OBJECTIVE: Early evaluation of the natriuretic response is recommended to guide diuretic therapy in acute decompensated heart failure (ADHF). However, its implementation in daily practice is hampered by implementation barriers and increased time constraints. The Readily Available Urinary Sodium Analysis in Patients with Acute Decompensated Heart Failure (EASY-HF) study assessed the feasibility, efficacy and safety of a nurse-led urinary sodium-based diuretic titration protocol with the use of a point-of-care urinary sodium sensor.
RESULTS: The EASY-HF study was a single-centre, randomized, open-label study comparing diuretic management at the treating physician\'s discretion as standard of care (SOC) with a nurse-led natriuresis-guided protocol in patients with ADHF. The LAQUAtwin Sodium Meter (HORIBA) was used as point-of-care sensor to measure urine sodium concentration. The primary endpoint was natriuresis after 48 h. Secondary endpoints included safety profile and user-friendliness of both the protocol and the point-of-care sensor. Sixty patients were randomized towards SOC (n = 30) versus protocolized care (n = 30). The mean age was 80 ± 8 years, 25% were women and median N-terminal pro-B-type natriuretic peptide was 4667 (2667-7709) ng/L. Natriuresis after 48 h was significantly higher in the protocolized versus SOC group (820 ± 279 vs. 657 ± 273 mmol; p = 0.027). Pre-defined safety endpoints were similar among both groups. The sensor-based protocol was evaluated as easy to use by the nursing staff, and preferred over urinary collections.
CONCLUSIONS: A nurse-led diuretic titration protocol via a point-of-care urinary sodium sensor was feasible, safe and resulted in an increased natriuresis in ADHF compared to SOC.

Diuresis to achieve decongestion is a central aim of therapy in patients hospitalized for acute decompensated heart failure (ADHF). While multiple approaches have been tried to achieve adequate decongestion rapidly while minimizing adverse effects, no single diuretic strategy has shown superiority, and there is a paucity of data and guidelines to utilize in making these decisions. Observational cohort studies have shown associations between urine sodium excretion and outcomes after hospitalization for ADHF. Urine chemistries (urine sodium ± urine creatinine) may guide diuretic titration during ADHF, and multiple randomized clinical trials have been designed to compare a strategy of urine chemistry-guided diuresis to usual care. This review will summarize current literature for diuretic monitoring and titration strategies, outline evidence gaps, and describe the recently completed and ongoing clinical trials to address these gaps in patients with ADHF with a particular focus on the utility of urine sodium-guided strategies.

OBJECTIVE: Worsening renal function (WRF) is a frequent complication in acute heart failure (AHF) with a controversial prognostic value. We aimed to study the usefulness of natriuresis to evaluate WRF.
METHODS: We conducted an observational, prospective, multicenter study of patients with AHF who underwent a furosemide stress test. The patients were classified according to whether WRF was present or absent and according to the median natriuretic response. The main endpoint was the combination of mortality, rehospitalization due to HF, and heart transplant at 6 months of follow-up.
RESULTS: One hundred and fifty-six patients were enrolled, and WRF occurred in 60 (38.5%). The patients were divided into 4 groups: a) 47 (30.1%) no WRF/low UNa (UNa ≤ 109 mEq/L); b) 49 (31.4%) no WRF/high UNa (UNa > 109 mEq/L); c) 31 (19.9%) WRF/low UNa and d) 29 (18.6%) WRF/high UNa. The parameters of the WRF/low UNa group showed higher clinical severity and worse diuretic and decongestive response. The development of WRF was associated with a higher risk of the combined event (HR, 1.88; 95%CI, 1.01-3.50; P = .046). When stratified by natriuretic response, WRF was associated with an increased risk of adverse events in patients with low natriuresis (HR, 2.28; 95%CI, 1.15-4.53; P = .019), but not in those with high natriuresis (HR, 1.18; 95%CI, 0.26-5.29; P = .826).
CONCLUSIONS: Natriuresis could be a useful biomarker for interpreting and prognosticating WRF in AHF. WRF is associated with a higher risk of adverse events only in the context of low natriuresis.

