Proposal for New Classification and Practical Use of Diuretics According to Their Effects on the Serum Chloride Concentration: Rationale Based on the "Chloride Theory"

Exploring Neurohormonal Modulation by Acetazolamide in Heart Failure

Background Heart failure (HF) is commonly managed by addressing water and sodium (Na) balance, with arterial circulation playing a major role in influencing renal Na and water excretion. Recently, chloride (Cl) has been recognized as an important factor in HF, associated with volume regulation and its modulation of renin-angiotensin-aldosterone system (RAAS) activity through macula densa signaling, which impacts Na retention and neurohormonal activation. Acetazolamide, a carbonic anhydrase inhibitor, can enhance decongestion in HF by increasing urinary Na and Cl excretion when added to loop diuretics, a mechanism supported by prior studies demonstrating improved urine output and decongestion. Objective This study investigates the neurohormonal effects of acetazolamide in acute HF, focusing on its ability to enhance decongestion, reduce neurohormonal activation (e.g., renin and aldosterone), and modulate RAAS markers. Methods In this prospective, single-center observational study, 80 patients with acute HF were enrolled and divided into two groups: a case group (n=40) receiving acetazolamide with standard therapy and a control group (n=40) on standard therapy alone. Patients were matched based on clinical characteristics to reduce selection bias. Baseline characteristics, neurohormonal profiles, including plasma renin activity (PRA) and aldosterone, electrolyte levels, and clinical outcomes were compared. Results The acetazolamide group exhibited higher urinary Cl excretion (108.9±25.3 mEq/L vs. 79.2±22.7 mEq/L; p<0.001) and reduced PRA and aldosterone levels (1.3±0.4 ng/mL/h and 88±21 pg/mL) compared to controls (1.7±0.6 ng/mL/h and 128±29 pg/mL; p=0.002 and p=0.006, respectively). These reductions in PRA and aldosterone are significant as they correlate with improved volume status and reduced neurohormonal stress, which are critical components in HF management. Improved clinical outcomes included a greater percentage of patients becoming symptom-free within 72 hours (77.5% vs. 52.5%; p=0.018) and shorter hospitalization (5.6±1.4 days vs. 7.1±1.7 days; p=0.028). Conclusion Acetazolamide in addition to standard therapy enhances decongestion and reduces neurohormonal activation in acute HF, suggesting its dual benefit in fluid management and neurohormonal modulation. Further research is needed to confirm these benefits, assess long-term effects, and overcome limitations, including the study's single-center observational design.

Serum Chloride and the Response to Acetazolamide in Patients With Acute Heart Failure and Volume Overload: A Post Hoc Analysis From the ADVOR Trial

BACKGROUND

Chloride plays a crucial role in renal salt sensing. This study investigates whether serum chloride is associated with clinical outcomes and decongestive response to acetazolamide in patients with acute decompensated heart failure.

METHODS

This post hoc analysis includes all 519 patients from the ADVOR trial (Acetazolamide in Decompensated Heart Failure With Volume Overload), randomized to intravenous acetazolamide or matching placebo on top of intravenous loop diuretics. The impact of baseline serum chloride on the main trial end points and the treatment effect of acetazolamide was assessed, as was the evolution of serum chloride under decongestive treatment.

RESULTS

Hypochloremia (<96 mmol/L) and hyperchloremia (>106 mmol/L) were present in 80 (15%) and 53 (10%), respectively, at baseline. Hypochloremia was associated with significantly slower decongestion, a longer length of hospital stay, and increased risk of all-cause mortality and heart failure readmissions. Acetazolamide increased the odds of successful decongestion and reduced length of stay irrespectively of baseline serum chloride levels. No statistically significant interaction between serum chloride levels and the effect of acetazolamide on death or heart failure readmissions was observed. The placebo group exhibited a progressive decline in serum chloride, which was effectively prevented by acetazolamide (P<0.001).

CONCLUSIONS

Hypochloremia is associated with diuretic resistance and worse clinical outcomes. Add-on acetazolamide therapy improves decongestion across the entire range of serum chloride and prevents the drop in chloride levels caused by loop diuretic monotherapy.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03505788.

