What are the types of cardiorenal syndrome in an adult patient with a history of heart failure or kidney disease?

Cardiorenal Syndrome Types

Cardiorenal syndrome is classified into five distinct types based on the primary organ dysfunction (heart versus kidney) and temporal course (acute versus chronic), with Types 1-4 representing unidirectional organ injury and Type 5 representing systemic disease affecting both organs simultaneously. 1

The Five Types of Cardiorenal Syndrome

Type 1: Acute Cardiorenal Syndrome

• Acute heart failure causes acute kidney injury (AKI) 1
• Most commonly encountered in patients presenting with acute decompensated heart failure or acute cardiogenic shock 2
• Pathophysiology involves decreased cardiac output reducing renal perfusion, which activates neurohormonal compensatory mechanisms 3
• This is the most common type seen in clinical practice 4

Type 2: Chronic Cardiorenal Syndrome

• Chronic heart failure causes chronic kidney disease (CKD) 1
• Characterized by chronic renal hypoperfusion, sustained neurohormonal activation, and venous congestion 3
• Long-term activation of the renin-angiotensin-aldosterone (RAA) system creates a vicious cycle of deterioration 3
• Progressive and permanent kidney damage develops over time 2

Type 3: Acute Renocardiac Syndrome

• Acute kidney injury or acute renal failure causes acute cardiac failure 1
• Abrupt worsening of renal function (such as acute kidney ischemia or glomerulonephritis) leads to acute cardiac disorders including heart failure, arrhythmias, or ischemia 2, 5
• The kidney is the primary failing organ that subsequently injures the heart 6

Type 4: Chronic Renocardiac Syndrome

• Chronic kidney disease causes chronic cardiac dysfunction, including heart failure 1
• Left ventricular hypertrophy and diastolic dysfunction are common cardiac manifestations 3
• CKD contributes to decreased cardiac function, cardiac hypertrophy, and increased risk of adverse cardiovascular events 2, 5
• Up to a quarter of patients with CKD have symptoms suggestive of heart failure before a formal diagnosis is made 1

Type 5: Secondary Cardiorenal Syndrome

• Systemic conditions cause both cardiac and renal dysfunction simultaneously 2, 6
• Examples include diabetes mellitus, sepsis, and other systemic diseases that affect both organs concurrently 2, 5
• Both heart and kidney are injured by the same underlying systemic process rather than one organ causing injury to the other 6

Clinical Significance of Classification

The classification reflects the presumed primary and secondary problem, which is critical for directing management strategies. 3

• Types 1 and 2 are particularly relevant when managing heart failure medications, as drugs like loop diuretics can worsen renal function through hypovolemia and reduced renal perfusion 3
• The bidirectional link between cardiac and renal function means that estimated glomerular filtration rate (eGFR) correlates strongly with left ventricular function well before any diagnosis of renal failure or heart failure has been made 1
• Patients with cardiorenal syndrome have significantly worse outcomes, including increased mortality (5.9% vs 3.2% at 1 month; 15.2% vs 7.6% at 1 year) and prolonged hospitalization compared to those with isolated cardiac or renal disease 3

Common Pitfall

Do not assume a unidirectional relationship—heart failure itself is associated with high risk of renal dysfunction and development of CKD, while conversely, poor renal function predicts left ventricular dysfunction. 1 This bidirectional nature is why the classification system includes both cardiorenal (Types 1-2) and renocardiac (Types 3-4) subtypes, allowing clinicians to identify the primary failing organ and tailor management accordingly 6, 5.