Hypothermic Heart Preservation Research Articles

An optimal experimental design for the development of preservative heart solutions

Background: The aim of this study was to determine the optimal composition of a new medium for long-term hypothermic heart preservation. Methods: The independent effects of 19 compounds were evaluated using an in vitro porcine model. Tissue viability was assessed by measuring the reduction of methyltetrazolium salt, oxygen consumption and energetic compound levels on myocardial biopsies after 24-, 48- or 72-hour incubation periods. Screening of several compounds at two concentrations was performed to greatly reduce the number of experiments. Results: Pyruvate, aspartic acid, chlorpromazine and polyethylene glycol displayed protective properties, whereas calcium (2 mmol/liter), nifedipine, mannitol, magnesium (16 mmol/liter) and reduced glutathione showed deleterious effects. On the basis of these data, the composition of a new preservation solution (Group 1, n = 6) was compared with St Thomas solution (Group II, n = 6) in an isolated, 24-hour pig heart preservation model. During reperfusion, left ventricular developed pressure and coronary blood flow were significantly higher ( p < .01) in Group I, suggesting better preservation. Conclusions: Our technique allows for rapid and efficient screening of many compounds currently used in the composition of preservation solutions for cardiac surgery.

Microperfusion techniques for long-term hypothermic preservation

Background The aim of this study was to compare several methods of hypothermic heart preservation. Methods We preserved isolated pig hearts for 24 hours in cold cardioplegia (4° C), using either continuous microperfusion (Group I) or simple storage (Group II), and with a new preservative solution (NPS, groups IA and IIA) vs St. Thomas’ solution (groups IB and IIB). The main characteristics of the NPS include (1) prevention of cell swelling with polyethelene glycol (PEG), (2) low calcium and magnesium, and (3) presence of metabolic substrates, such as glucose, insulin, pyruvate, aspartate, alanyl-glutamine, and membrane stabilization compounds such as ethanol and chlorpromazine. Results The 4 above groups were compared with hearts harvested and immediately reperfused (control group). During preservation, only Group IB showed significant edema (40% ± 8.4% water gain). Adenylate charge was 25% to 50% higher in microperfused Groups IA and IB (0.678 ± 0.049 and 0.795 ± 0.071, respectively) as compared with simple-storage groups IIA and IIB (0.605 ± 0.048 and 0.524 ± 0.160, respectively). Ultrastructural analysis showed that tissue injury occurred mainly in Group IIB (altered mitochondria, chromatin clumping). Functional data showed better recovery of NPS groups as compared with St. Thomas groups: coronary flow was identical in Group IB and control (57.8 ± 22 and 56.6 ± 14 ml/min/100 g, respectively), and in IA > IB ( p < 0.001) and IIA > IIB ( p < 0.01); the rate pressure products were higher in NPS groups compared with St. Thomas groups (IA > IB, p < 0.01); IIA > IIB, p < 0.05). Conclusions The microperfusion method associated with the NPS provides excellent protection in long-term hypothermic heart preservation.

Fructose-1,6-diphosphate and a glucose-free solution enhances functional recovery in hypothermic heart preservation

Background Fructose-1,6-diphosphate (FDP) has been shown to protect tissue during hypoxia under various ischemic conditions, including isolated heart perfusion. We tested the hypothesis that adding FDP to St. Thomas solution can extend hypothermic heart preservation time. Methods Sixteen adult Sprague-Dawley rats were used. Under general anesthesia, the hearts were removed and preserved at 4°C in St. Thomas solution (30 ml/kg) for 12 hours. FDP (5 mM) was added to the St. Thomas solution in the study group ( n = 8), whereas no FDP was used in the control group ( n = 10). The hearts were reperfused after 12 hours of preservation using a working heart model. Results In the study group, cardiac output ranged from 13.00 ± 2.34 to 17.66 ± 1.71 ml/min, maximum aortic flow was 3.40 ± 1.99 to 9.26 ± 1.72 ml/min, left ventricular stroke volume ranged from 0.074 ± 0.014 to 0.092 ± 0.009 ml, left ventricular stroke work ranged from 6.22 ± 0.39 to 7.95 ± 0.44 ml/mmHg, and maximum left ventricular generated power was 14.38 ± 2.94 to 20.16 ± 2.49 Joules/min. All of these parameters were higher than those in the control group ( p < 0.001). Coronary vascular resistance and myocardial tissue wet/dry weight ratio were lower in the study group than in the control group ( p < 0.05). Conclusions Heart function was better preserved when FDP was added to St. Thomas solution during hypothermic rat heart preservation. The mechanism is not totally clear, but enhancement of high-energy phosphate production during ischemia is possible. Key words: heart, procurement, hypothermia, fructose-1,6-diphosphate.

