Predictors of graft longevity in pediatric heart transplantation

Heart Transplantation for Pediatric and Congenital Cardiac Disease: A Comparison of Two Eras over 23 Years and 188 Transplants at a Single Institution

BACKGROUND

To assess changes in patterns of practice and outcomes over time, we reviewed all patients who underwent heart transplantation (HTx) at our institution and compared two consecutive eras with significantly different immunosuppressive protocols (cohort 1 [80 HTx, June 1995-June 2006]; cohort 2 [108 HTx, July 2006-September 2018]).

METHODS

Retrospective study of 180 patients undergoing 188 HTx (June 1995-September 2018; 176 first time HTx, 10 second HTx, and 2 third HTx). In 2006, we commenced pre-HTx desensitization for highly sensitized patients and started using tacrolimus as our primary postoperative immunosuppressive agent. The primary outcome was mortality. Survival was modeled by the Kaplan-Meier method. Univariable and multivariable Cox proportional hazard models were created to identify prognostic factors for survival.

RESULTS

Our 188 HTx included 18 neonates, 85 infants, 83 children, and 2 adults (>18 years). Median age was 260.0 days (range: 5 days-23.8 years). Median weight was 7.5 kg (range: 2.2-113 kg). Patients in cohort 1 were less likely to have been immunosensitized preoperatively (12.5% vs 28.7%, P = .017). Nevertheless, Kaplan-Meier analysis suggested superior survival in cohort 2 (P = .0045). Patients in cohort 2 were more likely to be alive one year, five years, and ten years after HTx. Multivariable analysis identified the earlier era (hazard ratio [HR] [95% confidence interval] for recent era = 0.32 [0.14-0.73]), transplantation after prior Norwood operation (HR = 4.44 [1.46-13.46]), and number of prior cardiac operations (HR = 1.33 [1.03-1.71]) as risk factors for mortality.

CONCLUSIONS

Our analysis of 23 years of pediatric and congenital HTx reveals superior survival in the most recent 12-year era, despite the higher proportion of patients with elevated panel reactive antibody in the most recent era. This improvement was temporally associated with changes in our immunosuppressive strategy.

B-type natriuretic peptide trends after pediatric heart transplantation

BNP is increasingly utilized in the management of pediatric HT recipients. Performing a retrospective single-center chart review, we sought to describe BNP changes during the first year after HT and identify factors that affect its trend. After exclusion for rejection, 316 BNP levels from 50 patients were evaluated. BNP underwent an exponential decline 120 days after HT followed by a plateau. Log10 BNP decline strongly correlated with time (r = -0.70, p < 0.0001). Initial BNP was less in pretransplant VAD (p = 0.0016) and lower post-HT inotrope use (p = 0.0043). Infant recipients, IT >4 h, and those bridged medically were associated with higher plateau BNP. Multivariable logistic regression demonstrated IT >4 h independently predicted plateau BNP in the upper quartile (OR 7.1, p = 0.02). No significant change in BNP coincided with rejection (N = 6 patients) without severe hemodynamic compromise. BNP correlated modestly with right atrial pressure (r = 0.4652, p < 0.0001) and pulmonary capillary wedge pressure (r = 0.2660, p < 0.001), but poorly with echocardiogram (r = -0.18, p = 0.003). Trending BNP could help provide insight into how the graft recovers after HT and IT >4 h independently predicted higher plateau BNP and may reflect subtle changes in graft performance.

Donors' characteristics and impact on outcomes in pediatric heart transplant recipients

