Morphology of canine hearts after 24 hours' preservation and orthotopic transplantation.

Ten dogs underwent orthotopic cardiac transplantation after preservation of the donor heart for 24 hours in an oxygenated hypothermic, hypertonic, intracellular solution, either with (five dogs) or without (five dogs) continuous, oxygenated, low-pressure perfusion. Eight dogs survived for 24 hours after transplantation, at which time they were put to death. The two nonsurvivors were among the five with nonperfused hearts. Examination of all 10 donor hearts showed differences between the two groups: Four of five nonperfused hearts showed severe transmural myocardial coagulation necrosis but only small foci of contraction band necrosis (myofibrillar degeneration). The perfused hearts, however, showed more extensive subendocardial areas of contraction-band necrosis, but only minimal and focal coagulation necrosis, indicating less severe hypoxic damage. These results indicate that oxygenated perfusion with a hypothermic, hypertonic, intracellular solution may permit improved transplant survival after extended cardiac preservation.     

The effect of superoxide dismutase and catalase on the extended preservation of the ex vivo heart for transplantation

The applicability of heart transplantation remains limited in part by the inability to preserve the excised heart for long periods of time. Free radical scavengers have been shown to protect the anoxic myocardium by preventing damage to the cell membrane and may, therefore, be effective in extending successful preservation of donor hearts. We perfused 10 sheep hearts for 8 hours in an ex vivo perfusion system. The effect of superoxide dismutase combined with catalase, 60,000 units/L, was studied in five sheep, and five received placebo. Control determinations and determinations after 8 hours of preservation were obtained with the heart perfused with autologous blood at 37 degrees C at an aortic perfusion pressure of 60 mm Hg and flow of 180 to 200 ml/min. After control readings, the hearts were arrested and perfused with a cold (6 degrees to 8 degrees C) oxygenated buffered crystalloid solution with or without superoxide dismutase and catalase at a perfusion pressure of 30 cm H2O for 8 hours. Left and right ventricular compliance was measured sequentially with separate intraventricular balloons. After 8 hours of ex vivo preservation, hearts receiving superoxide dismutase and catalase had significantly better left and right ventricular performance, higher myocardial oxygen consumption, and lower lactate production than the control group. The hearts preserved with superoxide dismutase and catalase showed significantly better left and right ventricular compliance, much less increase in heart weight, and no change in the diastolic pressures. The results suggest that superoxide dismutase combined with catalase may be effective in extending ex vivo preservation of hearts for cardiac transplantation.     

Experimental heart transplantation in dogs--preservation of isolated hearts for 36 hours by retrograde coronary sinus microperfusion

In this study, the method of preserving isolated canine hearts for transplantation was established. The newly-developed method is named retrograde coronary sinus microperfusion technique. Canine hearts were arrested and cooled to 4 degrees C by means of normograde coronary perfusion with Collins' solution containing 10% fluorocarbon (FC) in order to avoid myocardial damage during warm ischemic time. Then, the hearts, immersed in Collins' solution, were retrogradely perfused through a coronary sinus at a rate of 60 ml/hr or 30 ml/hr with above-mentioned solution. After preservation for 36 hours, heterotopic heart transplantation was performed in an abdominal cavity of a recipient dog. The 36 hour-preserved hearts restored their cardiac beat after reperfusion with recipient blood. Histological observation did not show any abnormal findings in these preserved hearts. In order to evaluate the cardiac functions of preserved hearts for 24 to 36 hours, left ventricular end-systolic pressure-volume ratio (Emax) and end-diastolic pressure-volume relation were measured. Both were well restored in 24 hour-preserved hearts. The 36 hour-preserved hearts resulted in Emax within a satisfactory range, while end-diastolic pressure was elevated in all cases. This was markedly impaired with infusion of isoproterenol. These results strongly suggested that transplantation using 24 hour-preserved hearts could be performed well. On the other hand, the 36 hour-preserved hearts were considered to function satisfactorily under careful management after grafting. The retrograde coronary sinus microperfusion method developed here was found to be useful for a distant heart procurement.     

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.     

