Cardiac function and myocardial performance of 24-hour-preserved asphyxiated canine hearts

Heart Transplantation With Donation After Circulatory Death

Heart transplantation remains the preferred option for improving quality of life and survival for patients suffering from end-stage heart failure. Unfortunately, insufficient supply of cardiac grafts has become an obstacle. Increasing organ availability with donation after circulatory death (DCD) may be a promising option to overcome the organ shortage. Unlike conventional donation after brain death, DCD organs undergo a period of warm, global ischemia between circulatory arrest and graft procurement, which raises concerns for graft quality. Nonetheless, the potential of DCD heart transplantation is being reconsidered, after reports of more than 70 cases in Australia and the United Kingdom over the past 3 years. Ensuring optimal patient outcomes and generalized adoption of DCD in heart transplantation, however, requires further development of clinical protocols, which in turn require a better understanding of cardiac ischemia-reperfusion injury and the various possibilities to limit its adverse effects. Thus, we aim to provide an overview of the knowledge obtained with preclinical studies in animal models of DCD heart transplantation, to facilitate and promote the most effective and efficient advancement in preclinical research. A literature search of the PubMed database was performed to identify all relevant preclinical studies in DCD heart transplantation. Specific aspects relevant for DCD heart transplantation were analyzed, including animal models, graft procurement and storage conditions, cardioprotective approaches, and graft evaluation strategies. Several potential therapeutic strategies for optimizing graft quality are identified, and recommendations for further preclinical research are provided.

Transplantation of Hearts Donated after Circulatory Death

Cardiac transplantation has become limited by a critical shortage of suitable organs from brain-dead donors. Reports describing the successful clinical transplantation of hearts donated after circulatory death (DCD) have recently emerged. Hearts from DCD donors suffer significant ischemic injury prior to organ procurement; therefore, the traditional approach to the transplantation of hearts from brain-dead donors is not applicable to the DCD context. Advances in our understanding of ischemic post-conditioning have facilitated the development of DCD heart resuscitation strategies that can be used to minimize ischemia-reperfusion injury at the time of organ procurement. The availability of a clinically approved ex situ heart perfusion device now allows DCD heart preservation in a normothermic beating state and minimizes exposure to incremental cold ischemia. This technology also facilitates assessments of organ viability to be undertaken prior to transplantation, thereby minimizing the risk of primary graft dysfunction. The application of a tailored approach to DCD heart transplantation that focuses on organ resuscitation at the time of procurement, ex situ preservation, and pre-transplant assessments of organ viability has facilitated the successful clinical application of DCD heart transplantation. The transplantation of hearts from DCD donors is now a clinical reality. Investigating ways to optimize the resuscitation, preservation, evaluation, and long-term outcomes is vital to ensure a broader application of DCD heart transplantation in the future.

Efficacy of MCI-186, a free-radical scavenger and antioxidant, for resuscitation of nonbeating donor hearts

OBJECTIVE

Oxygen-derived free radicals are responsible in part for reperfusion injury in globally ischemic myocardium. In this study, the efficacy for resuscitation of nonbeating donor hearts of MCI-186, a free-radical scavenger and antioxidant, was investigated in a pig transplantation model.

METHODS

Cardiac arrest was induced by asphyxiation. After 30 minutes of global ischemia, the hearts were excised and immediately reperfused from the aortic root with normoxemic blood cardioplegia (PO2 100 mm Hg) for 20 minutes, followed by perfusion with hyperoxemic blood (PO2 300 mm Hg). MCI-186 (3 mg/kg) was administered into the aortic root for the first 30 minutes of reperfusion in the treated group (n = 6), and untreated hearts were used as a control group (n = 6). Transplantation was performed with the heart beating.

RESULTS

Posttransplantation recovery of cardiac output, end-systolic pressure-volume ratio, and first derivative of pressure of the left ventricle in the treated group were significantly better than those in the control group. The coronary sinus-aortic root difference in malondialdehyde levels remained low throughout reperfusion in the treated group but abruptly increased after initiation of oxygenated blood perfusion in the control group. The MCI-186-treated hearts showed low degree of edema and well-preserved ultrastructure with normal-appearing organelles, whereas the untreated hearts had marked swelling of mitochondria and scant glycogen granules.

