Table 1.

Classification and characteristics of the five cardiorenal syndrome subtypes.

CRS Subtype	Description	References
Type 1	It develops when there is an acute deterioration of cardiac function due to conditions such as cardiogenic shock, ADHF, cardiac surgery, and acute coronary syndrome leading to AKI (defined by an increase in serum creatinine ≥ 0.3 mg/dL) or renal dysfunction.	[11,12]
Type 2	It characterizes chronic CVD, such as chronic HF, that leads to CKD. CKD increases the frequency of hospitalizations and deaths from pump failure and arrhythmia.	[2,13,14]
Type 3	Describes a sudden worsening of renal function, such as AKI or glomerulonephritis, causing acute cardiac dysfunction (e.g., HF, arrhythmia, or pulmonary edema).	[15,16]
Type 4	It defines CKD as leading to the progression of CVD. CVD may include decreased cardiac function, diastolic dysfunction, ventricular hypertrophy, or increased risk of adverse cardiovascular events due to pressure and fluid overload, representing a risk factor for death.	[17,18]
Type 5	This syndrome appears when an acute or chronic systemic disease such as diabetes mellitus, sepsis, systemic lupus erythematosus, vasculitis, and sarcoidosis, leads to simultaneous cardiac and renal dysfunction.	[11]

Abbreviations: ADHF: acute decompensated heart failure, AKI: acute kidney injury, CKD: chronic kidney disease, CRS: cardiorenal syndrome, CVD: cardiovascular disease, HF: heart failure.