition of nucleoside transport inhibition prevented high-energy phosphate depletion during cold storage: after 24 h, adenosine triphosphate content in group I was 9.4 +/- 3.1 mumol/g versus 17.7 +/- 3.6 mumol/g dry weight in group II (P less than 0.05); 2) addition of nucleoside transport inhibition to cardioplegia and during reperfusion resulted in greater high-energy phosphate content (adenosine triphosphate in group III was 7.9 +/- 3.5 mumol/g vs. 17.8 +/- 2.8 mumol/g in group VI [P less than 0.05]) and improved hemodynamics upon reperfusion (hearts in group III did not recover, maximum isometric left ventricular pressure development was 1,635 +/- 577 mmHg/sec in group IV, 1,915 +/- 423 mmHg/sec in group V, and 2,437 +/- 201 mmHg/sec in group VI [P less than 0.05, group VI vs. groups IV and V]); and 3) hearts treated with nucleoside transport inhibition in cardioplegia and during reperfusion (group VIII) could be transplanted successfully in contrast to group VII hearts. These data indicate that nucleoside transport inhibition in dogs is highly effective in long-term preservation of donor hearts.     

Ischemic preconditioning with opening of mitochondrial adenosine triphosphate-sensitive potassium channels or Na/H exchange inhibition: which is the best protective strategy for heart transplants?

OBJECTIVE: This study was designed to compare ischemic preconditioning with opening of mitochondrial adenosine triphosphate-sensitive potassium channels and Na(+)/H(+) exchange inhibition in an isolated heart model of cold storage, simulating the situation of cardiac allografts. METHODS: Sixty-seven isolated isovolumic buffer-perfused rat hearts were arrested with and stored in Celsior solution (Imtix-Sangstat) at 4 degrees C for 4 hours before a 2-hour reperfusion. Group I hearts served as controls and were arrested with and stored in Celsior solution. In group II, hearts were preconditioned by two 5-minute episodes of global ischemia, each separated by 5 minutes of reperfusion before arrest with Celsior solution. Group III hearts were arrested with and stored in Celsior solution supplemented with 100 micromol/L of the mitochondrial adenosine triphosphate-sensitive potassium channel opener diazoxide. In group IV, hearts received an infusion of diazoxide (30 micromol/L) during the first 15 minutes of reperfusion. Group V hearts underwent a protocol combining both interventions used in groups III and IV. In group VI, hearts were arrested with and stored in Celsior solution supplemented with 1 micromol/L of the Na(+)/H(+) exchange inhibitor cariporide. Group VII hearts received an infusion of cariporide (1 micromol/L) during the first 15 minutes of reperfusion. In group VIII, hearts underwent a protocol combining both interventions used in groups VI and VII. Group IX hearts were ischemically preconditioned as in group II, and sustained Na(+)/H(+) exchange inhibition during both storage and early reperfusion was used as in group VIII. RESULTS: On the basis of comparisons of postischemic left ventricular contractility and diastolic function, coronary flow, total creatine kinase leakage, and myocardial water content, values indicative of improved protection were obtained by combining ischemic preconditioning with Na(+)/H(+) exchange inhibition by cariporide given during storage and initial reperfusion. The endothelium-dependent vasodilatory postischemic responses to 5-hydroxytryptamine or acetylcholine and endothelium-independent responses to papaverine were not affected by these interventions. CONCLUSIONS: These data suggest that cardioprotection conferred by the Na(+)/H(+) exchange inhibitor cariporide is additive to that of ischemic preconditioning and might effectively contribute to improve donor heart preservation during cardiac transplantation.     

