ABC | Volume 115, Nº1, July 2020

Review Article Leite et al. Acute cardiorenal syndrome Arq Bras Cardiol. 2020; 115(1):127-133 result in misclassification of ACRS regarding its diagnosis and severity. 16 Methods This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. 17 Data search in the MEDLINE, EMBASE and LILACS databases included the full texts of original publications, such as clinical trials, cohort studies, case-control studies and meta-analyses, issued from January 1998 to June 2018, written in English, Spanish and Portuguese. The database search was conducted with the following descriptors: ( cardiorenal syndrome ) OR (worsening renal function) AND ( heart failure ) AND ( diagnosis ) AND ( prognosis ). This study used the PICO (Population, Intervention, Control and Outcome) framework for literature search and reviewed the diagnostic criteria for ACRS and their prognostic implication for the outcomes ‘in-hospital mortality’, ‘mortality after hospital discharge’, and ‘length of hospital stay’. Case reports and experimental animal models were excluded. Results Regarding database search, 368 abstracts met the established criteria. Other 9 articles were retrieved in other sources, while 278 duplicate abstracts were removed. Of the 99 abstracts left, 61 were selected, 35 of which were excluded for not meeting the previously established criteria (PICO). The full text of the resulting 26 articles was then assessed regarding their scientific quality, and 4 articles were excluded for not meeting the criteria. The remaining 22 articles were analyzed in this study (Figure 1). Temporal classification of acute cardiorenal syndrome Studies with access to pre-admission serum creatinine have revealed AKI in one third of the patients presenting to the emergency department, 18 while 50% of patients have been reported to develop AKI within the first 48 hours from admission. Tayaka et al., 19 in a study comparing renal function changes up to the fourth day of hospitalization with those from the fifth day onward, have reported higher mortality within 1 year from hospital discharge in patients with late renal injury. A post hoc analysis of the Pre-RELAX study has shown that the drop in systolic blood pressure in the first 48 hours of vasodilator therapy was an independent predictor of AKI up to the fifth day of hospitalization. 20 Those results suggest that therapy-related reduction in renal perfusion pressure is one of the major mechanisms leading to AKI in the first days of hospitalization. Acute cardiorenal syndrome can be classified into intermittent or persistent. Intermittent ACRS occurs when serum creatinine levels vary during hospitalization with a reduction in its values up to discharge time. Persistent ACRS occurs when either creatinine elevation or GFR decrease persist up to discharge time. 21,22 Incidence of acute cardiorenal syndrome Studies have shown a large variation in the incidence of ACRS, whose estimates range from 19% to 45%. That variation can be attributed to differences among the studies regarding Figure 1 – Flowchart of the studies assessed (PRISMA methodology 17 ). 368 reports identified in the databases 09 articles retrieved in other sources 99 after eliminating duplicates 35 excluded Exclusion: (3) review (1) case report 61 studies selected 26 articles in full text assessed for eligibility 22 studies included in qualitative synthesis Inclusion Eligibility Selection Identification 128