Myocardial preservation in clinical cardiac transplantation

Myocardial Preservation in Clinical Cardiac Transplantation S.M. Wildhirt, M. Weis, C. Schulze, N. Conrad, G. Rieder, D.H. Boehm, B. Meiser, A. Kornberg, H. Reichenspurner, W. von Scheidt, and B. Reichart

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PTIMAL myocardial protection remains a primary goal in clinical and experimental cardiac transplantation. A variety of formulas and solutions have been developed and tested in recent years. However, a “gold standard” has not been achieved and various preservation solutions are currently used.1–5 One problem may be objectifying the potency of the solution to prevent myocardial injury during cold ischemia, which will be evident functionally during reperfusion. In addition, many donor- and recipient-dependent factors influence the functional status of the allograft, which leads to difficulties in the assessment of protective effects of a given solution. Finally, the important question regarding short- or long-term effects one solution might have with respect to myocardial function and the development of chronic rejection remains unsolved. From recent clinical and experimental evidence it appears that improved protection is documented by reduction of reperfusion injury. This includes reduction of oxygenderived free-radical–induced injury, prevention of contracture by calcium overload, prevention of tissue edema, preservation of endothelial integrity, and reduction of endothelial cell activation.6 –11 All of these factors, among others, may contribute to the process of chronic rejection by early enhanced activation of the coronary endothelium.12 In the present study we analyzed the clinical course of transplant recipients receiving allografts preserved with either University of Wisconsin or Celsior preservation solution with regard to hemodynamics and endothelial function of the coronary microvasculature. METHODS Donor hearts were perfused with either UW solution (1000.0 mL; n 5 20; Belzer UW, DuPont Pharma, Bad Homburg, Germany) or with Celsior preservation solution (1000.0 mL; n 5 21, Pasteur Merieux, Lyon, France). Patients were kept on standard immunosuppressive therapy, which included either tacrolimus (FK 506) or cyclosporine in combination with either mycophenolate mofetil or azathioprine and prednisolone. Except for the immunosuppressive regime all medications were discontinued 12 to 24 hours prior to data and sample collection. Early postoperative cardiac function (PODs 1 to 5) was determined by the amount of catecholamines and vasodilators required to maintain mean arterial pressure (MAP) between 80 and 100 mm Hg, with systolic pressures between 110 and 150 mm Hg and diastolic pressures between 65 and 90 mm Hg. In addition, left-ventricular filling pressures were maintained between 10 and © 1999 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010

15 mm Hg. Systemic vascular resistance was maintained between 800 and 1500 dynes z s z cm25 and pulmonary vascular resistance at ,300 dynes z s z cm25. Mean dosages of catecholamines (epinephrine, norepinephrine, dobutamine, and dopamine) or vasodilators, including nitroglycerine, enoximone, and epoprostenol (PGI2), required for maintenance of predefined hemodynamics, were calculated within the first 120 hours after transplantation. Comparable values for MAP, systolic and diastolic pressures, as well as systemic and pulmonary vascular resistance were found within this time frame. Coronary flow velocity reserve (CFVR) was assessed endothelium independent by intracoronary adenosine infusion (Ad; 80.0 and 160.0 mg/min over 5 minutes each) and endothelium dependence by infusion of acetylcholine (Ach; 1.0 and 30.0 mg/min over 5 minutes each). Polymerase chain reaction (RT-PCR) for detection of NOS and endothelin gene expression was performed in endomyocardial biopsy samples, as reported previously.13 Determination of endothelin (femtomoles per milliliter) and nitrite (micromoles per liter) plasma levels have been described in detail elsewhere.13,14

RESULTS

Patients who received hearts preserved with Celsior solution required significantly more catecholamines and vasodilators to achieve a hemodynamic status within the predefined range; these included dobutamine, enoximone, and nitroglycerine. This occurred despite comparable pretransplant pulmonary vascular resistance (PVR) and transpulmonary gradients (TPG) in patients with Celsior-preserved hearts when compared with UW patients. No differences were noted among groups with respect to coronary microvascular response (flow velocity reserve) to adenosine (160 mg/min; Celsior: 2.48 6 0.1 vs UW: 2.6 6 0.2, P 5 NS) and acetylcholine (30 mg/min; Celsior: 2.51 6 0.16 vs UW: 2.7 6 0.2, P 5 NS). However, it appeared that in Celsior-preserved, but not in UW-perfused hearts, total ischemic time was associated with impaired CFVR to Ach. Densitometric analysis showed a significant difference in myocardial inducible NOS (iNOS) From the Departments of Cardiac Surgery, Cardiology, Surgical Research, Ludwig-Maximilians University, Munich, Germany. Address reprint requests to Dr Stephen M. Wildhirt, Department of Cardiac Surgery, Ludwig-Maximilians University, Marchioninistrasse 15, 81377 Munich, Germany. E-mail: wildhirt @hch.med.uni-muenchen.de. 0041-1345/99/$–see front matter PII S0041-1345(98)01481-X 147

Transplantation Proceedings, 31, 147–148 (1999)

