The Value of Neutrophil-to-Lymphocyte Ratio and Epicardial Adipose Tissue Thickness in Heart Failure With Preserved Ejection Fraction

Background Using epicardial adipose tissue thickness (EATt) and neutrophil-to-lymphocyte ratio (NLR) as individual indicators provides beneficial insight into the prognosis of patients suffering from heart failure with preserved ejection fraction (HFpEF). Aim In our study, we aimed to evaluate whether the combined evaluation of NLR and EATt would provide an advantage for identifying high-risk HFpEF patients according to hospitalization for heart failure (HHF) and left ventricular diastolic dysfunction (LVDD). Method A total of 168 outpatients with HFpEF were retrospectively analyzed. The predictive performance of two inflammatory variables was assessed by the receiver operating characteristic curve and a one-way analysis of variance (ANOVA) test. The patients were stratified into three distinct risk categories based on the established cut-off values for EATt and NLR as follows: Group I, high risk; Group II, middle risk; and Group III, low risk. Results Patients in Group I had the highest risk for HHF and the presence of LVDD (p=0.001 for HHF, p=0.011 for LVDD). Patients in Group I also exhibited more symptomatic and a greater number of comorbidities. In Group I, more structural remodeling (enlarged left ventricular end-systolic volume index (LVESVI) and left atrial volume index (LAVI)) and associated signs of increased intracardiac pressure (elevated E/A ratio, medial E/e’) were observed. Conclusion The results of our study indicate that the use of both EATt and NLR among patients with HFpEF may provide better accuracy in predicting HHF and LVDD compared to the use of either EATt or NLR alone.


Introduction
Heart failure with preserved ejection fraction (HFPEF) has become increasingly recognized as a significant public health concern on a worldwide basis [1]. The prevalence of HFpEF accounts for half of all heart failure cases and is projected to increase by approximately 50% by 2035 [2,3].
Systemic inflammation is believed to exert a significant influence on the pathogenesis of HFpEF. It has been observed that a prolonged inflammatory response can expedite the progression of HFpEF [1,4] and serve as a sign of the prognosis [5,6]. Simultaneously, systemic inflammatory mechanisms play an important role in increasing epicardial adipose tissue (EAT) and changing the nature of its secretion towards adipocytokines, which are pro-inflammatory [7][8][9]. These adipokines promote cardiomyocyte stiffness, coronary endothelial dysfunction, and myocardial fibrosis, all of which contribute to the development of HFpEF [10][11][12].
An increased EAT thickness (EATt), as detected by 2D transthoracic echocardiography (2D-TTE), is indicative of the accumulation of EAT [13]. Increased EATt has demonstrated an association with left ventricular diastolic dysfunction (LVDD) in pediatric patients, and augmentation of EATt in HFpEF is linked to Cardiology (Andover, Massachusetts) with an X5-1 probe. All echocardiographic data were stored for offline analysis. 2D datasets were analyzed using the dedicated software. Interventricular septum dimension (IVSd), posterior wall dimension (PWd), left ventricular end-systolic volume (LVESV), and end-diastolic volume (LVEDV) were obtained through the analysis of 2D datasets. The measurement of EATt was done by using the reference line running through the right ventricular free wall and the aortic annulus. Then, the vertical length between the right ventricular free wall and the parietal pericardium was measured as EATt at enddiastole in three cardiac cycles ( Figure 2) [23]. Left ventricular ejection fraction (LVEF) was measured using the modified biplane Simpson's method. Left atrial volume (LAV) was measured using the biplane arealength method. LVEDVI, LVESVI, and LAVI were calculated by dividing LVEDV, LVESV, and LAV by body surface area, respectively. Early diastolic velocity (E wave) and late diastolic velocity (A wave) for the mitral valve (MV) and for the tricuspid valve were measured using pulsed wave (PW) Doppler from the apical fourchamber view, respectively. Peak longitudinal systolic velocity (Sm), peak longitudinal early diastolic velocity (e'), and peak longitudinal late diastolic velocity (a') were measured using tissue Doppler imaging from the lateral and septal mitral annulus and the lateral tricuspid annulus, respectively. Left ventricular diastolic dysfunction in the left ventricle with preserved ejection fraction was defined according to the 2016 American Society of Echocardiography guidelines for the Evaluation of Left Ventricular Diastolic Function by Echocardiography [24]. Two experienced cardiologists independently interpreted all echocardiographic images. The inter-and intra-observer variabilities in echocardiographic measurements were 97% and 98%, respectively.

