Compensatory Distal Reabsorption Drives Diuretic Resistance in Human Heart Failure

Full Decongestion in Acute Heart Failure Therapy

Incomplete decongestion is the main cause of readmission in the early post-discharge period of a hospitalization for acute heart failure. Recent heart failure guidelines have highlighted initiation and rapid up-titration of quadruple therapy with angiotensin receptor neprilysin inhibitor, beta adrenergic receptor blocker, mineralocorticoid receptor antagonist, and sodium glucose cotransporter 2 inhibitor to prevent hospitalizations for heart failure with reduced ejection fraction. However, full decongestion remains the foremost therapeutic goal of hospitalization for heart failure. While early addition of sodium glucose cotransporter 2 inhibitors and mineralocorticoid receptor antagonists may be helpful, the value of the other therapeutics comes after decongestion is complete.

Contemporary Decongestive Strategies in Acute Heart Failure

Congestion is the primary driver of hospital admissions in patients with heart failure and the key determinant of their outcome. Although intravenous loop diuretics remain the predominant agents used in the setting of acute heart failure, the therapeutic response is known to be variable, with a significant subset of patients discharged from the hospital with residual hypervolemia. In this context, urinary sodium excretion has gained attention both as a marker of response to loop diuretics and as a marker of prognosis that may be a useful clinical tool to guide therapy. Several decongestive strategies have been explored to improve diuretic responsiveness and removal of excess fluid. Sequential nephron blockade through combination diuretic therapy is one of the most used methods to enhance natriuresis and counter diuretic resistance. In this article, I provide an overview of the contemporary decongestive approaches and discuss the clinical data on the use of add-on diuretic therapy. I also discuss mechanical removal of excess fluid through extracorporeal ultrafiltration with a brief review of the results of landmark studies. Finally, I provide a short overview of the strategies that are currently under investigation and may prove helpful in this setting.

Evaluation of renal sodium handling in heart failure with preserved ejection fraction: A pilot study

The pathophysiology behind sodium retention in heart failure with preserved ejection fraction (HFpEF) remains poorly understood. We hypothesized that patients with HFpEF have impaired natriuresis and diuresis in response to volume expansion and diuretic challenge, which is associated with renal hypo-responsiveness to endogenous natriuretic peptides. Nine HFpEF patients and five controls received saline infusion (0.25 mL/kg/min for 60 min) followed by intravenous furosemide (20 mg or home dose) 2 h after the infusion. Blood and urine samples were collected at baseline, 2 h after saline infusion, and 2 h after furosemide administration; urinary volumes were recorded. The urinary cyclic guanosine monophosphate (ucGMP)/plasma B-type NP (BNP) ratio was calculated as a measure of renal response to endogenous BNP. Wilcoxon rank-sum test was used to compare the groups. Compared to controls, HFpEF patients had reduced urine output (2480 vs.3541 mL; p = 0.028), lower urinary sodium excretion over 2 h after saline infusion (the percentage of infused sodium excreted 12% vs. 47%; p = 0.003), and a lower baseline ucGMP/plasma BNP ratio (0.7 vs. 7.3 (pmol/mL)/(mg/dL)/(pg/mL); p = 0.014). Patients with HFpEF had impaired natriuretic response to intravenous saline and furosemide administration and lower baseline ucGMP/plasma BNP ratios indicating renal hypo-responsiveness to NPs.

Combinational Diuretics in Heart Failure

PURPOSE OF REVIEW

Diuretics are the cornerstone therapy for acute heart failure (HF) and congestion. Patients chronically exposed to loop diuretics may develop diuretic resistance as a consequence of nephron remodelling, and the combination of diuretics will be necessary to improve diuretic response and achieve decongestion. This review integrates data from recent research and offers a practical approach to current pharmacologic therapies to manage congestion in HF with a focus on combinational therapy.

RECENT FINDINGS

Until recently, combined diuretic treatment was based on observational studies and expert opinion. Recent evidence from clinical trials has shown that combined diuretic treatment can be started earlier without escalating the doses of loop diuretics with an adequate safety profile. Diuretic combination is a promising strategy for overcoming diuretic resistance in HF. Further studies aiming to get more insights into the pathophysiology of diuretic resistance and large clinical trials confirming the safety and efficacy over standard diuretics regimens are warranted.

Renal Sodium Avidity in Heart Failure

BACKGROUND

Increased renal sodium avidity is a hallmark feature of the heart failure syndrome.

SUMMARY

Increased renal sodium avidity refers to the inability of the kidneys to elicit potent natriuresis in response to sodium loading. This eventually causes congestion, which is a major contributor to hospital admissions and mortality in heart failure.

KEY MESSAGES

Important novel concepts such as the renal tamponade hypothesis, accelerated nephron loss, and the role of hypochloremia, the sympathetic nervous system, inflammation, the lymphatic system, and interstitial sodium buffers are involved in the pathophysiology of renal sodium avidity. A good understanding of these concepts is crucially important with respect to treatment recommendations regarding dietary sodium restriction, fluid restriction, rapid up-titration of guideline-directed medical therapies, combination diuretic therapy, natriuresis-guided diuretic therapy, use of hypertonic saline, and ultrafiltration.

Diuretic Tolerance to Repeated-Dose Furosemide in Infants Born Very Preterm with Bronchopulmonary Dysplasia

OBJECTIVES

To assess the presence and timing of furosemide diuretic tolerance in infants with bronchopulmonary dysplasia (BPD), and to determine if tolerance is modified by thiazide co-administration.

STUDY DESIGN

We performed a retrospective cohort study among infants born very preterm with BPD exposed to repeated-dose furosemide for 72 hours, measuring net fluid balance (total intake minus total output) as a surrogate of diuresis in the 3 days before and after exposure. The primary comparison was the difference in fluid balance between the first and third 24 hours of furosemide exposure. We fit a general linear model for within-subject repeated measures of fluid balance over time, with thiazide co-administration as an interaction variable. Secondary analyses included an evaluation of weight trajectories over time.

RESULTS

In 83 infants, median fluid balance ranged between + 43.6 and + 52.7 ml/kg/d in the 3 days prior to furosemide exposure. Fluid balance decreased to a median of + 29.1 ml/kg/d in the first 24 hours after furosemide, but then increased to +47.5 ml/kg/d by the third 24-hour interval, consistent with tolerance (P < .001). Thiazides did not modify the change in fluid balance during furosemide exposure for any time-period. Weight decreased significantly in the first 24 hours after furosemide and increased thereafter (P < .001).

CONCLUSIONS

The net fluid balance response to furosemide decreases rapidly during repeated-dose exposures in infants with BPD, consistent with diuretic tolerance. Clinicians should consider this finding in the context of an infant's therapeutic goals. Further research efforts to identify safe and effective furosemide dosage strategies are needed.

Empagliflozin in Heart Failure: Regional Nephron Sodium Handling Effects

SIGNIFICANCE STATEMENT

The effect of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on regional tubular sodium handling is poorly understood in humans. In this study, empagliflozin substantially decreased lithium reabsorption in the proximal tubule (PT) (a marker of proximal tubular sodium reabsorption), a magnitude out of proportion to that expected with only inhibition of sodium-glucose cotransporter-2. This finding was not driven by an "osmotic diuretic" effect; however, several parameters changed in a manner consistent with inhibition of the sodium-hydrogen exchanger 3. The large changes in proximal tubular handling were acutely buffered by increased reabsorption in both the loop of Henle and the distal nephron, resulting in the observed modest acute natriuresis with these agents. After 14 days of empagliflozin, natriuresis waned due to increased reabsorption in the PT and/or loop of Henle. These findings confirm in humans that SGLT2i have complex and important effects on renal tubular solute handling.