Energy state of the myocardium during long-term cold storage and subsequent reperfusion

Long-term preservation of dog hearts was performed over 24 h using Bretschneider-HTK cardioplegia and cold storage. Preservation was assessed in terms of conservation of myocardial tissue levels of high-energy phosphates (HEP) and functional outcome after cardiac transplantation. Serial left ventricular biopsies were taken and analysed for ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and creatine phosphate. Myocardial structure was studied by electron microscopical examination of a similar biopsy specimen. Cardiac performance was measured before and after cardiac transplantation. Several techniques of cardioplegic arrest were studied: single dose cardioplegia, multidose cardioplegia and continuous perfusion with the cardioplegic solution. In all groups, the hearts were stored at 0.5 degree C for 24 h. In the group of single dose Bretschneider-HTK cardioplegia, myocardial ATP content after 24 h of cold storage was only 25% of control. The total sum of nucleotides at that time interval was however 65% of the control value. Reperfusion of these hearts using a support dog (whole blood reperfusion) did not result in any recovery of ATP. Creatinine phosphate however showed an overshoot. Accumulated nucleosides were washed out. The hearts showed electrical activity but were severely arrhythmic. Contractility was poor. In the group of multidose Bretschneider-HTK cardioplegia, HEP preservation was better than after single dose cardioplegia. ATP content was about 50% of control. The total sum of nucleotides was 85% of control. Ultrastructural assessment of the myocytes revealed only slight ischaemic damage to the mitochondria. Reperfusion on cardiopulmonary bypass after cardiac transplantation did not show any restoration of ATP, but a steady catabolism of HEP. The nucleosides adenosine and inosine were not washed out upon reperfusion. After cardiac transplantation, none of these hearts could be weaned from cardiopulmonary bypass due to irreversible low cardiac output. Histological examination demonstrated irreversible myocardial tissue damage. In the group of continuous cold Bretschneider cardioplegia, HEP content was completely preserved throughout the 24 h of perfusion. Ultrastructure of the myocytes was normal. Reperfusion of the transplanted hearts showed a mild breakdown of ATP to 70% of control values accompanied by a slight accumulation of nucleosides. Haemodynamic recovery however was perfect and none of the hearts needed positive inotropic support. Myocytes after reperfusion had a normal subcellular appearance.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lipid peroxidation results in compromised functional recovery of isolated rabbit hearts after low-pressure, hypothermic, perfused preservation for 24 hours.

Low-pressure, hypothermic perfusion of isolated rabbit hearts for 24 hours compromises contractile function. This occurs despite continuous recirculation of an oxygenated solution. This investigation tested the hypothesis that such functional impairment results from irreversible tissue damage consequent to ischemia-induced lipid peroxidation. Decreases in coronary flow were measured during preservation and related to concentrations of thiobarbituric acid reactive species (TBA+, primarily malondialdehyde, a by-product of lipid peroxidation) in the tissue after preservation. The concentration of TBA+ species and the percent decrease in coronary flow rates at 30 minutes and 24 hours were positively correlated (r = 0.591 and r = 0.646, respectively). India ink was used as a marker of microvascular perfusion. Hearts showing the greatest magnitude of ischemia (evidenced by decreased percentages of perfused microvessels) had the highest levels of TBA+ species (r = 0.924). Moreover, hearts that had the highest levels of TBA+ species in the tissue exhibited the lowest levels of left ventricular function (as measured on a modified Langendorff apparatus; r = 0.767). We conclude that impaired coronary flow rates during perfused preservation portend compromised myocardial contractility. Furthermore, these changes occur largely within the first 30 minutes of perfusion. It is likely that early decrements in microvascular perfusion and consequent tissue injury owing to lipid peroxidation underlie impaired myocardial function after preservation.     

Cardiac function and myocardial performance of 24-hour-preserved asphyxiated canine hearts.