FIGURE 2: How to measure epicardial adipose tissue thickness (EATt) from the parasternal long-axis view
The ascertainment of one-year hospitalization for heart failure We investigated the one-year follow-up of HHF after the first outpatient visit. The one-year HHF was determined from electronic medical records. The criteria for HHF were defined as follows: (1) the presence of pulmonary and/or systemic congestion findings; (2) the need for intravenous diuretics; (3) a BNP level of 100 pg/mL or higher; and/or (4) the presence of low cardiac output findings.

The definition of comorbidity burden
Comorbidities were defined based on physician documentation and a review of the medical records. Comorbidity burden was defined by a simple score based on the assignment of the following comorbidities (one point each): obesity, coronary artery disease, hypertension, hyperlipidemia, diabetes mellitus, atrial fibrillation, and chronic renal disease.
Continuous variables were assessed for normality using the Kolmogorov-Smirnov test. Continuous variables were presented as mean ± standard deviation or median (interquartile range (IQR)). Categorical variables were expressed as numbers and percentages. Continuous variables with a normal distribution were compared using the student's t-test, and continuous variables with a non-normal distribution were compared using the Mann-Whitney U test. Categorical variables were compared using the chi-square test. Receiver operating characteristics curve (ROC) analysis was examined to determine optimal cut-off values of EATt and NLR for HHF. Patients were classified by the cut-off values of EATt and NLR. Analysis of variance (ANOVA) was used to compare the groups obtained from the cut-off values of EATt and NLR according to HHF and LVDD. A value of p<0.05 was considered statistically significant. The data analysis was performed with the SPSS 25.0 software program (IBM Corp., Armonk, NY). Figure 3 presents a graphical abstract of the analysis.

FIGURE 3: Graphical abstract
Comorbidities-induced systemic inflammation leads to increased epicardial adipose tissue and neutrophil-tolymphocyte ratio. Two proinflammatory variables play a major role in the development of heart failure with preserved ejection fraction. In addition, these markers play a contributory role in increased left ventricular filling pressure, which results in hospitalization for heart failure.

Predictive value of epicardial adipose tissue thickness and neutrophilto-lymphocyte ratio for heart failure hospitalization
Receiver operating characteristic curves were constructed to assess the ability of the EATt and NLR to predict HHF. The area under the ROC curve (AUC) of EATt and NLR in HFpEF patients was 0.767 and 0.785 (p=0.001 for EATt and NLR), respectively ( Figure 4, Table 3). EATt ≥9.45 mm predicted HHF with a specificity of 64% and sensitivity of 71%. NLR ≥2.83 predicted HHF with a specificity of 70% and sensitivity of 70%.   Our results showed that NLR ≥2.83 and EATt ≥9.45 mm were associated with significantly higher rates of HHF, separately. We further investigated the predictive value of the combination of NLR and EATt. One-way analysis of the variance test also found that the combination of NLR ≥2.83 and EATt ≥9.45 mm had the highest risk for HHF and LVDD (p=0.001 for HHF, p=0.011 for LVDD) (Figures 5A, 5B). Patients in Group I were more symptomatic, with more frequent chronic renal disease and coronary artery disease, a higher comorbidity burden, and a higher rate of diuretic treatment assignment ( Table 4).  Group I had a worse renal function test, and a larger median BNP level, CRP, NLR, and neutrophil count. It also had a lower mean lymphocyte count than the other groups ( Table 5). Patients in Group I exhibited significantly worse systolic and diastolic function as compared with Group II and Group III (