BACKGROUND

The effect of SGLT2i on regional tubular sodium handling is poorly understood in humans but may be important for the cardiorenal benefits.

METHODS

This study used a previously reported randomized, placebo-controlled crossover study of empagliflozin 10 mg daily in patients with diabetes and heart failure. Sodium handling in the PT, loop of Henle (loop), and distal nephron was assessed at baseline and day 14 using fractional excretion of lithium (FELi), capturing PT/loop sodium reabsorption. Assessments were made with and without antagonism of sodium reabsorption through the loop using bumetanide.

RESULTS

Empagliflozin resulted in a large decrease in sodium reabsorption in the PT (increase in FELi=7.5%±10.6%, P = 0.001), with several observations suggesting inhibition of PT sodium hydrogen exchanger 3. In the absence of renal compensation, this would be expected to result in approximately 40 g of sodium excretion/24 hours with normal kidney function. However, rapid tubular compensation occurred with increased sodium reabsorption both in the loop ( P < 0.001) and distal nephron ( P < 0.001). Inhibition of sodium-glucose cotransporter-2 did not attenuate over 14 days of empagliflozin ( P = 0.14). However, there were significant reductions in FELi ( P = 0.009), fractional excretion of sodium ( P = 0.004), and absolute fractional distal sodium reabsorption ( P = 0.036), indicating that chronic adaptation to SGLT2i results primarily from increased reabsorption in the loop and/or PT.

CONCLUSIONS

Empagliflozin caused substantial redistribution of intrarenal sodium delivery and reabsorption, providing mechanistic substrate to explain some of the benefits of this class. Importantly, the large increase in sodium exit from the PT was balanced by distal compensation, consistent with SGLT2i excellent safety profile.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

ClinicalTrials.gov ( NCT03027960 ).

Association of Urine Galectin-3 With Cardiorenal Outcomes in Patients With Heart Failure

BACKGROUND AND OBJECTIVES

Approaches to distinguishing pathological cardiorenal dysfunction in heart failure (HF) from functional/hemodynamically mediated changes in serum creatinine are needed. We investigated urine galectin-3 as a candidate biomarker of renal fibrosis and a prognostic indicator of cardiorenal dysfunction phenotypes.

METHODS

We measured urine galectin-3 in 2 contemporary HF cohorts: the Yale Transitional Care Clinic (YTCC) cohort (n = 132) and the Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist (TOPCAT) trial (n = 434). We assessed the association of urine galectin-3 with all-cause mortality in both cohorts and the association with an established marker of renal tissue fibrosis, urinary amino-terminal propeptide of type III procollagen (PIIINP) in TOPCAT.

RESULTS

In the YTCC cohort, there was significant effect modification between higher urine galectin-3 and lower estimated glomerular filtration rates (eGFRs) (Pinteraction = 0.046), such that low eGFR levels had minimal prognostic importance if urine galectin-3 levels were low, but they were important and indicated high risk if urine galectin-3 levels were high. Similar observations were noted in the TOPCAT study (Pinteraction = 0.002). In TOPCAT, urine galectin-3 also positively correlated with urine PIIINP at both baseline (r = 0.43; P < 0.001) and at 12 months (r = 0.42; P < 0.001).

CONCLUSIONS

Urine galectin-3 levels correlated with an established biomarker of renal fibrosis in 2 cohorts and was able to differentiate high- vs low-risk phenotypes of chronic kidney disease in HF. These proof-of-concept results indicate that additional biomarker research to differentiate cardiorenal phenotypes is warranted.

Conduction System Pacing: Have We Finally Found the Holy Grail of Physiological Pacing?

The late fifties are considered a high point in the history of cardiac pacing, since this era is marked by the first pacemaker implantation, which has since evolved into life-saving therapy. Right ventricular apical and biventricular pacing are the classic techniques that are recommended as first-l ine approaches for most indications in current guidelines. However, conduction system pacing has emerged as being able to deliver a more physiological form of pacing and is becoming mainstream practice in a growing number of centres. In this review, we aim to compare traditional pacing methods with conduction system pacing.

A Personalized Approach to the Management of Congestion in Acute Heart Failure

Heart failure (HF) is the common final pathway of several conditions and is characterized by hyperactivation of numerous neurohumoral pathways. Cardiorenal interaction plays an essential role in the progression of the disease, and the use of diuretics is a cornerstone in the treatment of hypervolemic patients, especially in acute decompensated HF (ADHF). The management of congestion is complex and, to avoid misinterpretations and errors, one must understand the interface between the heart and the kidneys in ADHF. Congestion itself may impair renal function and must be treated aggressively. Transitory elevations in serum creatinine during decongestion is not associated with worse outcomes and diuretics should be maintained in patients with clear hypervolemia. Monitoring urinary sodium after diuretic administration seems to improve the response to diuretics as it allows for adjustments in doses and a personalized approach. Adequate assessment of volemia and the introduction and titration of guideline-directed medical therapy are mandatory before discharge. An early visit after discharge is highly recommended, to assess for residual congestion and thus avoid readmissions.

Combination Diuretic Therapy to Counter Renal Sodium Avidity in Acute Heart Failure: Trials and Tribulations

In contrast to significant advances in the management of patients with chronic heart failure over the past few years, there has been little change in how patients with acute heart failure are treated. Symptoms and signs of fluid overload are the primary reason for hospitalization of patients who experience acute decompensation of heart failure. Intravenous loop diuretics remain the mainstay of therapy in this patient population, with a significant subset of them showing suboptimal response to these agents leading to incomplete decongestion at the time of discharge. Combination diuretic therapy, that is, using loop diuretics along with an add-on agent, is a widely applied strategy to counter renal sodium avidity through sequential blockade of sodium absorption within renal tubules. The choice of the second diuretic is affected by several factors, including the site of action, the anticipated secondary effects, and the available evidence on their efficacy and safety. While the current guidelines recommend combination diuretic therapy as a viable option to overcome suboptimal response to loop diuretics, it is also acknowledged that this strategy is not supported by strong evidence and remains an area of uncertainty. The recent publication of landmark studies has regenerated the interest in sequential nephron blockade. In this article, we provide an overview of the results of the key studies on combination diuretic therapy in the setting of acute heart failure and discuss their findings primarily with regard to the effect on renal sodium avidity and cardiorenal outcomes.

The importance of forward flow and venous congestion in diuretic response in acute heart failure: Insights from the ESCAPE trial

AIMS

Previous studies have suggested venous congestion as a stronger mediator of negative cardio-renal interactions than low cardiac output, with neither factor having a dominant role. While the influence of these parameters on glomerular filtration have been described, the impact on diuretic responsiveness is unclear. The goal of this analysis was to understand the hemodynamic correlates of diuretic response in hospitalized patients with heart failure.