A method of 24-hour storage of asphyxiated canine hearts for orthotopic cardiac transplantation was studied to expand the geographical size of the donor pool. Left ventricular function of asphyxiated hearts preserved for 24 hours (group 1, n = 8) was compared with that of hearts donated on-site (group 2, n = 5). Group 1 donors were pretreated with verapamil hydrochloride, propranolol hydrochloride, and prostacyclin. The donor hearts were perfused with warm blood cardioplegia in situ after 10 minutes of asphyxiation and then perfused with cold crystalloid cardioplegia for 2 hours. The hearts were excised and stored in ice-cold University of Wisconsin solution for 22 hours. At orthotopic transplantation, coronary perfusion with warm blood cardioplegia was performed before the graft aorta was unclamped. Conventional cardiac variables (eg, cardiac output and maximum rate of rise of left ventricular pressure), myocardial performance, and diastolic compliance of grafted hearts were assessed 1 hour after weaning from bypass. All recipients in both groups were easily weaned from cardiopulmonary bypass without inotropic agents, and there were no significant differences in cardiac variables between the two groups. These results strongly suggest that cadaver hearts can be preserved for 24 hours with satisfactory cardiac function.     

Effect of adenosine on recovery of lowered viability of preserved rat hearts measured by 31P magnetic resonance spectroscopy

The restoration of the viability of rat hearts preserved for 5 hr by 50 microM adenosine (ADN) was evaluated in terms of the cardiac function after preservation and the recovery of myocardial high energy phosphates measured by 31P magnetic resonance spectroscopy. The hearts were perfused with modified Krebs-Ringer's solution (mKRS) with ADN (ADN group) or without AND (non-ADN group) for 1 hour after 5 hr of preservation by the simple immersion method. Control hearts were perfused but not preserved. ATP and phosphocreatine had decreased to 47.2 +/- 6.6% and 28.0 +/- 8.6% of the base line by 5 hr of preservation, but the levels returned to 147.2 +/- 2.3% and 127.4 +/- 5.6% after 1 hr of perfusion with ADN; at the same time, in the non-ADN group, they were 103.8 +/- 2.3% and 115.8 +/- 8.3% respectively. The same hearts were next perfused for 3 hr with standard Krebs-Ringer's solution so as to beat after the perfusion with mKRS. After 3 hr of beating, LV dP/dt was 3330 +/- 116 mmHg/s in the ADN group, which was not significantly different from the control (3034 +/- 60 mmHg/s). However, in the non-ADN group, the value was 2516 +/- 201 mmHg/s and significantly lower (p less than 0.05) than the control. The rate-pressure product was 19350 +/- 1154 in the ADN group, not significantly different from the control (20899 +/- 709), but it was 14559 +/- 1339 in the non-ADN group, which was significantly lower (p less than 0.01) than the control.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypothermic perfusion of rabbit kidneys with solutions containing gelatin polypeptides.

Rabbit kidneys were perfused with a solution of extracellular electrolyte composition, made hypertonic with glucose and containing the gelatin polypeptide preparation Haemaccel (Hoechst) as the only colloid. Perfusions were carried out at 5 and 10 C for 19 hr, and function was tested by autografting. All of the kidneys perfused at the higher temperature showed immediate life-sustaining function after transplantation and contralateral nephrectomy, whereas only one graft of five perfused at the lower temperature showed any function. The suitability of the Haemaccel solution as a vehicle for introducing the cryoprotective agent glycerol was tested by perfusing kidneys for 4 hr with a solutiont containing 2% glycerol; the function of these organs was similar to that of kidneys transplanted without perfusion. Ultrastructural examination of kidneys perfused for 24 hr at 10 C showed excellent structural preservation, but measurements of water and ion contents and the penetration of marker molecules in nonmetabolizing kidneys showed 2.8% Haemaccel to be somewhat less effective than 6% bovine serum albumin in stabilizing these values. The Haemaccel perfusate is considered to be highly suitable for the introduction and removal of cryoprotective agents, and the results of hypothermic preservation by continuous perfusion are encouraging.     

Experimental myocardial preservation study of adding perfluorochemicals (FC43) in lidocaine cardioplegia.

