Thoracic transplantation

Impact of the 18th birthday on waitlist outcomes among young adults listed for heart transplant: A regression discontinuity analysis

BACKGROUND

Patients listed for heart transplant after their 18th birthday purportedly wait longer to receive a donor heart compared with patients listed before their 18th birthday. It is unclear whether there is an actual difference in wait times and whether any difference in wait time is associated with lower likelihood of transplant and/or higher risk of mortality.

METHODS

Organ procurement and transplant network data were used to identify all patients listed for heart transplant between 2006 and 2014 within a 1-year period before and after their 18th birthday. The primary study end-point was the waiting time to receive a donor heart. Secondary end-points included the probability of transplant and waitlist mortality. Regression discontinuity analysis was used to analyze the effect of age on either side of the sharp cut-off value of age 18 years (6,574 days of life), when allocation of donor hearts transitions from the pediatric to adult allocation system.

RESULTS

A total of 360 patients met the study inclusion criteria, including 207 (57.5%) listed during the 12-month period before their 18th birthday under the pediatric allocation system, and 153 (42.5%) listed during the 12 months after their 18th birthday under the adult allocation system. The pediatric cohort was more likely to be listed Status 1A. Otherwise, the 2 groups shared similar baseline characteristics. Overall, patients listed after their 18th birthday waited 8.5 months longer to receive a transplant than adolescents listed before their 18th birthday (p = 0.01) and had a 47% lower probability of receiving a transplant (p = 0.001), but there was no difference in waitlist mortality (p = 0.37).

CONCLUSIONS

Patients listed for heart transplant shortly after their 18th birthday have significantly longer wait-times compared with patients listed shortly before their 18th birthday and a lower probability of transplant, but no significant difference in waitlist mortality. For medically fragile adolescents at high risk of death, birth date may be a relevant factor in the timing of heart transplant listing.

Predicting the graft survival for heart-lung transplantation patients: an integrated data mining methodology

BACKGROUND

Predicting the survival of heart-lung transplant patients has the potential to play a critical role in understanding and improving the matching procedure between the recipient and graft. Although voluminous data related to the transplantation procedures is being collected and stored, only a small subset of the predictive factors has been used in modeling heart-lung transplantation outcomes. The previous studies have mainly focused on applying statistical techniques to a small set of factors selected by the domain-experts in order to reveal the simple linear relationships between the factors and survival. The collection of methods known as 'data mining' offers significant advantages over conventional statistical techniques in dealing with the latter's limitations such as normality assumption of observations, independence of observations from each other, and linearity of the relationship between the observations and the output measure(s). There are statistical methods that overcome these limitations. Yet, they are computationally more expensive and do not provide fast and flexible solutions as do data mining techniques in large datasets.

PURPOSE

The main objective of this study is to improve the prediction of outcomes following combined heart-lung transplantation by proposing an integrated data-mining methodology.

METHODS

A large and feature-rich dataset (16,604 cases with 283 variables) is used to (1) develop machine learning based predictive models and (2) extract the most important predictive factors. Then, using three different variable selection methods, namely, (i) machine learning methods driven variables-using decision trees, neural networks, logistic regression, (ii) the literature review-based expert-defined variables, and (iii) common sense-based interaction variables, a consolidated set of factors is generated and used to develop Cox regression models for heart-lung graft survival.

RESULTS

The predictive models' performance in terms of 10-fold cross-validation accuracy rates for two multi-imputed datasets ranged from 79% to 86% for neural networks, from 78% to 86% for logistic regression, and from 71% to 79% for decision trees. The results indicate that the proposed integrated data mining methodology using Cox hazard models better predicted the graft survival with different variables than the conventional approaches commonly used in the literature. This result is validated by the comparison of the corresponding Gains charts for our proposed methodology and the literature review based Cox results, and by the comparison of Akaike information criteria (AIC) values received from each.

CONCLUSIONS

Data mining-based methodology proposed in this study reveals that there are undiscovered relationships (i.e. interactions of the existing variables) among the survival-related variables, which helps better predict the survival of the heart-lung transplants. It also brings a different set of variables into the scene to be evaluated by the domain-experts and be considered prior to the organ transplantation.

Living donor lobar grafts improve pediatric lung retransplantation survival

OBJECTIVE

Lung retransplantation is a controversial practice due to increased morbidity and mortality and the scarcity of available donor organs. Living donor lobar lung transplantation increases the number of available donor organs and facilitates a more organized procedure than traditional cadaveric donation for this complex reoperation. The purpose of this study was to evaluate our experience with pediatric lung retransplantation and to compare the outcomes of living donor lobar lung transplantation with cadaveric donation.

METHODS

Retrospective review of a prospectively collected database identified 39 children who underwent lung retransplantation from 1991 to 2004. Retransplantation was performed with living donor lobar lung transplantation in 13 patients and cadaveric donation in 26 patients. Short- and long-term outcomes were compared between the 2 groups.

