Chronic Secondary Cardiorenal Syndrome: The Sixth Innovative Subtype.

Abstract

Heart failure, as the leading cause of cardiovascular death, has seen an increased prevalence nowadays, along with renal insufficiency. It's estimated that 25–63% of heart failure patients have the comorbidity of renal insufficiency, an independent risk factor of various cardiovascular events and predictors of poor prognosis (1). A therapeutic principle of heart failure emphasizing decongestive treatment is limited by the demand for sufficient perfusion in terms of renal insufficiency therapy, making the treatment of both concomitant diseases more complicated and contradictory, with mild balance; hence, the great interest in cardiorenal interactions has broadened among researchers and clinicians, and the concept of cardiorenal syndrome (CRS) was first proposed in 2004. CRS, defined as a pathophysiological process of adverse interaction between the heart and kidneys, encompasses a spectrum of diseases involving acute or chronic dysfunction in one organ that induces decompensated dysfunction in the other, and eventually they evolve into an interrelated and vicious cycle of declining function in both organs. CRS was first categorized into five subtypes in 2008 based on sequential organ involvement and the course of progression over time (i.e., acute or chronic), including acute cardiorenal syndrome, chronic cardiorenal syndrome, and acute renocardiac syndrome, chronic renocardiac syndrome, secondary cardiorenal syndrome, of which a brief definition, etiology, and pathophysiology are given in Table 1 (2). With the consideration that the previous secondary CRS subtype has a shortcoming in that it is not as symmetrical as the first four subtypes, as well as the huge difference of pathophysiological changes, the treatment principles of the two organs, and of gradually increasing in-depth knowledge of fibrosis pathogenesis over the past few years, it's become quite necessary to propose a new CRS classification. And that's why we now first propose the sixth innovative CRS subtype on the basis of the concept of “chronic co-impairment” of the heart and kidneys, further classifying traditional secondary CRS as acute secondary CRS and chronic secondary CRS, thus making the novel six kinds of CRS categories paired and matched correspondingly. The most common precipitant of acute secondary CRS is biotoxin damage and a cytokine storm generated by acute sepsis, and the primary treatment principles are cause-related treatment as aggressive anti-infective therapy, as well as symptomatic treatment of cardiac and renal dysfunction. However, the novel type 6 CRS (chronic secondary CRS) is actually more prevalent in clinical practice, and its pathophysiological and clinical characteristics as well as diagnosis and treatment principles vary dramatically from other subtypes of CRS, which will be described in detail in the following article. Table 1 New classification of CRS based on disease acuity and sequential organ involvement.