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 multifaceted approach to management, focusing on treating the underlying cause while balancing fluid status, and the most effective management strategy involves a combination of diuretics, ACE inhibitors or ARBs, beta-blockers, and aldosterone antagonists, with careful monitoring of renal function, electrolytes, and cardiac status. The classification of cardiorenal syndrome into five types (Type 1: acute heart failure leading to acute kidney injury, Type 2: chronic heart failure causing progressive kidney disease, Type 3: acute kidney injury leading to heart dysfunction, Type 4: chronic kidney disease contributing to heart failure, and Type 5: systemic conditions affecting both organs) is crucial for guiding treatment decisions 1.

Management Strategies

• Diuretics like furosemide (20-80mg IV or oral daily, adjusted based on response) are commonly used to manage fluid overload, but require careful monitoring to avoid worsening kidney function 1.
• ACE inhibitors or ARBs (such as enalapril 2.5-20mg twice daily or losartan 25-100mg daily) may be beneficial despite initially causing slight increases in creatinine, as they have been shown to improve outcomes in patients with heart failure and chronic kidney disease 1.
• Beta-blockers (metoprolol 12.5-200mg daily) and aldosterone antagonists (spironolactone 12.5-50mg daily) may be added cautiously to the treatment regimen, as they have been shown to improve survival and reduce morbidity in patients with heart failure 1.
• Fluid restriction (typically 1.5-2L daily), sodium restriction (2-3g daily), and daily weight monitoring are essential components of management, as they help to balance fluid status and prevent further kidney damage 1.

Monitoring and Adjustments

• Regular monitoring of renal function, electrolytes, and cardiac status is crucial, with adjustments to medication dosing as needed, to prevent adverse outcomes and improve patient outcomes 1.
• The use of isosmolar contrast agents, such as iodixanol, is recommended in patients with chronic kidney disease undergoing angiography, as they have been shown to reduce the risk of contrast-induced nephropathy 1.
• The identification of chronic kidney disease is critical to proper medical therapy, and all patients with cardiovascular disease should be screened for evidence of kidney disease by estimating glomerular filtration rate, testing for microalbuminuria, and measuring the albumin-to-creatinine ratio 1.

From the Research

Definition and Pathophysiology of Cardiorenal Syndrome

• 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.

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.
• Novel therapies that hold promise include arginine vasopressin antagonists, adenosine A1 receptor antagonists, and ultrafiltration 3.

Prognosis and Epidemiology

• The presence of cardiorenal syndrome is associated with a poor prognosis 4.
• Impaired renal function in heart failure patients often reflects more advanced stages of cardiac failure, and thus is associated with a worse prognosis 5.
• Upward of 60% of patients admitted for acute decompensated heart failure have chronic kidney disease (CKD), as defined by an eGFR of <60 ml/min per 1.73 m^2 2.

Education and Research

• The mission of the American Heart Association is to describe the epidemiology and pathogenesis of cardiorenal syndrome and to outline the need for a cardiorenal education track that will guide future cardiorenal trials and integrate the clinical and research needs of this important field in the future 6.
• Registered and advanced practice nurses should maintain the knowledge and skills of understanding the pathology of cardiorenal syndrome to improve the evaluation and management of patients who present with cardiorenal syndrome 4.