Effects of potassium cardioplegia on high-energy phosphate kinetics during circulatory arrest with deep hypothermia in the newborn piglet heart

The protective effects of hypothermia and potassium-solution cardioplegia on high-energy phosphate levels and intracellular pH were evaluated in the newborn piglet heart by means of in vivo phosphorus nuclear magnetic resonance spectroscopy. All animals underwent cardiopulmonary bypass, cooling to 20 degrees C, 120 minutes of circulatory arrest, rewarming with cardiopulmonary bypass, and 1 hour off extracorporeal support with continuous hemodynamic and nuclear magnetic resonance spectroscopic evaluation. Group I (n = 5) was cooled to 20 degrees C; group II (n = 4) was given a single dose of 20 degrees C cardioplegic solution; group III (n = 7) was given a single dose of 4 degrees C cardioplegic solution; and group IV (n = 4) received 4 degrees C cardioplegic solution every 30 minutes. At end ischemia, adenosine triphosphate, expressed as a percent of control value, was lowest in group I 54% +/- 6.5% but only slightly greater in group II 66% +/- 7.0%. Use of 4 degrees C cardioplegic solution in groups III and IV resulted in a significant decrease in myocardial temperature, 9.9 degrees C versus 17 degrees to 20 degrees C, and significantly higher levels of adenosine triphosphate at end ischemia; with group III levels at 72% +/- 6.0% and group IV levels at 73% +/- 6.0%. Recovery of adenosine triphosphate with reperfusion was not related to the level of adenosine triphosphate at end ischemia and was best in groups I and II, with a recovery level of 95% +/- 4.0%. In group IV, no recovery of adenosine triphosphate occurred with reperfusion, resulting in a significantly lower level of adenosine triphosphate, 74% +/- 6.0%, than in groups I and II. Recovery of ventricular function was good for all groups but was best in hearts receiving a single dose of 4 degrees C cardioplegic solution. In this model, multiple doses of cardioplegic solution were not associated with either improved adenosine triphosphate retention during arrest or improved ventricular function after reperfusion, and in fact resulted in a significantly lower level of adenosine triphosphate with reperfusion. The complete recovery of adenosine triphosphate in groups I and II, despite a nearly 50% adenosine triphosphate loss during ischemia, may result from a decrease in the catabolism of the metabolites of adenosine triphosphate consumption in the newborn heart.     

The experimental study on long-term cardiac preservation: the efficacy of low-flow continuous perfusion with fluorocarbon

We compared the effect of simple immersion and continuous perfusion on long-term cardiac preservation, and evaluated the effectiveness of perfusion with oxygenated fluorocarbon solution. The isolated rabbit hearts were preserved for 24 hours at 4 degrees C using the following five preservation techniques: (1) simple immersion with Collins M solution (Group I), (2) perfusion with oxygenated Collins M solution at a flow rate of 10 ml/hr (Group II), (3) perfusion with the same solution as in Group II at a flow rate of 20 ml/hr (Group III), (4) perfusion with oxygenated Collins M solution containing 10% fluorocarbon at a flow rate of 10 ml/hr (Group IV), (5) perfusion with the same solution as in Group IV at a flow rate of 20 ml/hr (Group V). The hearts of Group I showed a significant decrease of myocardial ATP and an increase of myocardial lactate during preservation compared to the hearts of perfusion groups. Assessment of isovolumic left ventricular function following 24-hour preservation using a support animal showed a significant decrease of Max dp/dt and increase of end-diastolic pressure in the hearts of Group I. Perfusion with fluorocarbon (Group IV and V) significantly increased oxygen consumption compared to Group II and III in association with minimum accumulation of myocardial lactate, indicating that aerobic metabolism during preservation is better maintained in the fluorocarbon-perfused hearts. Moreover, CPK release and myocardial water gain during preservation were significantly less, and left ventricular function following preservation was significantly better in these hearts. Increasing the flow rate from 10 ml/hr to 20 ml/hr resulted in sustained increase in perfusion pressure (1.80 +/- 0.53 to 3.70 +/- 0.34 mmHg) and myocardial water content (79.2 +/- 0.4 to 87.2 +/- 0.3%) during preservation in the hearts of Group III, but it did not further improve left ventricular function despite significant enhancement of myocardial oxygen uptake in both Group III and V. These results suggest that hypothermic low-flow continuous perfusion with oxygenated Collins M solution is superior to simple immersion with the same solution for long-term cardiac preservation, and that the addition of fluorocarbon to the perfusate enhances the efficacy of such a perfusion.     

