DISCUSSION
The present study demonstrates that, in some parts of the world, shortage of donors is not the most important limiting factor of heart transplantation. Our cohort comprises complete donor and recipient information of Brazilian’s Mid-West region, with a population of over 15 million people. We have found that, over a two-year period, the donor’s heart utilization rate was less than 20%. The main reasons for donor refusal were non-medical, which included lack of an organized system of heart procurement at distant sites and absence of complementary tests to assess heart’s condition. Other less prevalent, but not least important factors, were severe hemodynamic instability and ventricular dysfunction on echocardiography. Gomes and colleagues10 described disparities in access to transplantation services within Brazil’s regions due to logistical challenges, uneven resource allocations and under-capacitated health care facilities. In Brazil, stark geographical and social inequalities in morbidity and mortality rates exist within and between these regions attributed to development status mainly related to differences in demographic density, GDP, and level of development.
The relatively high refusal rate in our center certainly had a negative impact on waiting list recipient’s mortality of 15.9%. That mortality rates might be explained as well by unavailability of ventricular assist devices for those recipients in need. In the United States, approximately 60% of available hearts are discarded11. Institutions have algorithms for deciding which heart to transplant, but still the most prevalent criteria relies on personal experience and clinical intuition. Khush et al.12 found in a large populational database that 48% of the potential donor hearts were rejected, in large part, because of female sex, older donor age, and medical comorbidities. Many of these hearts are being rejected needlessly. This is particularly relevant considering the decrease utilization of donor hearts over time. One study found that the use rates decreased by an average of 4.2% per year, from a high of 56% in 2002 to a low of 37% in 200711. Feldman and colleagues8corroborated the low rate of donor utilization in Brazil in a cohort of very young donors (mean age of 23.5 years), mostly due to poor donor management protocols. Likewise our experience with long-distance donors, they8 have confirmed the unavailability of echocardiography at donor assessment. This may reduce the use of many potential grafts because of concerns regarding organ quality and recovery. Suboptimal or even good grafts that are poorly managed could increase the risk of primary graft dysfunction13. Therefore, optimization of donation process is crucial to increase the number and the quality of heart transplantation14.
No standardized approach exist for management and weighing of donor and recipient risk factors, resulting in considerable variability between transplant centers in clinical practice4. Changing a local culture of rejecting a donor’s heart for any reason is difficult, but feasible. Using a systematic, multidisciplinary approach to examine why they were turning down potential donor hearts, Smith and colleagues15 improved their utilization rate from 46 to 75% and increased OHT numbers from 22 to 35 in 1 year without adversely affecting 1-year survival. Strategies to achieve this goal need optimization of the entire process of organ procurement, transportation, and functional recovery after transplant14.
In order to attain a more objective clinical decision in assessing a heart for transplantation, the development of a validated donor risk score that takes into account all the relevant factors would be a useful tool for clinicians. Risk calculators in cardiac surgery16,17 have gained great importance for predicting major adverse events after surgical procedures, which helped in indication for surgery, adequate patient consent and in inclusion criteria to controlled clinical trials. Two studies, Smits et al.9 using European database and Weiss et al18 using the UNOS database, designed and validated donor heart scores that accurately reflected the likelihood of donor heart acceptance and predicted long-term mortality.
In the present study, we used the European donor score to objectively stratify donor characteristics that possibly were taken into account in the decision to accept the organ, and subsequent transplant outcomes. The majority of donors were classified as high-risk. Donors accepted for transplantation had a slightly lower score when compared to those refused. Since the scoring system was calculated for the purpose of the study, it seems that other factors rather than the scoring system were used in the decision to proceed with the transplant. In our experience, recipient’s clinical condition did not influence on the decision to accept a higher risk donor either. That information is against the general recommendation that expanded donor criteria hearts should be considered for sicker patients in urgent need of transplantation19. Long-distance procurement does not seem to have an impact on that too. Despite there were some differences between local and long-distance donors, they were mostly related to worse hemodynamics in the former and less access to echocardiography and coronary angiograms in the latter. As far as donor scoring system is concerned, high-risk donors were similarly prevalent in local and long-distance offers. Expanded donor criteria did not compromise survival or hemodynamics at 12 months in a previous study20. There is considerable evidence that use of marginal donors generally results in satisfying results and therefore is justifiable to alleviate the donor organ scarcity21,22.
Donor scoring system did not have any influence on the occurrence of primary graft dysfunction and long-term mortality. As opposed to other donor-related factors, the only predictor of long-term survival in our population was recipient’s age greater than 50 years. That information stresses the safety of expanding the donor pool to marginal donors. When determining the impact of donor scoring system on long-term mortality, we adjusted the analysis to previously well-known confounding factors23 such as recipient age, primary diagnosis, urgency status at time of transplant, donor to recipient height ratio, weight and gender match, and ischemia time.
Recipient’s age has been proposed as a risk factor for post-transplant complications24. One of the components of the RADIAL score25, which predicts primary graft dysfunction, is recipient’s age greater than 60 years of age. Joyce and colleagues26 studied 24,540 heart transplants entered into the UNOS database. One of the predictors of 1-year post-transplant mortality was recipient’s age > 55 years. Donor age and ischemic time were predictors in that model too, as opposed to our data. They created a new scoring system that would account for the interplay between donor, recipient and combined risk factors in predicting 1-year survival. Recipient health factors and comorbidities outweighed most donor factors. Most importantly, the most frequent component of a high-risk score was recipient age greater than 55 years along with the presence of an LVAD and end-organ dysfunction.