METHODS AND RESULTS

We analyzed patients from the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE) dataset. Diuretic efficiency (DE) was defined as the average daily net fluid output per doubling of the peak loop diuretic dose. We evaluated a pulmonary artery catheter hemodynamic-guided cohort (n = 190) and a transthoracic echocardiogram (TTE) cohort (n = 324) where DE was evaluated with hemodynamic and TTE parameters. Metrics of "forward flow" such as cardiac index, mean arterial pressure and left ventricular ejection fraction were not associated with DE (p > 0.2 for all). Worse baseline venous congestion was paradoxically associated with better DE as assessed by right atrial pressure (RAP), right atrial area (RAA), and right ventricular systolic and diastolic area (p < 0.05 for all). Renal perfusion pressure (capturing both congestion and forward flow) was not associated with diuretic response (p = 0.84).

CONCLUSIONS

Worse venous congestion was weakly associated with better loop diuretic response. Metrics of "forward flow" did not demonstrate any correlation with diuretic response. These observations raise questions about the concept of central hemodynamic perturbations as the primary drivers of diuretic resistance on a population level in HF.

Serum Chloride and Heart Failure

Despite significant advances in management, heart failure continues to impose a significant epidemiologic burden with high prevalence and mortality rates. For decades, sodium has been the serum electrolyte most commonly associated with outcomes; however, challenging the conventional paradigm of sodium's influence, recent studies have identified a more prominent role in serum chloride in the pathophysiology of heart failure. More specifically, hypochloremia is associated with neurohumoral activation, diuretic resistance, and a worse prognosis in patients with heart failure. This review examines basic science, translational research, and clinical studies to better characterize the role of chloride in patients with heart failure and additionally discusses potential new therapies targeting chloride homeostasis that may impact the future of heart failure care.

Tackling Congestion in Acute Heart Failure: Is It the Primetime for "Combo Diuretic Therapy?"

Symptoms and signs of congestion are the primary reason for hospitalization of patients with acute heart failure. Efficient fluid and sodium removal remain the main goals of therapy, and loop diuretics are the recommended agents in this setting. However, the therapeutic response to these medications is known to be variable, and a significant subset of patients is discharged from the hospital with residual fluid overload. Therefore, sequential blockade of the nephron has been proposed as a more effective decongestive strategy. Pilot studies have suggested significant increase in diuresis and natriuresis with combination diuretic therapy. Recently, two groups of investigators examined this hypothesis on a larger scale in randomized placebo-controlled trials; one targeted the proximal tubules upstream of the loop of Henle (Acetazolamide in Decompensated Heart Failure with Volume Overload - ADVOR), while the other one blocked sodium-chloride cotransporters in the distal convoluted tubules (Combination of Loop with Thiazide Diuretics for Decompensated Heart Failure - CLOROTIC). Herein, we discuss the results of these two trials with special focus on their impact on extraction of sodium, i.e., the main determinant of extracellular volume, and put them in the context of previous studies of combination diuretic therapy as well as extracorporeal ultrafiltration.

Diuretics and Ultrafiltration in Heart Failure

Fluid overload is a risk factor for increased morbidity and mortality, especially in patients with heart disease. The treatment options are limited to diuretics and mechanical fluid removal using ultrafiltration or renal replacement therapy. This paper provides an overview of the challenges of managing fluid overload, outlines the risks and benefits of different pharmacological options and extracorporeal techniques, and provides guidance for clinical practice.

Diuretic resistance in patients with kidney disease: Challenges and opportunities

Edema caused by kidney disease is called renal edema. Edema is a common symptom of many human kidney diseases. Patients with renal edema often need to take diuretics.However, After taking diuretics, patients with kidney diseases are prone to kidney congestion, decreased renal perfusion, decreased diuretics secreted by renal tubules, neuroendocrine system abnormalities, abnormal ion transporter transport, drug interaction, electrolyte disorder, and hypoproteinemia, which lead to ineffective or weakened diuretic use and increase readmission rate and mortality. The main causes and coping strategies of diuretic resistance in patients with kidney diseases were described in detail in this report. The common causes of DR included poor diet (electrolyte disturbance and hypoproteinemia due to patients' failure to limit diet according to correct sodium, chlorine, potassium, and protein level) and poor drug compliance (the patient did not take adequate doses of diuretics. true resistance occurs only if the patient takes adequate doses of diuretics, but they are not effective), changes in pharmacokinetics and pharmacodynamics, electrolyte disorders, changes in renal adaptation, functional nephron reduction, and decreased renal blood flow. Common treatment measures include increasing in the diuretic dose and/or frequency, sequential nephron blockade,using new diuretics, ultrafiltration treatment, etc. In clinical work, measures should be taken to prevent or delay the occurrence and development of DR in patients with kidney diseases according to the actual situation of patients and the mechanism of various causes. Currently, there are many studies on DR in patients with heart diseases. Although the phenomenon of DR in patients with kidney diseases is common, there is a relatively little overview of the mechanism and treatment strategy of DR in patients with kidney diseases. Therefore, this paper hopes to show the information on DR in patients with kidney diseases to clinicians and researchers and broaden the research direction and ideas to a certain extent.

Comparison of chlorthalidone and spironolactone as additional diuretic therapy in patients with acute heart failure and preserved ejection fraction

AIMS

Patients with acute heart failure (AHF) require intensification in the diuretic strategy. However, the optimal diuretic strategy remains unclear. In this work, we aimed to evaluate the effect of chlorthalidone compared with spironolactone on diuretic efficacy and safety profile in a cohort of patients with AHF and preserved ejection fraction (AHF-pEF).

METHODS AND RESULTS

It was a prospective observational study in a single centre in Spain, included 44 consecutive patients admitted between June 2020 and March 2021, with AHF-pEF in which an additional diuretic was prescribed. The primary endpoint was changes in urinary sodium at 24 and 72 h, and the secondary were urine output, and other security endpoints. Mixed linear regression models were used to analyse the endpoints. Estimates were reported as least squares mean with their respective 95% confidence intervals. The median age of the study population was 85 years (82.5-88.5), and 30 (68.2%) were women. After multivariate analysis, the linear mixed regression analysis confirmed a greater natriuretic response of chlorthalidone over spironolactone, especially at 24 h (P = 0.009). Multivariate analysis also showed a greater cumulative diuretic response in those treated with chlorthalidone (P = 0.001). We did not find significant differences in glomerular filtration rate, serum sodium, and serum potassium at 72 h, neither significant differences were found in 24 and 72 h in systolic blood pressure.

CONCLUSION

In patients with AHF and left ventricular ejection fraction ≥50% receiving intravenous loop diuretics, chlorthalidone administration was associated with a greater short-term natriuresis.

Renin-Angiotensin-Aldosterone System Activation and Diuretic Response in Ambulatory Patients With Heart Failure

Rationale & Objective

Heart failure treatment relies on loop diuretics to induce natriuresis and decongestion, but the therapy is often limited by diuretic resistance. We explored the association of renin-angiotensin-aldosterone system (RAAS) activation with diuretic response.

Study Design

Observational cohort.

Setting & Population

Euvolemic ambulatory adults with chronic heart failure were administered torsemide in a monitored environment.

Predictors

Plasma total renin, active renin, angiotensinogen, and aldosterone levels. Urine total renin and angiotensinogen levels.

Outcomes

Sodium output per doubling of diuretic dose and fractional excretion of sodium per doubling of diuretic dose.

Analytical Approach

Robust linear regression models estimated the associations of each RAAS intermediate with outcomes.