Effect of oxygenated crystalloid cardioplegia on the functional and metabolic recovery of the isolated perfused rat heart

The use of an oxygenated crystalloid cardioplegic solution to improve myocardial preservation during elective cardiac arrest was evaluated with the isolated perfused rat heart used as a model. Experiments were conducted at 4 degrees C and 20 degrees C. The oxygen tension of the nonoxygenated and oxygenated cardioplegic solutions averaged 117 and 440 mm Hg, respectively. At 4 degrees C, the adenosine triphosphate content of hearts subjected to 120 minutes of oxygenated cardioplegia was significantly higher than that of the nonoxygenated cardioplegia group. However, functional recovery during reperfusion was similar for both groups. At 20 degrees C, the myocardial adenosine triphosphate concentration decreased at a significantly faster rate during ischemia in the group receiving nonoxygenated cardioplegia compared with the oxygenated cardioplegia group. Hearts subjected to 180 minutes of ischemia with oxygenated cardioplegia had a normal ultrastructural appearance whereas hearts subjected to 120 minutes of nonoxygenated cardioplegia showed severe ischemic damage. Myocardial functional recovery in the group receiving oxygenated cardioplegia exceeded that of the group receiving nonoxygenated cardioplegia. The use of myocardial adenosine triphosphate concentration at the end of the ischemic period to predict subsequent cardiac output, peak systolic pressure, and total myocardial work showed significant positive correlations.     

Enhanced myocardial preservation by nicotinic acid, an antilipolytic compound. Improved cardiac performance after hypothermic cardioplegic arrest

The effect of nicotinic acid, an antilipolytic drug, on myocardial preservation was studied on the basis of cardiac performance after 2 hours of cardioplegic arrest. Isolated in situ pig hearts were subjected to 120 minutes of hypothermic potassium (35 mEq) crystalloid cardioplegic arrest followed by 60 minutes of reperfusion. The experimental group received nicotinic acid 0.08 mmol/L 15 minutes before cardioplegic arrest, whereas the control group received 15 minutes of unmodified perfusion. There was a marked decline in myocardial creatine phosphate levels during cardioplegic arrest in both groups that returned to the baseline level during reperfusion without a significant intergroup difference, and adenosine triphosphate levels remained stable throughout the experiment in both groups. Myocardial oxygen consumption during reperfusion was significantly higher in hearts treated with nicotinic acid, which was consistent with a significantly greater cardiac contractile force as evaluated by isovolumetric left ventricular pressure measurements. There appeared to be less cardiac membrane damage as measured by creatine kinase release during reperfusion, which was significantly inhibited by treatment with nicotinic acid. The present study supports the conclusion that nicotinic acid improves cardiac performance after hypothermic cardioplegic arrest.     

Successful cardiac preservation for 12 hours using nondepolarizing cold cardioplegia. A canine model

Abstract Isolated canine hearts were preserved for 12 h at 5 °C followed by normothermic reperfusion for 2 h. Dogs were divided into two groups: group 1 ( n = 7) received a nondepolarizing preservation solution in multidose, and group 2 ( n = 6) received single-flushed University of Wisconsin (UW) solution, both administered in multidose fashion. At the end o reperfusion, the myocardial adenosine triphosphate concentration and left ventricular systolic and diastolic function were preserved better in group 1 than in group 2. Myocardial mitochondrial ultra-tructural integrity was identical in the two groups. These results suggested that in a 124 heart preservation, nondepolarizing solution administered in multidose fashion protects the myocardium from the deleterious effects of hypothermia and cardioplegia better than UW solution.     