OBJECTIVE: Lidocaine exhibits a cardioplegic action via acute inhibition of sodium influx into the myocardial cells. In terms of the cardiac function and calcium dynamics in the myocardial cells, we investigated the myocardial protective effect of addition of FC43 of Perfluorochemicals, which has an excellent oxygen transport function to meet the myocardial oxygen demand, on lidocaine-induced cardioplegia. METHODS: Isolated rat hearts were perfused with Langendorff mode and were divided to three experimental groups. During of preservation, these hearts were perfused continuously with the next three solution, potassium chloride was added to Krebs-Henseleit bicarbonate buffer to make potassium concentration of 20 mM in the first group (Group A), 2 mM lidocaine was added to Krebs-Henseleit bicarbonate buffer in the second group (Group B), and 2 mM lidocaine and 20% FC43 were added to Krebs-Henseleit bicarbonate buffer in the third group (Group C). After 60 minutes of continuous perfusion, the cardiac function and the intracellular calcium concentration in Groups A and B during cardioplegia were measured. Furthermore, after 360 minutes of continuous coronary perfusion, the cardiac function were measured in Group B and Group C. RESULTS AND CONCLUSIONS: Lidocaine cardioplegia showed a good recovery of cardiac function, because lidocaine induced prompt cardiac arrest by blocking sodium influx and inhibited the intracellular calcium overload by the following inhibition of sodium-calcium channels. Moreover, our results suggested that combining Perfluorochemicals with lidocaine produced a more effective myocardial-preservation that meets the myocardial oxygen demand during long-term cardiac arrest.     

Prolonged preservation of the blood-perfused canine heart with glycolysis-promoting solution.

BACKGROUND: Prolonged ischemia and inadequate myocardial preservation remain significant perioperative risk factors in cardiac transplantation. Long-term preservation techniques that have been effective in small rodent hearts have not been as effective in larger animal models or in clinical studies. We developed a cardioplegia solution formulated to promote high-energy phosphate production from glycolysis and determined its efficacy in a blood perfused canine heart model subjected to 24 hours of ischemia. METHODS: Hearts harvested from adult dogs (n = 6 per group) were flushed with a histidine-buffered cardioplegia solution containing glucose or University of Wisconsin solution. The hearts were maintained at 4 degrees C for 24 hours then reperfused with autologous blood. After reperfusion, left ventricular pressures were measured with an intracavitary balloon at varying balloon volumes and compared with control nonischemic hearts. Predicted stroke volume and ejection fraction were calculated at an end-systolic pressure of 70 mm Hg and end-diastolic pressure of 15 mm Hg. RESULTS: Developed pressure was better preserved in the hearts that received histidine-buffered solution (93+/-9 versus 38+/-7 mm Hg, p<0.05), along with a higher end-diastolic volume at 15 mm Hg (31+/-3 versus 22+/-2 mL histidine-buffered versus University of Wisconsin solutions, respectively, p<0.05). Stroke volume and ejection fraction were also higher in the histidine group (17+/-2.5 versus 2.3+/-1.2 mL and 50%+/-3.5% versus 9% +/-4.5%, respectively) in the presence of dobutamine. CONCLUSIONS: The highly buffered glycolysis-promoting cardioplegia solution provided effective preservation of the blood perfused canine heart with superior recovery of pump performance after 24 hours of hypothermic ischemia compared with University of Wisconsin solution in this model.     

Myocardial ultrastructure following prolonged in vitro preservation and heterotopic cardiac transplantation

Myocardial ultrastructure, using semiquantitative electron microscopy, was compared between two different means of prolonged, in vitro myocardial preservation followed by successful canine, cervical heterotopic cardiac transplantation: (1) 3-hr preservation in 4°C, 158 mM NaCl, (2) 24 hr continuous, low-pressure, nonpulsatile, modified Krebs solution with pretreatment of the donor with Diltiazem (1 mg/kg). All grafts in both groups resumed spontaneous beating after heterotopic allotransplantation and defibrillation. Twenty-four-hour preservation resulted in minimal ultrastructural changes with only mild lightening of the mitochondrial matrix and slight cristae damage. Similar findings were observed 24 hr post-transplantation. In contrast, 3-hr, 4°C, NaCl preservation resulted in focal zones of hypercontraction, clearing of the mitochondrial matrix and cristae damage, and an increase in intracellular lipid deposition which persisted after 24 hr post-transplantation. It is concluded that the continuous perfusion technique may better preserve cellular integrity than current standard preservation modalities in spite of an eightfold increase in total ischemic time.     

