Myocardial and endothelial protection for heart transplantation in the new millenium: lessons learned and future directions

Post-transplant inotrope score is associated with clinical outcomes after adult heart transplantation

BACKGROUND

Inotrope score has been proposed as a marker of clinical outcome after adult heart transplantation (HTx) but is rarely used in practice.

METHODS

Inotrope score during the first 48 h after HTx was calculated in 81 patients as: dopamine + dobutamine + amrinone + milrinone (dose × 15) + epinephrine (dose × 100) + norepinephrine (dose × 100) + enoximone + isoprenaline (dose × 100), with each drug in µg/kg/min. Determinants of inotrope score were identified with linear regression. Cox regression was used to determine the association of inotrope score with mortality.

RESULTS

The mean recipient age was 52 ± 11 years, and 32 (39.5%) patients were female. Determinants of inotrope score were preoperative C-reactive protein, serum urea, congenital heart disease, and donor cardiac arrest (R2  = .30). Inotrope score was associated with 5-year mortality, independent of recipient age and gender (HR 1.03, 95% CI 1.00-1.07). This association was attenuated when adjusting for female-to-male transplant and ischemia time. Inotrope score was also strongly associated with continuous veno-venous hemofiltration (OR 1.07, 95% CI 1.03-1.12).

CONCLUSION

High inotrope score post-HTx was observed in recipient congenital heart disease and was associated with a higher risk of mortality and acute kidney injury.

Supplemental Cardioplegia During Donor Heart Implantation: A Systematic Review and Meta-Analysis

BACKGROUND

The optimal donor heart preservation and management strategy during heart transplantation remains controversial. We report the results of a systematic review and meta-analysis of the effect of supplemental cardioplegia administration during donor heart implant for transplantation.

METHODS

We searched MEDLINE and Embase databases until February 2019 for studies comparing patients who received transplants with the donor heart given supplemental cardioplegia or not. Data were extracted by 2 independent investigators. The main outcomes were early morbidity and mortality.

RESULTS

Included were 7 retrospective observational studies (4 comparing to historical controls) and 3 randomized controlled trials enrolling 1125 patients. Supplemental cardioplegia included crystalloid and blood cardioplegia given continuous retrograde or as terminal "hot shots." Supplemental cardioplegia was associated with improved early mortality (risk ratio [RR], 0.55; 95% confidence interval [CI], 0.35-0.87; P < .01), greater rates of spontaneous return of sinus rhythm (RR, 2.62; 95% CI, 1.50-4.56; P < .01), shorter intensive care stay (mean difference, -3.4 days; 95% CI, -5.1 to -1.6; P < .01), and lower incidence of ischemic changes seen on endomyocardial biopsy specimens (RR, 0.49; 95% CI, 0.35-0.69; P < .01) compared with controls. Midterm mortality was not different between groups (incident rate ratio, 0.80; 95% CI, 0.51-1.26; P = .34).

CONCLUSIONS

Administration of supplemental cardioplegia may be associated with a reduction in organ ischemic injury and shorter intensive care stay as well as improvement in early survival after transplantation. This strategy may be a simple and cost-effective adjunct to improve outcomes of heart transplantation, especially in an era of increasing use of marginal donor organs. Further investigation will be needed to confirm the findings of this hypothesis-generating study.

Primary graft dysfunction in heart transplantation

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) is common early postheart transplantation; however, use of standardized definitions remains inconsistent. This review focuses on understanding the incidence, classification, risk factors, and management of PGD.

RECENT FINDINGS

The incidence and mortality of PGD in heart transplant varies considerably in the published literature ranging from 1.0% to 31% and 3% to 75%, respectively. There is also considerable variation in management strategies with current data favoring early intervention.

SUMMARY

PGD in heart transplantation remains a challenging problem associated with significant mortality and morbidity. There is need for a consistent and accessible definition to better define associated risk factors and optimize management strategies.

