Discussion
The main finding of this study is that the IMRS, developed in a general hospitalised cohort using commonly available standardised objective laboratory parameters, was associated with all-cause mortality in patients with HFpEF with a similar predictive ability as the HF-specific GWTG-HF risk score. Furthermore, in combination, these two scores (ie, IMRS and GWTG-HF risk score) are complementary in predicting all-cause mortality, providing additional risk prediction when evaluated together. Consistent with previous studies, we have also validated the ability of NT-proBNP to reclassify long-term mortality risk of patients hospitalised with acute HFpEF in complement to clinical scores.
HFpEF is a growing cause of morbidity and mortality in older adults.1–4 Several series have reported a mortality ranging from 15% to 30% at 5 years.8–10 Our population is representative of these series, with a mortality rate of 24% over a median follow-up of 2 years. We have also observed a high prevalence of co-morbidities including DM, CAD, CKD and Afib in our population. This study shows that patients with an intermediate risk by the GWTG-HF risk score can be reclassified as high risk using IMRS. For better impact on clinical management, a novel strategy is warranted. Since there are no clinical guideline supported specific therapeutics available for high-risk population, the practical implication would be to use these risk scores for close monitoring and management of early stage decompensation in this subpopulation.
The GWTG-HF risk score was validated in patients with acute HF including reduced and preserved ejection fraction.22 28 Central to this score are age, race, markers of renal function, heart rate and systolic BP. While GWTG-HF risk score was developed to predict in-hospital mortality, we demonstrate in our study that it also predicts long-term survival in patients with HFpEF. Compared with GWTG-HF risk score, the IMRS considers more comprehensive laboratory based markers such as RDW and WCC count that have also been shown to be predictive of outcome in HF.29 RDW, which emerged as strong correlate of mortality in our study, was also recently shown to predict mortality in acute HF with both HFrEF and HFpEF as well as in atherosclerosis.30–32 In a study by Imai et al in which 278 consecutive patients with acute decompensated HFpEF were enrolled, RDW emerged as an independent predictor of poor outcome due to non-cardiac events.32 Thus, more CBC markers such as RDW should be integrated in HF risk scores. As outlined by our univariable analysis, age is a strong factor that drives outcome in both scores. An interesting question would be if a new combined risk score can improve risk stratification and outcome in this patient population.
NT-proBNP improved the net reclassification of both scores. BNP or NT-proBNP have been used as a supportive diagnostic criteria for HFpEF as recently reviewed by Santaguida et al.33–36 BNP has previously been shown to improve the net reclassification for in-hospital mortality when added to GWTG-HF score, although the net reclassification was lower as it addressed in-hospital mortality.22 Among other biomarkers, troponin (including higher sensitivity troponin) has been shown to be associated with adverse in-hospital and postdischarge outcomes in patients with acutely decompensated HFpEF.37 While biomarkers such as ST-2, galectin-3, growth differentiating factor-15 (GDF-15) have also been predictive of outcome in HFpEF,38–40 their incremental value to well-validated and simple clinical scores remains to be proven. In addition to clinical and laboratory data, several investigators have assessed the importance of echocardiographic parameters in patients with HFpEF such as haemodynamic parameters namely right ventricular systolic pressure41 and deformation imaging parameters focusing on left ventricle42 or left atrium.43 To evaluate the incremental role of these parameters to the risk scores is the subject of ongoing research.
As is being implemented in several centres, clinical risk scores are being automatically generated using electronic medical records. Several centres are using these scores to guide pathways of care following discharge.44 We therefore envision that incorporating multiple risk scores should not be an added burden on care and could help identify features of risk captured by complementary scores. Our study also identifies the direction to develop novel risk scores that incorporate NT-proBNP and other commonly available biomarkers such as RDW, which could further improve and simplify pathway of care in HF management.
Limitations
The present study should be interpreted in the context of its limitations. First, this is a retrospective single-centre cohort study with relatively smaller sample size, and therefore, validation is required. The study cohort, however, is representative of the recent trials and registries and the data, and each chart was carefully reviewed. Second, we did not collect data to calculate the scores for patients with HF and reduced ejection fraction to compare with HFpEF. Other biomarkers such as GDF-15 were not measured in our cohort. It will be interesting, though challenging, to see the incremental value of other biomarkers in addition to NT-proBNP to risk models derived from other cohorts. We did not include rehospitalisation as a secondary end-point as patients were followed at different institutions during the study period leading to incomplete data collection. Finally, we only used variables available on admission and future studies to investigate whether improvement of factors related to these scores or BNP have an impact on longer outcome.