Introduction

Heart failure (HF) is a frequent cause of death and disability worldwide1. According to the European Society of Cardiology (ESC) HF denotes an abnormality of the cardiac structure and function, resulting in failure of the heart to deliver oxygen at a rate commensurate with the requirements of the metabolizing tissues2,3. Acute heart failure (AHF) denotes the rapid onset, or a massive exaggeration of existing symptoms and signs of HF3. Accordingly, there are patients with de novo AHF and those with AHF as a consequence of the worsening of Chronic Heart Failure (CHF).

HF is a complex syndrome with a versatile underlying pathophysiology, highlighted by disturbed hemodynamics and a deranged metabolism4. Insufficient tissue perfusion due to impaired performance of the failing heart as well as tissue congestion due to venous volume overload, a consequence of right-sided HF, cause impaired intestinal nutrient absorption, diminished biosynthetic capacity of the liver5, and worsened renal function in HF6,7. Consequently, the decreased serum levels of cholesterol, increased concentrations of urea and creatinine, as well as wasting and chronic inflammation reflect the poor overall status associated with an increased mortality rate in HF patients8.

Considering the persistent hemodynamic and metabolic burden imposed on CHF patients we hypothesized that the clinical and laboratory characteristics are worse and the mortality rate higher in AHF patients with worsening of CHF compared to de novo AHF patients. Therefore, we compared the clinical and laboratory characteristics of patients with worsening of CHF with those of de novo AHF patients and evaluated the association between worsening of CHF and mortality in AHF patients.

Results

Clinical characteristics

The patients’ baseline characteristics have been described elsewhere9 and are shown in Table 1. Out of 152 included patients, 105 (69.1%) were patients with worsening of CHF and 47 (30.9%) were de novo AHF patients. As seen in Table 1, both groups were similar regarding age, sex, smoking status, body mass index (BMI) and New York Heart Association (NYHA) functional classification. Compared to de novo AHF patients, patients with worsening of CHF had a significantly lower mean arterial pressure (MAP) and heart rate (Table 1), whereas respiratory rate and the incidence of dyspnoea and ortopnoea were similar in both groups (Supplementary Table 1). Venous congestion, a consequence of right-sided HF, was more frequent in patients with worsening of CHF; this was exemplified by a significantly higher incidence of jugular venous distension (JVD), enlarged liver, and peripheral edema (Table 1). The incidence of ascites was higher, albeit not statistically significantly in patients with worsening of CHF compared to de novo AHF patients (Table 1). Furthermore, systolic pulmonary artery pressure (SPAP) was significantly higher in patients with worsening of CHF compared to de novo AHF patients, whereas ejection fraction (EF) (Table 1), the incidence of aortic insufficiency, aortic stenosis, and dilatation of right or left ventricle did not differ significantly between the groups (Supplementary Table 1).

Table 1 Baseline characteristics, vital signs and symptoms of AHF patients with worsening of CHF vs. de novo AHF patients.
Full size table

Regarding comorbidities, the incidence of chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), and cardiomyopathy (CM) were significantly higher, and the incidence of acute coronary syndrome (ACS) was significantly lower in AHF patients with worsening of CHF compared to de novo AHF patients (Supplementary Table 2). In contrast, the incidence of hyperlipidemia, hypercholesterolemia, hypertension, type 2 diabetes mellitus (T2DM) as well as coronary and peripheral atherosclerosis was similar in both groups.

Laboratory parameters

The markers of kidney function urea and creatinine, were significantly higher and glomerular filtration rate (GFR) significantly lower in patients with worsening of CHF compared to de novo AHF patients (Table 2). While the N-terminal pro-Brain Natriuretic Peptide (NT-proBNP) and interleukin-6 (IL-6) levels were significantly higher, the levels of alanine aminotransferase (ALT), total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol, as well as leukocytes, and platelets were significantly lower in patients with worsening of CHF compared to de novo AHF patients (Table 2). Levels of aspartate transaminase (AST), C-reactive protein (CRP), triglycerides and erythrocytes did not differ significantly between groups (Table 2). While the levels of total serum protein and albumin, as well as glucose, sodium, and potassium were not significantly different between groups, the chloride levels were significantly lower in patients with worsening of CHF compared to de novo AHF patients (Supplementary Table 3).

