C-Reactive Protein and White Blood Cell Count in Cardiogenic Shock

This study examines the prognostic impact of C-reactive protein (CRP) and white blood cell (WBC) counts in patients with cardiogenic shock (CS). Data regarding the prognostic impact of inflammatory biomarkers in CS are scarce. All consecutive patients with CS from 2019 to 2021 admitted to a cardiac intensive care unit (ICU) were included at one institution. Laboratory measurements were retrieved from the day of admission (i.e., day 1), as well as days 2, 3, 4, and 8. The primary endpoint was 30-day all-cause mortality. Statistical analyses included univariate t-tests, Spearman’s correlations, C-statistics, Kaplan–Meier, and Cox regression analyses. From a total of 240 consecutive patients admitted with CS, 55% died within 30 days. CRP levels on days 3 to 8 were associated with reliable discrimination for 30-day all-cause mortality (area under the curve (AUC): 0.623–0.754), whereas CRP on day 1 was not (AUC = 0.514). In line, CRP > 100 mg/L on day 3 (56% vs. 37%; log-rank p = 0.023; HR = 1.702; 95% CI 1.060–2.735; p = 0.028) and especially a CRP increase of at least 200% from days 1 to day 3 (51% vs. 35%; log-rank p = 0.040; HR = 1.720; 95% CI 1.006–2.943; p = 0.048) were associated with an increased risk of all-cause mortality. Furthermore, WBC on day 1 discriminated 30-day all-cause mortality (AUC = 0.605; p = 0.005) with an increased risk of all-cause mortality in patients admitted with WBC > 10 × 106/mL (59% vs. 40%; log-rank p = 0.036; HR = 1.643; 95% CI 1.010–2.671; p = 0.045). In conclusion, WBC count on admission as well as CRP levels during the course of ICU treatment were associated with 30-day all-cause mortality. Specifically, an increase of CRP levels by at least 200% from day 1 to day 3 during the course of ICU treatment was associated with an increased risk of 30-day all-cause mortality. The present study is one of the first to describe the prognostic value of inflammatory biomarkers in consecutive all-comer CS patients treated at a cardiac ICU.


Introduction
Cardiogenic shock (CS) remains one of the leading causes of in-hospital death, with a corresponding mortality rate of approximately 50%. Despite ongoing demographic changes, acute myocardial infarction (AMI) still represents the main cause of CS, and mortality rates

Study Patients, Design and Data Collection
The present study prospectively included all consecutive patients presenting with CS on admission to the cardiac ICU at the University Medical Center Mannheim, Germany, from June 2019 to May 2021. All relevant clinical data related to the index event were documented using the electronic hospital information system as well as the IntelliSpace Critical Care and Anaesthesia information system (ICCA, Philips, Philips GmbH Market DACH, Hamburg, Germany) implemented at the ICU, organizing patient data such as admission documents, vital signs, laboratory values, treatment data, and consult notes. Collected data were then pseudonymized and transferred to an electronic database (Microsoft Excel, Version 16.0, Microsoft, Redmond, WA, USA) in compliance with data protection laws. The database was password protected from unauthorized access.
Important laboratory data, ICU-related scores, hemodynamic measurements, and ventilation parameters were assessed on the day of admission (i.e., day 1), as well as on days 2, 3, 4, and 8. Furthermore, baseline characteristics, prior medical history, length of index hospital stay, data derived from imaging diagnostics, as well as pharmacological therapies were documented. Documentation of source data was performed by intensivists and ICU nurses during routine clinical care.
The present study derived from an analysis of the "Cardiogenic Shock Registry Mannheim" (CARESMA-registry), representing a prospective single-center registry including consecutive patients presenting with cardiogenic shock being acutely admitted to the ICU for internal medicine of the University Medical Center Mannheim (UMM), Germany (clinicaltrials.gov identifier: NCT05575856). The registry was carried out according to the principles of the Declaration of Helsinki and was approved by the medical ethics committee II of the Medical Faculty Mannheim, University of Heidelberg, Germany.
The medical center covers a general emergency department (ED) for emergency admission of traumatic, surgical, neurological, and cardiovascular conditions. Interdisciplinary consultation is an inbuilt feature of this 24/7 service and connects to a stroke unit, four intensive care units (ICU), and a chest pain unit (CPU) to alleviate rapid triage of patients. The cardiologic department itself includes a 24 h catheterization laboratory, an electrophysiologic laboratory, a hybrid operating room, and telemetry units. Since 2020, the University Medical Center has been a certified cardiac arrest center (CAC), including the ability to implant extracorporeal life support (ECLS) devices, such as Impella and veno-arterial extracorporeal membrane (VA-ECMO) (i.e., i-cor ® , Xenios AG, Heilbronn, Germany, and Cardiohelp, Getinge, Gothenburg, Sweden) [18][19][20].

