St. Thomas' Hospital Solution Research Articles

Mechanoenergetic function and troponin T release following cardioplegic arrest induced by St Thomas' and histidine-tryptophan-ketoglutarate cardioplegia – an experimental comparative study in pigs☆☆☆

The study compares the single dose histidine-tryptophan-ketoglutarate (HTK) cardioplegia to the repeatedly delivered St Thomas' Hospital Solution (STHS) with respect to preservation of left ventricular mechanoenergetics and leakage of troponin T in a porcine experimental model. Fourteen pigs were randomized to a single infusion of 30 ml/kg HTK cardioplegia (n=7) or 500 ml STHS (n=7) followed by 200 ml after 20 and 40 min. After 1 h of aortic cross-clamping on cardiopulmonary bypass (CPB), the pigs were weaned and the hearts reperfused for 4 h. Stroke work (SW) was determined by a conductance catheter in the left ventricle. Myocardial oxygen consumption (MvO(2)) was measured as a function of coronary blood flow and arterial-to-coronary sinus oxygen saturation difference. Troponin T was sampled from the coronary sinus. The slope of the SW-MvO(2) relationship increased by 1.09 (+/-0.53) in the HTK group compared with 0.33 (+/-0.70) in the STHS group following ischemia and 4 h of reperfusion (P=0.04). Troponin T was significantly higher in the HTK group compared with the STHS group (P=0.04). Repeatedly delivered STHS gives better preservation of postischemic mechanoenergetic function and lower troponin T release compared with single dose HTK cardioplegia, indicating improved cardioprotection with STHS.

Improved Myocardial Function After Cold Storage With Preservation Solution Supplemented With a Carbon Monoxide–Releasing Molecule (CORM-3)

Carbon monoxide-releasing molecules (CO-RMs) are pharmacologically active as they protect against cardiac graft rejection and cold ischemia-mediated renal dysfunction. We investigated the cardioprotective role of carbon monoxide (CO) released from CORM-3 against cold ischemia-mediated injury in the heart and evaluated its potential application in the clinical setting of cardiac transplantation. Isolated rat hearts underwent cold ischemic storage for 4 or 6 hours using St Thomas Hospital solution that was supplemented with either CORM-3 (50 mumol/liter) or its inactive counterpart (iCORM-3), which does not release CO. Hearts were then reperfused. Both functional parameters and release of cardiac enzymes were assessed. Addition of CORM-3 to the preservation solution resulted in a significant improvement in systolic and diastolic function as well as coronary flow when compared with hearts treated with iCORM-3. In addition, lower levels of the cardiac enzymes creatine kinase and lactate dehydrogenase were measured in the perfusate of hearts stored with CORM-3. The improved functional recovery and reduced enzyme release after cardiac cold storage with CORM-3, but not iCORM-3, indicate that CO is the main mediator of myocardial protection. Thus, CO-RMs can be used as adjuvants to improve the preservation of hearts for transplantation.

Conservation of phosphorylation state of cardiac phosphofructokinase during in vitro hypothermic hypoxia.

We investigated the metabolic effects of buffering agents alpha-amino-4-imidazole-propionic acid (Histidine), N, N-bis(2-hydroxyethyl)glycine (bicine), N, N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES) on anaerobic energy production (via glycolysis) and conservation of key regulatory enzyme activity, and phosphofructokinase (PFK) throughout prolonged hypothermic hypoxia in porcine hearts. Hearts from 35 to 40 kg pigs were flushed with one of the following five solutions: St. Thomas' Hospital solution (STHS); modified University of Wisconsin (UW) solution; and three solutions containing modified UW plus 90 mM of histidine, bicine, or BES. The hearts were then stored at 4 degrees C for 10 h. After 10 h of hypothermic hypoxia, lactate values were 6.7-12.9 micromol/g higher than control; this reflected an increase in anaerobic end product of 35-67%. The consequences of enhanced anaerobic metabolism were higher ATP, total adenylate, Energy Charge, and ATP/ADP ratios in most of the buffered groups after 4-10 h cold storage; effectiveness of the buffers employed correlated with buffering capacity (BES proved to be the most effective). PFK remained activated throughout most of the 10-h period in hearts stored with buffers and did not undergo the rapid inactivation experienced by hearts stored in STHS. Conservation of PFK integrity with buffering agents was not related to a pH-mediated event; changes in kinetic parameters suggested that this protection was due to an irreversible posttranslational modification, specifically a dephosphorylation event.