Enhancement of Hypothermic Heart Preservation with Fructose 1,6-Diphosphate

Background. We hypothesized that the addition of fructose 1,6-diphosphate (FDP) to a hypothermic heart preservation solution could improve metabolic recovery because it has several beneficial effects.Materials and Methods. Twenty adult Sprague-Dawley rats were used to study hypothermic heart preservation. The hearts were removed under general anesthesia and preserved at 4°C in Euro-Collins solution (30 ml/kg) for 8 h. In the study group (N = 10), FDP (5 mM) was added to the Euro-Collins solution. In the control group (N = 10), no FDP was added. Heart function was studied after preservation using a working heart model. The ability of various concentrations of fructose 1,6-phosphate to passively diffuse through an egg phosphatidylcholine multilamellar vesicle (MLV) membrane bilayer was examined.Results. Cardiac output ranged from 17.0 ± 1.9 to 24.9 ± 1.6 ml/min in the study group vs 2.0 ± 1.0–12.3 ± 1.7 ml/min for controls, average aortic flow was 10.8 ± 1.4 ml/min in the study group vs −1.3 ± 1.6 ml/min for controls, and maximum LV generated power was 22.8 ± 1.7 J/min vs 10.1 ± 1.6 J/min for controls. Coronary flow, left ventricular stroke volume and stroke work, and myocardial oxygen consumption were much higher in the study group than in the control group. Coronary vascular resistance was lower in the study group than in the control group. Electron microscopic study indicated that many myocytes displayed patches of swollen mitochondria in the control group, but was rarely observed in the study group. The addition of 50 mM FDP caused substantial changes in MLV permeability. No dose of sucrose buffers outside the vesicles resulted in a significant changes of MLV permeability.Conclusions. Our results indicate that the addition of FDP to Euro-Collins solution significantly improves hypothermic rat heart preservation, and FDP appeared to cross the membrane bilayer.

Improved hypothermic preservation of rat hearts by furosemide

The effect of furosemide, a blocker of the Na +/K +/Cl - cotransporter, on hypothermic preservation of rat hearts was studied with use of the Langendorff perfusion system and electron microscopy. Furosemide significantly improved the mechanical recovery and the coronary flow of the hearts preserved for 8 hours in St. Thomas' Hospital cardioplegic solution at a temperature of 4 ° C. Furosemide at the concentration of 100 μmol/L was found to have an optimal effect, whereas at high concentrations (1000 μmol/L) it was found to have toxic effects. In addition, furosemide reduces the time elapsed between the end of the preservation time and the resumption of myocardial contractions. Ultrastructural evaluations were done in which the presence of swollen mitochondria was chosen as a criterion of hypothermic ischemic damage to the myocardium. Morphometric analysis indicated that the mitochondrial volume of hearts stored for 8 hours in St. Thomas' Hospital cardioplegic solution increased by 72% as compared with the mitochondrial volume of hearts that were not exposed to the hypothermic ischemic conditions (control group). The addition of 100 μmol/L furosemide to the cardioplegic solution resulted in a significant reduction of mitochondrial swelling during the period of 8 hours' storage, which amounted only to 28% as compared with the figure for the control group. The reduction of mitochondrial swelling by furosemide and the improved mechanical and coronary flow recoveries are thought to be related to the blocking of the sarcolemmal Na +/K +/Cl - cotransporter and consequently the reduction of the Na + influx during hypothermic ischemic storage.(J T HORAC C ARDIOVASC S URG 1995;110:523-31)

Comparison of different techniques of hypothermic pig heart preservation

The aim of this study was to compare several methods of hypothermic heart preservation. Isolated pig hearts were preserved for 24 hours in cold candioplegic solution (St. Thomas' Hospital modified solution) by continuous perfusion (group D, microperfusion (group II), or simple storage (group III). The findings were then compared with those from hearts harvested and immediately reperfused (the control group). Group III hearts showed lower adenosine triphosphate preservation (0.47 ± 0.18 μmol/g) than did group I and II hearts and the control hearts (1.86 ± 0.40, 1.98 ± 0.27, and 1.84 ± 0.55 μmol/g, respectively). Electronic microscopy studies also revealed that the-myocardial cells in the group III hearts appeared to be damaged. After the hearts had undergone preservation, myoeardial function was studied for 60 minutes under nonworking conditions using an ex vivo functional testing system. For group III, the mean left ventricular developed pressure and ventricular compliance (16 ± 22 and 63 ± 48 mm Hg, respectively) differed significantly from those for group I (83 ± 26 and 0 ± 0 mm Hg, respectively), group n (83 ± 33 and 14 ± 18 mm Hg, respectively), and the control group (115 ± 13 and 0 ± 0 mm Hg, respectively). We concluded from our findings that perfusion methods are superior to cold storage but inadequate to maintain heart viability for the long term during hypothermia. These techniques must be improved before they can be adopted for clinical use.