Results

The analysis included 56 participants, and the median age was 65 years; 50% were women, and 41% were Black. The median home diuretic dose was 80-mg furosemide equivalents. In unadjusted and multivariable-adjusted models, higher levels of RAAS measures were generally associated with lower diuretic efficiency. Higher plasma total renin remained significantly associated with lower sodium output per doubling of diuretic dose (β = -0.41 [-0.76, -0.059] per SD change) with adjustment; higher plasma total and active renin were significantly associated with lower fractional excretion of sodium per doubling of diuretic dose (β = -0.48 [-0.83, -0.14] and β = -0.51 [-0.95, -0.08], respectively) in adjusted models. Stratification by RAAS inhibitor use did not substantially alter these associations.

Limitations

Small sample size; highly selected participants; associations may not be causal.

Conclusions

Among multiple measures of RAAS activation, higher plasma total and active renin levels were consistently associated with lower diuretic response. These findings highlight the potential drivers of diuretic resistance and underscore the need for high-quality trials of decongestive therapy enhanced by RAAS blockade.

Classic and Novel Mechanisms of Diuretic Resistance in Cardiorenal Syndrome

Despite the incompletely understood multiple etiologies and underlying mechanisms, cardiorenal syndrome is characterized by decreased glomerular filtration and sodium avidity. The underlying level of renal sodium avidity is of primary importance in driving a congested heart failure phenotype and ultimately determining the response to diuretic therapy. Historically, mechanisms of kidney sodium avidity and resultant diuretic resistance were primarily extrapolated to cardiorenal syndrome from non-heart failure populations. Yet, the mechanisms appear to differ between these populations. Recent literature in acute decompensated heart failure has refuted several classically accepted diuretic resistance mechanisms and reshaped how we conceptualize diuretic resistance mechanisms in cardiorenal syndrome. Herein, we propose an anatomically based categorization of diuretic resistance mechanisms to establish the relative importance of specific transporters and translate findings toward therapeutic strategies. Within this categorical structure, we discuss classic and novel mechanisms of diuretic resistance.

Development, validation, and implementation of an UHPLC-MS/MS method for the quantitation of furosemide in infant urine samples

Furosemide is a diuretic drug used to increase urine flow in order to reduce the amount of salt and water in the body. It is commonly utilized to treat preterm infants with chronic lung disease of prematurity. There is a need for a simple and reliable quantitation of furosemide in human urine. We have developed and validated an ultra-high performance liquid chromatography-tandem mass spectrometry method for furosemide quantitation in human urine with an assay range of 0.100-50.0 μg/ml. Sample preparation involved solid-phase extraction with 10 μl of urine. Intra-day accuracies and precisions for the quality control samples were 94.5-106 and 1.86-10.2%, respectively, while inter-day accuracies and precision were 99.2-102 and 3.38-7.41%, respectively. Recovery for furosemide had an average of 23.8%, with an average matrix effect of 101%. Furosemide was stable in human urine under the assay conditions. Stability for furosemide was shown at 1 week (room temperature, 4, -20 and -78°C), 6 months (-78°C), and through three freeze-thaw cycles. This robust assay demonstrates accurate and precise quantitation of furosemide in a small volume (10 μl) of human urine. It is currently being implemented in an ongoing pediatric clinical study.

Contemporary Drug Treatment of Advanced Heart Failure with Reduced Ejection Fraction

The introduction of multiple new pharmacological agents over the past three decades in the field of heart failure with reduced ejection fraction (HFrEF) has led to reduced rates of mortality and hospitalizations, and consequently the prevalence of HFrEF has increased, and up to 10% of patients progress to more advanced stages, characterized by high rates of mortality, hospitalizations, and poor quality of life. Advanced HFrEF patients often show persistent or progressive signs of severe HF symptoms corresponding to New York Heart Association class III or IV despite being on optimal medical, surgical, and device therapies. However, a subpopulation of patients with advanced HF, those with the most advanced stages of disease, were often insufficiently represented in the major trials demonstrating efficacy and tolerability of the drugs used in HFrEF due to exclusion criteria such as low BP and kidney dysfunction. Consequently, the results of many landmark trials cannot necessarily be transferred to patients with the most advanced stages of HFrEF. Thus, the efficacy and tolerability of guideline-directed medical therapies in patients with the most advanced stages of HFrEF often remain unsettled, and this knowledge is of crucial importance in the planning and timing of consideration for referral for advanced therapies. This review discusses the evidence regarding the use of contemporary drugs in the advanced HFrEF population, covering components such as guideline HFrEF drugs, diuretics, inotropes, and the use of HFrEF drugs in LVAD recipients, and provides suggestions on how to manage guideline-directed therapy in this patient group.

Assessment of Proximal Tubular Function by Tubular Maximum Phosphate Reabsorption Capacity in Heart Failure

BACKGROUND AND OBJECTIVES

The estimated glomerular filtration rate (eGFR) is a crucial parameter in heart failure. Much less is known about the importance of tubular function. We addressed the effect of tubular maximum phosphate reabsorption capacity (TmP/GFR), a parameter of proximal tubular function, in patients with heart failure.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We established TmP/GFR (Bijvoet formula) in 2085 patients with heart failure and studied its association with deterioration of kidney function (>25% eGFR decrease from baseline) and plasma neutrophil gelatinase-associated lipocalin (NGAL) doubling (baseline to 9 months) using logistic regression analysis and clinical outcomes using Cox proportional hazards regression. Additionally, we evaluated the effect of sodium-glucose transport protein 2 (SGLT2) inhibition by empagliflozin on tubular maximum phosphate reabsorption capacity in 78 patients with acute heart failure using analysis of covariance.

RESULTS

Low TmP/GFR (<0.80 mmol/L) was observed in 1392 (67%) and 21 (27%) patients. Patients with lower TmP/GFR had more advanced heart failure, lower eGFR, and higher levels of tubular damage markers. The main determinant of lower TmP/GFR was higher fractional excretion of urea (P<0.001). Lower TmP/GFR was independently associated with higher risk of plasma NGAL doubling (odds ratio, 2.20; 95% confidence interval, 1.05 to 4.66; P=0.04) but not with deterioration of kidney function. Lower TmP/GFR was associated with higher risk of all-cause mortality (hazard ratio, 2.80; 95% confidence interval, 1.37 to 5.73; P=0.005), heart failure hospitalization (hazard ratio, 2.29; 95% confidence interval, 1.08 to 4.88; P=0.03), and their combination (hazard ratio, 1.89; 95% confidence interval, 1.07 to 3.36; P=0.03) after multivariable adjustment. Empagliflozin significantly increased TmP/GFR compared with placebo after 1 day (P=0.004) but not after adjustment for eGFR change.

CONCLUSIONS

TmP/GFR, a measure of proximal tubular function, is frequently reduced in heart failure, especially in patients with more advanced heart failure. Lower TmP/GFR is furthermore associated with future risk of plasma NGAL doubling and worse clinical outcomes, independent of glomerular function.

Impact of Loop Diuretic on Outcomes in Patients with Heart Failure and Reduced Ejection Fraction

PURPOSE OF REVIEW

Loop diuretics are the cornerstone of the treatment of congestion in heart failure patients. The manuscript aims to summarize the most updated information regarding the use of loop diuretics in heart failure.