Table 2 Laboratory parameters of AHF patients with worsening of CHF vs. de novo AHF patients.
Full size table

Mortality

Significantly more patients with AHF caused by worsening of CHF died in the hospital as well as within 3 months after hospitalization compared to de novo AHF patients (Table 3). In line with this, the univariable logistic regression analyses showed a significant positive association of worsening of CHF with hospital and 3-month mortality (Table 4). While this association did not remain significant for in-hospital mortality after adjusting for age, sex, BMI, NT-proBNP, MAP, GFR, and either urea, IL-6, and LDL cholesterol, or COPD, CKD, CM, ACS, and NYHA, the adjustment did not qualitatively change the results for 3-month mortality (Table 4).

Table 3 Mortality rate of AHF patients with worsening of CHF vs. de novo AHF patients.
Full size table
Table 4 Logistic regression analyses to assess the influence of the AHF class (worsening of CHF compared to de novo AHF) on hospital and 3-month mortality.
Full size table

Discussion

The present study clearly shows that AHF developed from CHF represents a more severe condition that is associated with higher mortality when compared to de novo AHF.

Compared to de novo AHF patients, AHF patients with worsening of CHF presented with markedly higher concentrations of NT-proBNP, a marker of heart congestion and elevated left-sided filling pressure10, indicating a more pronounced left ventricular dysfunction, accompanied by a lower MAP and higher SPAP and in turn, more severe right-sided HF with consequently more severe venous congestion.

Interestingly, despite a higher incidence of JVD, enlarged liver and peripheral edema, the body weight in AHF patients with worsening of CHF was significantly lower than in de novo AHF patients. This finding most probably reflects a more pronounced impairment of the intestinal absorption of nutrients due to a more severe intestinal edema, as well as a more severe chronic inflammation, the postulated common link between CHF, wasting syndrome and hypoalbuminemia8,11,12. In line with this, our AHF patients with worsening of CHF had lower serum levels of albumin (albeit not statistically significant) and significantly higher concentrations of IL-6 when compared to de novo AHF patients.

It is generally accepted that the augmented translocation of bacterial endotoxins from the edematous intestine into the circulation13 as well as insufficient binding and neutralization of endotoxines by circulating lipoproteins, whose levels are decreased in HF14,15, underlie the persistent inflammatory response in HF16. Additionally, the pro-inflammatory activation of venous endothelial cells by circumferential stretch due to congestion contributes to the chronic inflammation in HF17. Accordingly, lower serum levels of LDL cholesterol and HDL cholesterol together with a more severe congestion, in patients with worsening of CHF compared to de novo AHF patients may well explain the more pronounced inflammatory response, reflected by higher IL-6 levels.

The augmented inflammatory response, which is known to promote the formation and clearance of leukocyte - platelet complexes18,19, is most likely responsible for the lower leukocyte and platelet levels in our AHF patients with worsening of CHF.

It is well established that decreased cholesterol and lipoprotein serum levels are strongly and independently associated with increased mortality in HF8,14. In contrast to total, LDL, and HDL cholesterol, which were significantly lower in patients with worsening of CHF, triglyceride levels were similar in both studied groups.

Serum levels of lipids and lipoproteins are determined by their intestinal absorption, hepatic synthesis, and removal from the circulation by various catabolic routes. Accordingly, modulation of these physiological processes by the underlying AHF pathophysiology, such as congestion, which was more severe in AHF patients with worsening of CHF, may explain the different levels of total, LDL, and HDL cholesterol in the studied groups. Similar triglyceride levels in the two studied groups may indicate either that the triglyceride synthesis is not affected by the underlying AHF pathophysiology or that the decreased triglyceride synthesis is counterbalanced by a likewise decreased triglyceride catabolism. The latter possibility is likely, because lipoprotein lipase, a serum enzyme responsible for triglyceride degradation, is decreased by inflammation20, which indeed was more severe in AHF patients with worsening of CHF than in de novo AHF patients.