Fluorochemical emulsion APE-LM substantially improves cardiac preservation.

We determined the efficacy of a novel fluorochemical emulsion for long-term hypothermic preservation of hearts. Rat hearts were preserved for 12 h at 12 degrees C with use of continuous low-pressure coronary perfusion with one of three oxygenated media (n = 6 hearts/groups): an "extracellular" crystalloid solution; APE-LM, a novel fluorochemical emulsion of perfluoroperhydrophenanthrene in egg yolk phospholipid; and FC-43, the Fluosol-43 (Oxypherol) fluorochemical emulsion of perfluorotributylamine in Pluronic F68. The emulsion media contained the same components as the crystalloid medium. All three media contained 0.5% albumin. An isolated working heart perfusion system was used to quantify the function of preserved hearts and controls (fresh hearts, n = 6). The APE-LM-preserved hearts were not significantly different from control hearts in contractile function, output, and energetics during a 4-h 37 degrees C reperfusion period. The control and APE-LM-preserved hearts had significantly better performance than crystalloid- and FC-43-preserved hearts. All preserved hearts gained fluid during preservation. The edema of APE-LM-preserved hearts, but not that of the other two preserved groups, was reversed during 37 degrees C reperfusion. These data provide the first evidence that a unique fluorochemical emulsion improves long-term preservation of cardiac tissue and produces significantly better recovery of cardiac function after preservation. This salutary effect was specifically associated with APE-LM emulsion and may result from its high O2 capacity, its biologically compatible emulsifier, and its superior physical properties, which include very small emulsion particle size (0.1-0.15 micron), low viscosity, and minimal toxicity.

University of Wisconsin solution for human donor heart preservation: Initial clinical experience

Although in vitro and primate orthotopic transplant experiments have suggested the superiority of University of Wisconsin solution (UWS) compared with crystalloid cardioplegia and saline solution storage for hypothermic heart preservation, concerns about the viscosity and the high potassium concentration of UWS have precluded its use in human cardiac transplantation. To test the safety and efficacy of UWS, 16 patients received hearts arrested with, flushed with, and stored in UWS at 4 °C for a mean ischemic time of 153.3 ± 30.7 minutes. After reperfusion, the hearts contracted vigorously and attained a stable sinus rhythm within 4.0 ± 2.4 minutes, and the patients were weaned from bypass in 24.5 ± 8.0 minutes. There was no evidence of acute or chronic ischemic myocardial injury by enzymatic analysis, electrocardiography, or biopsy specimen histology. The results suggest UWS can be safely used, within currently accepted limits of donor ischemic time, to arrest and preserve human hearts for transplantation. Further studies of preservation are required to compare UWS with crystalloid cardioplegia and saline solution storage and to test the ability of UWS to prolong the period of safe donor hypothermic ischemia in clinical heart transplantation.

炭酸ガスの心保存に及ぼす影響

炭酸ガスの心保存に及ぼす影響

Three solutions for preservation of the rabbit heart at 0° C: A comparison with phosphorus-31 nuclear magnetic resonance spectroscopy

Phosphorus-31 nuclear magnetic resonance has been used to measure changes in tissue adenosine triphosphate and pH that occur during hypothermic preservation of rabbit hearts. Three potential preservation solutions were studied: the St. Thomas' Hospital no. 1 cardioplegic solution, Bretschneider's HTP solution, and a solution originated in our laboratory, CP5, which we have previously studied in the rabbit heart with functional assessment by Langendorff perfusion. After being flushed with one of these solutions, each heart was stored at 0 degrees C for 12 hours, during which time it was subjected to repeated phosphorus-31 nuclear magnetic resonance scans. It was shown that adenosine triphosphate levels decayed more slowly with CP5 than with either of the other solutions or in the control experiments. Adenosine triphosphate decay was also slower with Bretschneider's HTP than with St. Thomas' Hospital solution, but pH was somewhat better maintained with Bretschneider's HTP than with either other solution or in the control hearts, although the pH did not decrease drastically in any group. CP5 was designed to prevent cell swelling and to reduce the uptake of calcium during storage, for which reasons it contains 30 mmol/L glucose and 0.1 mmol/L calcium. The potassium content is somewhat higher and the sodium and magnesium content somewhat lower than in St. Thomas' Hospital solution, with the objective of stabilizing intracellular concentrations of these ions during storage.