From the Cardiovascular Division, Department of Internal Medicine, University of Minnesota, Minneapolis, MN.
Abstract
Objective: To present a review of cardiorenal syndrome type 1 (CRS1).
Methods: Review of the literature.
Results: Acute kidney injury occurs in approximately one-third of patients with acute decompensated heart failure (ADHF) and the resultant condition was named CRS1. A growing body of literature shows CRS1 patients are at high risk for poor outcomes, and thus there is an urgent need to understand the pathophysiology and subsequently develop effective treatments. In this review we discuss prevalence, proposed pathophysiology including hemodynamic and nonhemodynamic factors, prognosticating variables, data for different treatment strategies, and ongoing clinical trials and highlight questions and problems physicians will face moving forward with this common and challenging condition.
Conclusion: Further research is needed to understand the pathophysiology of this complex clinical entity and to develop effective treatments.
Acute decompensated heart failure (ADHF) is an epidemic facing physicians throughout the world. In the United States alone, ADHF accounts for over 1 million hospitalizations annually, with costs in 2012 reaching $30.7 billion [1]. Despite the advances in chronic heart failure management, ADHF continues to be associated with poor outcomes as exemplified by 30-day readmission rates of over 20% and in-hospital mortality rates of 5% to 6%, both of which have not significantly improved over the past 20 years [2,3]. One of the strongest predictors of adverse outcomes in ADHF is renal dysfunction. An analysis from the Acute Decompensated Heart Failure National Registry (ADHERE) revealed the combination of renal dysfunction (creatinine > 2.75 mg/dL and blood urea nitrogen (BUN) > 43 mg/dL) and hypotension (systolic blood pressure (SBP) < 115 mm Hg) upon admission was associated with an in-hospital mortality of > 20% [4]. The Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure (OPTIMIZE-HF) registry documented a 16.3% in-hospital mortality when patients had a SBP < 100 mm Hg and creatinine > 2.0 mg/dL at admission [5].
The presence of acute kidney injury in the setting of ADHF is a very common occurrence and was termed cardiorenal syndrome type 1 (CRS1) [6]. The prevalence of CRS1 in single-centered studies ranged from 32% to 40% of all ADHF admissions [7,8]. If this estimate holds true throughout the United States, there would be 320,000 to 400,000 hospitalizations for CRS1 annually, highlighting the magnitude of this problem. Moreover, with the number of patients with heart failure expected to continue to rise, CRS1 will only become more prevalent in the future. In this review we discuss the prevalence, proposed pathophysiology including hemodynamic and nonhemodynamic factors, prognosticating variables, data for different treatment strategies, ongoing clinical trials, and highlight questions and problems physicians will face moving forward in this common and challenging condition.
Pathogenesis of CRS1
Hemodynamic Effects
The early hypothesis for renal dysfunction in ADHF centered on hemodynamics, as reduced cardiac output was believed to decrease renal perfusion. However, analysis of invasive hemodynamics from patients with ADHF suggested that central venous pressure (CVP) was actually a better predictor of the development of CRS1 than cardiac output. In a single-center study conducted at the Cleveland Clinic, hemodynamics from 145 patients with ADHF were evaluated and surprisingly baseline cardiac index was greater in the patients with CRS1 than patients without renal dysfunction (2.0 ± 0.8 L/min/m 2 vs 1.8 ± 0.4 L/min/m 2; P = 0.008). However, baseline CVP was higher in the CRS1 group (18 ± 7 mm Hg vs 12 ± 6 mm Hg; P = 0.001), and there was a heightened risk of developing CRS1 as CVP increased. In fact, 75% of the patients with a CVP of > 24 mm Hg developed renal impairment [9]. In a retrospective study of the Evaluation Study of Congestive Heart Failure and Pulmonary Arterial Catheter Effectiveness (ESCAPE) trial, the only hemodynamic parameter that correlated with baseline creatinine was CVP. However, no invasive measures predicted worsening renal function during hospitalization [10]. Finally, an experiment that used isolated canine kidneys showed increased venous pressure acutely reduced urine production. Interestingly, this relationship was dependent on arterial pressure; as arterial flow decreased smaller increases in CVP were needed to reduce urine output [11]. Together, these data suggest increased CVP plays an important role in CRS1, but imply hemodynamics alone may not fully explain the pathophysiology of CRS1.