Discussion
The main findings from the current study were as follows: (1)  The rise in EATt and NLR may have the potential to raise the probability of HHF due to the resultant elevation in intracardiac pressure and natriuretic peptides. A noteworthy observation pertaining to this finding is that a marked augmentation in both EAT mass and the inflammatory reaction was noted in the mouse model deficient in ACE2. As a result, there was a notable elevation in the left ventricular filling pressure [25,26]. This observation may indicate that increased EATt and elevated NLR correlate with more severe symptoms, worse exercise capacity, and poorer cardiopulmonary performance among HFpEF patients [27]. Our study also consistently revealed that patients with high EATt (≥9.45 mm) and high NLR (≥2.45) had more impaired functional capacity with higher LV medial E/e', a noninvasive indicator of LV filling pressure. These data highlight that strategies to decrease the signs of an inflammatory response, such as EATt and NLR, may also reduce the progression of hemodynamic impairment to improve HHF in patients with HFpEF.
Our findings demonstrated for the first time the deleterious effects of inflammation on LV diastolic function with the combined use of two inflammatory variables. The current study revealed that patients with elevated levels of both EATt and NLR exhibited notably poor LV diastolic function. The present finding implies that the concurrent elevation of EATt and NLR could potentially act as a trigger for LVDD or indicate an intensified inflammatory reaction linked to LVDD. Elevated EATt has been observed to promote the secretion of adipokines with pro-inflammatory properties, thereby potentially contributing to an increase in NLR. This may lead to myocardial fibrosis, LVDD, and impaired relaxation [28,29].
Increased EATt and elevated NLR as a sign of aggravated inflammation may serve as a crucial mechanism involved in facilitating LV structural remodeling [30,31], which in turn causes left atrial (LA) electrical remodeling over time in HFpEF patients [32][33][34]. Given the mechanistic relationship between atria and ventricles, an increase in LV filling pressures may be paralleled by LA dilatation and may contribute to generating a proarrhythmogenic substrate in patients with a high-grade pro-inflammatory state. Therefore, the results of our study highlight that increased EATt and elevated NLR may enhance the MV E/A ratio and LV medial E/e', thereby accelerating the development of structural remodeling, such as LV remodeling, LA dilatation, and promoting the emergence of electrophysiological substrates for atrial fibrillation (AF) in HFpEF ( Table 4 and Table 5).
Comorbidity burden can be a significant marker of inflammation levels in the HFpEF [16,35]. Patients with multiple comorbidities are more likely to have elevated levels of NLR and increased EAT volume [17,36,37]. Therefore, the observed association between systemic inflammation and increased NLR and EATt may be consistent with the notion that patients with HFpEF who exhibit higher NLR and EATt suffer from a greater number of comorbidities. The presence of a greater comorbidity burden, indicative of an elevated systemic inflammation response, may potentially play a role in the pathophysiology of HFpEF via similar mechanisms such as inflammation. This inflammatory pathway may contribute to the development of cardiac fibrosis and impaired diastolic function [29]. Overall, comorbidity burden may seem to indicate the association between elevated inflammatory response and hemodynamic derangements, as well as their resultant effects in patients with HFpEF.

Limitations
Our study is a single-center and retrospective study. Due to the relatively low number of patients, statistical findings are only arguably verified. We only assessed EATt in two dimensions by echocardiography. Although the determination of EAT volume by cardiac magnetic resonance is more accurate, there are also studies in which EATt was determined by echocardiography [38][39][40]. Therefore, we did not quantify the volume of EAT due to planimetric measurement. This study only included outpatients with HFpEF; it would have also been valuable to include inpatients with newly diagnosed HFpEF. In addition, we evaluated one-year outcomes after index admission. Further studies with larger sample sizes and longer follow-ups are needed to better verify the association between EATt and both inflammatory biomarkers and hard endpoints in HFpEF patients.

Conclusions
The concomitant use of EATt and NLR may potentially yield a more accurate assessment of the susceptibility to HHF and the emergence of cardiac impairment in comparison with the individual use of EATt and NLR, which reflect systemic inflammation. This emphasizes the importance of addressing the underlying inflammation in the pathogenesis of HFpEF.