What is cardiorenal syndrome (CRS), a condition characterized by impaired renal function and cardiovascular disease?

From the Guidelines

Cardiorenal syndrome is a complex condition that requires a multidisciplinary approach, focusing on treating the underlying cause while balancing fluid status, and individualized treatment based on the specific type of cardiorenal syndrome, with careful monitoring to avoid worsening kidney function. The management of cardiorenal syndrome involves a comprehensive understanding of the bidirectional relationship between heart and kidney dysfunction, where failure of one organ accelerates failure of the other. It is classified into five types: Type 1 (acute heart failure causing acute kidney injury), Type 2 (chronic heart failure leading to progressive kidney disease), Type 3 (acute kidney injury causing cardiac dysfunction), Type 4 (chronic kidney disease contributing to heart failure), and Type 5 (systemic conditions affecting both organs simultaneously) 1.

Key Considerations

• Diuretics like furosemide (20-80mg IV or oral daily, adjusted based on response) are commonly used, but require careful monitoring to avoid worsening kidney function.
• ACE inhibitors or ARBs (such as lisinopril 2.5-40mg daily or losartan 25-100mg daily) may benefit both organs but require close monitoring of potassium and creatinine.
• SGLT2 inhibitors (empagliflozin 10-25mg daily or dapagliflozin 5-10mg daily) have shown promising results in both heart and kidney protection.
• Volume status assessment is crucial, using physical examination findings, daily weights, and input/output monitoring.

Treatment Approach

The pathophysiology of cardiorenal syndrome involves neurohormonal activation, oxidative stress, and inflammatory pathways that create a vicious cycle of worsening organ function, explaining why treating one system in isolation often proves insufficient. A multidisciplinary care approach involving both cardiology and nephrology is essential for optimal management. In patients with chronic kidney disease, isosmolar contrast agents are preferred for angiography to reduce the risk of contrast-induced nephropathy 1.

Monitoring and Adjustments

Regular monitoring of renal function, potassium levels, and volume status is crucial to adjust treatment accordingly. The use of the Cockroft-Gault formula to estimate creatinine clearance is recommended for dose adjustments of renally cleared medications 1. Close collaboration between cardiologists and nephrologists is necessary to provide individualized care and optimize outcomes for patients with cardiorenal syndrome.

From the Research

Definition and Pathophysiology of Cardiorenal Syndrome

• The cardiorenal syndrome refers to a group of complex, bidirectional pathophysiological pathways involving dysfunction in both the heart and kidney 2.
• The mechanisms in the cardiorenal syndrome include venous congestion, arterial underfilling, neurohormonal activation, inflammation, and endothelial dysfunction 2.
• Arterial underfilling may lead to activation of the renin-angiotensin-aldosterone system and sympathetic nervous system, leading to sodium reabsorption and vasoconstriction 2.

Clinical Features and Diagnosis

• The hallmark of the cardiorenal syndrome is intense sodium avidity and diuretic resistance, often requiring a combination of diuretics with varying pharmacological targets, and monitoring of urinary response to guide escalations in therapy 2.
• To rule out intrinsic kidney disease that is distinct from the cardiorenal syndrome, one should obtain a careful history, review longitudinal eGFR trends, assess albuminuria and proteinuria, and review the urine sediment and kidney imaging 2.

Epidemiology and Prognosis

• The presence of cardiorenal syndromes is associated with a poor prognosis 3.
• Impaired renal function in heart failure patients often reflects more advanced stages of cardiac failure, and thus is associated with a worse prognosis 4.

Treatment and Management

• Strategies for increasing forward perfusion in states of low cardiac output and cardiogenic shock may include afterload reduction and inotropes and, in the most severe cases, mechanical circulatory support devices, many of which have kidney-specific considerations 2.
• Invasive means of decongestion may be required including ultrafiltration or KRT such as peritoneal dialysis, which is often better tolerated from a hemodynamic perspective than intermittent hemodialysis 2.
• Current therapies for cardiorenal syndrome as well as ongoing studies are mostly focused on haemodynamic adjustments, but future studies should focus on interventions targeting different components of this complex network 5.