CONCLUSION

MCI-186 exerts a cardioprotective action at least partly by inhibition of lipid peroxidation. Antioxidant therapy at the initial reperfusion is essential to successful resuscitation of nonbeating hearts by continuous myocardial perfusion.

Efficacy of an endothelin-A receptor antagonist in heart transplantation from asphyxiated canine non-heart-beating donors

OBJECTIVE

Hypoxic perfusion before arrest, an indeterminate period of warm ischemia, and subsequent reperfusion are major causes of cardiac allograft dysfunction in non-heart-beating donors (NHBDs). The present study was undertaken to elucidate the cardioprotective effects of ET(A) receptor antagonist FR139317 for hearts obtained from asphyxiated NHBDs in a canine transplantation model.

METHODS

Hypoxic cardiac arrest was induced in 17 donor dogs. FR139317 (10 mg/kg) was given to 7 of the dogs over a period of 10 min before disconnecting the ventilator. The hearts were preserved with FR 139317-supplemented cardioplegic solution (FR group). The remaining 10 did not receive FR 139317 at any time during the experiment (control group). Orthotopic transplantation was performed after a mean myocardial ischemic time of 4h.

RESULTS

During the agonal period, the highest systolic pulmonary artery pressure in the FR group was lower than that in the control group (47 +/- 14 vs. 58 +/- 27 mmHg). All animals in the FR group were weaned from cardiopulmonary bypass, whereas only five of the controls were weaned, two of which were identified to have dominant right ventricular failure. After transplantation, recovery rates of the left ventricular end-systolic pressure-volume ratio (E(max)) and the maximum first derivative of pressure measured over time (max dP/dt) were not significantly different between the groups, but recovery rates of the cardiac index, left ventricular minimum dP/dt and exponential time constant of LV relaxation (tau) in the FR group were higher than those in the control group.

CONCLUSIONS

The ET(A) receptor antagonist FR 139317 reduced pressure overload on the right ventricle by decreasing the peak pulmonary artery pressure before donor arrest. Cardioprotective effects of this agent for heart transplantation from NHBDs are manifested by preserved diastolic properties of the left ventricle.

Resuscitation of Non-Beating Donor Hearts Using Continuous Myocardial Perfusion: The Importance of Controlled Initial Reperfusion

BACKGROUND

Warm ischemia is a major cause of cardiac allograft failure in transplants from non-heart-beating donors. To minimize myocardial ischemia, we used a continuous myocardial perfusion technique for resuscitation of donor hearts. The purpose of the present study was to investigate an optimal duration of controlled initial reperfusion.

METHODS

Cardiac arrest was induced by asphyxia in 18 donor pigs. The hearts were harvested 30 minutes after global warm ischemia. Continuous myocardial reperfusion was immediately commenced from the aortic root with blood cardioplegic solution (20 degrees C, 40 mm Hg) and then with oxygenated blood (20 degrees to 37 degrees C, 40 to 60 mm Hg). Animals were divided into three groups according to the duration of the initial reperfusion: group I = 5 minutes, group II = 20 minutes, and group III = 60 minutes. Orthotopic transplantation was performed while keeping the heart beating by continuous myocardial perfusion. Cardiac function was evaluated before anoxia and after transplantation. Lactate extractions were determined during reperfusion. Myocardial edema was assessed by heart weight and posterior wall thickness of the left ventricle.

RESULTS

Recovery rates of cardiac function in group II hearts after transplantation were better than in groups I and III (cardiac output, 61% +/- 9% versus 41% +/- 5% versus 44% +/- 4%, respectively; p < 0.05; left ventricular end-systolic pressure-volume ratio, 64% +/- 8% versus 36% +/- 9% versus 42% +/- 6%, respectively; p < 0.05). Lactate extractions in groups II and III returned to 0 within 20 minutes of reperfusion. Myocardial edema after transplantation in group II hearts was less than in groups I and III.

CONCLUSIONS

The best recovery was observed in the non-beating donor hearts resuscitated by continuous myocardial perfusion when the initial controlled reperfusion with lukewarm blood cardioplegic solution at 40 mm Hg lasted for 20 minutes.

The effect of short-term coronary perfusion using a perfusion apparatus on canine heart transplantation from non-heart-beating donors

BACKGROUND

We investigated the effects of briefly perfusing hearts from non-heart-beating donors (NHBDs) with a Celsior solution before cardiac transplantation.