Improved recovery of cardiac function after hypothermic ischemic storage with ouabain

We investigated the hypothesis that ouabain would reduce energy expenditure in the hypothermic, ischemic heart by inhibiting membrane-bound sodium/potassium-activated adenosine triphosphatase and lead to improved function on reperfusion. Additionally, we compared ouabain with another potential adjunct, the calcium channel blocker verapamil. The isolated rabbit heart was used as a model, and three experimental groups were studied after 1, 6, 12, and 24 hours of 4 degrees C ischemia. Hearts in group I were stored in a standard high potassium solution; hearts in groups II and III were stored in the same solution supplemented with verapamil (2 mg/L) and ouabain (3 mg/L), respectively. After ischemia, all hearts were reperfused for 45 minutes on a modified Langendorff apparatus, and left ventricular function was measured before freeze-clamping the heart for metabolite determination. At 1 and 6 hours, hearts in all groups functioned well, but the group III hearts had higher levels of adenosine triphosphate, phosphocreatine, total adenine nucleotides, and glycogen. After 12 hours of ischemia, function was significantly better in group III hearts (p less than 0.01) compared with that of hearts in groups I and II. Group III hearts also exhibited higher levels of high energy phosphates and glycogen. After 24 hours of storage, all hearts functioned poorly, and there was a marked decline in measured metabolites. Although we could show no improvement with the addition of verapamil, ventricular function was improved after storage in a high potassium hypothermic solution containing ouabain. Because ouabain inhibits the hydrolysis of adenosine triphosphate by sodium/potassium-activated adenosine triphosphatase, this result suggests that the glycoside maintains energy-rich phosphates necessary for optimal resumption of cardiac function.     

Effects of nucleoside transport inhibition on long-term ex vivo preservation of canine hearts.

The effect of nucleoside transport inhibition on 24-hour preservation of canine hearts was studied in 36 hearts arrested either with a cold hyperkalemic cardioplegic solution without (group I) or with supplementation of a specific nucleoside transport inhibitor (R75231, 1 mg/L) (groups II and III). The hearts were excised and stored for 24 hours at 0.5 degrees C. Then they were reperfused for 3 hours with use of a closed perfusion system primed with normal blood (groups I and II) or with blood supplemented with the same nucleoside transport inhibitor (0.32 mg/L) (group III). Serial biopsy specimens for determination of myocardial purines were taken. Creatine kinase and heat-stable lactate dehydrogenase release from the myocardium were examined during reperfusion. Recovery of function was studied during reperfusion by measurement of isometric contraction in a fluid-filled intraventricular balloon. After 24 hours of preservation, without the use of the drug, myocardial inosine and hypoxanthine accumulated to, respectively, 4.05 +/- 1.18 and 0.28 +/- 0.08 mumol/gm dry weight. In the drug-treated groups (II and III pooled), significantly less inosine and hypoxanthine accumulated (1.68 +/- 0.33 and 0.05 +/- 0.02 mumol/gm dry weight, respectively) (p < 0.05 versus group I). Upon reperfusion, intramyocardial adenosine was lost in the control hearts and maintained in the drug-treated hearts. Hypoxanthine accumulated significantly (p < 0.05) during reperfusion in group I (1.08 +/- 0.43 versus 0.16 +/- 0.13 in group II and 0.03 +/- 0.03 mumol/gm dry weight in group III). The rate of creatine kinase and heat-stable lactate dehydrogenase release was significantly lower (p < 0.05) in group III (that is, pretreatment and posttreatment with the drug) than in the control group. Functional recovery of hearts in group III was superior to that in group II (p < 0.05), while hearts in group I showed no recovery at all. We conclude that nucleoside transport inhibition improves long-term preservation of the heart and that the mechanism of this protection may be related to an increase in endogenous adenosine and reduction of myocardial hypoxanthine content.     

Optimal level of hypothermia for prolonged myocardial protection assessed by 31P nuclear magnetic resonance.

The optimal level of hypothermia during myocardial preservation for cardiac transplantation is not known. Phosphorus 31 nuclear magnetic resonance spectroscopy was used to assess the effect of different preservation temperatures (15 degrees C in group 1, 4 degrees C in group 2) on the myocardial high-energy phosphate profiles during prolonged global ischemia and subsequent reperfusion of isolated rat hearts. Adenosine triphosphate depletion during ischemia was more gradual in group 2, leading to significant differences in myocardial adenosine triphosphate concentrations between the two groups after 3 hours of ischemia. The fall in intracellular pH during ischemia was significantly less pronounced in hearts preserved at 4 degrees C as compared with those at 15 degrees C. The postischemic recovery of both the left ventricular peak systolic pressure and the maximum rate of increase of left ventricular pressure was enhanced in group 2, although the ischemic period was 3 hours longer than in group 1. Hypothermia at 4 degrees C as compared with 15 degrees C appears to prolong myocardial protection with respect to adenosine triphosphate preservation, prevention of the fall in intracellular pH, and the enhancement of postischemic hemodynamic recovery.     