Perfusion preservation maintains myocardial ATP levels and reduces apoptosis in an ex vivo rat heart transplantation model

BACKGROUND: Machine perfusion preservation improves reperfusion function of many solid organs, compared with conventional storage, but has received limited clinical attention in preserving hearts for transplantation. We evaluated representative extracellular (Celsior) and intracellular (University of Wisconsion) storage solutions using static and perfusion protective strategies over a clinically relevant preservation period. METHODS: Rat hearts were preserved for 200 minutes by either static storage or perfusion preservation in Celsior or University of Wisconsin solutions. Three conditions were studied: conventional static storage; static storage using either solution with 5.5 mmol/L glucose added; and perfusion preservation using either solution with 5.5 mmol/L glucose added. Glucose was provided as U-13C-labeled glucose, and glycolysis and oxidative metabolism during preservation were quantified from incorporation of (13)C into glycolytic and tricarboxylic acid cycle intermediates. Adenosine triphosphate levels after preservation, and apoptosis and cardiac function after reperfusion were measured. RESULTS: Both perfusion preservation groups had higher myocardial oxygen consumption during storage and better early graft function, compared with static preservation groups (P < .05). Adenosine triphosphate levels were higher after storage in the perfusion groups (P < .01). Apoptosis was reduced in the perfusion groups (P < .01). Comparing perfusion groups, hearts preserved with Celsior had higher myocardial oxygen consumption and glucose utilization during perfusion storage and exhibited decreased reperfusion coronary vascular resistance and myocardial water content, compared with the UW perfusion group (P < .05). CONCLUSIONS: Perfusion preservation results in greater metabolism during storage and superior cardiac function with improved myocyte survival, compared with static storage. Extracellular preservation solutions appear more effective for perfusion preservation, possibly by augmenting cellular metabolism.     

A novel bisindolylmaleimide derivative enhances functional recovery of heart after long-term hypothermic heart preservation

BACKGROUND: Functional recovery following heart transplantation mainly depends on the ability of preservative solution in providing the physical and biochemical environment so as to maintain the viability of the tissue during preservation and in reperfusion. Here we demonstrate the protective effects of a novel bisindolylmaleimide derivative, MS1, on enhancing the functional recovery of the heart following long-term hypothermic preservation when added to the preservative solution. METHODS: After anesthesia and artificial ventilation, the hearts were rapidly isolated and perfused with Kreb's Henseleit buffer at 37 degrees C in working mode. After 30 minutes of perfusion, the hearts were arrested with cardioplegic solution and preserved in University of Wisconsin solution with (UW-MS1 group) or without MS1 (UW-Vehicle group) for 12 h at 4 degrees C. After 12 hours, the hearts were reperfused for 60 minutes. RESULTS: MS1 treated hearts showed: a) significant recovery of cardiac functions (P<0.001), b) well-preserved myocardial ATP levels (P<0.001), c) less myocardial water content (P<0.01), d) reduced oxidative stress (P<0.001), e) less intracellular swelling and well-preserved mitochondria, and g) activation of cell survival cascades compared to the control hearts preserved in UW solution without MS1. In contrast, these protective effects of MS1 were abolished on opening the permeability transition pore before MS1 treatment. CONCLUSION: These results altogether indicate the efficacy of this compound in protecting the myocardium against reperfusion injury and thus making this drug a clinically useful tool in patients undergoing reperfusion after cardiac surgeries.     