Pretreatment of brain dead rabbits with pinacidil before prolonged cold-storage with an extracellular solution alters aortic endothelial function

Objective: Endothelial injury occurs during heart transplantation and contributes to the development of cardiac allograft vasculopathy. We have evaluated in a brain death model in the rabbit whether pre-treatment with the potassium channel opener (PCO) pinacidil before prolonged hypothermic storage with an extracellular solution would improve vascular endothelial recovery. Methods Rabbits were randomized into 4 experimental groups ( n = 8 per group). In the control group (CTRL), abdominal aortic rings were assessed immediately after 90 minutes of anesthesia. In the brain death group (BD), aortic rings were assessed immediately after 90 minutes of brain death. In the STH group, aortic rings taken from brain dead rabbits were stored for 24 hours at 4°C with the extracellular preservation solution of St. Thomas Hospital (STH) before assessment. In the STH + PCO group, the potassium channel opener pinacidil, 1 mg/kg, was administered intravenously to brain dead rabbits 10 minutes before explantation. Aortic rings were then stored for 24 hours at 4°C with the STH solution before evaluation. Brain death was induced by rapid inflation of a sub-durally placed balloon and validated by clinical and electroencephalographic data. Concentration-response curves to acetylcholine (ACH, 10 -9 to 10 -4 mol/liter) and nitroglycerin (NGL, 10 -9 to 10 -5 mol/liter) were constructed in phenylephrinepre-contracted rings. Results ACH evoked a similar concentration-dependent relaxation in the CTRL (E max: 95.8 ± 2.9%; EC 50: -6.86 ± 0.13 log M) and BD groups (E max: 90.8 ± 3.8%; EC 50: -6.75 ± 0.15 log M). The concentration-relaxation curve was shifted rightward in the STH group (E max: 76.7 ± 7.1%; EC 50: -6.75 ± 0.16 log M) in comparison with the CTRL and BD groups, but there were no significant differences in either E max or EC 50 values. After pinacidil pre-treatment, there was a further significant shift to the right of the concentration-relaxation curve to ACH (E max: 77.4 ± 5.0%; EC 50: -6.14 ± 0.19 log M, p < 0.05 vs CTRL, BD and STH). There were no significant differences between groups in the concentration-relaxation curves to NGL in endothelium-intact and endothelium-denuded vascular rings (either E max or EC 50). Conclusion Pre-treatment of brain dead rabbits with pinacidil before prolonged cold-storage with STH solution significantly impaired endothelium-dependent vasorelaxation in comparison to storage with STH solution. The role of PCO pre-treatment in the context of cardiac transplantation needs to be reconsidered.

Effect of amino acid cardioplegia on myocardial metabolism and function of ischemic canine heart.

To evaluate the effect of amino acid cardioplegia on myocardial metabolism and function of ischemic canine heart, canine cardiopulmonary bypass (CPB) model was established and the dog heart was subjected to a 120 min ischemic arrest. Animals were divided into 3 groups, group 1: warm blood cardioplegia induction and terminal perfusion plus 4 C ST. Thomas hospital solution (STS) during ischemia; group 2: warm blood cardioplegia enriched with amino acid (L-asparte and L-glutamate 13 mmol/L each) and STS without amino acid (A. G.) and group 3: both warm blood cardioplegic solution and STS enriched with A. G. . The result demonstrated that the cardiac function of animals in group 2 and 3 had a significantly better recovery after ischemic-re-perfusion. By the end of ischemia the content of myocardial ATP in group 3 was distinctly higher than that in group 1 (P < 0.05), with the release of cardiac enzyme being the least. Myocardial ultra-structure almost remained intact before and after ischemia. Our experiment suggests that the cardioplegia arrest with warm blood and cold crystalloid solution enriched with amino acids could diminish the ischemia-re-perfusion injuries of the heart and enhance the effect of myocardial protection.