Inhibitors of the Na+-coupled glucose transporter SGLT2 (SGLT2i) primarily shift the reabsorption of large amounts of glucose from the kidney\'s early proximal tubule to downstream tubular segments expressing SGLT1, and the non-reabsorbed glucose is spilled into the urine together with some osmotic diuresis. How can this protect the kidneys and heart from failing as observed in individuals with and without type 2 diabetes? Mediation analyses identified clinical phenotypes of SGLT2i associated with improved kidney and heart outcome, including a reduction of plasma volume or increase in hematocrit, and lowering of serum urate levels and albuminuria. This review outlines how primary effects of SGLT2i on the early proximal tubule can explain these phenotypes. The physiology of tubule-glomerular communication provides the basis for acute lowering of GFR and glomerular capillary pressure, which contributes to lowering of albuminuria but also to long term preservation of GFR, at least in part by reducing kidney cortex oxygen demand. Functional co-regulation of SGLT2 with other sodium and metabolite transporters in the early proximal tubule explains why SGLT2i initially excrete more sodium than expected and are uricosuric, thereby reducing plasma volume and serum urate. Inhibition of SGLT2 reduces early proximal tubule gluco-toxicity and by shifting transport downstream may simulate \"systemic hypoxia\", and the resulting increase in erythropoiesis, together with the osmotic diuresis, enhances hematocrit and improves blood oxygen delivery. Cardio-renal protection by SGLT2i is also provided by a fasting-like and insulin-sparing metabolic phenotype and, potentially, by off-target effects on the heart and microbiotic formation of uremic toxins.

Sodium-glucose transporter-2 (SGLT-2) inhibitors have emerged as novel oral glucose-lowering agents for type 2 diabetes. SGLT-2 inhibitors improve glycemic control by blocking sodium-glucose cotransport in the renal proximal tubules, thereby promoting glycosuria. In this review, it is discussed mechanistically how SGLT-2 inhibitors might be particularly relevant to use in patients with or at high risk for heart failure. On a daily base, SGLT-2 inhibitors block ~330-495 mEq sodium reabsorbed in the proximal tubules, although substantial amounts can be reabsorbed more distally in the nephron. Increased sodium offering to the distal nephron is sensed at the macula densa and may attenuate neurohumoral activation, thereby improving salt sensitivity, augmenting diuretic efficacy of loop and thiazide diuretics, and potentiating the native natriuretic peptide system. Whether the favorable profile offered by SGLT-2 inhibitors is renoprotective and whether SGLT-2 inhibition can relieve and/or prevent congestion beyond traditional diuretic drugs warrants further investigation.

Acute heart failure (AHF) often leads to unfavorable outcomes due to fluid overload. While diuretics are the cornerstone treatment, acetazolamide may enhance diuretic efficiency by reducing sodium reabsorption. We performed a systematic review and meta-analysis on the effects of acetazolamide as an add-on therapy in patients with AHF compared to diuretic therapy. PubMed, Embase, and Cochrane databases were searched for randomized controlled trials (RCT). A random-effects model was employed to compute mean differences and risk ratios. Statistical analysis was performed using R software. The GRADE approach was used to rate the certainty of the evidence. We included 4 RCTs with 634 patients aged 68 to 81 years. Over a mean follow-up of 3 days to 34 months, acetazolamide significantly increased diuresis (MD 899.2 mL; 95% CI 249.5 to 1549; p < 0.01) and natriuresis (MD 72.44 mmol/L; 95% CI 39.4 to 105.4; p < 0.01) after 48 h of its administration. No association was found between acetazolamide use and WRF (RR 2.4; 95% CI 0.4 to 14.2; p = 0.3) or all-cause mortality (RR 1.2; 95% CI 0.8 to 1.9; p = 0.3). Clinical decongestion was significantly higher in the intervention group (RR 1.35; 95% CI 1.09 to 1.68; p = 0.01). Acetazolamide is an effective add-on therapy in patients with AHF, increasing diuresis, natriuresis, and clinical decongestion, but it was not associated with differences in mortality.

The central role of natriuretic peptides (NPs) in the complex cardio-renal integrated physiology and organ failure has been revealed over the last four decades. Atrial natriuretic peptide (ANP), the oldest representative of the NPs family, is produced through conversion of proANP to the mature peptide by corin, a trans-membrane protease localized to the cardiac myocyte membrane. Similarly, brain natriuretic peptide (BNP) is generated by furin, which cleaves proBNP to BNP in myocytes. Though the components of NPs system, their synthesis and target organs are well established, understanding their role in the interplay between the heart and the kidney is steadily evolving. In this context, Feldman et al. (New England Journal of Medicine, 389, 1685) recently described patients with hypertension, cardiomyopathy, atrial arrhythmia and left atrial fibrosis, associated with a homozygous loss-of-function variant of the gene encoding corin (Cor-/-). Notably, reduced baseline urinary electrolyte and creatinine excretion have been observed in one of the studied patients. This renal excretory functional impairment could be attributed to the lack of cardiac-derived ANP in these patients, as implied by Feldman et al. Yet, in this mini-review we suggest that this aberrant renal manifestation may principally stem from lack of local ANP production at renal tissue, as corin is normally expressed in proximal tubules, Henle\'s loop and collecting ducts, with locally produced ANP provoking Na+ and water exertion. Collectively, it seems that beside the classic well-established cardio-renal axis, the renal NPs system functions as local endocrine machinery in the regulation of sodium excretion.

