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

Creatine kinase and troponin after myocardial preservation using HTK solution (Custoidol) for clinical heart transplantation

Myocardial preservation by Bretschneider histidine-tryptophan-ketoglutarate (HTK) solution (Custoidol) was studied in transplanted patients. Post-operative creatine kinase (CK), CK-MB and troponin I were higher in patients with an ischemic time of >or=4 hours; however, values were within the acceptable range for clinical heart transplantation.

Pretransplant rinse of hearts preserved with colloid-free UW solution and more effective heart preservation: studies in a rat abdominal heart transplant model

BACKGROUND

University of Wisconsin solution (UW) provides effective heart preservation under hypothermic conditions, but it can be deleterious at warmer temperatures. Re-warming during the implantation of the graft may be a problem. This study examined the damaging effect of peri-operative warm ischemia in a transplant setting and recovery from such damage. The amelioration of damage by rinsing the graft before re-warming and transplantation was also examined.

METHODS

Rat donor hearts were preserved for 2 hr (0 degrees C) as follows: Series A was preserved with colloid-free UW (MUW), St. Thomas' solution (ST), or calcium-supplemented MUW (MUW+Ca) followed by either transplantation or warming (22 degrees C) for 10 min before transplantation. Series B was preserved with MUW, rinsed with fresh MUW, ST, MUW+Ca, or low-potassium MUW before warming and transplantation. All heart isografts were transplanted heterotopically with an indwelling left intraventricular balloon-tipped catheter. Graft function was measured 1 and 7 days after transplantation.

RESULTS

Grafts re-warmed rapidly during implantation. Function (left ventricular developed pressure, contractility, and relaxation) was significantly and persistently diminished in MUW-preserved grafts subjected to additional warming before transplantation. Preservation with ST was less effective than MUW despite being unaffected by warming. Preservation with MUW+Ca and rinsing with fresh MUW or ST before re-warming allowed recovery of function within 7 days despite significantly diminished function on day 1.

CONCLUSION

This study demonstrated that an increase in the peri-transplant warm ischemic period was detrimental when hearts were preserved with MUW. Preservation with calcium-supplemented MUW or rinsing the heart with fresh MUW or ST before transplantation ameliorated this damage.

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

Isolated canine hearts were preserved for 12 h at 5 degrees 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 of reperfusion, the myocardial adenosine triphosphate concentration and left ventricular systolic and diastolic function were preserved better in groupl than in group 2. Myocardial mitochondrial ultrastructural integrity was identical in the two groups. These results suggested that in a 12-h heart preservation, nondepolarizing solution administered in multidose fashion protects the myocardium from the deleterious effects of hypothermia and cardioplegia better than UW solution.

Cyclic nucleotide analogs as biochemical tools and prospective drugs

Cyclic AMP (cAMP) and cyclic GMP (cGMP) are key second messengers involved in a multitude of cellular events. From the wealth of synthetic analogs of cAMP and cGMP, only a few have been explored with regard to their therapeutic potential. Some of the first-generation cyclic nucleotide analogs were promising enough to be tested as drugs, for instance N(6),O(2)'-dibutyryl-cAMP and 8-chloro-cAMP (currently in clinical Phase II trials as an anticancer agent). Moreover, 8-bromo and dibutyryl analogs of cAMP and cGMP have become standard tools for investigations of biochemical and physiological signal transduction pathways. The discovery of the Rp-diastereomers of adenosine 3',5'-cyclic monophosphorothioate and guanosine 3',5'-cyclic monophosphorothioate as competitive inhibitors of cAMP- and cGMP-dependent protein kinases, as well as subsequent development of related analogs, has proven very useful for studying the molecular basis of signal transduction. These analogs exhibit a higher membrane permeability, increased resistance against degradation, and improved target specificity. Furthermore, better understanding of signaling pathways and ligand/protein interactions has led to new therapeutic strategies. For instance, Rp-8-bromo-adenosine 3',5'-cyclic monophosphorothioate is employed against diseases of the immune system. This review will focus mainly on recent developments in cyclic nucleotide-related biochemical and pharmacological research, but also highlights some historical findings in the field.