RECENT FINDINGS

Diuretic response can be highly variable between patients and needs to be carefully evaluated during and after the hospitalization. Diuretic resistance can lead to residual congestion which affects prognosis and can be difficult to detect. The effect of loop diuretics on long-term prognosis remains uncertain but patients with advanced heart failure typically have renal dysfunction and are more inclined to develop loop diuretic resistance, which may lead to an incomplete decongestion and thus to a worse prognosis. Loop diuretics are the most potent diuretics available and their use is recommended in order to alleviate symptoms, improve exercise capacity, and reduce hospitalizations in patients with heart failure. Their use should be limited to the lowest dose necessary to maintain euvolemia because a low dose does not increase the risk of decompensation but reduce the risk of adverse effects and allow the up-titration of disease-modifying drugs.

The Effect in Renal Function and Vascular Decongestion in Type 1 Cardiorenal Syndrome Treated with Two Strategies of Diuretics, a Pilot Randomized Trial

Aim

The main treatment strategy in type 1 cardiorenal syndrome (CRS1) is vascular decongestion. It is probable that sequential blockage of the renal tubule with combined diuretics (CD) will obtain similar benefits compared with stepped-dose furosemide (SF).

Methods

In a pilot double-blind randomized controlled trial of CRS1 patients were allocated in a 1:1 fashion to SF or CD. The SF group received a continuous infusion of furosemide 100 mg during the first day, with daily incremental doses to 200 mg, 300 mg and 400 mg. The CD group received a combination of diuretics, including 4 consecutive days of oral chlorthalidone 50 mg, spironolactone 50 mg and infusion of furosemide 100 mg. The objectives were to assess renal function recovery and variables associated with vascular decongestion.

Results

From July 2017 to February 2020, 80 patients were randomized, 40 to the SF and 40 to the CD group. Groups were similar at baseline and had several very high-risk features. Their mean age was 59 ± 14.5 years, there were 37 men (46.2%). The primary endpoint occurred in 20% of the SF group and 15.2% of the DC group (p = 0.49). All secondary and exploratory endpoints were similar between groups. Adverse events occurred frequently (85%) with no differences between groups (p = 0.53).

Conclusion

In patients with CRS1 and a high risk of resistance to diuretics, the use of CD compared to SF offers the same results in renal recovery, diuresis, vascular decongestion and adverse events, and it can be considered an alternative treatment. ClinicalTrials.gov with number NCT04393493 on 19/05/2020 retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02637-y.

Natriuresis guided therapy in acute heart failure: rationale and design of the Pragmatic Urinary Sodium-based Treatment algoritHm in Acute Heart Failure (PUSH-AHF) trial

Aims

Insufficient diuretic response frequently occurs in patients admitted for acute heart failure (HF) and is associated with worse clinical outcomes. Recent studies have shown that measuring natriuresis early after hospital admission could reliably identify patients with a poor diuretic response during hospitalization who might require enhanced diuretic treatment. This study will test the hypothesis that natriuresis‐guided therapy in patients with acute HF improves natriuresis and clinical outcomes.

Methods

The Pragmatic Urinary Sodium‐based treatment algoritHm in Acute Heart Failure (PUSH‐AHF) is a pragmatic, single‐centre, randomized, controlled, open‐label study, aiming to recruit 310 acute HF patients requiring treatment with intravenous loop diuretics. Patients will be randomized to natriuresis‐guided therapy or standard of care. Natriuresis will be determined at set time points after initiation of intravenous loop diuretics, and treatment will be adjusted based on the urinary sodium levels in the natriuresis‐guided group using a pre‐specified stepwise approach of increasing doses of loop diuretics and the initiation of combination diuretic therapy. The co‐primary endpoint is 24‐h urinary sodium excretion after start of loop diuretic therapy and a combined endpoint of all‐cause mortality or first HF rehospitalization at 6 months. Secondary endpoints include 48‐ and 72‐h sodium excretion, length of hospital stay, and percentage change in N‐terminal pro brain natriuretic peptide at 48 and 72 h.

Conclusion

The PUSH‐AHF study will investigate whether natriuresis‐guided therapy, using a pre‐specified stepwise diuretic treatment approach, improves natriuresis and clinical outcomes in patients with acute HF.

FGF-23 (Fibroblast Growth Factor-23) and Cardiorenal Interactions

BACKGROUND

Animal models implicate FGF-23 (fibroblast growth factor-23) as a direct contributor to adverse cardiorenal interactions such as sodium avidity, diuretic resistance, and neurohormonal activation, but this has not been conclusively demonstrated in humans. Therefore, we aimed to evaluate whether FGF-23 is associated with parameters of cardiorenal dysfunction in humans with heart failure, independent of confounding factors.

METHODS

One hundred ninety-nine outpatients with heart failure undergoing diuretic treatment at the Yale Transitional Care Center were enrolled and underwent blood collection, and urine sampling before and after diuretics.

RESULTS

FGF-23 was associated with several metrics of disease severity such as higher home loop diuretic dose and NT-proBNP (N-terminal pro-B-type natriuretic peptide), and lower estimated glomerular filtration rate, serum chloride, and serum albumin. Multivariable analysis demonstrated no statistically significant association between FGF-23 and sodium avidity measured by fractional excretion of sodium, or proximal or distal tubular sodium reabsorption, either before diuretic administration or at peak diuresis (P≥0.11 for all). Likewise, FGF-23 was not independently associated with parameters of diuretic resistance (diuretic excretion, cumulative urine and sodium output, and loop diuretic efficiency [P≥0.33 for all]) or neurohormonal activation (plasma or urine renin [P≥0.36 for all]). Moreover, the upper boundary of the 95% CI of all the partial correlations were ≤0.30, supporting the lack of meaningful correlations. FGF-23 was not associated with mortality in multivariable analysis (P=0.44).

CONCLUSIONS

FGF-23 was not meaningfully associated with any cardiorenal parameter in patients with heart failure. While our methods cannot rule out a small effect, FGF-23 is unlikely to be a primary driver of cardiorenal interactions.

Compensatory post-diuretic renal sodium reabsorption is not a dominant mechanism of diuretic resistance in acute heart failure

AIMS

In healthy volunteers, the kidney deploys compensatory post-diuretic sodium reabsorption (CPDSR) following loop diuretic-induced natriuresis, minimizing sodium excretion and producing a neutral sodium balance. CPDSR is extrapolated to non-euvolemic populations as a diuretic resistance mechanism; however, its importance in acute decompensated heart failure (ADHF) is unknown.

METHODS AND RESULTS

Patients with ADHF in the Mechanisms of Diuretic Resistance cohort receiving intravenous loop diuretics (462 administrations in 285 patients) underwent supervised urine collections entailing an immediate pre-diuretic spot urine sample, then 6-h (diuretic-induced natriuresis period) and 18-h (post-diuretic period) urine collections. The average spot urine sodium concentration immediately prior to diuretic administration [median 15 h (13-17) after last diuretic] was 64 ± 33 mmol/L with only 4% of patients having low (<20 mmol/L) urine sodium consistent with CPDSR. Paradoxically, greater 6-h diuretic-induced natriuresis was associated with larger 18-h post-diuretic spontaneous natriuresis (r = 0.7, P < 0.001). Higher pre-diuretic urine sodium to creatinine ratio (r = 0.37, P < 0.001) was the strongest predictor of post-diuretic spontaneous natriuresis. In a subgroup of patients (n = 43) randomized to protocol-driven intensified diuretic therapies, the mean diuretic-induced natriuresis increased three-fold. In contrast to the substantial decrease in spontaneous natriuresis predicted by CPDSR, no change in post-diuretic spontaneous natriuresis was observed (P = 0.47).