RESULTS

Perioperative mortality was 1/13 (7.7%) in the patients who had living donor lobar lung transplantation versus 11/26 (42.3%) in the cadaveric donation group (P = .03). Five-year survival for living donor lobar lung transplantation and cadaveric donation was 40.4% and 29.7%, respectively (P = .27). Both groups had a significant improvement in their forced expiratory volume in 1 second 6 months after retransplantation (P < .001). Multivariate analysis identified the use of cadaveric donation (relative risk = 6.16, P = .001) and early graft dysfunction (relative risk = 6.19, P = .001) as the major independent predictors of decreased survival following retransplantation.

CONCLUSIONS

Living donor lobar lung transplantation reduces perioperative mortality and is an independent predictor of improved survival following pediatric lung retransplantation. This strategy offers significant benefit for this high-risk group and preserves the limited supply of donor lungs for other children at risk of dying while waiting for lung transplantation.

A decade of living lobar lung transplantation: perioperative complications after 253 donor lobectomies

Living lobar lung transplantation places two donors at risk for each recipient. We examined the perioperative outcomes associated with the 253 donor lobectomies performed at our institution during our first decade of living lobar lung transplantation. There have been no perioperative or long-term deaths. 80.2% of donors (n = 203) had no perioperative complications, while fifty (19.8%) had one or more complication. The incidence of intraoperative complications was 3.6%. Complications requiring reoperation occurred in 3.2% of donors. 15.0% of donors had other perioperative complications; the most serious were two donors who developed pulmonary artery thrombosis, while the most common was the need for an additional thoracostomy tube or a thoracostomy tube for >/=14 d for persistent air leaks and/or drainage. Right-sided donors were more likely to have a perioperative complication than left-sided donors (odd ratio 2.02, p = 0.04), probably secondary to right lower and middle lobe anatomy. This experience has shown donor lobectomy to be associated with a relatively low morbidity and no mortality, and is important if this procedure is to be considered an option at more pulmonary transplant centers, given continued organ shortages and differences in philosophical and ethical acceptance of live

A decade of living lobar lung transplantation: recipient outcomes

OBJECTIVE

Living lobar lung transplantation was developed as a procedure for patients considered too ill to await cadaveric transplantation.

METHODS

One hundred twenty-eight living lobar lung transplantations were performed in 123 patients between 1993 and 2003. Eighty-four patients were adults (age, 27 +/- 7.7 years), and 39 were pediatric patients (age, 13.9 +/- 2.9 years).

RESULTS

The primary indication for transplantation was cystic fibrosis (84%). At the time of transplantation, 67.5% of patients were hospitalized, and 17.9% were intubated. One-, 3-, and 5-year actuarial survival among living lobar recipients was 70%, 54%, and 45%, respectively. There was no difference in actuarial survival between adult and pediatric living lobar recipients (P =.65). There were 63 deaths among living lobar recipients, with infection being the predominant cause (53.4%), followed by obliterative bronchiolitis (12.7%) and primary graft dysfunction (7.9%). The overall incidence of acute rejection was 0.8 episodes per patient. Seventy-eight percent of rejection episodes were unilateral. Age, sex, indication, donor relationship, preoperative hospitalization status, use of preoperative steroids, and HLA-A, HLA-B, and HLA-DR typing did not influence survival. However, patients on ventilators preoperatively had significantly worse outcomes (odds ratio, 3.06, P =.03; Kaplan-Meier P =.002), and those undergoing retransplantation had an increased risk of death (odds ratio, 2.50).

CONCLUSION

These results support the continued use of living lobar lung transplantation in patients deemed unable to await a cadaveric transplantation. We consider patients undergoing retransplantations and intubated patients to be at significantly high risk because of the poor outcomes in these populations.

Living lobar transplantation

Although cadaveric transplantation remains the preferred option for patients who have end-stage lung disease, living lobar transplantation provides organ availability that can be life saving in severely ill pediatric and adult patients who will either die or become unsuitable recipients before a cadaveric organ becomes available. In addition, living lobar transplantation provides acceptable long-term survival when compared with recipients of cadaveric grafts; however, because this procedure presents risks to two healthy donors, appropriate recipient and donor selection and timing of transplantation are critical to minimize the morbidity to the donor and maximize the chance of a successful outcome in the recipient. The results of the authors' experience have demonstrated that the donor procedure is safe, well tolerated physiologically, and that the great majority of donors are extremely satisfied with their decision to donate. Although there have been no deaths in the donor cohort, a risk of death between 0.5% to 1% should be quoted pending further data. These encouraging results are important if this procedure is to be considered as an option at more pulmonary transplant centers in view of the institutional, regional, and intra- and international differences in the philosophical and ethical acceptance of the use of live organ donors for transplantation.