Association between quality of life and prognosis of candidate patients for heart transplantation: a cross-sectional study

ABSTRACT Objective: to verify the association between the prognostic scores and the quality of life of candidates for heart transplantation. Method: a descriptive cross-sectional study with a convenience sample of 32 outpatients applying to heart transplantation. The prognosis was rated by the Heart Failure Survival Score (HFSS) and the Seattle Heart Failure Model (SHFM); and the quality of life by the Minnesota Living With Heart Failure Questionnaire (MLHFQ) and the Kansas City Cardiomyopathy Questionnaire (KCCQ). The Pearson correlation test was applied. Results: the correlations found between general quality of life scores and prognostic scores were (HFSS/MLHFQ r = 0.21), (SHFM/MLHFQ r = 0.09), (HFSS/KCCQ r = -0.02), (SHFM/KCCQ r = -0.20). Conclusion: the weak correlation between the prognostic and quality of life scores suggests a lack of association between the measures, i.e., worse prognosis does not mean worse quality of life and the same statement is true in the opposite direction.


Introduction
The availability of solid organs for transplantation is a problem worldwide (1)(2)(3)(4) . There had been an expressive increase in the number of cardiac transplantations (CT) in the world until the mid-1990s. Since then, due to improvements in the clinical management of heart failure (HF) and the inherent limitation of donors, the number of CT remains stable: 4,000 to 5,000 (5) . In Brazil, in 2016, of the 631 patients entered in the CT queue, 145 died before receiving a heart, with only 357 CT being performed, which reaches 1.7 transplants per million population (6) . These facts reinforce the need for an accurate indication for CT, considering the risk stratification of the patients and the patient's desire to transplant.
In this context, studies have described the prognostic scores in HF as well-used and accurate measures to stratify risk (7)(8) and when associated to the peak of oxygen consumption (VO2) can help the indication of transplantation, according to the suggestion of the International Society for Heart and Lung Transplantation -ISHLT (9) , whereas the specific instruments of Quality of Life (QoL) have shown to be accurate in assessing QoL in patients with HF (10)(11) .
Besides, scholars (12)(13)(14) recommend that nursing progresses in research practices to evaluate outcomes such as QoL, prognosis and readmission in patients with advanced HF and transplant candidates, as well as after CT and clinical follow-up. Therefore, as the improvement of QoL, in addition to increased survival, is one of the objectives to be achieved with the indication of the CT, and as HF has an impact on QoL, besides as a poor prognosis, this article aims to check the association between the prognostic scores and the QoL of candidates for CT.   Lymphocytes.  The MLHFQ (17) is composed of 21 questions divided by two dimensions (physical and emotional) and total score. The total score is calculated with the sum of the questions ranging from 0 to 105, in which the higher the score, the worse the QoL.

Method
And the KCCQ (18) Table 1 presents the sociodemographic and clinical characteristics of the participants.

Results
When classified by the HFSS, 89.2% of the patients were described as medium and low risk for mortality in one year ahead, however, when classified by the SHFM, 90.6% were described as medium and high risk for mortality in one year ahead.
The mean QoL scores of the participants by the MLHFQ and KCCQ questionnaires are described in Table 2.    Faria VS, Matos LN, Trotte LA, Rey HCV, Guimarães TCF.

Discussion
The weak correlation between the prognostic scores and the QoL scores found in this study suggests that the patient's perception, measured by QoL, as well as the prognostic score are a complementary measure to be used in clinical practice to aid the indication of CT.
No studies were found in the literature that associate prognostic scores with specific QoL instruments in HF, however one study evaluated the relationship between SHFM and a generic QOL instrument (19) . Also, some studies have discussed the impact on the mortality of the specific instruments that measure QOL in HF (20)(21)(22) .
One study longitudinally evaluated the relationship between SHFM and the health status valuation measured by the generic instrument EuroQol 5D (EQ-5D). Through a linear regression, they evaluated 2,331 patients with a 2.5-year follow-up, with FC (NYHA) II to IV, LVEF ≤ 35%, showing that the increase of 1 unit in SHFM decreased by 0.03 points the EQ-5D in the baseline assessment and that each year that the SHFM increased in one point, the EQ-5D decreased 0.006 points. These results showed that patients with high mortality risk had significantly lower EQ-5D and had higher rates of decline over time (19) .
Regarding the impact on mortality, one study   (21) .
In addition, a systematic review and a meta-analysis of prospective cohorts with patients with stabilized HF and with follow-up of at least 1 month, published between 2002 and 2013, used KCCQ and MLHFQ to assess mortality and concluded that these instruments are significant mortality predictors besides the traditional risk factors (22) .  (24) .
Although it is assumed that the advanced stage disease presents more symptoms, causes greater dysfunction and consequently is related to poorer quality of life and worse prognosis (25)(26) , this may be true Another approach would be to verify causality between instruments. In addition to these issues, an important study would be on the applicability of these tools in clinical practice, such as the feasibility of implementation in the workflow, integration with the institution's electronic records and studies on costs, allowing the infrastructure to collect data and analyze them.

Conclusion
The weak correlation between the prognostic and QoL scores suggests the non-association between the scores, i.e., worse prognosis does not mean worse QoL and the opposite is also true.
The evaluation of the association between the HFSS and SHFM prognostic scores with specific instruments of QoL (MLHFQ and KCCQ) in candidates for CT is important and necessary, and the present study contributed to the pioneering nature of this practice in Brazil and also made it when using the KCCQ in the Brazilian population.