Cardiorenal, Renocardiac, and Reno-CardioCardiac Syndromes: An Updated Review on General Definitions, Pathophysiology, and Therapies (Part 1)

Background: Acute and chronic heart or kidney failure affect each other in cardiorenal syndromes (CRS). In CRS, hemodynamic and non-hemodynamic changes occur, causing acute or progressive renal and cardiac failures. CRS is classified into five types based on the first organ failure and causes failure of the other organ. We believe that the current CRS classification is not the correct one that effectively describes the underlying cause of CRS. Hence, we consider it better to be classified into three categories (cardiorenal, renocardiac, and cardio-reno-cardiac syndrome) and then subdivided into acute and chronic types or types 1 and 2 (respectively, according to the onset of the underlying type of failure (i.e., acute or chronic). Other subtypes that occur inthe heart and dysfunction occur simultaneously are acute cardio-reno-cardiac syndrome (type 5) and Chronic cardio-reno-cardiac syndrome (type 6). Aim: In Part 1 of the review series, the pathophysiological mechanisms and clinical and therapeutic applications of all types of CRS will be narratively discussed and updated. Furthermore, we provide a comprehensive review of diagnostic biomarkers and their clinical significance in the identification, outcome prediction, and treatment of all CRS types. Method: An extensive search of PubMed, Google, EMBASE, Scopus, and Google Scholar was conducted for review articles, original articles, and commentaries published between Jan 2010 and Aug 2024 using different phrases, texts, and keywords, such as CRS, renocardiac syndrome, and CRS. The topics included secondary CRS, CRS pathogenesis, CRS therapy, SLGT inhibitor use in CRS, novel therapy in CRS types, and prevention of CRSs. Conclusion: Renal and cardiac failure in patients with CRS seem to have different pathophysiological mechanisms. Early detection and treatment can improve the outcomes of CRS. Clinical manifestations and therapy protocols vary according to pathophysiology. Hence, new guidelines and research on universal diagnostic and treatment techniques are urgently required. Moreover, the current nomenclature for CRS is confusing; therefore, we believe that a new nomenclature system should be introduced, reducing confusion and making differentiation between CRS types easier and less confusing.