Renal dysfunction, also a strong predictor of mortality in HF21,22, was more pronounced in our AHF patients with worsening of CHF than in de novo AHF patients. This was reflected by a markedly decreased GFR and concomitantly increased serum levels of urea and creatinine. The reduction in GFR may be due to several factors including kidney hypoperfusion23, renal co-morbidities24, renal venous congestion25,26, or inflammatory cytokines such as IL-627. Accordingly, a higher incidence of CKD, together with a more severe venous congestion and a more pronounced inflammatory response, as well as higher serum levels of NT-proBNP, an established predictor of worsening renal function in CHF28, may well explain the more severe impairment of renal function in our AHF patients with worsening of CHF compared to de novo AHF patients.

Besides their deleterious effects on the kidneys, inflammatory cytokines such as IL-6 exert a direct detrimental effect on the myocardial structure and function by promoting oxidative stress and endothelial dysfunction, thus contributing to the progression of HF29. Therefore, a more pronounced inflammatory state, reflected by higher IL-6 levels, seems to be an important underlying pathophysiology responsible for worse clinical status of our AHF patients with worsening of CHF compared to de novo AHF patients.

The above-mentioned differences between the groups regarding the clinical characteristics observed in our AHF patients with worsening of CHF translated into a higher mortality rate, whereby the impact on 3-month mortality was more pronounced than the impact on hospital mortality. This is in line with two recent reports showing a strong association of the chronicity of HF with 6-month and 3-year mortality, but only a weak association with 1-month mortality30,31. In the present study, the strong association of worsening of CHF with 3-month mortality was weakened, but remained significant upon adjustment for comorbidities and established risk factors in HF8,32,33. This implies that other features inherent to this group of patients underlie their increased mortality compared to de novo AHF patients.

There are several limitations to our present study: The design precludes conclusions on the pathophysiological mechanisms in terms of cause and consequence, or temporal development and onset of signs, and symptoms associated with worsened status and increased mortality. Furthermore, our data do not facilitate the examination whether the duration of HF chronicity affects mortality rates. Finally, the limited number of participants in this monocentric study influences the statistical power of our analyses. Therefore, further large studies are needed to confirm our results.

Based on our results, we conclude that AHF developed from CHF is a more severe condition than de novo AHF and is associated with higher mortality rates.

Methods

Study design and patients

Study design, inclusion and exclusion criteria as well as patient characteristics for our AHF cohort have been reported previously9,34. In short, we performed a prospective observational study on hospitalized patients with AHF in Zagreb, Croatia, between 2013 and 2015. Written informed consent was obtained from each patient and the study, which was approved by the Ethics Committees of the University Hospital Centre Sisters of Charity, Zagreb, Croatia and the Medical University of Graz, Austria, was conducted in adherence to the ethical guidelines of the Declaration of Helsinki35. All patients were treated according to the ESC Guidelines for AHF3,36.

Measurements of SPAP

SPAP was approximated the tricuspid valve velocity, estimated central vein pressure (resembling right atrium pressure), and Bernoulli equation from a Doppler echocardiography.

Laboratory procedures

The collection of blood samples, standard laboratory methods, and the determination of the NT-proBNP concentration have been described in our previous reports on our AHF cohort34,37. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined with the Abbott Architect c8000 (Chicago, IL, USA).

Statistical analyses

Categorical data are shown as absolute and relative frequencies, whereas continuous data are summarized as median and range (minimum to maximum) due to the skewed distribution of many of the laboratory parameters. Patients with de novo AHF and with worsening of CHF were compared by Mann-Whitney U test or Fisher’s exact test. The impact of worsening of CHF as compared to de novo AHF on hospital and 3-month mortality was assessed by logistic regression analysis. In addition to a univariable model, we also adjusted for age, sex, BMI, NT-proBNP, GFR, MAP, urea, IL-6, and LDL cholesterol, as well as for age, sex, BMI, NT-proBNP, MAP, GFR, COPD, CKD, CM, ACS, and NYHA, the comorbidities as well as clinical and laboratory parameters known to be associated with mortality in HF patients. We checked the variance inflation factor to prevent multi-collinearity among the covariates. Results are presented as odds ratios (OR) with the respective 95% confidence interval (CI). All analyses are exploratory and a p-value of <0.05 was considered significant. R version 3.4.2. was used for all statistical analyses.