Inclusion and Exclusion Criteria, Study Endpoints
For the present study, all consecutive patients with CS and measurements of CRP and WBC count on day 1 were included. No further exclusion criteria were applied. The diagnosis of CS was determined according to the current recommendations of the Acute Cardiovascular Care Association of the European Society of Cardiology [21]. Accordingly, cardiogenic shock was defined as hypotension (SBP < 90 mmHg) for more than 30 min despite adequate filling status or the need for vasopressor or inotropic therapy to achieve SBP > 90 mmHg. Additionally, signs of end-organ hypoperfusion must be present such as oliguria with urine output < 30 mL/hour, altered mental status, cold clammy skin, and increased serum lactate > 2 mmol/L. All-cause mortality at 30 days was documented using the electronic hospital information system and by directly contacting state resident registration offices ('bureau of mortality statistics'). Identification of patients was verified by place of name, surname, day of birth, and registered living address. No patient was lost to follow-up with regard to all-cause mortality at 30 days.

Measurement of WBC Count and C-Reactive Protein
All analyses were performed in accredited laboratories under DIN ISO EN 15,189 conditions. WBC counts were determined using dipotassium-ethylenediaminetetraacetic acid (K2-EDTA) whole blood on the hematology analyzer XN-10 on a fully automated XN-9000 platform (both Sysmex, Kobe, Japan) using a combination of flow cytometry, impedance technique, and fluorescence measurement. During the study period, two different detection systems for CRP were applied. The analyses were carried out using either serum or lithium heparin (LiHep) plasma after centrifugation in accordance with the manufacturer's instructions. From 2019 until August 2020, CRP measurements were performed on the SIEMENS Vista Dimension 1500 (Siemens Healthineers TM , Erlangen, Germany) platform using nephelometric detection. The manufacturer provides an analytical measurement range of 2.90 to 190 mg/L for this assay. Thereafter, CRP levels were measured with the Siemens Atellica Solution CH 930™ (Siemens Healthineers TM , Erlangen, Germany). This assay is based on a latex-enhanced immunoturbidimetric detection technique. The manufacturer provides an analytical measurement range of 4.00 to 304 mg/L for this assay with a limit of detection of 4.00 mg/L. All assays were applied as stated by the respective manufacturers without further modification or validation.
Important laboratory values apart from CRP and WBC counts were measured during routine clinical care as previously published [22].