Activation of ATP-dependent K + channels enhances myocardial protection due to cold high potassium cardioplegia: A force-frequency relationship study

The hypothesis that nicorandil might enhance myocardial protection due to cold St Thomas' Hospital (STH) solution ([K +] o 16 mmol/1) through opening of cardiac K ATP channels was assessed in isometrically contracting guinea-pig papillary muscles submitted to 120 min of cardioplegic hypoxia followed by 60 min of normothermic reoxygenation. Right ventricular papillary muscles were paced (2 ms, 4 mA) in an organ bath and superfused with oxygenated (O 2 content 16 ml/l) Tyrode's solution (37 °C. The force-frequency relationship in the range 1600-300 ms cycle length (CL) was studied. Preparations were randomized to receive 120 min cold (20 °C), non-oxygenated (O 2 content 5 ml/1) STH solution while continuously stimulated at 1600 ms CL, with: (1) saline (No-additive, n = 12); (2) DMSO 1% (Vehicle, n = 8); (3) nicorandil 1 mmol/l ( n = 8): (4) nicorandil 1 mmol/I plus glibenclamide 1 μmol/l, the latter also given, before STH solution, in Tyrode's solution for 15 min ( n = 8); (5) glibenclamide 1 μmol/l, also circulated, before STH solution, in Tyrode's solution for 15 min ( n = 8); (6) nitroglycerin 100 μmol/l ( n = 4); in addition, we studied: (7) STH solution with no-additive and no-pacing ( n = 4); (8) cold Tyrode's in place of cold STH solution ( n = 4). Isotropic state was investigated by measuring: (i) velocity of developed tension (DT), obtained by dividing DT by time to peak tension; (ii) percentage (from precardioplegia values) velocity changes of DT; (iii) log velocity of DT. Post-cardioplegic recovery of contractility (including force-frequency relationship) was assessed in all preparations: (a) 60 min after reoxygenation with Tyrode's solution; (b) after further 15 min superfusion with the positive isotropic agent dobutamine (10 ymol/1). In parallel experiments, action potential duration (APD) 50% changes induced by nicorandil or glibenclamide plus nicorandil in spontaneously beating atrial ( n = 4) or electrically driven (1600 ms CL) ventricular ( n = 8) tissues during 10 min of STH solution were investigated. Based on force-frequency relationship, at 60 min reoxygenation, in absence of cardioplegia, the lowest recovery of myocardial contractility was seen (stunning). In STH solution, there was moderate to severe stunning, which was unaffected by removing pacing during cardioplegia, or by vehicle or nitroglycerin. In contrast, nicorandil improved recovery of contractility (F =3.01, P = 0.0106). After dobutamine, nicorandil preparations showed the highest positive isotropic response, which was completely offset by glibenclamide (F = 3.47. P = 0.0046). Multivariate statistical analysis (at 1600 ms CL only) showed correlations (0.59<multiple r < 0.71, P = 0.00001) between log percent velocity of DT and the presence of nicorandil (at 60 min reoxygenation: protective) or glibenclamide (after dobutamine: detrimental) whereas nitroglycerin and the other covariates had no effect. In atrial tissue only, nicorandil accelerated substantially the shortening of APD 50% during cardioplegia, an effect prevented by pretreatment with glibenclamide. In conclusion, addition of nicorandil to cold STH solution improved ventricular mechanical recovery after hypoxia and reoxygenation. This effect is likely to be due to K ATP channel opening since it was prevented by glibenclamide. Nicorandil action cannot be attributed to its nitrate-like properties since in this investigation nitroglycerin failed to afford protection. Ventricular myocardial protection seems unrelated to APD 50% shortening.

Studies on the role of sodium/hydrogen exchange system in myocardial ischemia-reperfusion injury.

This study aimed at the exploration of the relationship between Na(+)-H+ exchange system and myocardial ischemia-reperfusion injury (MRI) in an attempt to provide a theoretic basis for the prevention and treatment of MRI. We used the isolated working guinea pig hearts as the experimental model to mimick cardiopulmonary bypass, which included 120 min hypothermic ischemic cardioplegic arrest followed by 60 min normothermic reperfusion. The hearts were divided into 2 groups: the control group receiving St. Thomas' Hospital Solution (STS) and the treated group receiving STS + amiloride, a Na(+)-H+ exchange blocker. The results showed that during reperfusion, [Na+]i and [Ca2+]i overloads, poor recovery of cardiac function, increases in CPK release and OFR generation, reduction of ATP content and serious damage of ultrastructure were seen in group 1; whereas there were no [Na+]i and [Ca2+]i overloads and better recovery of cardiac function accompanied by improved results of biochemical assay and less damage of ultrastructure was found in group 2. Our study indicates that amiloride can inhibit Na(+)-H+ exchange system in cardiac cells during early reperfusion period, which prevents [Na+]i overload produced by Na(+)-H+ exchange, and stops Na(+)-Ca2+ exchange activated by high level of [Na+]i, thus attenuating [Ca2+]i overload caused by Na(+)-Ca2+ exchange and myocardial injury. Therefore, we conclude that Na(+)-H+ exchange blocker, amiloride, can exert significant protective effects on MRI and its use may prove to be a new clinical approach to prevention and cure of MRI.

