Table 1.

Classification system of cardiorenal syndrome (CRS).

	Description	Examples of inciting events	Examples of consequences
Type 1 CRS	Acute HF leads to AKI	(i) ADHF	(i) AKI
		(ii) Cardiogenic shock	(ii) Diuretic resistance
		(iii) Hypertensive pulmonary edema
Type 2 CRS	Chronic HF leads to progressive CKD	(i) Chronic systolic HF	(i) Progressive CKD
		(ii) Chronic HF with preserved systolic function
Type 3 CRS	Acute renal dysfunction leads to acute cardiac dysfunction	(i) AKI	(i) ADHF
		(ii) Glomerulonephritis	(ii) Acute HF
			(iii) Ischemia
			(iv) Arrhythmia
			(v) Decreased CO
Type 4 CRS	CKD leads to chronic cardiac dysfunction and/or increased risk of CV events	(i) CKD	(i) Systolic dysfunction
			(ii) LVH
			(iii) Diastolic dysfunction
			(iv) Coronary calcification
			(v) Decreased coronary perfusion
Type 5 CRS	Systemic disorder leads to cardiac and renal dysfunction	(i) Sepsis	(i) Acute HF
		(ii) Vasculitis	(ii) Chronic HF
		(iii) Diabetes	(iii) AKI
		(iv) Amyloidosis	(iv) CKD

Adapted from [3]. ADHF: acutely decompensated heart failure; AKI: acute kidney injury; CKD: chronic kidney disease; CO: cardiac output; CV: cardiovascular; HF: heart failure; LVH: left ventricular hypertrophy.