Statistical Methods
Quantitative data is presented as the mean ± standard error of the mean (SEM), median, and interquartile range (IQR), and ranges depending on the distribution of the data. They were compared using the Student's t-test for normally distributed data or the Mann-Whitney U test for nonparametric data. Deviations from a Gaussian distribution were tested by the Kolmogorov-Smirnov test. Qualitative data are presented as absolute and relative frequencies and were compared using the chi-square test. Box plots for CRP and WBC counts were created for the comparisons of survivors and non-survivors on days 1, 2, 3, 4, and 8. On day 1, Spearman's rank correlation for nonparametric data was used to test for the association of CRP and WBC counts with medical and laboratory parameters.
C-statistics were applied by calculation of the ROC and investigation of the corresponding AUC within the entire cohort on days 1, 2, 3, 4, and 8 in order to evaluate the prognostic performance of CRP and WBC counts with respect to the 30-day all-cause mortality. Kaplan-Meier analyses according to the median CRP levels and WBC counts on day 1 and day 3 were performed within the entire study cohort, and univariate hazard ratios (HR) were given together with 95% confidence intervals. Finally, the prognostic impact of a CRP increasement of at least 200% from day 1 to day 3 was investigated compared to patients without ("non-CRP increase"). The "non-CRP increase" group comprised patients with a CRP increase of less than 200%, stable CRP levels, or decreasing CRP levels during the first 3 days of ICU treatment. Finally, multivariate Cox regression models were developed using the "forward selection" option.
The results of all statistical tests were considered significant for p ≤ 0.05. SPSS (Version 28, IBM, Armonk, NY, USA) and GraphPad Prism (Version 9, GraphPad Software, San Diego, CA, USA) were used for statistics.
In contrast, CRP levels on day 1 were not associated with 30-day all-cause mortality (log-rank p = 0.161). However, on day 3, an increased 30-day all-cause mortality rate was observed in patients with CRP > 100 mg/L compared to patients with CRP levels of less or equal 100 mg/L (56% vs. 37%; log-rank p = 0.023; HR = 1.702; 95% CI 1.060-2.735; p = 0.028) (Figure 3).  Finally, a CRP increase of at least 200% in patients with CS within the first 3 days was associated with an increased risk of 30-day all-cause mortality compared to patients with a CRP increase of less than 200% (51% vs. 35%; log-rank p = 0.040; HR = 1.720; 95% CI 1.006-2.943; p = 0.048) (Figure 4). Finally, a CRP increase of at least 200% in patients with CS within the first 3 days was associated with an increased risk of 30-day all-cause mortality compared to patients with a CRP increase of less than 200% (51% vs. 35%; log-rank p = 0.040; HR = 1.720; 95% CI 1.006-2.943; p = 0.048) (Figure 4).