Heart preservation in HTK solution: role of coronary vasculature in recovery of cardiac function

BACKGROUND: Poor myocardial tolerance to prolonged cold ischemia remains a major concern in heart transplantation. In this study, we estimated superiority of Histidine-Tryptophan-Ketoglutarate (HTK) over University of Wisconsin (UW) as a cardiac preservation solution. METHODS: Isolated rat hearts were mounted on a Langendorff apparatus to estimate the baseline cardiac function. The hearts were arrested and stored at 4 degrees C in UW and HTK solution for 8 hours, and then reperfused. The aortic flow, coronary flow, cardiac output, rate pressure product, and left ventricular dp/dt in the HTK group recovered significantly more than the UW group. The values of myocardial total adenine nucleotides and the adenosine triphosphate to adenosine diphosphate ratio were higher in the HTK than in the UW group. We also examined coronary vascular responsiveness using left coronary arteries dissected from the rat hearts before flushing, before storage, after storage, and after reperfusion. RESULTS: The maximal relaxation response to acetylcholine was significantly higher in the HTK than in the UW group after reperfusion, although there were no significant differences at each stage before reperfusion. In addition, the endothelium-independent relaxation response to sodium nitroprusside in the HTK group was also well preserved after reperfusion. CONCLUSIONS: These results indicate that HTK is superior to UW solution for cardiac preservation. HTK protects coronary vasculature during preservation, which together with reperfusion might lead to improved functional cardiac recovery following preservation.     

The mutual effect of ultrasound stimulation and exogenous ATP on myocardial protection during cardiac arrest

We have reported that ultrasound stimulations have a protective effect toward ischemic insult upon myocardial cells during cardioplegic arrest. However, the exact mechanism of ultrasound stimulation was not known. To elucidate this mechanism, we investigated the effect of ultrasound stimulation (UI) and/or 0.1 mMATP added to the cardioplegic solution (A) on ventricular function and adenine nucleotide changes in isolated perfused rat hearts. The hearts were perfused by working heart mode for 10 min. to determine baseline values of hemodynamic variables and they received infusion of cardioplegic solutions, followed by 20 min cardiac arrest with myocardial temperature 37 degrees C. Subsequently to the ischemic arrest, aerobic reperfusion was continued for 30 min. In group I, neither UI was irrigated nor ATP was added to cardioplegic solution. In group II and IV, ATP was added and in group III and IV, UI (1010 KHz, 0.25 W/cm2) was irrigated during cardiac arrest. Myocardial ATP was measured by Luciferase method. Myocardial ATP content after 20 min of cardiac arrest showed 12.4, 25.3, 14.5 and 32.5 (nmol/mg protein) in group I, II, III, and IV respectively, whereas it was 32.6 at the pre-ischemic cardiac arrest. The recovery of aortic output after 30 min of reperfusion revealed 30.9%, 78.9%, 79.6%, 85.4%. These data suggested the ATP depletion during cardiac arrest was attenuated by the UI and exogeneous ATP, resulted in the high recovery level of ventricular function during reperfusion.     

Opening of mitochondrial potassium channels: a new target for graft preservation strategies?

