Neutrophil/lymphocyte ratio predicts in‐hospital complications in Takotsubo syndrome. Results from a prospective multi‐center registry

Abstract Background Several hematological indices including subtypes of leukocytes populations have been associated with cardiovascular outcome. Takotsubo syndrome (TTS) is a form of acute heart failure syndrome featured by several in‐hospital complications (IHCs). Hypothesis Hematological indices at admission may predict IHCs in TTS patients. Methods One hundred and sixty consecutive patients with TTS were enrolled in a multicenter prospective registry. Clinical data, admission hemogram, and IHCs were recorded. Results Incidence of IHCs was 37%, including pulmonary edema 9%, cardiogenic shock 9%, need of invasive ventilation 10%, death 8%, stroke 2.5%, and left ventricular thrombi 6%. Patients with IHCs were older, more frequently male, with physical stressor‐induced TTS, lower left ventricular ejection fraction at admission. Neutrophil/lymphocyte ratio (NLr) (12 ± 12 vs 7 ± 8, P = .002) and white blood cells/mean platelet volume ratio (1.2 ± 0.5 vs 1.0 ± 0.5, P = .03) at admission were significantly higher in patients with IHCs. NLr values were predictor of IHCs (Odds ratios [OR] 1.07, 95% CI 1.03‐1.11, P < .01). When stratified according to NLr into tertiles, the rate of IHCs was from first to third tertile was, respectively, 22%, 31%, and 58%. NLr values in the higher tertile were independent predictors of IHCs even at multivariate analysis (OR 3.7, 95% CI 1.5‐9.4, P < .01). NLr values higher than 5 were able to predict IHCs with a sensitivity of 82% and specificity of 58%; negative predictive power was 84% (area under the ROC curve 0.73). Conclusions NLr is an independent predictor of IHCs in patients admitted with TTS. Admission hemogram may represent a potential tool for prediction of IHCs in TTS.


| INTRODUCTION
Takotsubo syndrome (TTS) is a form of acute heart failure featured by transient left ventricular dysfunction that can mimic acute myocardial infarction. 1 It mostly affects postmenopausal women after either a physical or an emotional stress. Recent studies showed that TTS is featured by high rate of in-hospital complications (IHCs), mainly cardiovascular 2 and adverse events at long term. 3 Several algorithms based on the use of clinical and echocardiographic parameters have been proposed for in-hospital risk stratification in TTS patients 2 ; less is known, however, on the prognostic role of hematological indices in TTS.
In previous studies, the neutrophil/lymphocyte ratio (NLr) has been related with the occurrence of in-hospital cardiovascular complications and mayor cardiovascular adverse events in patients with acute coronary syndrome (ACS) 4 . 5 Aim of this study was therefore to evaluate whether the assessment of a hematological index, such as NLr at admission could be useful to predict clinical outcomes during hospitalization in TTS patients. The study was held according to declaration of Helsinki and approved by local ethics committees; all participants provided a written informed consent.

| Clinical examination and echocardiography
All patients underwent a clinical examination and a detailed anamnesis was collected including: age, gender, and kind of triggering stressor.
Medical history, including history of neurologic disorders (cerebrovascular accidents, neurodegenerative disorders, and epilepsy), was also recorded.
A two-dimensional Doppler Echocardiographic examination at admission, at third day, and at discharge was performed. The left ventricular ejection fraction (LVEF) was calculated using the Simpson method from the apical four-chamber and two-chamber view. Coronary angiography was performed in all patients at admission.

| Blood tests
The complete blood cell count was performed after blood samples with K2EDTA tubes (Terumo Europe NV, Leuven, Belgium), which were always collected at the time of admission. The analysis was performed with the fully automated hematological analyzer Advia 2120 (Siemens Healthcare Diagnostics, Tarrytown NY). The local reference ranges are 150 to 400 × 10 9 /L for the platelet count, 4.3 to 10.0 × 10 9 /L for total white blood cells, 2.0 to 7.0 × 10 9 /L for neutrophils, and 0.95 to 4.5 × 10 9 /L for lymphocytes. The entire investigation was carried out using the same analyzer and the quality of results was validated throughout the study period by regular internal quality control procedures and participation in an external quality assessment scheme.
The values of NLr, white blood cell count/mean platelet volume (MPV) ratio, MPV/platelets ratio, and platelet count/lymphocyte ratio were, respectively, calculated by dividing the absolute number of each variable obtained in the same blood sample collected at admission.

| Outcomes
The primary clinical endpoint was occurrence of IHCs including overall mortality, pulmonary oedema, need of invasive ventilation, cardiogenic shock, stroke, and LV thrombosis.