METHODS

Donor hearts were left in situ for 20 minutes after cardiac arrest was induced by rapid exsanguination. Twelve donor-recipient pairs of mongrel dogs were divided into 2 groups, the simple immersion (SI, n = 6) group and the coronary perfusion (CP, n = 6) group. Both groups underwent coronary flushing with Celsior, after which hearts from the SI group were stored using simple immersion for 4 hours and hearts from the CP group underwent 1 hour of further perfusion followed by storage for 3 hours. Orthotopic transplantation was then performed. We measured cardiac output, end-systolic maximal elastance (E(max)), left ventricular pressure, and rate pressure product 1 and 2 hours after weaning from cardiopulmonary bypass (CPB). Two hours after weaning from CPB, the hearts were harvested for histopathologic study and to determine the percentage of water content.

RESULTS

The cardiac output (CO) recovery rate was significantly higher in the CP group than in the SI Group 1 hour after weaning from CPB (p < 0.05). The CO recovery rate, E(max), and rate pressure product were significantly higher and the percentage of water content was significantly lower in the CP group than in the SI Group 2 hours after weaning from CPB (p < 0.05). Histopathologic damage was more severe in the SI group.

CONCLUSIONS

The results of this study suggest that short-term coronary perfusion with a Celsior solution may be useful for heart transplantation from NHBDs.

Nicorandil ameliorates posttransplant dysfunction in cardiac allografts harvested from non-heart-beating donors

OBJECTIVE

Warm ischemia is a major cause of cardiac allograft dysfunction in non-heart-beating donors (NHBDs). We evaluated the cardioprotective effects of nicorandil, an adenosine triphosphate-sensitive potassium channel opener, on the early posttransplant left ventricular (LV) function of hearts harvested from asphyxiated canine NHBDs.

METHODS

Hypoxic cardiac arrest was induced in 12 donor dogs. In 6, nicorandil was administered intravenously at 100 micrograms/kg + 25 micrograms/kg/min after respiratory arrest and hearts were preserved with nicorandil-supplemented cardioplegic solution (nicorandil group). The remaining 6 did not receive nicorandil at any time during the experiment (control group). Hearts were orthotopically transplanted after a mean myocardial ischemic time of 4 hours.

RESULTS

All 12 recipients were weaned from cardiopulmonary bypass without inotropic support. In the control group, posttransplant cardiac indices and left ventricular end-systolic pressure (LVESP) decreased significantly, while LV max-dP/dt and Tau increased over pretransplant values. No differences were seen in parameters between pretransplant and posttransplant values in the nicorandil group. Posttransplant cardiac indices, LVESP, and LV max + dP/dt were higher in the nicorandil group than in controls, while posttransplant LV max-dP/dt in the nicorandil group was lower.

CONCLUSIONS

Our results indicate that pretreatment with nicorandil during hypoxic perfusion before cardiac arrest and subsequent preservation with nicorandil-supplemented cardioplegia ameliorates early posttransplant LV dysfunction of hearts harvested from asphyxiated NHBDs.

Posttransplant function of a nonbeating heart is predictable by an ex vivo perfusion method

BACKGROUND

We attempted to predict the posttransplant cardiac function of nonbeating donor hearts.

METHODS

A total of 13 dogs were studied. Hearts were left in situ for 45 minutes after cardiac arrest caused by exsanguination. Hearts were then excised and reperfused in an ex vivo perfusion apparatus after 60 minutes of warm ischemia to test whether they could eject against an 80 mm Hg afterload from a preload of 10 mm Hg. Thereafter, all hearts were transplanted orthotopically.

RESULTS

Four of 13 hearts were able to eject in the apparatus (group A). However, the other nine hearts could not eject under the defined conditions (group B). All four hearts in group A showed good posttransplant hemodynamics (systolic arterial pressure > 80 mm Hg with mean left atrial pressure < 10 mm Hg) without dopamine. However, none of nine hearts in group B could support the circulation without dopamine.

CONCLUSIONS

Nonbeating donor heart function evaluated in the perfusion apparatus predicts posttransplant heart function. This method may be applicable for selection of transplantable hearts from nonbeating heart donors.