BACKGROUND: This study was designed to assess the protective effects of the mitochondrial adenosine triphosphate-sensitive potassium channel (KATP) opener diazoxide as an additive to heart preservation solution. METHODS: Forty isolated isovolumic buffer-perfused rat hearts were divided into four groups. Groups I and III hearts were arrested with and cold-stored in Celsior solution for 4 hr and 10 hr, respectively. In Groups II and IV, hearts underwent a protocol similar to that used in Group I and III, respectively, except that Celsior was supplemented with 100 micromol/L of diazoxide. RESULTS: The protective effects of diazoxide were primarily manifest as a better preservation of diastolic function and a reduction of myocardial edema. The improvement of postischemic systolic function was observed only after prolonged exposure to diazoxide in Group IV, compared with Group III. The endothelium-dependent and endothelium-independent coronary flow postischemic responses were not affected by the supplementation of Celsior with diazoxide. CONCLUSIONS: Pharmacologic activation of mitochondrial KATP channels seems to be an effective means of improving preservation of cold-stored hearts, which is consistent with the presumed role of these channels as end effectors of the cardioprotective preconditioning pathway.     

Oxygen requirements of the isolated rat heart during hypothermic cardioplegia. Effect of oxygenation on metabolic and functional recovery after five hours of arrest

Previous studies from this laboratory demonstrated that the use of an oxygenated cardioplegic solution in the hypothermic arrested rat heart resulted in improved preservation of high-energy phosphate stores (adenosine triphosphate and creatine phosphate), mechanical recovery during reperfusion, and preservation of myocardial ultrastructure. In the current study the effect of cardioplegic solutions oxygenated with 30%, 60%, and 95% oxygen was evaluated in the isolated rat heart with reference to the maintenance of adenosine triphosphate, creatine phosphate, oxygen consumption, functional recovery, and mitochondrial oxidative phosphorylation in vitro. Results indicate that the hearts receiving cardioplegic solutions supplemented with 95% oxygen and 5% carbon dioxide maintained adenosine triphosphate and creatine phosphate at control values for at least 5 hours. The oxygen consumption during elective cardiac arrest, mechanical performance during reperfusion, and in vitro mitochondrial oxygen uptake and phosphorylation rate were highest in the hearts receiving cardioplegic solutions supplemented with 95% oxygen when compared to solutions with 30% and 60% oxygen. Addition of glucose and insulin to the cardioplegic solution (95% oxygen) increased the adenosine triphosphate levels but failed to improve function after reperfusion. Although myocardial adenosine triphosphate and creatine phosphate were well preserved by the oxygenated cardioplegic solution, there was a discrepancy between the adenosine triphosphate levels at the end of the arrest period, which represents the potential for mechanical function, and the actual function of the hearts after 5 hours.     

Optimal myocardial preservation with an acalcemic crystalloid cardioplegic solution

The effect of the calcium and oxygen contents of a hyperkalemic glucose-containing cardioplegic solution on myocardial preservation was examined in the isolated working rat heart. The cardioplegic solution was delivered at 4 degrees C every 15 minutes during 2 hours of arrest, maintaining a myocardial temperature of 8 degrees +/- 2 degrees C. Hearts were reperfused in the Langendorff mode for 15 minutes and then resumed the working mode for a further 30 minutes. Groups of hearts were given the oxygenated cardioplegic solution containing an ionized calcium concentration of 0, 0.25, 0.75, or 1.25 mmol/L or the same solution nitrogenated to reduce the oxygen content and containing 0 or 0.75 mmol ionized calcium per liter. The myocardial adenosine triphosphate concentrations at the end of arrest in these six groups of hearts were 15.6 +/- 1.2, 9.5 +/- 0.5, 8.2 +/- 1.1, 4.9 +/- 1.8, 10.1 +/- 2.0, and 1.6 +/- 0.4 nmol/mg dry weight, respectively. At 5 minutes of working reperfusion, the percentages of prearrest aortic flow were 80 +/- 2, 62 +/- 4, 33 +/- 6, 37 +/- 5, 48 +/- 7 and 46 +/- 8, respectively. The differences among the groups in adenosine triphosphate concentrations and in functional recovery diminished during reperfusion. In hearts given the hypoxic calcium-containing solution, there was a marked increase in coronary vascular resistance during the administration of successive doses of cardioplegic solution, which was rapidly reversible upon reperfusion. These data indicate that hearts given the acalcemic oxygenated solution had better adenosine triphosphate preservation during arrest and better functional recovery than hearts in any other group. Addition of calcium to the oxygenated cardioplegic solution decreased adenosine triphosphate preservation and functional recovery. Oxygenation of the acalcemic solution increased adenosine triphosphate preservation and functional recovery. The lowest adenosine triphosphate levels at end arrest were observed in hearts given the hypoxic calcium-containing solution. In the setting of hypothermia and multidose administration, the addition of calcium to a cardioplegic solution resulted in increased energy depletion during arrest and depressed recovery.     