Beneficial effect of additional cardioplegia flush during hypothermic static cardiac preservation

BACKGROUND: The effects of various preservative solutions and methods have been studied to prolong the safety period of cardiac preservation. In this study, we used cardioplegic solution (CS) during cardiac preservation and investigated how flush CS yields good preservation of isolated hearts compared with only cold immersion. METHODS: Male Wistar rat hearts were arrested with 4 degrees C St. Thomas crystalloid CS. All hearts were immersed for 6 hr in a 4 degrees C Euro-Collins solution. Hearts were classified into seven groups by period and number of infusions of CS (20 ml/kg) during simple immersion of hearts. Infusion of CS during preservation was not used for group I. Infusion was performed at two hours after starting immersion for group II, at 3 hr for group III, at 4 hr for group IV, at 5 hr for group V, every hour for group VI, and every 2 hr for group VII. After preservation, the hearts were reperfused with blood using a support rat. Myocardial adenosine triphosphate was measured immediately after immersion of hearts. Biochemical examination of coronary effluents was performed at 15 min after reperfusion, and cardiac function was evaluated at 40 min after reperfusion. Myocardial specimens were subsequently taken for measurement of water content. RESULTS: Percentage recovery of left ventricular developed pressure and dp/dt in groups III, VI, and VII were higher than those in group I at each balloon volume, and left ventricular end-diastolic pressure in these groups was also significantly lower than that in group I. Levels of creatine kinase-MB and lactate in groups VI and VII after reperfusion were significantly lower than those in group I. Myocardial adenosine triphosphate was significantly better preserved in groups III, IV, VI, and VII than in group I. However, no significant difference in cardiac function or myocardial adenosine triphosphate was found among groups III, IV, VI, and VII. CONCLUSIONS: The use of CS during cardiac preservation is effective in preserving cardiac function and myocardial enzymes, and infusion may be sufficient if performed once-only at 3 or 4 hr from starting immersion in 6 hr storage of isolated rat hearts.     

Coronary oxygen persufflation for heart preservation in pigs: analyses of endothelium and myocytes

BACKGROUND: Coronary oxygen persufflation (COP) has been shown to prolong heart preservation time up to 14 hr in a mature pig model, with excellent recovery after orthotopic transplantation. The aim of the present study was to assess the structural, metabolic, and functional myocardial and endothelial integrity after COP in mature pig hearts. METHODS: Cardioplegic arrest was induced by original crystalloid Bretschneider solution (HTK 3h, n=6), modified Bretschneider solution (mHTK+COP, n=6), or University of Wisconsin solution (UW+COP, n=6). Hearts were stored for 3 (HTK 3h) or 14 hr (mHTK+COP, UW+COP) at 0 degrees to 1 degrees C. In addition, COP hearts were persufflated. After heterotopic transplantation and reperfusion for 7 days, hearts were analyzed by light microscopy or electron microscopy for structural injuries. Endothelial function, cardiac enzymes, metabolic parameters, and myocardial water content (MWC) were determined. Six recipient hearts served as controls. RESULTS: Quantitative light microscopic analyses and semiquantitative electron microscopic analyses showed an equal amount of damage in all groups including HTK 3h hearts. No rejection was observed. Substance P induced an equal dilatation in all hearts. Serum levels of cardiac enzymes were similar in all groups, but energy-enriched phosphates were significantly reduced, and MWC was augmented in the HTK 3h hearts and in the UW+COP hearts, in contrast to the mHTK+COP transplants. CONCLUSIONS: The lack of structural defects related to the COP technique, similar endothelial function, and an even better metabolic state of the mHTK+COP hearts versus HTK 3h hearts demonstrate the efficacy of the COP technique for prolongation of myocardial preservation time up to 14 hr.     

Successful long-term preservation of the neonatal heart with a modified intracellular solution.

Current methods of myocardial preservation for transplantation are suboptimal. A newly developed intracellular cardioplegic and storage solution (modified University of Wisconsin solution, group 1) was compared in a randomized, blinded fashion with our present clinical protocol, Stanford cardioplegic solution and saline storage (group 2) in an isolated neonatal pig model. After arrest and storage for 12 hours at 4 degrees C, biopsy specimens were taken from six group 1 hearts and five group 2 hearts for examination under an electron microscope and assessment of high-energy phosphate levels and water content. The remainder (group 1, n = 7; group 2, n = 6) were reperfused with blood for 50 minutes, after which function curves were obtained at left ventricular end-diastolic pressures of 3 to 12 mm Hg and biopsy tissue was taken. Eight control hearts (group 3) were cannulated in situ and perfused on the circuit without arrest or intervening ischemia. Stroke and minute work index curves were approximately threefold and fivefold higher for group 1 (modified University of Wisconsin solution) than for group 2 (Stanford), respectively (p less than 0.01). The hearts preserved with University of Wisconsin solution did not differ in function from unpreserved control hearts (group 3). High-energy phosphate levels were better maintained in group 1 than group 2 (p less than 0.05), and water content was lower (p less than 0.01). Semiquantitative grading of electron micrographs paralleled the functional and biochemical results. Conclusion: Modified University of Wisconsin intracellular solution provides markedly better heart preservation than conventionally used cardioplegic and storage solutions.     