CONCLUSION

On a population level, CPDSR was not an important driver of diuretic resistance in hypervolemic ADHF. Contrary to CPDSR, a greater diuretic-induced natriuresis predicted a larger post-diuretic spontaneous natriuresis. Basal sodium avidity, rather than diuretic-induced CPDSR, appears to be the predominant determinate of both diuretic-induced and post-diuretic natriuresis in hypervolemic ADHF.

Multinephron Segment Diuretic Therapy to Overcome Diuretic Resistance in Acute Heart Failure: A Single-Center Experience

BACKGROUND

The concept of multinephron segment diuretic therapy (MSDT) has been recommended in severe diuretic resistance with only expert opinion and case-level evidence. The purpose of this study was to investigate the safety and efficacy of MSDT, combining 4 diuretic classes, in acute heart failure (AHF) complicated by diuretic resistance.

METHODS AND RESULTS

A retrospective analysis was conducted in patients hospitalized with AHF at a single medical center who received MSDT, including concomitant carbonic anhydrase inhibitor, loop, thiazide, and mineralocorticoid receptor antagonist diuretics. Subjects served as their own controls with efficacy evaluated as urine output and weight change before and after MSDT. Serum chemistries, renal replacement therapies, and in-hospital mortality were evaluated for safety. Patients with severe diuretic resistance before MSDT were analyzed as a subcohort. A total of 167 patients with AHF and diuretic resistance received MSDT. MSDT was associated with increased median 24-hour urine output in the first day of therapy compared with the previous day (2.16 L [0.95-4.14 L] to 3.08 L [1.74-4.86 L], P = .003) in the total cohort and in the Severe diuretic resistance cohort (0.91 L [0.43-1.43 L] to 2.08 L [1.13-3.96 L], P < .001). The median cumulative weight loss at day 7 or discharge was -7.4 kg (-15.3 to -3.4 kg) (P = .02). Neither serum sodium, chloride, potassium, bicarbonate, or creatinine changed significantly relative to baseline (P > .05 for all).

CONCLUSIONS

In an AHF cohort with diuretic resistance, MSDT was associated with increased diuresis without changes in serum chemistries or kidney function. Prospective studies of MSDT in AHF and diuretic resistance are warranted.

Efficacy and safety of diuretics in heart failure with preserved ejection fraction: a scoping review

OBJECTIVE

Diuretics reduce congestion in patients with heart failure with preserved ejection fraction (HFpEF). However, comparison of clinical effects across diuretic classes or combinations of diuretics in patients with HFpEF are not well described. Therefore, we sought to conduct a scoping review to map trial data of diuretic efficacy and safety in patients with HFpEF.

REVIEW METHODS AND RESULTS

We searched multiple bibliometric databases for published literature and ClinicalTrials.gov, and hand searched unpublished studies comparing different classes of diuretics to usual care or placebo in patients with HFpEF. We included randomised controlled trials or quasi-experimental studies. Two authors independently screened and extracted key data using a structured form. We identified 13 published studies on diuretics in HFpEF, with 1 evaluating thiazide use, 7 on mineralocorticoid receptor antagonists (MRAs) and 5 on sodium-glucose co-transporter 2 inhibitors (SGLT2i). There remain 17 ongoing trials evaluating loop diuretics (n=1), MRAs (n=5), SGLT2i (n=10) and a polydiuretic (n=1), including 2 well-powered trials of SGLT2i that will be completed in 2021.

CONCLUSIONS

The limited number of published trials evaluating different classes of diuretics in patients with HFpEF have been generally small and short term. Ongoing and emerging trials of single or combination diuretics with greater power will be useful to better define their safety and efficacy. SCOPING REVIEW REGISTRATION: doi:10.18131/g3-dejv-tm77.

Ambulatory Management of Worsening Heart Failure: Current Strategies and Future Directions

Heart failure (HF) is a highly prevalent and morbid disease in the USA. The chronic, progressive course of HF is defined by periodic exacerbations of symptoms, described as 'worsening heart failure' (WHF). Previously, episodes of WHF have required hospitalization for intravenous diuretics; however, recent innovations in care delivery models for patients with HF have allowed a transition from the acute care setting to the ambulatory setting. The development of remote monitoring strategies, including device-based algorithms and implantable haemodynamic monitoring systems, has facilitated more advanced surveillance of patients, aiming to prevent the clinical deterioration that leads to hospitalization. Additionally, the establishment of multidisciplinary HF clinics has provided the setting and resources for the outpatient treatment of WHF, specifically the administration of intravenous diuretics. Here we review the current state of ambulatory HF management, including mechanisms for patient monitoring and treatment, and outline future opportunities for outpatient management of this patient population.

The pathophysiology and management of diuretic resistance in patients with heart failure

OBJECTIVES

The objectives of the study are to investigate the causes of diuretic resistance in patients with advanced congestive heart failure (CHF), since diuretics are the cornerstone of treatment of these patients. Several studies have shown that diuretic resistance in patients with advanced CHF is common, ranging from 25% to 50% in hospitalized patients.

METHODS

In order to get a current perspective as to the magnitude of diuretic resistance in such patients, a focused Medline search of the English language literature was conducted between 2015 and 2020 using the search terms, CHF, diuretics, treatment, resistance, frequency, and 30 papers with pertinent information were selected.

RESULTS

The analysis of data from the selected papers demonstrated that diuretic resistance is common in hospitalized patients with advanced CHF and frequently associated with renal failure, which is secondary to CHF.

CONCLUSIONS

Diuretic resistance appears to be common in patients with advanced CHF and it is mostly due to decreased cardiac output, low blood pressure, decreased glomerular filtration rate, decreased filtration of sodium, and increased tubular reabsorption of sodium. Diuretic resistance in such patients can be overcome with the combination of loop diuretics with thiazide and thiazide-like diuretics, aldosterone antagonists, as well as other agents. The data from these studies in combination with collateral literature will be discussed in this review.

Loop Diuretics in Severe Bronchopulmonary Dysplasia: Cumulative Use and Associations with Mortality and Age at Discharge

OBJECTIVES

To measure between-center variation in loop diuretic use in infants developing severe bronchopulmonary dysplasia (BPD) in US children's hospitals, and to compare mortality and age at discharge between infants from low-use centers and infants from high-use centers.

STUDY DESIGN

We performed a retrospective cohort study of preterm infants at <32 weeks of gestational age with severe BPD. The primary outcome was cumulative loop diuretic use, defined as the proportion of days with exposure between admission and discharge. Infant characteristics associated with loop diuretic use at P < .10 were included in multivariable models to adjust for center differences in case mix. Hospitals were ranked from lowest to highest in adjusted use and dichotomized into low-use centers and high-use centers. We then compared mortality and postmenstrual age at discharge between the groups through multivariable analyses.

RESULTS

We identified 3252 subjects from 43 centers. Significant variation between centers remained despite adjustment for infant characteristics, with use present in an adjusted mean range of 7.3% to 49.4% of days (P < .0001). Mortality did not differ significantly between the 2 groups (aOR, 0.98; 95% CI, 0.62-1.53; P = .92), nor did postmenstrual age at discharge (marginal mean, 47.3 weeks [95% CI, 46.8-47.9 weeks] in the low-use group vs 47.4 weeks [95% CI, 46.9-47.9 weeks] in the high-use group; P = .96).

CONCLUSIONS

A marked variation in loop diuretic use for infants developing severe BPD exists among US children's hospitals, without an observed difference in mortality or age at discharge. More research is needed to provide evidence-based guidance for this common exposure.

