Ultrafiltration in heart failure with cardiorenal syndrome

Getting to the Heart of the Matter: Review of Treatment of Cardiorenal Syndrome

Acute decompensated heart failure is a common cause of hospitalization with worsening kidney function or acute kidney injury often complicating the admission, which can result in further dysfunction of both systems in the form of a cardiorenal syndrome. Therapy in this arena has been largely empiric as rigorous clinical trial data to inform therapeutic choices are lacking. Here we review and discuss the available clinical evidence for common approaches to the management of this condition. A multidisciplinary approach to the care of patients with cardiorenal syndrome that relies on the experience of nephrologists and cardiologists to individualize treatment is critical given the paucity of rigorous clinical trial data.

Focus on renal congestion in heart failure

Hospitalizations due to heart failure are increasing steadily despite advances in medicine. Patients hospitalized for worsening heart failure have high mortality in hospital and within the months following discharge. Kidney dysfunction is associated with adverse outcomes in heart failure patients. Recent evidence suggests that both deterioration in kidney function and renal congestion are important prognostic factors in heart failure. Kidney congestion in heart failure results from low cardiac output (forward failure), tubuloglomerular feedback, increased intra-abdominal pressure or increased venous pressure. Regardless of the cause, renal congestion is associated with increased morbidity and mortality in heart failure. The impact on outcomes of renal decongestion strategies that do not compromise renal function should be explored in heart failure. These studies require novel diagnostic markers that identify early renal damage and renal congestion and allow monitoring of treatment responses in order to avoid severe worsening of renal function. In addition, there is an unmet need regarding evidence-based therapeutic management of renal congestion and worsening renal function. In the present review, we summarize the mechanisms, diagnosis, outcomes, prognostic markers and treatment options of renal congestion in heart failure.

Rationale and design of the Aquapheresis Versus Intravenous Diuretics and Hospitalization for Heart Failure (AVOID-HF) trial

BACKGROUND

In patients hospitalized with acutely decompensated heart failure, unresolved signs and symptoms of fluid overload have been consistently associated with poor outcomes. Regardless of dosing and type of administration, intravenous loop diuretics have not reduced heart failure events or mortality in patients with acutely decompensated heart failure. The results of trials comparing intravenous loop diuretics to mechanical fluid removal by isolated venovenous ultrafiltration have yielded conflicting results. Studies evaluating early decongestive strategies have shown that ultrafiltration removed more fluid and was associated with fewer heart failure-related rehospitalization than intravenous loop diuretics. In contrast, when used in the setting of worsening renal function, ultrafiltration was associated with poorer renal outcomes and no reduction in heart failure events.

METHODS

The AVOID-HF trial seeks to determine if an early strategy of ultrafiltration in patients with acutely decompensated heart failure is associated with fewer heart failure events at 90 days compared with a strategy based on intravenous loop diuretics. Study subjects from 40 highly experienced institutions are randomized to either early ultrafiltration or intravenous loop diuretics. In both treatment arms, fluid removal therapies are adjusted according to the patients' hemodynamic condition and renal function. The study was unilaterally terminated by the sponsor in the absence of futility and safety concerns after the enrollment of 221 subjects, or 27% of the originally planned sample size of 810 patients.

CONCLUSIONS

The AVOID-HF trial's principal aim is to compare the safety and efficacy of ultrafiltration vs that of intravenous loop diuretics in patients hospitalized with acutely decompensated heart failure. Because stepped treatment approaches are applied in both ultrafiltration and intravenous loop diuretics groups and the primary end point is time to first heart failure event within 90 days, it is hoped that the AVOID-HF trial, despite its untimely termination by the sponsor, will provide further insight on how to optimally decongest patients with fluid-overloaded heart failure.

The acute cardiorenal syndrome type I: considerations on physiology, epidemiology, and therapy

Acute cardiorenal syndrome, also known as cardiorenal syndrome type 1, is defined as an abrupt worsening of cardiac function that occurs in at least 30 % of patients with acute decompensated heart failure and can lead to the development of acute kidney injury. The changes in renal function that occur in this setting have variable prognostic implications, as both poorer and better outcomes have been reported when renal function worsens during treatment of heart failure decompensation. Furthermore, it remains unclear when worsening renal function is actually a manifestation of true acute kidney injury or simply an indicator of hemoconcentration. Given these gaps in the understanding of the significance of renal function changes in the setting of decompensated heart failure, it is not surprising that studies on the effects of available therapies, including diuretics, vasoactive drugs, and mechanical fluid removal have yielded inconsistent results. The purpose of this review is to analyze critically the current knowledge on the pathophysiology, epidemiology, prognosis, and treatment of acute cardiorenal syndrome.

Efficacy and safety of ultrafiltration in decompensated heart failure patients with renal insufficiency

Ultrafiltration (UF) is an alternative strategy to diuretic therapy for the treatment of patients with decompensated heart failure. The impact of UF in decompensated heart failure with renal insufficiency remains unclear. A literature search was conducted for randomized controlled trials (RCTs) that investigated the use of UF in decompensated heart failure patients with renal insufficiency.Seven RCTs with 569 participants were eligible for analysis. There was significantly more 48 hour weight loss (WMD 1.59, 95% CI 0.32 to 2.86; P = 0.01; I2 = 68%) and 48 hour fluid removal (WMD 1.23, 95% CI 0.63 to 1.82; P < 0.0001; I2 = 43%) in the UF group compared to the control group. Serum creatinine (WMD 0.05; 95% CI -0.23 to 0.33; P = 0.61; I2 = 77%) and serum creatinine changes (WMD 0.05; 95% CI -0.15 to 0.26; P = 0.61; I2 = 77%) were similar between the UF and control groups. All-cause mortality (OR 0.95; 95% CI 0.58 to 1.55; P = 0.83; I2 = 0.0%) and all-cause rehospitalization (OR 0.97; 95% CI 0.49 to 1.92; P = 0.94; I2 = 52%) were also similar between the UF and control groups. Adverse events such as infection, anemia, hemorrhage, worsening heart failure, and other cardiac disorders did not differ significantly between the UF and control groups.UF is an effective and safe therapeutic strategy and produces greater weight loss and fluid removal without affecting renal function, mortality, or rehospitalization in patients with decompensated heart failure complicated by renal insufficiency.

[Renal dysfunction in heart failure and hypervolumenia : Importance of congestion and backward failure]

Traditionally, renal dysfunction in congestive heart failure (cardiorenal syndrome type 1) has been attributed to reduced cardiac output and low mean arterial perfusion pressure, which elicit a series of neurohumoral activations resulting in increased renal vascular resistance and decreased renal function.During the last decade, several studies have shown that the extent of renal dysfunction is not so closely associated with indices of forward failure-such as the cardiac index or mean arterial pressure-but rather with indicators of congestion, such as left ventricular enddiasystolic pressure or central venous pressure (CVP), which are indicators of backward failure. The impact of backward failure on renal function is not confined to an elevation of CVP, the renal drainage pressure, but includes a broad spectrum of mechanisms. Involved are the organ systems right heart, lung, the liver, the proinflammatory signals originating from the intestines, but also renal interstitial edema (renal compartment syndrome) and the intraabdominal pressure.The therapeutic measures must focus on the modulation of the preload adapted to the specific situation of an individual patient. This includes diuretics aiming at different segments of the tubulus system including antagonists of aldosteron and ADH, extracorporeal fluid elimination by ultrafiltration or peritoneal dialysis.