Impaired Endothelial Nitric Oxide Synthase Homodimer Formation Triggers Development of Transplant Vasculopathy - Insights from a Murine Aortic Transplantation Model

Transplant vasculopathy (TV) represents a major obstacle to long-term graft survival and correlates with severity of ischemia reperfusion injury (IRI). Donor administration of the nitric oxide synthases (NOS) co-factor tetrahydrobiopterin has been shown to prevent IRI. Herein, we analysed whether tetrahydrobiopterin is also involved in TV development. Using a fully allogeneic mismatched (BALB/c to C57BL/6) murine aortic transplantation model grafts subjected to long cold ischemia time developed severe TV with intimal hyperplasia (α-smooth muscle actin positive cells in the neointima) and endothelial activation (increased P-selectin expression). Donor pretreatment with tetrahydrobiopterin significantly minimised these changes resulting in only marginal TV development. Severe TV observed in the non-treated group was associated with increased protein oxidation and increased occurrence of endothelial NOS monomers in the aortic grafts already during graft procurement. Tetrahydrobiopterin supplementation of the donor prevented all these early oxidative changes in the graft. Non-treated allogeneic grafts without cold ischemia time and syngeneic grafts did not develop any TV. We identified early protein oxidation and impaired endothelial NOS homodimer formation as plausible mechanistic explanation for the crucial role of IRI in triggering TV in transplanted aortic grafts. Therefore, targeting endothelial NOS in the donor represents a promising strategy to minimise TV.

The use of controlled reperfusion strategies in cardiac surgery to minimize ischaemia/reperfusion damage

Ischaemia and reperfusion occur during almost every cardiac operation, and one of the key elements to achieve a successful operation is to counteract the detrimental effects of induced ischaemia and reperfusion during the operation. The cardiac surgeon is in a unique position to protect the heart before ischaemia is induced and to avoid further damage during the reperfusion period. The surgeon can alter the composition of the reperfusate and the conditions of reperfusion so that the ischaemia/reperfusion injury is minimal, even after very complex procedures that require long aortic cross-clamp periods. This in turn allows him to perform a near-perfect surgical repair of the underlying disease without the pressure of time. The vast knowledge gained in this field over the years has led to application in other organs, such as the limbs (acute limb ischaemia), lungs (lung transplantation), kidney and liver (kidney and liver transplantation), and more recently even for the brain [acute cerebral artery occlusion (stroke)] and the whole body (cardiopulmonary resuscitation). Further improvements in reperfusion strategies will allow salvage of tissue and even whole body after ischaemic periods thought previously to be irreversibly damaged.

Limitation of myocardial and endothelial injury of the rat heart graft after preservation with Centre de Résonance Magnétique Biologique et Médicale (CRMB) solution

Myocardial injury caused by prolonged storage compromises post-transplantation contractile performance and induces endothelial injury. The aim of this study was to compare a solution developed in our laboratory [Centre de Résonance Magnétique Biologique et Médicale (CRMBM) solution] with a widely used solution (Celsior, Genzyme, Saint Germain en Laye, France). Metabolic and contractile parameters as well as indexes of endothelial injury were measured in a heterotopic rat heart transplantation model with a 3-h ischaemia and a 1-h reperfusion. The two solutions were randomly used for cardioplegia and graft preservation in six experiments each. During reperfusion, developed pressure and rate pressure product were higher with CRMBM compared with Celsior (P = 0.0002 and P = 0.0135, respectively). Phosphocreatine and adenosine triphosphate (ATP) concentrations after reperfusion were significantly higher with CRMBM (P = 0.0069 and P = 0.0053, respectively). Endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) protein expression were decreased to the same extent after reperfusion compared with baseline with CRMBM (P = 0.0001 and P < 0.0001, respectively) and Celsior (P = 0.0007 and P < 0.0001, respectively). Total nitrate concentration (NOx) was significantly increased after reperfusion with CRMBM (P < 0.0001 versus baseline and P < 0.0001 versus Celsior). Na,K-ATPase activity was decreased in both groups versus baseline after reperfusion (P < 0.0001 for CRMBM and P < 0.0001 for Celsior). We showed limitation of both myocardial and endothelial damage with CRMBM compared with Celsior during heterotopic rat heart transplantation in vivo.