Natriuretic Equation to Predict Loop Diuretic Response in Patients With Heart Failure

BACKGROUND

Most acute decompensated heart failure admissions are driven by congestion. However, residual congestion is common and often driven by the lack of reliable tools to titrate diuretic therapy. The authors previously developed a natriuretic response prediction equation (NRPE), which predicts sodium output using a spot urine sample collected 2 h after loop diuretic administration.

OBJECTIVES

The purpose of this study was to validate the NRPE and describe proof-of-concept that the NRPE can be used to guide diuretic therapy.

METHODS

Two cohorts were assembled: 1) the Diagnosing and Targeting Mechanisms of Diuretic Resistance (MDR) cohort was used to validate the NRPE to predict 6-h sodium output after a loop diuretic, which was defined as poor (<50 mmol), suboptimal (<100 mmol), or excellent (>150 mmol); and 2) the Yale Diuretic Pathway (YDP) cohort, which used the NRPE to guide loop diuretic titration via a nurse-driven automated protocol.

RESULTS

Evaluating 638 loop diuretic administrations, the NRPE showed excellent discrimination with areas under the curve ≥0.90 to predict poor, suboptimal, and excellent natriuretic response, and outperformed clinically obtained net fluid loss (p < 0.05 for all cutpoints). In the YDP cohort (n = 161) using the NRPE to direct therapy mean daily urine output (1.8 ± 0.9 l vs. 3.0 ± 0.8 l), net fluid output (-1.1 ± 0.9 l vs. -2.1 ± 0.9 l), and weight loss (-0.3 ± 0.3 kg vs. -2.5 ± 0.3 kg) improved substantially following initiation of the YDP (p < 0.001 for all pre-post comparisons).

CONCLUSIONS

Natriuretic response can be rapidly and accurately predicted by the NRPE, and this information can be used to guide diuretic therapy during acute decompensated heart failure. Additional study of diuresis guided by the NRPE is warranted.

Congestive nephropathy: a neglected entity? Proposal for diagnostic criteria and future perspectives

Venous congestion has emerged as an important cause of renal dysfunction in patients with cardiorenal syndrome. However, only limited progress has been made in differentiating this haemodynamic phenotype of renal dysfunction, because of a significant overlap with pre-existing renal impairment due to long-term hypertension, diabetes, and renovascular disease. We propose congestive nephropathy (CN) as this neglected clinical entity. CN is a potentially reversible subtype of renal dysfunction associated with declining renal venous outflow and progressively increasing renal interstitial pressure. Venous congestion may lead to a vicious cycle of hormonal activation, increased intra-abdominal pressure, excessive renal tubular sodium reabsorption, and volume overload, leading to further right ventricular (RV) stress. Ultimately, renal replacement therapy may be required to relieve diuretic-resistant congestion. Effective decongestion could preserve or improve renal function. Congestive acute kidney injury may not be associated with cellular damage, and complete renal function restoration may be a confirmatory diagnostic criterion. In contrast, a persistently low renal perfusion pressure might induce renal dysfunction and histopathological lesions with time. Thus, urinary markers may differ. CN is mostly seen in biventricular heart failure but may also occur secondary to pulmonary arterial hypertension and elevated intra-abdominal pressure. An increase in central venous pressure to >6 mmHg is associated with a steep decrease in glomerular filtration rate. However, the central venous pressure range that can provide an optimal balance of RV and renal function remains to be determined. We propose criteria to identify cardiorenal syndrome subgroups likely to benefit from decongestive or pulmonary hypertension-specific therapies and suggest areas for future research.

Intensification of pharmacological decongestion but not the actual daily loop diuretic dose predicts worse chronic heart failure outcome: insights from TIME-CHF

BACKGROUND

Both loop diuretics (LDs) and congestion have been related to worse heart failure (HF) outcome. The relationship between the cause and effect is unknown. The aim of this study was to investigate the interaction between congestion, diuretic use and HF outcome.

METHODS

Six hundred and twenty-two chronic HF patients from TIME-CHF were studied. Congestion was measured by means of a clinical congestion index (CCI). Loop diuretic dose was considered at baseline and month 6. Treatment intensification was defined as the increase in LD dose over 6 months or loop diuretic and thiazide or thiazide-like diuretic co-administration. The end-points were survival and HF hospitalisation-free survival.

RESULTS

High-LD dose at baseline and month 6 (≥ 80 mg of furosemide per day) was not identified as an independent predictor of outcome. CCI at baseline remained independently associated with impaired survival [hazard ratio (HR) 1.34, (95% confidence interval) (95% CI) (1.20-1.50), p < 0.001] and HF hospitalisation-free survival [HR 1.09, 95% CI (1.02-1.17), p = 0.015]. CCI at month 6 was independently associated with HF hospitalisation-free survival [HR 1.24, 95% CI (1.11-1.38), p < 0.001]. Treatment intensification was independently associated with survival [HR 1.75, 95% CI (1.19-1.38), p = 0.004] and HF hospitalisation-free survival [HR 1.69, 95% CI (1.22-2.35), p = 0.002]. Patients undergoing treatment intensification resulting in decongestion had better outcome than patients with persistent (worsening) congestion despite LD dose up-titration (p < 0.001).

CONCLUSION

Intensification of pharmacological decongestion but not the actual LD dose was related to poor outcome in chronic HF. If treatment intensification translated into clinical decongestion, outcome was better than in case of persistent or worsening congestion.

Usefulness of acetazolamide in the management of diuretic resistance

Worsening symptoms and fluid overload are the hallmarks of heart failure (HF) decompensation, and fluid removal is central to improvement. Despite high-dose loop diuretics, patients with decompensated HF may develop suboptimal diuresis/diuretic resistance. Sequential nephron blockade with a combination of loop and thiazide/thiazide-like diuretics may be insufficient, resulting in poor outcomes. We present a case wherein urine output improved significantly with acetazolamide. Although the diuretic capacity of acetazolamide is weak on its own, it might be efficient in aiding the efficacy of loop diuretics. We discuss the pathophysiological basis and evidence behind its potential role in diuretic resistance. Drawing from current understanding, we propose a stepwise approach to diuresis in such patients.

Pathophysiology of Diuretic Resistance and Its Implications for the Management of Chronic Heart Failure

Diuretic resistance implies a failure to increase fluid and sodium (Na+) output sufficiently to relieve volume overload, edema, or congestion, despite escalating doses of a loop diuretic to a ceiling level (80 mg of furosemide once or twice daily or greater in those with reduced glomerular filtration rate or heart failure). It is a major cause of recurrent hospitalizations in patients with chronic heart failure and predicts death but is difficult to diagnose unequivocally. Pharmacokinetic mechanisms include the low and variable bioavailability of furosemide and the short duration of all loop diuretics that provides time for the kidneys to restore diuretic-induced Na+ losses between doses. Pathophysiological mechanisms of diuretic resistance include an inappropriately high daily salt intake that exceeds the acute diuretic-induced salt loss, hyponatremia or hypokalemic, hypochloremic metabolic alkalosis, and reflex activation of the renal nerves. Nephron mechanisms include tubular tolerance that can develop even during the time that the renal tubules are exposed to a single dose of diuretic, or enhanced reabsorption in the proximal tubule that limits delivery to the loop, or an adaptive increase in reabsorption in the downstream distal tubule and collecting ducts that offsets ongoing blockade of Na+ reabsorption in the loop of Henle. These provide rationales for novel strategies including the concurrent use of diuretics that block these nephron segments and even sequential nephron blockade with multiple diuretics and aquaretics combined in severely diuretic-resistant patients with heart failure.