A new hydroxyl radical scavenger "EPC" on cadaver heart transplantation in a canine model

This study was performed to determine if an "arrested" heart, resuscitated with cardiopulmonary bypass (CPB) after the cessation of beating, can be successfully transplanted, and whether a hydroxyl radical scavenger EPC can reduce ischemic and reperfusion injury during resuscitation of the arrested heart and following orthotopic heart transplantation. A total of 16 pairs of canines were divided into a control group of eight pairs and an EPC-treated group of eight pairs. Cardiac arrest of the donor heart was induced by the discontinuation of respiratory support after the induction of brain death. The cadaver heart was then resuscitated and core-cooled to myocardial temperature of 15 degrees C using CPB. The donor heart was harvested using cold cardioplegia and orthotopically transplanted. All of the transplanted hearts in the EPC group were weaned from CPB without any inotropic support after 60 min of bypass support, whereas all the animals in the control group required 5 micrograms/kg/min dopamine (P = 0.001). Moreover, cardiac function (Emax) 1 h after orthotopic heart transplantation was better preserved in the EPC group than in the control group, at 110 +/- 36% vs. 70 +/- 21% of the post brain death values (P = 0.02) These findings demonstrate that EPC reduces posttransplant reperfusion injury, and thus it may prove to be a valuable adjunct in this challenging model.

The effect of graft perfusion with warm blood cardioplegia for cadaver heart transplantation

This study was designed to verify the effect of reperfusion of donor hearts in a perfusion apparatus after 60 min of global ischemia prior to heart transplantation. Thirteen dogs were exsanguinated from the femoral artery and cardiac arrest was achieved. The hearts were left in situ at room temperature (25 degrees C) for 60 min. In group A (n = 7), the hearts were excised and reperfused 60 min after cardiac arrest in the perfusion apparatus with substrate-enriched warm blood cardioplegia (WBCP) containing a hydroxyl radical scavenger, EPC, followed by 45 min of blood perfusion. Next, the hearts were preserved in cold (4 degrees C) University of Wisconsin (UW) solution. In group B (n = 6), the hearts were perfused with cold (4 degrees C) St. Thomas' solution 60 min after cardiac arrest and preserved in cold UW solution. Thereafter, all hearts in both groups were transplanted orthotopically to recipient dogs. In group A, 6 of 7 dogs were weaned from cardiopulmonary bypass (CPB). In group B, only 2 of 6 dogs were weaned from CPB. Moreover, 3 of the 6 hearts in group B did not start beating after transplantation (stone heart). This study suggested reperfusion of the donor heart in the perfusion apparatus with WBCP to be a beneficial preconditioning method when utilizing 60-min arrested hearts for transplantation.

Intravenous phenylephrine preconditioning of cardiac grafts from non-heart-beating donors

BACKGROUND

Hypoxia and warm ischemia produce severe injury to cardiac grafts harvested from non-heartbeating donors. To potentially improve recovery of such grafts, we studied the effects of intravenous phenylephrine preconditioning.

METHODS

Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non-heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 microg/kg (n = 7) before initiation of apnea. Non-heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia.

RESULTS

Phenylephrine 25 microg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 +/- 0.5 versus 7.7 +/- 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 +/- 5.3 versus 41.0 +/- 3.4 mm Hg; p = 0.04). Phenylephrine 25 microg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09).

CONCLUSIONS

Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest.

Controlled reperfusion of cardiac grafts from non-heart-beating donors

BACKGROUND

Hearts harvested from non-heart-beating donors sustain severe injury during procurement and implantation, mandating interventions to preserve their function. We tested the hypothesis that limiting oxygen delivery during initial reperfusion of such hearts would reduce free-radical injury.

METHODS

Rabbits sustained hypoxic arrest after ventilatory withdrawal, followed by 20 minutes of in vivo ischemia. Hearts were excised and reperfused with blood under conditions of high arterial oxygen tension (PaO2) (approximately 400 mm Hg), low PaO2 (approximately 60 to 70 mm Hg), high pressure (80 mm Hg), and low pressure (40 mm Hg), with or without free-radical scavenger infusion. Non-heart-beating donor groups were defined by the initial reperfusion conditions: high PaO2/ high pressure (n = 8), low PaO2/high pressure (n = 7), high PaO2/low pressure (n = 8), low PaO2/low pressure (n = 7), and high PaO2/high pressure/free-radical scavenger infusion (n = 7).