A new concept of long-term donor heart preservation: nucleoside transport inhibition.

Myocardial ischemia results in a breakdown of adenosine triphosphate (ATP), which is associated with an accumulation of its catabolites adenosine and inosine. Adenosine is a potent but ineffective cardioprotective agent because it is rapidly transported to the endothelium and irreversibly catabolized. With the use of specific nucleoside transport inhibition (NTI), however, endogenous adenosine may accumulate at its site of production, and its further breakdown and washout on reperfusion is prevented. In this study we tested this concept and assessed the effect of NTI drug administration on 24 hours' preservation of donor hearts for transplantation. Twelve dogs were randomly allocated to two groups. In the first group (group 1, n = 6) the hearts were arrested with a cold hyperkalemic cardioplegic solution, excised and stored for 24 hours at 0.5 degrees C. After 24 hours the hearts were transplanted orthotopically. In group 2 (n = 6) the same procedure was followed, but a specific NTI agent was added to the cardioplegic solution (1 mg/L) and administered intravenously to the recipient dog before reperfusion of the transplanted heart (0.1 mg/kg). Despite maximal positive inotropic support, none of the control animals (group 1) could be weaned from cardiopulmonary bypass: within 1 hour irreversible cardiogenic shock occurred in all animals. In group 2 all hearts could be weaned from cardiopulmonary bypass and were hemodynamically stable without positive inotropic support. Serial transmural left ventricular biopsies revealed in group 1 moderate catabolism of ATP during cold storage. On reperfusion a further decline of the ATP content was seen, and the accumulated nucleosides were washed out.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of donor nutritional status with sinusoidal lining cell viability and liver function in the rat

We have demonstrated that the sinusoidal lining cell injury sustained by rat liver allografts during hypothermic storage is a critical determinant of graft viability. The present study was designed to examine the effect of donor nutritional status on hepatic microcirculation and graft function. Rat livers from four nutritional groups (group I, fasted; group II, fed; group III, intraperitoneal glucose; and group IV, fed plus intraperitoneal glucose) were excised and stored for 24 hr in Marshall's isotonic citrate solution. Then the livers were perfused under anoxic conditions with trypan blue. The percentage of nonviable SLC in each group was 26.7 +/- 8.1, 24.9 +/- 7.9, 17.6 +/- 6.9, and 5.9 +/- 1.9 in groups I, II, III, and IV respectively; i.e., there was a significant improvement in SLC viability with nutritional repletion in group IV. Electron microscopy was performed on livers from groups I and IV following 30-hr preservation in University of Wisconsin solution and after 16-hr preservation in Marshall's isotonic citrate solution. Biopsies were taken at the end of storage and after 1 hr of reperfusion at 37 degrees C. At the end of preservation group IV livers contained glycogen and had much more normal liver ultrastructure than group I livers. After reperfusion there was partial recovery of normal SLC morphology in both groups and depletion of glycogen in group IV. Liver function was studied on the isolated perfused rat liver system at 37 degrees C following 30-hr storage in UW solution. Transaminase release into the perfusate was significantly lower in nutritionally repleted livers than in livers from fasted animals. A significant reduction in perfusate platelet count occurred only in livers from fasted animals. The results show that nutritional repletion can reduce the injury of cold preservation to both hepatocytes and endothelial cells and improve liver function in the postpreservation period.     

Effect of aprotinin to improve myocardial viability in myocardial preservation followed by reperfusion.

