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.     

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.     

含钾通道开放剂的HTK液对大鼠心功能以及线粒体结构和功能的影响

目的 观察含钾通道开放剂的供心保存液对心功能以及能量代谢、线粒体呼吸酶活性及超微结构的影响.方法 将SD大鼠分为HTK组、Pi组、5HD组、1098组和5HD+1098组.切取SD大鼠心脏,建立Langendorff灌注模型,平衡10 min,然后按分组进行如下处理:HTK组心脏以Histidine-Tryptophan-Ketoglutarate液(HTK液)停搏;Pi组心脏以含0.5 mmol/L吡那地尔(Pi)的HTK液停搏;1098组心脏以含0.5 mmol/L Pi和100 μmol/L HMR1098的HTK液停搏;5HD组心脏以含0.5 mmol/L Pi和100 μmol/L五羟葵酸(5HD)的HTK液停搏;5HD+1098组心脏以含0.5 μmol/L Pi、100 μmol/L 5HD和100μmol/L HMR1098的HTK液停搏.停搏后,将心脏置于各组相应的液体(4℃)中保存8 h,然后用含氧的37℃克-亨液(K-H液)再灌注60 min.观察各组平衡末、保存末、再灌注末时的心功能、线粒体呼吸酶活性、心肌ATP含量及心肌细胞线粒体超微结构的改变.结果 Pi组保存末、再灌注末的心功能(心率、左心室舒张末压、左心室发展压和冠状动脉流量)、心肌线粒体呼吸酶(NADH氧化酶、琥珀酸氧化酶、细胞色素C氧化酶)活性及ATP含量均优于其他各组(P<0.01或P<0.05),同时线粒体的结构改变也最轻.结论 含Pi的HTK液能改善大鼠心脏保存效果;Pi对能量状态的维持以及对线粒体结构与功能的保护可能是其心肌保护的重要机制.     

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)     

Captopril improves oxygen and glucose extraction in pig hearts during reperfusion after cold cardioplegic storage

The purpose of this study was to evaluate the haemodynamic and metabolic effects of captopril during reperfusion of pig hearts following 360 min global hypothermic cardioplegia and storage (HCS). The hearts were perfused with one litre of cold crystalloid cardioplegia (Bretschneider solution no. 3), excised and stored in saline at 4 degrees C for 360 min. The hearts were then reperfused with blood in a modified Langendorff model for 60 min. Left ventricular function, myocardial blood flow, and arteriovenous differences in oxygen, glucose and lactate were monitored intraoperatively and during reperfusion. Two groups of hearts were studied. Group I (captopril treated, n = 9): the pigs were pre-medicated with increasing oral doses of captopril for 3 weeks (12.5 mg-150 mg daily) and an intravenous dose (25 mg) upon arrival at the laboratory. Captopril was added to the cardioplegia (1000 microg/l) and to the reperfusion media (1000 microg/l). Group II (controls, n = 8): the pigs were given no premedication, captopril-free cardioplegia and the hearts were reperfused with captopril-free blood. Captopril increased myocardial oxygen and glucose extraction during reperfusion (p < 0.05 for both) while lactate remained unchanged after 360 min HCS. Treatments with captopril increased developed left ventricular pressure (DLVP) and relaxation (-dP/dtmax) during reperfusion (p < 0.05 for both), while contractility (+dP/dtmax) was unchanged. Heart rate was reduced in captopril-treated hearts (p < 0.05) while myocardial blood flow (MBF) was similar in the two groups. Captopril administration prior to and during HCS and postcardioplegic reperfusion improves oxygen and glucose extraction in large spontaneously beating porcine hearts during reperfusion. The underlying mechanisms seem to involve metabolic modulation, since myocardial uptake of oxygen and glucose was increased in the absence of changes in myocardial blood flow.     

Orthotopic transplantation of pig hearts harvested after 30 min of normothermic ischemia: controlled reperfusion with blood cardioplegia containing the Na-H-exchange inhibitor HOE 642

Objectives: The aim of our study was to develop a surgical technique for a successful transplantation of hearts harvested after 30 min of normothermic ischemia without donor pretreatment. Successful transplantation of ischemic compromised hearts could help to expand the severely limited donor pool. We used the pig model because this species is very susceptible to myocardial ischemia. Na⁺-H⁺-exchange (NHE) inhibitors have shown excellent protective properties in several in vitro and in vivo models of myocardial ischemia and reperfusion. Methods: In group I (n=12) hearts were harvested after 30 min of normothermic ischemia following cardiac arrest induced by exsanguination. Hearts were perfused with warm blood cardioplegia and transplanted orthotopically. In group II (n=9) controlled reperfusion with cold leucocyte-depleted blood cardioplegia was performed after 30 min of normothermic ischemia. In group III (n=8) the same procedure was performed as in group II but blood cardioplegia contained 1 mmol/l HOE 642. Results: In group I massive myocardial oedema was observed and none of the animals could be weaned from cardiopulmonary bypass (CPB). In contrast, all animals in groups II and III could be weaned from CPB with low dose inotropic support. In groups II and III the contractility of the hearts, expressed as maximal left and right ventricular stroke work index was significantly impaired after transplantation as compared with the preoperative value. Supplementation of blood cardioplegia with HOE 642 resulted in a significantly better recovery of the LVSWImax (Group II vs. III). Conclusions: Successful transplantation of pig hearts is possible after 30 min of normothermic ischemia without donor pretreatment if a controlled reperfusion with cold leucocyte-depleted blood cardioplegia is performed. HOE 642 given during reperfusion only improves posttransplant left ventricular function.     