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gene expression (Celsior: 1.9 6 0.2; UW: 1.3 6 0.2; P 5 .04). In addition, significantly higher endothelin (ET) gene expression was noted in hearts preserved with Celsior solution (Celsior: 2.9 6 0.2; UW: 2.1 6 0.3; P 5 .01). Overall, ET plasma levels in both groups were significantly higher when compared with healthy subjects, as shown previously by others.15 However, CS ET levels did not differ between groups (Celsior: 10.0 6 0.4; UW: 9.7 6 0.7; P 5 NS) and levels were significantly lower in coronary sinus when compared with aortic values, indicating transcardiac ET net extraction (Celsior aorta: 11.8 6 0.38; CS: 10.0 6 0.4; P 5 .0003 and UW aorta: 12.6 6 0.9; CS: 9.7 6 0.7; P 5 .003). In addition, there was a significant increase in transcardiac nitric oxide production (nitrite concentration in coronary sinus as compared with aortic levels) in Celsior-preserved hearts (Celsior aorta: 27.0 6 6.1; CS: 38.7 6 7.0; P 5 .04 and UW aorta: 39.6 6 7.9; CS: 43.5 6 6.6, P 5 NS). DISCUSSION

The present study clearly shows that Celsior-preserved hearts require more inotropic support in the early phase after orthotopic transplantation. The findings that allografts responded well to inotropes and that myocardial performance is comparable between both groups after 1 month suggest that myocardial stunning may have developed during preservation with Celsior solution. Microvascular endothelial function assessed 1 month after transplantation did not show differences among groups. However, a significant inverse correlation between ischemic time and impairment of coronary flow reserve was observed in the Celsior group. Whether or not alterations of the vasoactive factors nitric oxide and endothelin play an important role in myocardial and endothelial function in this clinical setting remains unsolved. However, it is known that cytokine-induced nitric oxide production is associated with graft contractile dysfunction, as shown recently.16 In addition, our group recently reported that cardiac nitric oxide production is associated with TNF-a levels soon after transplantation in patients with impaired flow reserve.13 Moreover, Ravalli and coworkers and Szabolcs et al detected increased iNOS expression in smooth muscle and infiltrating macrophages, which was associated with apoptotic cell death in human transplant recipients, suggesting an important role for iNOS activation in graft contractile and endothelial function.17,18 Enhanced myocardial protection may therefore be achieved by reduction of iNOS/NO activation within the allograft in the early phase after transplantation. The potent vasoconstrictor peptide endothelin was found to be increased in allograft recipients when compared with nontransplanted controls. The transcardiac net extraction of endothelin in both groups may reflect either an increased activation of ET receptors or an increased clearance of circulating endothelin. However, endothelin plays an important role in both acute and chronic rejection.15,19 ET is

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known to exert short-term (vasoconstriction) and long-term effects (mitogenesis) and has been shown to be increased in endothelial dysfunction and atherogenesis.20,21 Improved cardiac protection with UW solution was shown by supplementation of the solution with an endothelin receptor antagonist, further supporting that this potent vasoconstrictor peptide may be involved in allograft dysfunction under acute and chronic conditions.2 In conclusion, the data of the present study show that both solutions provide adequate myocardial protection in clinical cardiac transplantation. The necessity for increased inotropes and vasodilators in the Celsior group warrants further investigation in order to prove the superiority of this new solution. In addition, the association between impaired coronary flow reserve and ischemic time in the Celsior group needs further investigation—particularly when prolonged ischemic times are expected. Both the iNOS/NO and ET pathways are involved in alterations of myocardial and endothelial function and may be important therapeutic targets for improvement of cardioprotection in clinical heart transplantation. REFERENCES 1. Stein D, Drinkwater D, Laks H, et al: J Thorac Cardiovasc Surg 102:657, 1991 2. Okada K, Yamashita C, Okada M, et al: J Heart Lung Transplant 15:475, 1996 3. Oberhuber G, Schmid T, Thaler W, et al: Transplantation 58:739, 1994 4. Menasche P, Termignon JL, Pradier F, et al: Eur J Cardiothorac Surg 8:207, 1994 5. Reichenspurner H, Russ C, Wagner F, et al: Transplant Int 7(suppl):481, 1994 6. Brunner F: J Molec Cell Cardiol 29:2363, 1997 7. Boyle E, Pohlman T, Johnson M, et al: Ann Thorac Surg 63:277, 1997 8. Beyersdorf F, Mitrev Z, Sarai K, et al: J Thorac Cardiovasc Surg 106:137, 1993 9. Depre C, Vanoverschelde JL, Goudemant JF, et al: Circulation 92:1911, 1995 10. Dagassan P, Breu V, Clozel M, et al: J Cardiovasc Pharmacol 24:867, 1994 11. Entman ML, Smith CW: Cardiovasc Res 28:1301, 1994 12. Weis M, von Scheidt W: Circulation 96:2069, 1997 13. Wildhirt SM, Weis M, Schulze C, et al: Transplant Intern 11:519, 1998 14. Arendt RM, Schmoeckel M, Wilbert-Lampen U, et al: J Pharmacol Exp Ther 272:1, 1995 15. Dengler T, Zimmermann R, Tiefenbacher C, et al: J Heart Lung Transplant 14:1057, 1995 16. Lewis W, Tsao P, Rickenbacher P, et al: Circulation 93:721, 1996 17. Szabolcs M, Ravalli S, Minanov O, et al: Transplantation 65:804, 1998 18. Ravalli S, Albala A, Ming M, et al: Circulation 97:2338, 1998 19. Liu S, Wildhirt SM, Weismueller S, et al: Atherosclerosis 140:1, 1998 20. Levin ER: N Engl J Med 333:356, 1995 21. Lerman A, Holmes DR, Bell MR, et al: Circulation 92:2426, 1995