Background:The concept of cardiorenal syndrome (CRS) has been established more than 10 years ago. Five distinct types of CRS have been defined. In CRS type 3, acute kidney injury (AKI) induces cardiac complications such as ventricular decompensation due to arrhythmias, myocardial ischemia, or fluid retention with or without arterial hypertension. The risk of cardiovascular events in AKI has been known for many years, even long before the introduction of the CRS concept. However, epidemiological and clinical studies published in recent years increasingly emphasized CRS type 3 (and the remaining four types also) as separate entity which requires particular therapeutic attention in an interdisciplinary manner. However, only a limited number of experimental studies specifically addressed CRS type 3 so far. Our review aims to summarize experimental studies on the pathological mechanisms in CRS type 3. Methods:The following search criteria were employed in order to identify articles published on the topic: "cardiorenal syndrome 3" OR "cardiorenal syndrome type 3" OR "CRS type 3" OR "CRS 3" AND "experimental" OR "mouse" OR "mice" OR "rats" OR "animals"; additional criteria were "myocardium" AND "ischemia" AND "kidney" OR "renal". By applying the search criteria mentioned earlier, 10 references were finally selected.Results: By applying the search strategy, 10 experimental studies were finally selected. All included cardiac outcome analysis in AKI animals. The data clearly provide evidence for cardiac complications that evolve independently from excretory kidney dysfunction. Pathological processes that emerge in the heart of animals subjected to renal ischemia involve inflammation, a dysbalance of redox components, pro-apoptotic processes, and mitochondrial dysfunction. Conclusion:The findings may explain why AKI increases the risk of acute cardiac complications even if dialysis treatment has been initiated.

Background and Aim. In cardiorenal syndrome (CRS) type 3, acute kidney injury (AKI) induces and, sometimes, even perpetuates acute cardiac pathologies such as arrhythmias with or without cardiac decompensation or the latter due to other causes. Epidemiological data on CRS type 3 are limited. The aim of this study was to analyze epidemiological and outcome variables in CRS type 3. Methods. A single-center, retrospective and observational trial. All subjects with positive AKI alert, treated at the University Hospital Brandenburg between January and December 2019, were evaluated. Definition of CRS type 3 was according to predefined criteria. The three endpoint categories were in-hospital death, dialysis, and recovery of kidney function. Results. A total number of 1,334 AKI alerts were screened. Finally, 95 subjects received the diagnosis CRS type 3. The survival rates were 47.1% (females) and 43.6% (males). 46.8% of affected females and 33.3% of the males required dialysis therapy. Complete recovery at the time of discharge occurred in 35.8%, and no recovery at all was found in 54.7%. Conclusions. All three predefined study endpoints, the mortality, the prevalence of dialysis, and the percentage of subjects without recovery of kidney function, were notably high. Therefore, AKI patients with imminent or established cardiac complications require the highest attention of nephrologists in charge.

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Cardiorenal syndromes (CRS) have increasingly been recognized as distinct disorders that affect the heart and kidneys simultaneously, either with acute or chronic onset. The different types share common pathophysiological characteristics. The concept “cardiorenal” shall emphasize the inter- or even multidisciplinary approach to respective patients. Anticongestive therapy becomes mandatory in many subjects that suffer from CRS. In recent years, the role of dialysis treatment in a broader sense has been investigated in CRS in more detail. We performed a search for studies related to the topic in the following databases: MEDLINE, PROSPERO, and Web of Science. The following keywords were used for reference identification: “CRS”, “cardiorenal syndrome”, “dialysis”, “hemodialysis”, “hemofiltration”, “renal replacement therapy”, “kidney replacement therapy”, “peritoneal dialysis”, and “aquapheresis”. Finally, a total number of 22 studies, partly performed as retrospective cohort studies, and partly designed as prospective investigations, were included. The selected studies evaluated different modes of peritoneal dialysis (PD) or of non-PD procedures including intermittent hemodialysis, continuous procedures, and so-called aquapheresis. Inclusion and outcome parameters were almost not comparable between selected trials. Some studies revealed dialysis as effective, with reasonable tolerability. Particularly so-called “pure” ultrafiltration (e.g., aquapheresis) was associated with higher rates of adverse events. Future studies should be designed in a more homogenous manner, particularly concerning the inclusion criteria, the respective dialysis procedure applied, and endpoints in the short- and long-term.