RESULTS

After 45 minutes of reperfusion, low PaO2/ high pressure and high PaO2/low pressure had a significantly higher left ventricular developed pressure (63.6 +/- 5.6 and 63.1 +/- 5.6 mm Hg, respectively) than high PaO2/high pressure (40.9 +/- 4.5 mm Hg; p < 0.0000001 versus both). However, high PaO2/high pressure/free-radical scavenger infusion displayed only a trend toward improved ventricular recovery compared with high PaO2/ high pressure.

CONCLUSIONS

Initially reperfusing nonbeating cardiac grafts at low PaO2 or low pressure improves recovery, but may involve mechanisms other than decreased free-radical injury.

Study of efficacies of leukocyte-depleted terminal blood cardioplegia in 24-hour preserved hearts

To evaluate the effect of leukocyte-depleted terminal blood cardioplegia on prolonged preservation, 41 canine hearts were stored in modified Collins' solution and transplanted heterotopically. Hearts were transplanted soon after harvesting in group 1 and after 24-hour preservation in groups 2, 3, and 4. Blood cardioplegia was applied just before aortic unclamping in groups 3 and 4; group 3 received simple blood cardioplegia and group 4 received leukocyte-depleted cardioplegia. The percentage of the preload recruitable stroke work and diastolic compliance after transplantation compared with the preharvesting value in group 4 did not differ from those in group 1, but the percentage of the preload recruitable stroke work in groups 2 and 3 was significantly lower than that in groups 1 and 4. The percentage of diastolic compliance in groups 2 and 3 was significantly higher than that in groups 1 and 4. Coronary blood flow 40 minutes after aortic unclamping in group 4 did not differ from that in group 1, but was significantly higher than the blood flows in groups 2 and 3. Significant production of malondialdehyde was detected during terminal blood cardioplegia and 10 minutes after aortic unclamping in groups 2 and 3, but never in groups 1 and 4. After leukocyte-depleted terminal cardioplegia, the myocardial adenosine triphosphate content increased to the preharvesting value in group 4. Our results suggest that leukocyte-depleted terminal blood cardioplegia may be effective in replenishing the energy-depleted myocardium and reducing reperfusion injury, resulting in adequate cardiac function.

An in vitro evaluation of prostaglandin E1 and I2 on hypothermic injury to immature myocytes

The purpose of this study was to evaluate the functional and biochemical effects of Prostaglandin E1 (PGE1) and prostaglandin I2 (PGI2) on cardiac myocytes incubated under hypothermic conditions. Cardiac myocytes were isolated from neonatal rat ventricles and cultured for 4 days with MCDB 107 medium. Following this, 12.5 x 10(5) myocytes/flask were incubated at 4 degrees C for 24 h in media with PGE1, at concentrations of 0 M (group E0), 10(-9) M (group E1), 10(-8) M (group E2), 10(-7) M (group E3), or 10(-6) M (group E4); or with PGI2 at concentrations of 0 M PGI (group I0), 10(-9) M (group I1), 10(-8) M (group 12), 10(-7) M (group I3), or 10(-6) M (group I4). After hypothermic incubation, creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were measured, and the myocytes were then cultured for 24 h at 37 degrees C to evaluate the recovery of the myocyte beating rate. Of the PGI2 groups, only group I2 recovered significantly more than the control group (group I0), at 47.9 +/- 28.5% (mean +/- SD) of the control, being the beating rate prior to hypothermic incubation, whereas it was 18.1 +/- 9.7% in group I0 (P < 0.025); however, there were no significant differences among the PGE1 groups. Moreover, the release of CPK and LDH was significantly suppressed in group 12 compared to the control, being 57.7 +/- 27.6 mIU/flask (P < 0.05) and 275.1 +/- 83.0 mIU/flask (P < 0.025), respectively, in group I2, and 96.8 +/- 38.3 mIU/flask and 439.6 +/- 147.1 mIU/flask in group I0. Again, no significant differences were observed among the PGE1 groups. In conclusion, PGI2 was found to have a direct cytoprotective effect on immature myocytes which suggests that PGI2 may promote cardiac preservation in the neonatal period.