Improved cardiac preservation by the addition of nitroglycerine to colloid-free University of Wisconsin solution (MUW)

BACKGROUND

This study examines whether the addition of nitroglycerine, a known coronary vasodilator and nitric oxide donor, to colloid-free University of Wisconsin solution will improve and extend cardiac preservation.

METHODS

Rat hearts were flushed and stored in colloid-free University of Wisconsin solution with or without the addition of nitroglycerine for 12, 16 or 20 hours at 0 degrees C before heterotopic transplantation with an indwelling externalized intraventricular balloon-tipped catheter. One and 7 days after transplantation of the heart the catheter was connected to a pressure transducer and quantitative functional studies were performed.

RESULTS

After 12 hours preservation with nitroglycerine in colloid-free University of Wisconsin solution 6/6 grafts continued to beat for 7 days compared to 3/6 without nitroglycerine. After 16 hours preservation the addition of nitroglycerine 5/7 hearts continued to beat for 7 days compared to 0/6 without nitroglycerine (p < .05). Only 1/6 hearts beat for 7 days after 20 hours preservation with nitroglycerine. On Days 1 and 7, the left ventricular developed pressure (LVDP), contractility (max dP/dt) and rate of relaxation (peak -dP/dt) of 12 hour preserved hearts was better (p < .05) when nitroglycerine was present. The function of hearts preserved with the addition of nitroglycerine was similar after 12 and 16 hours preservation.

CONCLUSION

Nitroglycerine is a valuable additive to colloid-free University of Wisconsin solution, extending effective preservation of the rat heart to 16 hours and significantly improving left ventricular function after 12 and 16 hours preservation. The addition of nitroglycerine, however, did not extend preservation to 20 hours.

Organ preservation solutions in heart transplantation--patterns of usage and related survival

Despite experimental advantages for certain heart preservation solutions (HPS), their clinical popularity and related survival are uncertain. We surveyed all active UNOS heart transplant centers to determine their HPS. HPS survival benefits were tested using the UNOS heart transplant registry. Centers used from 1 to 3 types of 167 solutions. Of these formulations, 55.1% were commonly cited solutions. The other (custom) mixtures differed from those usually reported. All solutions were classified as intracellular (I, [Na++] < 70 mEq/L) or extracellular (E, [Na++] > or = 70 mEq/L). Significant variations in solution usage were observed among major regions of U.S. transplant activity (Northeast [NE], Southeast [SE], and West [W], P < 0.001). For example, 62.5% of University of Wisconsin (UW) and 49.3% of "Other" usage occurred in the NE; 75% of Roe and 100% of Collins usage occurred in the SE; and 100% of Krebs and 46% of Stanford usage occurred in the W. Logistic regression analyses of 9401 patients who underwent transplantation from 10/87 to 12/92 showed a reduction in the adjusted one month mortality odds ratio for grafts preserved with I rather than E solutions (0.85, P < 0.05). Compared with the most commonly used solution, Plegisol (20.1% of cases), the following adjusted odds ratios for one-month mortality were observed: UW, 1.09 (ns); Stanford, 0.80 (P < 0.10); Roe, 0.36 (P < 0.001); Collins, 0.82 (ns); Krebs, 0.14 (P < 0.01). Using the same one month comparison with Plegisol, 16.8% of grafts that received Custom-I solutions also fared better (0.75, P < 0.05) than the 21.4% that had Custom-E mixtures (0.91, ns). HPS usage varies greatly and there are regional preferences. There may be early survival benefits for certain intracellular HPS--however, further study is warranted to explore such relationships.

Discriminating between preservation and reperfusion injury in human cardiac allografts using heart weight and left ventricular mass

BACKGROUND

Myocardial edema caused by injury during preservation or reperfusion can affect cardiac function after heart transplantation. This study was designed to distinguish these forms of injury in human allografts.