University of Wisconsin versus St. Thomas' Hospital solution for human donor heart preservation

Prolongation of the safe period of ischemia of the heart is an efficient way to overcome donor organ shortage, as demonstrated in renal and hepatic transplantation. We present the results of a prospective, randomized study comparing preservation with University of Wisconsin solution (UWS) versus St. Thomas' Hospital solution (STS) in clinical heart transplantation. A total of 39 patients were enrolled in the study (n = 20 for UWS and n = 19 for STS). Hemodynamic, electron microscopic, and biochemical evaluation did not reveal any significant differences in postoperative myocardial performance. Only the number of intraoperative defibrillations (0.82 for UWS versus 1.7 for STS) and the rhythm stability after reperfusion ( 13 / 20 UWS hearts versus 6 / 19 STS hearts in sinus rhythm) were significantly different. Heart preservation with UWS and STS appears to be of comparable efficacy at mean ischemic times of less than 4 hours.

Simple 24-Hour Preservation of Rabbit Hearts with Hexanol and Pyruvate Cardioplegia

The effectiveness of a newly developed crystalloid cardioplegic solution containing 4 mM 1-hexanol and 10 mM pyruvate was compared with St Thomas' Hospital solution. After control perfusion with a Langendorff method, rabbit hearts ( n = 7 for each group) were arrested and stored in these solutions (4°C) for 24 h and subsequently reperfused for 45 min. The hexanol solution preserved both left ventricular systolic and diastolic function significantly better than St Thomas' Hospital solution. Developed pressure was significantly higher after preservation with the hexanol solution than with the St Thomas' Hospital solution a left ventricular balloon volumes larger than the mid volume ( P < 0.05). The maximum developed pressure after storage with the hexanol and St Thomas' Hospital solution were 77% and 42% of the maximum control values, respectively. Values for end-diastolic pressure at the maximum ventricular volume were 26.1 ± 9.8 and 66.7 ± 24.6 mmHg for the hexanol and St Thomas' Hospital solution, respectively ( P < 0.05). Creatine kinase release during the first 15 min of reperfusion was significantly lower with the hexanol solution as compared to St Thomas's Hospital solution (28.3 ± 8.3 vs 92.9 ± 52.6 IU/g wet weight, P < 0.05). In conclusion, a hexanol cardioplegic solution may be suitable for long-term cardiac preservation. Further evaluation of the effectiveness and safety of this solution is warranted.

Ultrastructural study comparing the myocardial protective effects of four different infusates (Bretschneider's, St Thomas's, standard Ringer's and blood potassium solutions) in the human heart

Comparative mitochondrial ultrastructural changes during myocardial ischaemic periods have been assessed when using four different solutions: Bretschneider's solution (BS) (K+ = 10 mEq/l) at 4°C; St Thomas's hospital solution (STS) (K+ = 20 mEq/l) at 4°C; standard Ringer's solution (SRS) (K+ = 2.7 mEq/l) at 4°C; blood potassium cardioplegic solution (BPS) (K+ = 21 mEq/l) at 15°C. BS (n = 8), STS (n = 10), SRS (n = 8) and BPS (n = 8) were infused in 34 patients undergoing aortic valve replacement (n = 17) or aortocoronary bypass grafting (n = 17), after aortic crossclamping, either in the aorta or in both coronary ostia, until the septal myocardial temperature reached 10-13°C for crystalloid solutions or 15°C for blood cardioplegia. Myocardial biopsies were taken from the left ventricular apex, on a beating heart, at the beginning and end of bypass. To assess the degree of ischaemic injury, an ultrastructural evaluation of the mitochondria was done and four histological classes have been defined: class I- dense matrix and cristae; class II — occasional mitochondrial swelling; class III — decrease in matrix density with extensive swelling; class IV — severe swelling and/or rupture of matrix. This study showed that: (1) only the St Thomas's and Bretschneider's solutions provide a rapid electromechanical asystole; (2) isolated hypothermic crystalloid solution with low potassium concentration (standard Ringer) is not sufficient either to induce cardiac arrest or to prevent detrimental mitochondrial changes; (3) Bretschneider's solution appears to provide the best ultrastructural mitochondrial preservation during myocardial ischaemia.