The effects of cardioplegia washout on myocardial preservation

Preservation of the myocardium in vitro is more effective than preservation in vitro when preservation conditions are apparently the same. The washout of cardioplegia from the myocardium by noncoronary blood flow has been implicated as a probable cause of the poorer myocardial preservation seen in vivo. Isolated dog hearts were used to study the effects of cardioplegia washout by low flow perfusion (0.05 ml/min/g LV weight) during a 2-hr preservation period. Six experimental groups of five hearts each underwent 2 hr of myocardial preservation at temperatures of 20 degrees C (three groups) or 30 degrees C (three groups). The three groups for each temperature consisted of retrograde coronary sinus perfusion (to simulate cardioplegia washout by collateral flow) with blood cardioplegia (BC), normal blood (NB), or no perfusion at all (No CSP). The quality of preservation in each group was assessed by measuring recovery of left ventricular function, tissue water and electrolyte content, and myocardial high-energy phosphate and adenylate content prior to, during, and following preservation. In hearts maintained at 20 degrees C, cardioplegia washout did not significantly affect left ventricular function or myocardial levels of H2O, Na, K, ATP, or total adenylates. When myocardial temperature was allowed to increase to 30 degrees C, preservation was better with low flow perfusion during the preservation period. Hearts warmed to 30 degrees C with no cardioplegia washout experienced a 50% loss of tissue ATP levels and recovered less than 30% of normal left ventricular function during a 150-min reperfusion period. In contrast, hearts slowly perfused during the preservation period maintained nearly normal levels of ATP and returned to normal function by 150 min of reperfusion. Although myocardial warming by noncoronary perfusion has a detrimental effect on myocardial preservation, the slow washout of cardioplegia per se has no apparent detrimental effect on preservation.     

Effects of pulsatile perfusion pressure and storage on hearts preserved for 24 hours under hypothermia, for transplantation.

Canine hearts preserved for 24 hours under hypothermic pulsatile perfusion at a systolic pressure of 25 mm Hg had better perfusion and transplantation survival results than hearts perfused at 50 or 80 mm Hg. Also, hearts perfused at a systolic pressure of 25 mm Hg did better than simple hypothermically stored hearts or fresh allografts. These findings indicate that hearts are adequately perfused for 24 hours under hypothermia for transplantation at a systolic pressure of 25 mm Hg.     

The importance of platelets for the isolated lamb heart perfused at 13 degrees C

To investigate whether or not the addition of functional platelets to a plasma perfusate could improve the preservation of isolated lamb hearts at 13°C for 18 hr, 13 hearts were perfused with platelet-poor plasma. They exhibited a rise in coronary vascular resistance, edema, and poor function upon terminal rewarming for left ventricular assessment. Twelve other hearts were perfused with platelet-rich plasma (PRP) harvested from a flow-through centrifuge. Platelets aggregated in the circuit and had altered in vitro function. These hearts also became edematous and could not tolerate left atrial perfusion at final assessment. The addition of Pluronic F68, a nonionic surface active agent, to PRP prevented platelet aggregation in the perfusion circuit and preserved platelet function in the perfusate. Six hearts perfused with this modified PRP had stable coronary vascular resistance, had no significant weight gain, and contracted vigorously upon terminal rewarming, with 4 out of 6 able to support left atrial perfusion. These results suggest that unaggregated, functional platelets reduce edema and stabilize coronary vascular resistance in the isolated heart perfused at cold temperatures.