The Pragmatic Urinary Sodium-based algoritHm in Acute Heart Failure (PUSH-AHF) study, published in August of 2023, was the first randomized clinical trial to compare natriuresis-guided decongestion (based on spot urinary sodium measurement) to standard of care in patients with acute heart failure with congestion receiving loop diuretic therapy. Based on results from their trial, the authors concluded that natriuresis-guided loop diuretic treatment was safe and improved natriuresis and diuresis without impacting long-term clinical outcomes. The original PUSH-AHF trial included limited information about renal outcomes and left clinicians with important questions about how natriuresis-guided decongestion might affect their patients\' renal function. On May 12, 2024, however, at the 2024 Annual Congress of the HFA-ESC, Dr. Kevin Damman provided an in-depth exploration of renal outcomes from the trial when he presented a pre-specified, secondary analysis, renal function in the PUSH-AHF trial. This review puts the sub-study findings into context by considering the history of the original trial from which they came from and explaining the need for a close study of its renal outcomes particularly. It highlights the potential impact of renal function in PUSH-AHF on clinical practice and future directions that should be considered by the cardiology research community.

Osteocrin (OSTN) is an endogenous protein sharing structural similarities with the natriuretic peptides [NPs; atrial (ANP), B-type (BNP) and C-type (CNP) NP], which are hormones known for their crucial role in maintaining pressure/volume homeostasis. Osteocrin competes with the NPs for binding to the receptor involved in their clearance (NPR-C). In the present study, having identified, for the first time, the major circulating form of OSTN in human and ovine plasma, we examined the integrated haemodynamic, endocrine and renal effects of vehicle-controlled incremental infusions of ovine proOSTN (83-133) and its metabolism in eight conscious normal sheep. Incremental i.v. doses of OSTN produced stepwise increases in circulating concentrations of the peptide, and its metabolic clearance rate was inversely proportional to the dose. Osteocrin increased plasma levels of ANP, BNP and CNP in a dose-dependent manner, together with concentrations of their intracellular second messenger, cGMP. Increases in plasma cGMP were associated with progressive reductions in arterial pressure and central venous pressure. Plasma cAMP, renin and aldosterone were unchanged. Despite significant increases in urinary cGMP levels, OSTN administration was not associated with natriuresis or diuresis in normal sheep. These results support OSTN as an endogenous ligand for NPR-C in regulating plasma concentrations of NPs and associated cGMP-mediated bioactivity. Collectively, our findings support a role for OSTN in maintaining cardiovascular homeostasis.

Acute heart failure (AHF) is characterized by the emergence or intensification of symptoms and signs indicative of congestion or systemic hypoperfusion, stemming from an underlying structural or functional cardiac disorder. Intravenous loop diuretics play a pivotal role in achieving effective decongestion and ensuring clinical stability; the efficacy of these medications is crucial for determining the patient\'s hospital course and early outpatient progression. Individuals who exhibit a suboptimal response to diuretics or develop diuretic resistance (DR) are at an elevated risk for cardiovascular mortality and readmission due to AHF. However, there is a lack of standardized definition and diagnostic criteria for DR. Early identification of patients with DR is critical, as they may benefit from more aggressive decongestion strategies to mitigate this resistance. Natriuresis, the excretion of sodium in urine, serves as a direct measure of a diuretic\'s effectiveness. Low levels of natriuresis have been linked to poorer outcomes. Several studies have underscored the prognostic significance of natriuresis across various heart failure scenarios. However, the relationship between natriuresis and in-hospital DR has not been extensively studied. Observational research has indicated that inadequate natriuresis following the administration of loop diuretics correlates with a diminished diuretic response and an increased likelihood of mortality and heart failure rehospitalization. Further investigation is warranted to assess the predictive value of basal natriuresis concerning DR, in-hospital outcomes, and early outpatient cardiovascular events. This would help in identifying patients who are likely to respond poorly to diuretic therapy and may require alternative or more intensive treatment approaches.