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.