Isolated canine hearts were preserved at 4 degrees C with multi-dose cardioplegic solution every hour for 6 hours. Reperfusion was observed for 2 hours under cross-circulation without cardiotonic drugs. The aprotinin group (n = 8), which received cardioplegic solution with added aprotinin (150 KIU/mL), was compared with the control group (n = 6). The increase in tissue adenosine triphosphate and total adenine nucleotide content during reperfusion was significant in the aprotinin group; there was no change in the control group, and the levels at the end of reperfusion tended to be higher in the aprotinin group than in the control group. Tissue adenosine diphosphate levels remained unchanged in both groups. Tissue adenosine monophosphate levels declined during reperfusion in both groups and were slightly lower in the control group. Tissue levels of cyclic adenosine monophosphate remained unchanged in the aprotinin group whereas they increased during ischemia and declined significantly during reperfusion in the control group. Tissue levels of cyclic guanosine monophosphate declined during reperfusion in both groups without difference. Creatine phosphate levels recovered in both groups without difference. Serum cyclic guanosine monophosphate concentration tended to be lower in the aprotinin group than in the control group. Serum creatine kinase-MB level increased slightly during reperfusion in both groups without difference. N-acetyl-beta-D-glucosaminidase levels were significantly suppressed during reperfusion in the aprotinin group as compared with the control group. These results suggest that aprotinin is effective in preserving adenine nucleotide and adenosine triphosphate levels and in stabilizing tissue cyclic adenosine monophosphate levels in prolonged hypothermic cardioplegic preservation followed by reperfusion.     

Continuous perfusion of donor hearts with oxygenated blood cardioplegia improves graft function

Donor hearts cannot be preserved beyond 6 h using cold storage (CS). Improving preservation methods may permit prolonged storage of donor heart. We compared graft function in large animal model after prolonged preservation (8 h) using continuous perfusion (CP) and CS method. Twenty‐four miniature pigs were used as donors and recipients. Donor hearts were either stored in University of Wisconsin solution (UW solution) for 8 h at 0–4 °C (CS group, n = 6) or were continuously perfused with oxygenated blood cardioplegia at 26 °C for 8 h (CP group, n = 6). After preservation, hearts were transplanted into recipients and reperfused for 3 h. Left ventricular (LV) function, cardiac output (CO), malondialdehyde (MDA) and adenosine triphosphate (ATP) levels, and water content were measured. Although water content of CP hearts was higher than that of CS, LV contractility and diastolic function of CP hearts were superior to those of CS. In addition, CP hearts performed better than CS hearts on CO in working heart state. ATP was better preserved and MDA levels were lower in CP hearts compared with those of CS (P < 0.0001). Donor hearts can be preserved longer using continuous perfusion with oxygenated blood cardioplegia and this method prevents time‐dependent ischemic injury.     

Oxygen-derived free radical damage in canine heart transplantation

To study the role of free radical-induced myocardial injury during heart transplantation, five groups of dog hearts were orthotopically transplanted. Control group I and experimental groups II, III, and IV (each n = 8) were reperfused for 1 hr after 49 min of operational ischemia. Control group V (n = 4) remained ischemic for 90 min. In the three experimental groups, the free radical scavengers superoxide dismutase (10 mg/kg; group II), catalase (10 mg/kg; group III), or both (10 mg/kg each; group IV) were administered just before reperfusion and during reperfusion for 1 hr. The generation of free radicals, remained at low levels in all groups during ischemia, but significantly increased when groups I-IV were reperfused. This increase was also associated with an increase in creatinine kinase MB isoenzyme. In the experimental groups, free radical scavengers significantly inhibited the appearance of thiobarbituric acid reactive substances and the release of creatinine kinase MB isoenzyme during reperfusion (P less than 0.05). Regarding cardiac functions, 60 min after the termination of the cardiopulmonary bypass, a significant improvement was demonstrated in the treated groups (P less than 0.05). These results indicate that (1) the generation of oxygen free radicals occurs primarily during reperfusion, (2) both superoxide dismutase and catalase reduce production of free radicals during this time, and (3) combined administration did not provide a greater improvement in cardiac metabolic recovery. This study confirms the efficacy of free radical scavengers during heart transplantation.