METHODS AND RESULTS

In 15 donor hearts preserved in University of Wisconsin solution, heart weight (HW) was obtained immediately after explantation and after transport before implantation. Left ventricular mass (LVM) was calculated separately in 18 patients with the use of epicardial two-dimensional echocardiograms obtained both before explantation from the donor and after transplantation and weaning from cardiopulmonary bypass. While changes in LVM could be due to preservation or reperfusion injury, changes in HW can only be due to edema occurring during transport. HW averaged 339 +/- 24 g (mean +/- SE) before and 340 +/- 24 g after transport (P = NS); however, LVM increased 14 g, from 164 +/- 8 to 178 +/- 11 g (P < .05, paired t test). LVM increased in 10 of 18 patients (56%). No correlation was demonstrated between duration of ischemia (mean, 172 +/- 13 minutes) and changes in HW or LVM. Two patients died as a result of primary graft failure. In the first, HW increased 54 g, 2 SD above the mean. In the second, LVM increased 66 g, 2 SD above the mean, but HW changed minimally.

CONCLUSIONS

While current preservation methods result in minimal change in HW during transport, reperfusion injury frequently increases LVM. LVM determination by two-dimensional echocardiography may prove valuable in detecting allograft injury.

Cardiac preservation is enhanced in a heterotopic rat transplant model by supplementing the nitric oxide pathway

Nitric oxide (NO) is a novel biologic messenger with diverse effects but its role in organ transplantation remains poorly understood. Using a porphyrinic microsensor, the first direct measurements of coronary vascular and endocardial NO production were made. NO was measured directly in the effluent of preserved, heterotopically transplanted rat hearts stimulated with L-arginine and bradykinin; NO concentrations fell from 2.1 +/- 0.4 microM for freshly explanted hearts to 0.7 +/- 0.2 and 0.2 +/- 0.08 microM for hearts preserved for 19 and 38 h, respectively. NO levels were increased by SOD, suggesting a role for superoxide-mediated destruction of NO. Consistent with these data, addition of the NO donor nitroglycerin (NTG) to a balanced salt preservation solution enhanced graft survival in a time- and dose-dependent manner, with 92% of hearts supplemented with NTG surviving 12 h of preservation versus only 17% in its absence. NTG similarly enhanced preservation of hearts stored in University of Wisconsin solution, the clinical standard for preservation. Other stimulators of the NO pathway, including nitroprusside, L-arginine, or 8-bromoguanosine 3',5' monophosphate, also enhanced graft survival, whereas the competitive NO synthase antagonist NG-monomethyl-L-arginine was associated with poor preservation. Likely mechanisms whereby supplementation of the NO pathway enhanced preservation included increased blood flow to the reperfused graft and decreased graft leukostasis. NO was also measured in endothelial cells subjected to hypoxia/reoxygenation and detected based on its ability to inhibit thrombin-mediated platelet aggregation and serotonin release. NO became undetectable in endothelial cells exposed to hypoxia followed by reoxygenation and was restored to normoxic levels on addition of SOD. These studies suggest that the NO pathway fails during preservation/transplantation because of formation of oxygen free radicals during reperfusion, which quench available NO. Augmentation of NO/cGMP-dependent mechanisms enhances vascular function after ischemia and reperfusion and provides a new strategy for transplantation of vascular organs.

Early cardiac allograft failure after orthotopic heart transplantation

Early cardiac graft failure has been reported to occur in 4-25% of patients undergoing orthotopic heart transplantation. To further elucidate the characteristics and prognosis of patients with graft failure, we retrospectively identified 10 patients from a series of 212 consecutive recipients with catastrophic graft dysfunction in the absence of acute cellular rejection, right ventricular failure secondary to pulmonary hypertension and technical factors. We present a case report and the experience from one transplant center, a review of the literature and possible strategies for the management of early graft failure. Mean onset of graft failure was 6.5 days (range intraoperative to 23 days). Multivariable analysis revealed a longer total ischemic time in patients with early graft dysfunction (200 +/- 14 vs. 166 +/- 4 min). No episodes of hyperacute rejection were observed. Pathologic changes noted on biopsy or autopsy included ischemia in 9 and vascular rejection in 1. The mortality at 60 days was 50%. Early use of aggressive mechanical and pharmacological support is described and appears to be important for graft salvage.