| Statistical analysis
Continuous variables were expressed as mean ± SD and compared with Student t test or Mann-Whitney U test as required. Categorical variables were presented as percentages and compared with χ 2 or Fisher test as required. The Kolmogorov-Smirnov test was used to identify variables with normal distribution.
Logistic regression analysis was used to identify predictors of outcome. Forward multivariable logistic regression analysis was used for correcting for principal confounders. Predictors at univariable logistic regression with a significance value ≤0.01 were included in multivariable analysis. Odds ratios (OR) with 95% confidence interval (CI) were calculated. Linear correlations were determined by measuring the Pearson's correlation coefficient.
A P < .05 was considered as statistically significant.
T A B L E 1 Baseline features according to occurrence of IHCs
NLr values >5 were able to predict the occurrence of IHCs with a sensitivity of 82% and a specificity of 58%; negative predictive power  (Figure 3).

| DISCUSSION
To the best of our knowledge, this is one of the first studies showing possible correlations between hemogram parameters and IHCs in TTS. Main findings of the study are the followings:

1) Patients that experienced IHCs presented higher values of white blood cells and neutrophils at admission;
2) NLr is an independent predictor of IHCs; 3) When stratified according to NLr tertiles, values in the higher tertile were independent predictors of IHCs.
TTS has been for a long time considered a benign disease, because of the completely reversible nature of the distinct wall motion abnormalities. However, several clinical studies have shown that TTS is a form of acute heart failure that can be associated with life-threatening complications. 7 Therefore, an early risk stratification with simple and fast clinical tools is crucial for clinical management of these patients.
The role of hemogram parameters in cardiovascular diseases has been extensively studied and a relationship between several inflammatory markers and cardiovascular diseases has been established mainly in the context of coronary artery disease. 8 Recent studies found that several subtypes of leukocytes compared with the total leukocyte count and specific subtype, including neutrophils, lymphocytes, and monocytes, have a better predictive value for cardiovascular events. 4,5,9 Lymphocytes regulate the inflammatory response and have an antiatherosclerotic role in which regulatory T-cell, a subclass of lymphocyte, may have an inhibitory effect on atherosclerosis. 10 Lymphocyte populations and population's ratios may be associated with early clinical presentation of coronary artery disease 11 or poor clinical outcome. 12 Neutrophils represent the first type of white cells that is generally observed, following damage, in myocardial tissue. 13 They also play an important role in the process of destabilization of the atherosclerotic plaque. Neutrophil count, however, is easily affected by individual variables, such as blood volume. Neutrophils secrete inflammatory mediators that can lead to vascular wall degeneration. 14  High levels of white blood cells have been associated with an increased risk of mortality in patients with ACS. 16 In any case, the total number of circulating leukocytes is the result of the combination of several variables, including genetics, gender, and age. A previous study also showed that a low lymphocyte count served as an early marker of physiologic stress and systemic collapse secondary to myocardial ischemia mediated by cortisol release. 17 Increased cortisol and catecholamine levels result in a reduction in the relative level of lymphocytes. 18,19 T A B L E 3 Univariate and multivariate forward stepwise logistic regression analysis: predictors of in-hospital cardiovascular complications suggesting a potential chronic inflammation among these patients.
However, during the acute phase of TTS, increased levels of catecholamines through IL-6 mechanism may result into persistent neutrophil inflammatory response to cell damage and relative reduction of lymphocytes levels. 27 Murakami et al, 28 in a Japanese registry of 107 patients with TTS, previously found that white blood cell count and brain natriuretic peptide were independent predictors of IHCs. NT-pro-BNP levels higher than median were found to be associated with 30-day major adverse cardiovascular events. 29 Additional clinical and echocardiographic parameters associated with IHCs in previous TTS cohorts were right ventricular involvement, LVEF, male sex, history of neurological disorder, and diabetes. 2,30 Recently, physical triggers have also been associated with a worse in and out-of-hospital outcome, especially in case of inflammatory response. 31

| LIMITATIONS
These are preliminary data to be confirmed in larger cohorts of patients. Further and more adequately powered prospective studies are warranted to clarify the assay standardization, the optimal cutoff, and the prognostic value of NLr in association with other biomarkers and clinical scores.
Prior to admission hemograms were unknown and a comparison with admission hemograms was not possible; baseline conditions associated with immunomodulation or chronic leukocytosis were not ruled out.

| CONCLUSIONS
NLr is an independent predictor of IHCs in patients admitted with TTS. Admission hemogram may be an easy and fast tool for risk stratification of IHCs in TTS.