Organ availability and acceptability limit pediatric HTx. What characteristics define an unacceptable or high-risk pediatric donor remains unclear. The purpose of this study was to characterize a large cohort of pediatric donors and determine the donor risk factors, including cumulative risk, that affect recipient survival. Data from the PHTS, a prospective multicenter study, were used to examine the impact of donor factors on the outcomes of patients listed <18 yr of age who received a HTx between 1993 and 2009. Donor data were available for 3149 of 3156 HTx (99.8%). Donor cause of death, need for inotropes, or CPR did not affect survival outcomes (p = 0.05). Ischemic time also did not have an impact on overall recipient survival; however, longer ischemic times negatively impacted one-yr post-transplant survival (p < 0.0001). There was no impact of cumulative risk factors on survival (p = 0.8). Although used in a minority of cases, hormonal therapy in the donor positively impacted survival (p = 0.03). In multivariate analysis, the only donor factor associated with decreased survival was smaller donor BSA, the other factors being related to the recipient characteristics. When analyzed by recipient age, there were no donor-related factors that affected survival for those who received a transplant at <6 months of age. Longer ischemic time (p < 0.0001) and greater age difference between the recipient and donor (p = 0.0098) were donor-related factors impacting early-phase survival for recipients who received a graft at ≥10 yr of age. Factors perceived to define a marginal or high-risk pediatric heart donor including inotrope use, CPR and donor cause of death may have less impact on outcomes than previously thought. Longer ischemic times did impact one yr, but not overall survival, and this impact was much greater with older donors. Parameters for accepting a donor heart can potentially be expanded, especially in the infant age group, but strong consideration should always be given to the interaction between ischemic time and donor age.

Short crossclamp heart transplantation: a modified technique

Prolongation of the ischemic time in heart transplantation adversely affects the performance of the donor heart. We compared the impact of ischemic time in 30 patients who had the conventional bicaval method with declamping just after the last anastomosis (group A) and 28 who had a modified short crossclamp technique with declamping after left atrial stump, aorta, and inferior vena caval anastomosis (group B). In the operating room, 4 (13.3%) group A patients need one inotropic and 26 (86.6%) need 2 or more; one (3.3%) needed intraaortic balloon pumping. In group B, one inotropic was used in 7 (25%) patients, 4 (14.2%) need 2 or more, and 17 (60.7%) needed no inotropic. Mean crossclamp time was 80.5 ± 4.7 min in group A and 62.4 ± 5.8 min in group B. Weaning from bypass was faster in group B. Transesophageal echocardiography at the end of the operation showed more complete de-airing in group B. There were no significant differences in intensive care unit stay or the incidence of postoperative neurologic complications between the 2 groups. Easier separation from bypass, even without a hot shot, and better echocardiographic systolic parameters postoperatively are the advantages of this modified technique.

Total donor ischemic time: relationship to early hemodynamics and intensive care morbidity in pediatric cardiac transplant recipients

OBJECTIVE

Single-center studies have failed to link modest increases in total donor ischemic time to mortality after pediatric orthotopic heart transplant. We aimed to investigate whether prolonged total donor ischemic time is linked to pediatric intensive care morbidity after orthotopic heart transplant.

DESIGN

Retrospective cohort review.

SETTING

Tertiary pediatric transplant center in the United Kingdom.

PATIENTS

Ninety-three pediatric orthotopic heart transplants between 2002 and 2006.

METHODS

Total donor ischemic time was investigated for association with early post-orthotopic heart transplant hemodynamics and intensive care unit morbidities.

RESULTS

Of 43 males and 50 females with median age 7.2 (interquartile range 2.2, 13.0) yrs, 62 (68%) had dilated cardiomyopathy, 20 (22%) had congenital heart disease, and nine (10%) had restrictive cardiomyopathy. The mean total donor ischemic time was 225.9 (sd 65.6) mins. In the first 24 hrs after orthotopic heart transplant, age-adjusted mean arterial blood pressure increased (p < .001), mean pulmonary arterial pressure fell (p = .012), but central venous pressure (p = .58) and left atrial pressure (p = .20) were unchanged. After adjustment for age, primary diagnosis, pre-orthotopic heart transplant mechanical support, and marginal donor factors, longer total donor ischemic time was significantly associated with lower mean arterial blood pressure (p < .001) in the first 24 hrs after orthotopic heart transplant, longer post-orthotopic heart transplant mechanical ventilation (p = .03), longer post-orthotopic heart transplant stay in the intensive care unit (p = .004), and longer post-orthotopic heart transplant stay in hospital (p = .02). Total donor ischemic time was not related to levels of mean pulmonary arterial pressure (p = .62), left atrial pressure (p = .38), or central venous pressure (p = .76) early after orthotopic heart transplant.

CONCLUSIONS

Prolonged total donor ischemic time has an adverse effect on the donor organ, contributing to lower mean arterial blood pressure, as well as more prolonged ventilation and intensive care unit and hospital stays post-orthotopic heart transplant, reflecting increased morbidity.