Altered Hemodynamics and End-Organ Damage in Heart Failure: Impact on the Lung and Kidney

Heart failure is characterized by pathologic hemodynamic derangements, including elevated cardiac filling pressures ("backward" failure), which may or may not coexist with reduced cardiac output ("forward" failure). Even when normal during unstressed conditions such as rest, hemodynamics classically become abnormal during stressors such as exercise in patients with heart failure. This has important upstream and downstream effects on multiple organ systems, particularly with respect to the lungs and kidneys. Hemodynamic abnormalities in heart failure are affected by processes that extend well beyond the cardiac myocyte, including important roles for pericardial constraint, ventricular interaction, and altered venous capacity. Hemodynamic perturbations have widespread effects across multiple heart failure phenotypes, ranging from reduced to preserved ejection fraction, acute to chronic disease, and cardiogenic shock to preserved perfusion states. In the lung, hemodynamic derangements lead to the development of abnormalities in ventilatory control and efficiency, pulmonary congestion, capillary stress failure, and eventually pulmonary vascular disease. In the kidney, hemodynamic perturbations lead to sodium and water retention and worsening renal function. Improved understanding of the mechanisms by which altered hemodynamics in heart failure affect the lungs and kidneys is needed in order to design novel strategies to improve clinical outcomes.

Mechanisms of Diuretic Resistance Study: design and rationale

INTRODUCTION

Diuretic resistance is a common complication impairing decongestion during hospitalization for acute decompensated heart failure (ADHF). The current understanding of diuretic resistance mechanisms in ADHF is based upon extrapolations from other disease states and healthy volunteers. However, accumulating evidence suggests that the dominant mechanisms in other populations have limited influence on diuretic response in ADHF. Additionally, the ability to rapidly and reliably diagnose diuretic resistance is inadequate using currently available tools.

AIMS

The Mechanisms of Diuretic Resistance (MDR) Study is designed to rigorously investigate the mechanisms of diuretic resistance and develop tools to rapidly predict diuretic response in a prospective cohort hospitalized with ADHF.

METHODS

Study assessments occur serially during the ADHF hospitalization and after discharge. Each assessment includes a supervised 6-hour urine collection with baseline blood and timed spot urine collections following loop diuretic administration. Patient characteristics, medications, physical exam findings, and both in-hospital and post-discharge HF outcomes are collected. Patients with diuretic resistance are eligible for a randomized sub-study comparing an increased loop diuretic dose with combination diuretic therapy of loop diuretic plus chlorothiazide.

CONCLUSIONS

The Mechanisms of Diuretic Resistance Study will establish a prospective patient cohort and biorepository to investigate the mechanisms of diuretic resistance and urine biomarkers to rapidly predict loop diuretic resistance.

Management of the Patient with Heart Failure and an Implantable Pulmonary Artery Hemodynamic Sensor

Purpose of Review

Heart failure (HF) management guided by hemodynamics obtained from an implantable pulmonary artery pressure (PAP) sensor (CardioMEMS) improves symptoms and reduces HF hospitalizations (HFH). This paper reviews the theoretical basis of pulmonary vascular physiology, summarizes recently published data about CardioMEMS, and provides practical guidelines for patient selection and management.

Recent Findings

Compared to patients managed by standard care, HF patients randomized to PAP-guided treatment have a higher frequency of medication adjustments, resulting in lower PAP and fewer HFH. Real-world analyses further support associations between implant of the CardioMEMS sensor with reductions in PAP, hospitalizations, and mortality.

Summary

Implantable, wireless hemodynamic sensor technology is a promising remote monitoring platform for chronic HF. A phased approach using a treatment algorithm may improve the efficiency and effectiveness of pressure-guided therapy.

Diuretic Resistance in Heart Failure

Purpose of review:

Diuretic resistance (DR) occurs along a spectrum of relative severity and contributes to worsening of acute heart failure (AHF) during an inpatient stay. This review gives an overview of mechanisms of DR with a focus on loop diuretics and summarizes the current literature regarding the prognostic value of diuretic efficiency and predictors of natriuretic response in AHF.

Recent findings:

The pharmacokinetics of diuretics are impaired in chronic heart failure, but little is known about mechanisms of DR in AHF. Almost all diuresis after administration of a loop diuretic dose occurs in the first few hours after administration and within-dose DR can develop. Recent studies suggest that DR at the level of the nephron may be more important than defects in diuretic delivery to the tubule. Because loop diuretics induce natriuresis, urine sodium (UNa) concentration may serve as a functional, physiologic and direct measure for diuretic responsiveness to a given loop diuretic dose.

Summary:

Identifying and targeting individuals with DR for more aggressive, tailored therapy represents an important opportunity to improve outcomes. A better understanding of the mechanistic underpinnings of DR in AHF is needed to identify additional biomarkers and guide future trials and therapies.

Right Heart Failure and Cardiorenal Syndrome

Cardiorenal syndrome is a complex interplay of dysregulated heart and kidney interaction that leads to multiorgan system dysfunction, which is not an uncommon occurrence in the setting of right heart failure. The traditional concept of impaired perfusion and forward flow recently has been modified to include the recognition of systemic venous congestion as a contributor, with direct and indirect mechanisms, including elevated renal venous pressure, reduced renal perfusion pressure, increased renal interstitial pressure, tubular dysfunction, splanchnic congestion, and neurohormonal and inflammatory activation. Treatment options beyond diuretics and vasoactive drugs remain limited and lack supportive evidence.

The use of peritoneal dialysis in heart failure: A systematic review

Heart failure (HF) is a major cause of morbidity and mortality. Extracorporeal (EC) therapy, including ultrafiltration (UF) and haemodialysis (HD), peritoneal dialysis (PD) and peritoneal ultrafiltration (PUF) are potential therapeutic options in diuretic-resistant states. This systematic review assessed outcomes of PD and compared the effects of PD to EC. A comprehensive search of major databases from 1966 to 2017 for studies utilising PD (or PUF) in diuretic-resistant HF was conducted, excluding studies involving patients with end-stage kidney disease. Data were extracted and combined using a random-effects model, expressed as odds ratio (OR). Thirty-one studies (n = 902) were identified from 3195 citations. None were randomised trials. Survival was variable (0-100%) with a wide follow-up duration (36 h-10 years). With follow-up > 1 year, the overall mortality was 48.3%. Only four studies compared PD with EC. Survival was 42.1% with PD and 45.0% with EC; the pooled effect did not favour either (OR 0.80; 95% confidence interval (CI): 0.24-2.69; p = 0.710). Studies on PD in patients with HF reported several benefits. Left ventricular ejection fraction (LVEF) improved after PD (OR 3.76, 95%CI: 2.24-5.27; p < 0.001). Seven of nine studies saw LVEF increase by > 10%. Twenty-one studies reported the New York Heart Association status and 40-100% of the patients improved by ≥ 1 grade. Nine of 10 studies reported reductions in hospitalisation frequency and/or duration. When treated with PD, HF patients had fewer symptoms, lower hospital admissions and duration compared to diuretic therapy. However, there is inadequate evidence comparing PD versus UF or HD. Further studies comparing these modalities in diuretic-resistant HF should be conducted.