Discussion
The present study examined the short-term prognostic impact of CRP and WBC counts in consecutive CS patients admitted to a cardiac ICU. The WBC count on day 1 showed reliable discrimination of 30-day all-cause mortality (AUC 0.605; p = 0.005). In line, baseline WBC count > 10 × 10 6 /mL was associated with an increased risk of 30-day all-cause mortality. In contrast, admission CRP levels were not predictive. However, increased CRP levels from day 3 on showed reliable discrimination for 30-day all-cause mortality (AUC 0.623-0.754; p ≤ 0.009). CRP levels ≥ 100 mg/L on day 3, as well as a CRP increase of ≥200% within the first 3 days, were associated with an increased risk of 30-day mortality. Both the prognostic values of WBC on day 1 and CRP on day 3 were confirmed using multivariate Cox regression analyses.
The prognostic value of CRP and WBC in cardiovascular diseases (i.e., AMI and acute decompensated heart failure (ADHF)) was examined in numerous studies; however, only a minor portion of the patients developed CS, and distinct sub-studies investigating the prognostic role of inflammatory biomarkers in CS patients are limited.
The characterization of CS as a systemic inflammatory disorder is supported by Johansson et al. Accordingly, a proposed disease entity called shock-induced endotheliopathy (SHINE) comprises CS of different types of acute critical illnesses. Global ischemiareperfusion drives endothelial cell damage and leads to inflammatory response [24]. According to Barron et al., high WBC counts were associated with an increased risk of 30-day all-cause mortality in 975 patients with AMI [25]. In line, WBC count was associated with higher rates of 30-day all-cause mortality, including 1892 patients with STEMI [17]. Ohlmann et al. showed an association between elevated CRP levels on admission and longterm mortality in patients after primary percutaneous interventions (PCI) in STEMI [26], which is in line with further studies [27,28]. In patients admitted with ADHF, elevated CRP levels on admission were shown to be associated with higher long-term mortality [4,29,30].
Pathophysiologically, CRP increase is predominantly upstream mediated by monocytic mediators such as IL-6 and is an activator of the classical complement pathway [9,31]. Tumor necrosis factor-alpha (TNF-alpha) and IL-1 beta are further regulatory mediators of CRP synthesis [32]. CRP increase can be triggered by various events and stimuli, such as trauma, systemic inflammatory response syndrome (SIRS), sepsis, cardiovascular, and rheumatological diseases [33]. Generally, CRP was shown to rise within 4-6 h after an inflammatory stimulus and peak after 36 to 50 h [34][35][36].
For instance, CRP levels in patients with SIRS were higher when complicated by additional infection and peaked around days 2-3 after admission [37]. This observation is in line with the findings of the present study, suggesting no association with baseline CRP (median 13 mg/dL) but improved predictive value on day 3 and thereafter.
Bahloul et al. investigated the course of biomarkers on the outcome of septic patients, and CRP appeared to peak between days 1-3. Of note, kinetics were different among survivors and non-survivors. CRP levels in survivors decreased after day 1 and remained high in non-survivors after an increase up to day 3 [38]. In line with this, Miki et al. showed that CRP levels and peaks in patients admitted with sepsis depended on the individuals' outcomes. Among survivors, CRP levels were the highest on day 1, whereas maximum CRP levels in non-survivors were reached on day 3 [39]. WBC did not exhibit such distinct kinetics [35].
Furthermore, various studies suggest that leucocytosis can be a consequence of physical stress. In line, high serum catecholamine levels correlated with an increased WBC count after performing exhausting exercises [40][41][42][43]. Another study revealed an increase in WBC, particularly granulocytes, in resuscitated patients compared to controls (p < 0.001), irrespective of infection [44]. This phenomenon can be explained by endogenous and exogenous epinephrine, which stimulates granulocytes to be released into circulation after demarginating from endothelial cells [45,46]. In line with this, Benschop et al. were able to induce leucocytosis by catecholamine administration in healthy subjects [47]. These findings may also be relevant for the leukocyte counts in our registry, as cardiopulmonary resuscitation occurred in 53.4% of the patients.
The prognostic value of CRP and WBC counts regarding CS was investigated in a few studies. Sasmita et al. recently identified an increased WBC count (>11.6 × 10 6 /mL) as an independent predictor of major adverse cardiac events (MACE) in 217 patients with CS at 30 days (HR 1.894, p = 0.001) [48]. Most recent studies have placed more emphasis on the leukocyte-neutrophile ratio (NLR) than the overall WBC count to predict outcomes in CS. This exceeds the feasibility of large-scaled studies as the differential leukocyte count is not routinely measured. However, it was shown that higher CRP levels in patients with AMI complicated by CS increased the occurrence of MACE at 1-year. In-hospital survivors of CS revealed significantly increased CRP levels on admission compared to non-survivors, according to Akkus et al. [49]. Alongside the influence of preclinical stress and resuscitation on inflammatory markers, assistive devices may influence the inflammatory burden in patients with CS. For instance, Schrage et al. listed septic complications in around 20-30% of patients with CS plus VA-ECMO support [50].
The present study has several limitations. Due to the single-center and observational study design, results may be influenced by measured and unmeasured confounding. Furthermore, previous studies could establish a link between IL-6 and the prognosis of CS patients. However, IL-6 is not regularly measured in our institution and consequently was beyond the scope of our registry. Additionally, procalcitonin (PCT) was determined in only a small proportion of patients admitted with CS (32%); therefore, the prognostic value of PCT levels in CS was beyond the scope of the present study. For the interpretation of CRP levels, patients' ethnicity was not registered, although ethnic background may affect CRP levels [51,52]. Besides, concomitant chronic diseases such as rheumatoid arthritis, systemic lupus erythematosus (SLE), and others that could possibly alter CRP levels have not been included in our registry. During the study period, two different assays for CRP measurement were used, which may lead to minor cofounding, although only minor differences were shown with regard to both assays [53]. Finally, CRP gene polymorphisms were shown to be associated with a marked increase in CRP and could therefore be confounders of our results [54].
In conclusion, the present study identified CRP and WBC as equally suitable prognostic markers at the early stages of cardiogenic shock, each at its preferential point in time. With respect to the observed kinetics and Kaplan-Meier analyses, we identified day 1 and day 3 as particularly worthy of predicting short-term mortality in patients with CS.