Outcomes of cardiac transplantation in highly sensitized pediatric patients

Despite aggressive immunosuppressive therapy, pediatric orthotopic heart transplant (OHT) candidates with elevated pre-transplant panel reactive antibody (PRA) carry an increased risk of rejection and early graft failure following transplantation. This study has aimed to more specifically evaluate the outcomes of transplant candidates stratified by PRA values. Records of pediatric patients listed for OHT between April 2004 and July 2008 were reviewed (n = 101). Survival analysis was performed comparing patients with PRA < 25 to those with PRA > 25, as well as patients with PRA < 80 and PRA > 80. Patients with PRA > 25 had decreased survival compared with those with PRA < 25 after listing (P = 0.004). There was an even greater difference in survival between patients with PRA > 80 and those with PRA < 80 (P = 0.002). Similar analyses for the patients who underwent successful transplantation showed no significant difference in post-transplant survival between patients with a pre-transplant PRA > 25 and those with PRA < 25 (P = 0.23). A difference approaching significance was noted for patients with PRA > 80 compared with PRA < 80 (P = 0.066). Patients with significantly elevated pre-transplant PRAs at the time of listing have a significantly worse outcome compared to those with moderately increased PRA values or non-sensitized patients. Further study is necessary to guide physician and family treatment decisions at the time of listing.

Donor-recipient race mismatch and graft survival after pediatric heart transplantation

BACKGROUND

Black recipient race has been shown to predict poorer graft survival after pediatric heart transplantation. We analyzed our single-center experience comparing graft survival by race and the impact of donor-recipient race mismatch.

METHODS

One hundred sixty-nine consecutive primary pediatric heart transplant patients were analyzed by donor and recipient race (white recipient, 99; black recipient, 60; other, 10). The groups were similar in preoperative characteristics. There were fewer donor-recipient race matches in blacks compared with whites (10 versus 71; p < 0.0001).

RESULTS

Although 30-day and 6-month graft survival was similar for black and white recipients (93.9% and 85.8% versus 93.3% and 83.3%, respectively), overall actuarial graft survival was significantly lower in blacks (p < 0.019). Blacks tended to have a higher incidence of positive retrospective crossmatch (n = 26, 43%) than whites (n = 29, 29%), but this was not statistically significant (p = 0.053). The median graft survival for black recipients was 5.5 years compared with 11.6 years for whites. Donor-recipient race mismatch predicted poorer graft survival (5-year graft survival 48.9% versus 72.3%; p = 0.0032). The median graft survival for donor-recipient race-matched patients was more than twice that for mismatched patients (11.6 years versus 4.4 years). Cox proportional hazard analysis showed that donor-recipient race mismatch neutralized the effect of race on graft survival.

CONCLUSIONS

Graft survival after pediatric heart transplantation is inferior for black recipients compared with white recipients. These differences may be explained by a high incidence of donor-recipient race mismatch, which also predicts poorer outcome for all racial groups with pediatric heart transplantation. These data may have implications for future donor allocation schemes.

Impact of donor-to-recipient weight ratio on survival after heart transplantation: analysis of the United Network for Organ Sharing Database

BACKGROUND

Generally accepted donor criteria for heart transplantation limit allografts from donors within approximately 20% to 30% of the recipient's weight. We analyzed the impact of donor-to-recipient weight ratio on survival after heart transplantation.

METHODS AND RESULTS

Adult heart transplant recipients reported to the United Network for Organ Sharing from 1999 to 2007 were divided into 3 groups based on donor-to-recipient weight ratio: <0.8, 0.8 to 1.2, and >1.2. Kaplan-Meier methodology was used to estimate survival. Propensity-adjusted Cox regression modeling was used to analyze predictors of mortality. A total of 15 284 heart transplant recipients were analyzed; 2078 had weight ratio of <0.8, 9684 had 0.8 to 1.2, and 3522 had >1.2. Kaplan-Meier survival was not statistically different between groups at 5 years (P=0.26). Among patients with weight ratio <0.8, 5-year survival was lower for recipients with high pulmonary vascular resistance (>4 Woods units; P=0.02). Among recipients with high pulmonary vascular resistance, 5-year survival was similar for those with weight ratio 0.8 to 1.2 and >1.2 (P=0.44). Furthermore, male recipients with elevated pulmonary vascular resistance who received hearts from female donors had a significantly worse survival than males who received hearts from male donors (P=0.01). Propensity-adjusted multivariable analysis demonstrated that weight ratio <0.8 did not predict mortality (hazard ratio, 1.09; 95% CI, 0.94 to 1.27; P=0.21). Five-year survival after propensity matching was not statistically different between those with weight ratio <0.8 versus >/=0.8 (P=0.37).