A comparative study of the most widely used solutions for cardiac graft preservation during hypothermia.

BACKGROUND: Reports conflict on the benefits of preservative solutions. We investigated the efficacy of the most widely used cardioplegic solutions by comparing extracellular solutions such as Celsior solution, St. Thomas Hospital solutions 1 and 2 (STH-1, STH-2), the modified University of Wisconsin solution (UW-1), Lyon Preservation solution (LYPS) from our laboratory, and intracellular solutions such as standard University of Wisconsin solution (UW), Bretschneider solution (HTK), Stanford solution (STF), and Euro-Collins solution (EC). METHODS: Male rats (n = 110) were randomized into 11 groups: LYPS, Celsior, STH-1, STH-2, UW-1, UW, HTK, STF, EC, and normal saline solution groups, and a control group. All hearts, except controls, were preserved by cold storage (8 hours at 4 degrees C) in the various solutions. We used an isolated non-working-heart model and biopsy specimens to assess heart preservation (n = 5/group). RESULTS: Hearts stored in the EC and saline solutions had poor left ventricular developed pressure (LVDP) x heart rate (HR) (1,407.5 +/- 154 and 1,390 +/- 439 mm Hg/mn, respectively). In contrast, hearts stored in LYPS and Celsior had a LVDP x HR close to control hearts (31,349 +/- 1,847, 27,620 +/- 1,207, and 36,627 +/- 1,322 mm Hg/mn, respectively), whereas hearts stored in STH-1, STH-2, UW-1, UW, HTK, and STF had intermediate functional response (14,278 +/- 2,176, 12,402 +/- 1,571, 11,428 +/- 1,629, 11,603 +/- 2,521, 7,045 +/- 537, and 7,086 +/- 1,206 mm Hg/mn, respectively). Hearts preserved with STH-2, UW, HTK, STF, EC, and saline solution showed significantly increased release of creatine kinase and lactate dehydrogenase than did control hearts or hearts preserved in Celsior, LYPS, STH-1, and UW-1. The energetic charge (EC = [(0.5 adenosine diphosphate + adenosine triphosphate) / (adenosine triphosphate + adenosine diphosphate + adenosine monophosphate)]) in STH-2, UW, HTK, STF, EC, and saline groups was significantly lower (p < 0.05) than in the other groups. CONCLUSION: Extracellular-type solutions provided better preservation than did intracellular-type solutions. However, UW and UW-1 (intracellular- and extracellular-type solutions) provided equivalent preservation of cardiac function. Preservation quality may be attributed to calcium, often added to extracellular solutions. Among extracellular solutions, Celsior and LYPS solution showed comparable efficacy on left ventricular function and seemed to offer better preservation than the other solutions tested in this study.     

Protein kinase C isoform-dependent myocardial protection by ischemic preconditioning and potassium cardioplegia