Unlocking the Potential of Acetazolamide: A Literature Review of an Adjunctive Approach in Heart Failure Management

Background: Heart failure (HF) patients often experience persistent fluid overload despite standard diuretic therapy. The adjunctive use of acetazolamide, a carbonic anhydrase inhibitor, in combination with loop diuretics has shown promise in improving decongestion and diuretic efficacy. This literature review aims to analyze six studies evaluating the effectiveness of acetazolamide as an additive treatment for acute decompensated heart failure (ADHF) and its impact on various outcomes. Methods: We searched the PubMed database using the terms "acetazolamide heart failure". We refined our search with specific filters (as shown our PRISMA flow diagram) and exclusion criteria, narrowing down our results to five studies. We included an extra study via expert recommendation, ultimately including six studies for comprehensive analysis. Results: The review highlights the positive effects of acetazolamide on decongestion, natriuresis, and diuresis in HF patients. However, it also showcases the limitations of these trials. Discussion: While the reviewed studies demonstrate the potential benefits of acetazolamide in enhancing decongestion and diuretic efficiency, there are limitations to consider, including small sample sizes, lack of blinding, and limited external validity. Further research is needed to confirm these findings, compare acetazolamide with other diuretic combinations, and explore its effects in a broader population of heart failure patients, including those in the United States. The use of acetazolamide in HF management warrants continued investigation to optimize its role in improving decongestion and patient outcomes.

Mechanistic insights into chloride-related heart failure progression according to the plasma volume status

Aims

Two types of heart failure (HF) progression were recently proposed on the basis of an increased vs. non‐increased serum chloride concentration. The applicability of this concept to real‐world HF pathophysiology requires further investigation. The present study evaluated the mechanisms of HF progression to a different type according to changes in the estimated plasma volume status (ePVS).

Methods and results

Data from 47 patients (32% men; 78.2 ± 9.7 years of age) with stable to worsening HF (37.5 ± 16 days) were analysed. Physical examination, standard blood tests, and b‐type natriuretic peptide (BNP) measurements were conducted. The ePVS was calculated as follows: ePVS (dL/g) = [100 − haematocrit (%)]/[haemoglobin (g/dL)]. For the study subjects as a whole (n = 47), changes in the ePVS correlated positively with changes in the serum chloride concentration from stable to worsening HF (r = 0.398, P = 0.0056). When divided into two groups of worsening HF with an increased (n = 31) vs. non‐increased serum chloride concentration (n = 16), no significant baseline differences in body weight, serum logBNP, or ePVS were detected between groups. Under worsening HF, the increase in body weight (2.34 ± 1.12 vs. 2.59 ± 1.56 kg, P = 0.57) and logBNP (0.39 ± 0.30 vs. 0.54 ± 0.31 pg/mL, P = 0.13) did not differ between groups, but the increase in the ePVS was smaller in the group with a non‐increased serum chloride concentration compared with that with an increased serum chloride concentration (0.292 ± 0.49 vs. 0.653 ± 0.60 dL/g, P = 0.044). An increase in the %change in ePVS ≥ 10% was less common in patients with a non‐increased chloride concentration (37% vs. 71%, P = 0.03). Patients with a non‐increased serum chloride concentration had more HF signs (3.31 ± 0.79 vs. 2.65 ± 0.71, P = 0.005) and a higher incidence of pulmonary rales (63% vs. 16%, P = 0.0024) than those with an increased serum chloride concentration.

Conclusions

According to the changes in the ePVS, HF progression may result from a difference between two HF types (i.e. increased vs. non‐increased serum chloride concentration) in the cardiac reserve in response to a given cardiac burden by modulating plasma volume status via the possible tonicity potential of chloride.

Chloride in Heart Failure Syndrome: Its Pathophysiologic Role and Therapeutic Implication

Until recently, most studies of heart failure (HF) focused on body fluid dynamics through control of the sodium and water balance in the body. Chloride has remained largely ignored in the medical literature, and in clinical practice, chloride is generally considered as an afterthought to the better-known electrolytes of sodium and potassium. In recent years, however, the important role of chloride in the distribution of body fluid has emerged in the field of HF pathophysiology. Investigation of HF pathophysiology according to the dynamics of serum chloride is rational considering that chloride is an established key electrolyte for tubulo-glomerular feedback in the kidney and a possible regulatory electrolyte for body fluid distribution. The present review provides a historical overview of HF pathophysiology, followed by descriptions of the recent attention to the electrolyte chloride in the cardiovascular field, the known role of chloride in the human body, and recent new findings regarding the role of chloride leading to the proposed ‘chloride theory’ hypothesis in HF pathophysiology. Next, vascular and organ congestion in HF is discussed, and finally, a new classification and potential therapeutic strategy are proposed according to the ‘chloride theory’.