Restoration of the cAMP second messenger pathway enhances cardiac preservation for transplantation in a heterotopic rat model

Current organ preservation strategies subject graft vasculature to severe hypoxia (PO2 approximately 20 Torr), potentially compromising vascular function and limiting successful transplantation. Previous work has shown that cAMP modulates endothelial cell (EC) antithrombogenicity, barrier function, and leukocyte/EC interactions, and that hypoxia suppresses EC cAMP levels. To explore the possible benefits of cAMP analogs/agonists in organ preservation, we used a rat heterotopic cardiac transplant model; dibutyryl cAMP added to preservation solutions was associated with a time- and dose-dependent increase in the duration of cold storage associated with successful graft function. Preservation was also enhanced by 8-bromo-cAMP, the Sp isomer of adenosine 3',5'monophosphorothioate, and types III (indolidan) and IV (rolipram) phosphodiesterase inhibitors. Neither butyrate alone nor 8-bromoadenosine were effective, and the cAMP-dependent protein kinase antagonist Rp isomer of adenosine 3',5'monophosphorothioate prevented preservation enhancement induced by 8-bromo-cAMP. Grafts stored with dibutyryl cAMP demonstrated a 5.5-fold increase in blood flow and a 3.2-fold decreased neutrophil infiltration after transplantation. To explore the role of cAMP in another cell type critical for vascular homeostasis, vascular smooth muscle cells were subjected to hypoxia, causing a time-dependent decline in cAMP levels. Although adenylate cyclase activity was unchanged, diminished oxygen tensions were associated with enhanced phosphodiesterase activity (59 and 30% increase in soluble types III and IV activity, respectively). These data suggest that hypoxia or graft ischemia disrupt vascular homeostasis, at least in part, by perturbing the cAMP second messenger pathway. Supplementation of this pathway provides a new approach for enhancing cardiac preservation, promoting myocardial function, and maintaining vascular homeostatic properties.

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.

Comparison of intermittent injection of nondepolarizing solution with a single flush of UW solution for donor heart preservation

Isolated canine hearts were preserved for 6 h at 5 degrees C followed by normothermic reperfusion for 2 h. The dogs were divided into two groups of nine hearts each; group 1 received a nondepolarizing preservation solution in multidose, and group 2 received a single flush of University of Wisconsin (UW) solution. Serum MB-CK and mitochondrial aspartate aminotransferase (m-AAT) concentrations and calcium overload during reperfusion were lower in group 1 than in group 2. At the end of reperfusion, myocardial ATP and total adenine nucleotide concentrations were higher and mitochondrial morphology appeared more intact in group 1 than in group 2. Left ventricular diastolic function was preserved better in group 1 than in group 2. These results suggest that in 6-h heart preservation, a nondepolarizing solution applied in multidose fashion protects the myocardium from the deleterious effects of hypothermia and cardioplegia better than a single flush of UW solution.

Six-hour preservation of the isolated working rat heart improved with University of Wisconsin solution

University of Wisconsin (UW) solution was compared with modified St. Thomas cardioplegic solution for 6-hour preservation of isolated working rat hearts. The hearts (9 in each group) were arrested with the respective solution and stored, still cannulated, for 6 hours at 4 degrees C. After retrograde reperfusion for 30 minutes, antegrade perfusion was begun at constant left atrial and aortic pressures. Following 25 minutes of antegrade perfusion the hemodynamic recovery of the UW-preserved hearts was superior to that of the other hearts (cardiac output 46.0 +/- 4.8% of the preischemic control values in the UW group and 10.0 +/- 6.0% in the St. Thomas group, p < 0.01). The adenosine triphosphate content was significantly higher in the UW-preserved hearts (18.8 +/- 0.9 vs. 14.7 +/- 1.6 mumol/g dry weight, p < 0.05). No significant intergroup difference was found in aspartate aminotransferase leak or tissue glycogen. The study demonstrated both better function and enhancement of high-energy phosphates with UW solution vs. modified St. Thomas solution in isolated rat hearts, although without difference in enzyme leakage or tissue glycogen, after 6-hour preservation.