OBJECTIVE: Ischemic preconditioning combined with potassium cardioplegia does not always confer additive myocardial protection. This study tested the hypothesis that the efficacy of ischemic preconditioning under potassium cardioplegia is dependent on protein kinase C isoform. METHODS: Isolated and crystalloid-perfused rat hearts underwent 5 cycles of 1 minute of ischemia and 5 minutes of reperfusion (low-grade ischemic preconditioning) or 3 cycles of 5 minutes of ischemia and 5 minutes of reperfusion (high-grade ischemic preconditioning) or time-matched continuous perfusion. These hearts received a further 5 minutes of infusion of normal buffer or oxygenated potassium cardioplegic solution. The isoform nonselective protein kinase C inhibitor chelerythrine (5 micromol/L) was administered throughout the preischemic period. All hearts underwent 35 minutes of normothermic global ischemia followed by 30 minutes of reperfusion. Isovolumic left ventricular function and creatine kinase release were measured as the end points of myocardial protection. Distribution of protein kinase C alpha, delta, and epsilon in the cytosol and the membrane fractions were analyzed by Western blotting and quantified by a densitometric assay. RESULTS: Low-grade ischemic preconditioning was almost as beneficial as potassium cardioplegia in improving functional recovery; left ventricular developed pressure 30 minutes after reperfusion was 70 +/- 15 mm Hg (P <.01) in low-grade ischemic preconditioning and 77 +/- 14 mm Hg (P <.001) in potassium cardioplegia compared with values found in unprotected control hearts (39 +/- 12 mm Hg). Creatine kinase release during reperfusion was also equally inhibited by low-grade ischemic preconditioning (18.2 +/- 10.6 IU/g dry weight, P <.05) and potassium cardioplegia (17.6 +/- 6.7 IU/g, P <.01) compared with control values. However, low-grade ischemic preconditioning in combination with potassium cardioplegia conferred no significant additional myocardial protection; left ventricular developed pressure was 80 +/- 17 mm Hg, and creatine kinase release was 14.8 +/- 11.0 IU/g. In contrast, high-grade ischemic preconditioning with potassium cardioplegia conferred better myocardial protection than potassium cardioplegia alone; left ventricular developed pressure was 121 +/- 16 mm Hg (P <.001), and creatine kinase release was 8.3 +/- 5.8 IU/g (P <.05). Chelerythrine itself had no significant effect on functional recovery and creatine kinase release in the control hearts, but it did inhibit the salutary effects not only of low-grade and high-grade ischemic preconditioning but also those of potassium cardioplegia. Low-grade ischemic preconditioning and potassium cardioplegia enhanced translocation of protein kinase C alpha to the membrane, whereas high-grade ischemic preconditioning also enhanced translocation of protein kinase C delta and epsilon. Chelerythrine inhibited translocation of all 3 protein kinase C isoforms. CONCLUSIONS: These results suggest that myocardial protection by low-grade ischemic preconditioning and potassium cardioplegia are mediated through enhanced translocation of protein kinase C alpha to the membrane. It is therefore suggested that activation of the novel protein kinase C isoforms is necessary to potentiate myocardial protection under potassium cardioplegia.     

Enhanced myocardial protection with adenosine

This study was undertaken to investigate whether adenosine administered during cardioplegic arrest could enhance myocardial protection and improve recovery of function after ischemia. Isolated perfused rabbit hearts were subjected to 120 minutes of hypothermic (32 degrees C) multidose cardioplegia-induced ischemia. Control hearts (n = 23) received modified St. Thomas's cardioplegia, and the remaining hearts received cardioplegia with either 100 microM (n = 11), 200 microM (n = 11), or 400 microM (n = 11) adenosine. After ischemia and 45 minutes of reperfusion, left ventricular contractility was superior in all groups of adenosine-treated hearts compared with control hearts. Furthermore, there was a significant incremental increase in functional recovery with increasing dose of adenosine. Postischemic diastolic stiffness was significantly better in all adenosine groups compared with controls. No differences were noted in coronary flow or myocardial water content between adenosinetreated and control hearts. These data demonstrate that adenosine administered in these concentrations provides myocardial protection and improved recovery of both systolic and diastolic function after global ischemia, presumably metabolically by reducing depletion of adenosine triphosphate or enhancing repletion of adenosine triphosphate and enabling improved postischemic recovery.     

Effects of supplemental L-arginine during warm blood cardioplegia.

OBJECTIVES: Effects of supplemental L-arginine, nitric oxide precursor, during warm blood cardioplegia were assessed in the blood perfused isolated rat heart. METHODS: The isolated hearts were perfused with blood at 37 degrees C from a support rat. After 20 minutes of aerobic perfusion, the hearts were arrested for 60 minutes with warm blood cardioplegia given at 20-minute intervals. This was followed by 60 minutes of reperfusion. The hearts were divided into the following three groups according to the supplemental drugs added to the cardioplegic solution. The control group (n = 10) received standard warm blood cardioplegia. The L-ARG group (n = 10) received warm blood cardioplegia supplemented with L-arginine (3 mmol/l). The L-NAME group (n = 10) received warm blood cardioplegia supplemented with L-arginine (3 mmol/l) and L-nitro-arginine methyl ester, a competitive inhibitor of nitric oxide synthase (1 mmol/l). After 60 minutes of cardioplegic arrest, cardiac function, myocardial metabolism and myocardial release of circulating adhesion molecules were measured during reperfusion. RESULTS: Left ventricular end-diastolic pressure was significantly lower (p<0.05) in the L-ARG group than in the control group and the L-NAME group during reperfusion. Isovolumic left ventricular developed pressure, dp/dt and coronary blood flow were significantly greater (p< 0.05) in the L-ARG group during reperfusion. The L-ARG group resulted in early recovery of lactate metabolism during reperfusion. Myocardial release of circulating intercellular adhesion molecule-1 (ICAM-1) and E-selectin were significantly less (p<0.05) in the L-ARG group at 15 minutes of reperfusion. CONCLUSIONS: The results suggest that augmented nitric oxide by adding L-arginine to warm blood cardioplegia can preserve left ventricular function and ameliorate endothelial inflammation. The technique can be a novel cardioprotective strategy in patients undergoing cardiac surgery.