Pretreatment with a potassium-channel opener before prolonged cardiac storage: an evaluation in an experimental brain death model

Decreased recipient survival following orthotopic heart transplantation with use of hearts from donors with projectile brain injury

BACKGROUND

Fatal gunshot injury to the brain can cause significant alterations in the neuroendocrine state and myocardial dysfunction. Therefore heart allografts from these donors may result in graft failure following orthotopic heart transplantation (OHTx). We evaluated whether receiving a heart from a donor who died from fatal gunshot wound to the brain independently affected the outcome of transplantation.

METHODS

A retrospective review of 113 consecutive patients undergoing OHTx at a university hospital from 1996 to 2002 was performed. Group 1 received hearts from donors with fatal gun shot brain injury (n = 17), and Group 2 received hearts from donors who died from other causes (n = 96).

RESULTS

Recipient age, gender, United Network for Organ Sharing (UNOS) status, indication for transplantation, and other co-morbid conditions were similar in both groups. Young male donors pre-dominated in Group 1, but other donor characteristics were not significantly different. The incidence of Grade 3A rejection was higher in Group 1 than Group 2 (35% vs 6.3%, p = 0.003), as was the incidence of post-operative infection (35% vs 7.2%, p = 0.004). Actuarial survival at 1 and 5 years was significantly lower in Group 1 than in Group 2 (81% and 74% vs 97% and 94%, respectively, p = 0.005). Multivariate logistic regression analysis also demonstrated that fatal gunshot brain injury, as cause of donor death, was a risk factor for recipient mortality (p = 0.01).

CONCLUSION

Receiving a heart from a donor with fatal gunshot brain injury is a significant risk factor for recipient mortality following OHTx. Cautious use of heart allograft from these donors, especially in low-risk recipients, may lead to improved outcome following heart transplantation.

Acute brain death abolishes the cardioprotective effects of ischemic preconditioning in the rabbit

BACKGROUND

Myocardial preconditioning with brief coronary artery occlusions before a sustained ischemic period is reported to reduce infarct size. We wished to evaluate whether ischemic preconditioning (IP) is efficient in an experimental brain death (BD) model in the rabbit.

METHODS

Rabbits were randomized into four experimental groups of eight animals each. In the control group (CTRL), anaesthetized rabbits were subjected to 30 min of left coronary marginal branch occlusion and 90 min of reperfusion without any pretreatment. In the CTRL+IP group, anaesthetized rabbits were preconditioned with a 3-min ischemia and 3-min reperfusion sequence before coronary occlusion. In the BD group, rabbits were subjected to 90 min of BD before 30 min of coronary occlusion and 90 min of reperfusion. In the BD+IP group, BD rabbits were preconditioned as in the CTRL+IP group before coronary occlusion. BD was induced by rapid inflation of an intracranial balloon and was validated by clinical and electroencephalographic examinations. At the termination of the experiment, left ventricular volume (LVV), myocardial volume at risk (VAR) and infarct volume (IV) were determined with methylene blue and tetrazolium staining and were measured using planimetry.

RESULTS

LW was not significantly different among the four experimental groups (CTRL, 6.54+/-0.90 cm3; CTRL+IP, 5.92+/-0.60 cm3; BD, 5.87+/-0.81 cm3; BD+IP, 6.16+/-0.95 cm3; P=ns). Furthermore, myocardial VAR, expressed as a percentage of LVV, was not significantly different between groups (CTRL, 20.0+/-4.2%; CTRL+IP, 22.32+/-2.25%; BD, 21.38+/-3.36%; BD+IP, 21.64+/-3.39%; P=NS). IV, expressed as a percentage of VAR, was significantly reduced in the CTRL+IP group compared with the CTRL group (15.76+/-8.47% vs. 49.95+/-1.51%; P<0.0001). In contrast, there was no significant difference in IV, expressed as a percentage of VAR, between the BD and the BD+IP groups (50.0+/-1.52% vs. 49.72+/-1.58%; P=NS).

CONCLUSION

The data indicate that the infarct-limiting effect of IP is lost in BD rabbits. Thus, the clinical potential of IP in the context of organ transplantation seems to be severely compromised.

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 degrees 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 degrees 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.