CONCLUSIONS

Weight ratio did not predict mortality after heart transplantation. However, recipients with elevated pulmonary vascular resistance who received undersized hearts had poor survival. Furthermore, in the setting of high pulmonary vascular resistance, male recipients who received hearts from female donors had worse survival than those who received hearts from male donors. Extending donor criteria to include undersized hearts in select recipients should be considered.

Humoral Rejection in Pediatric Orthotopic Heart Transplantation

BACKGROUND

Pediatric heart transplant grafts may fail without evidence of cellular rejection or transplant coronary artery disease. The role of antibody-mediated humoral rejection (HR) in graft failure has not yet been described in the pediatric population.

METHODS

We reviewed the medical records of 103 pediatric heart transplantations performed at our institution from July 1997 to June 2004. Biopsy specimens were evaluated for HR histologically and by immunoperoxidase and immunofluorescence staining. Risk factors for HR were determined by statistical analysis. Graft survival curves were constructed and compared for patients testing negative or positive for HR.

RESULTS

A total of 358 endomyocardial biopsies (EMBs) from 103 pediatric heart transplant patients (age 3 weeks to 20 years; 52% males) were analyzed for HR. Thirty-six grafts (32%) showed evidence of HR. Grafts with a history of HR during the first year after transplant had a 47% failure rate over 3 years, compared with 29% of those hearts with no evidence of HR (p = 0.06). Although patients with congenital heart disease (CHD) appeared to be at greatest risk for developing HR (p = 0.01), patients with positive donor-specific crossmatch data showed a trend toward more significant risks for HR (p = 0.055). Hemodynamic data (including pulmonary capillary wedge pressure [PCWP] and cardiac index [CI]), left ventricular ejection fraction (LVEF), gender matching, recipient age, race of recipient vs donor and pre-transplant panel-reactive antibody (PRA) were not predictive of HR.

CONCLUSIONS

Patients with a pathologic diagnosis of HR have increased graft failure rates and overall mortality. Patients with congenital heart disease and positive cross-match results may be at increased risk for HR.

The effect of ischemic time on survival after heart transplantation varies by donor age: An analysis of the United Network for Organ Sharing database

OBJECTIVES

(1) To examine the interaction of donor age with ischemic time and their effect on survival and (2) to define ranges of ischemic time associated with differences in survival.

METHODS

The United Network for Organ Sharing provided de-identified patient-level data. The study population included 33,640 recipients undergoing heart transplantation between October 1, 1987, and December 31, 2004. Recipients were divided by donor age into terciles: 0 to 19 years (n = 10,814; 32.1%), 20 to 33 years (11,410, 33.9%), and 34 years or more (11,416, 33.9%). Kaplan-Meier survival functions and Cox regression were used for time-to-event analysis. Receiver operating characteristic curves and stratum-specific likelihood ratios were generated to compare 5-year survival at various thresholds for ischemic time.

RESULTS

In univariate Cox proportional hazards regression, the effect of ischemic time on survival varied by donor age tercile: 0 to 19 years (P = .141), 20 to 33 years (P < .001), and 34 years or more (P < .001). These relationships persisted in multivariable regression. Threshold analysis generated a single stratum (0.37-12.00 hours) in the 0- to 19-year-old group with a median survival of 11.4 years. However, in the 20- to 33-year-old-group, 3 strata were generated: 0.00 to 3.49 hours (limited), 3.50 to 6.24 hours (prolonged), and 6.25 hours or more (extended), with median survivals of 10.6, 9.9, and 7.3 years, respectively. Likewise, 3 strata were generated in the group aged 34 years or more: 0.00 to 3.49 (limited), 3.50 to 5.49 (prolonged), and 5.50 or more (extended), with median survivals of 9.1, 8.5, and 6.3 years, respectively.

CONCLUSIONS

The effect of ischemic time on survival after heart transplantation is dependent on donor age, with greater tolerance for prolonged ischemic times among grafts from younger donors. Both donor age and anticipated ischemic time must be considered when assessing a potential donor.