Sodium restriction has long been the cornerstone of self-care for patients with heart failure (HF), given the relevance of fluid balance in HF and the potential contribution of dietary sodium to fluid overload. This recommendation persists even though the effects of sodium restriction on quality of life and prognosis of patients with HF have been consistently questioned over the past decade, owing to the lack of quality evidence to support this practice.
Does sodium restriction alter clinical outcomes of patients with HF over the long term? Here's an overview of what we know and what we still need to learn.
Why Sodium Restriction?
Heart failure, particularly HF with reduced ejection fraction, is characterized by an activation of the sympathetic nervous system (SNS) and the renin-angiotensin-aldosterone system (RAAS) as a compensatory response to maintain cardiac output through increased sodium and water retention. However, the long-term effects of this neurohormonal activation contribute to the progression of HF. In addition, systems that normally counteract SNS and RAAS activation are also altered in the setting of HF, contributing to further vasoconstriction and volume overload.
What Do the HF Guidelines Recommend?
Although guidelines from major organizations, including the American College of Cardiology Foundation/American Heart Association Foundation (ACCF/AHA), Canadian Cardiovascular Society (CCS), and European Society of Cardiology (ESC), endorse a sodium-restricted diet, owing to limited high-quality evidence, there is no consensus on the recommended daily intake (Table).
The ACCF/AHA guidelines recommend moderate sodium restriction in patients with symptomatic HF (class IIa, level C). In accordance with the 2012 AHA recommendations, ACCF/AHA guidelines advise limiting dietary sodium intake to < 1500 mg/d for the general population; the guidelines also consider this level appropriate for patients with stages A and B HF. Although no precise recommendation is given for patients with stage C or D HF, ACCF/AHA suggest these patients limit their sodium intake to < 3000 mg/d for symptom improvement.
In contrast to ACCF/AHA guidelines, ESC guidelines do not provide a specific maximum daily intake of sodium for patients with HF, but advise against excessive intake (defined as > 6000 mg/d of salt, equivalent to 2400 mg/d of sodium). The 2017 CCS guidelines suggest restricting dietary sodium intake to between 2000 mg/d and 3000 mg/d (weak recommendation; low-quality evidence).
Table. Daily Sodium Intake Recommendations for Patients With Heart Failure
| Organization |
Symptomatic Heart Failure |
Stage A and B Heart Failure |
Stage C and D Heart Failure |
|---|---|---|---|
| American College of Cardiology Foundation/American Heart Association |
Restrict sodium intake to < 1500 mg/d |
1500 mg/d |
Consider some degree of sodium restriction (eg, < 3000 mg/d) for symptom improvement |
| Restrict sodium intake to 2000-3000 mg/d |
Restrict sodium intake to 2000-3000 mg/d |
Restrict sodium intake to 2000-3000 mg/d |
|
| No specific maximum daily intake; advise restricting sodium intake to < 6000 mg/d of salt; (2400 mg/d of sodium) |
No specific maximum daily intake; advise restricting sodium intake to < 6000 mg/d of salt; (2400 mg/d of sodium) |
No specific maximum daily intake; advise restricting sodium intake to < 6000 mg/d of salt; (2400 mg/d of sodium) |
Conflicting Evidence
Epidemiologic evidence on the effects of sodium restriction on clinical outcomes in patients with HF has shown mixed results. An observational study that assessed sodium intake of ambulatory patients with HF over a mean period of 3 years suggests that patients with a sodium intake > 2800 mg/d are at greater risk for an acute HF event (hazard ratio [HR], 2.55; 95% CI, 1.61-4.04; P = .001) compared with patients with lower sodium intakes (< 2800 mg/d). These findings remained consistent, even after adjustments were made with respect to age, sex, caloric intake, left ventricular ejection fraction, body mass index, beta-blocker use, and furosemide use.
Other longitudinal studies, such as an observational study measuring 24-hour urinary sodium excretion in 302 outpatients with HF and a prospective study reviewing food diaries of 244 patients with HF, suggest shorter event-free survival in patients with mild HF (New York Heart Association [NYHA] class I/II) who follow a low-sodium diet (< 2000 mg/d), and potential for harm in patients with moderate to severe HF (NYHA class III/IV) whose sodium intake is > 3000 mg/d. A more recent longitudinal study analyzing data of patients with HF (NYHA class II/III) enrolled in the Heart Failure Adherence and Retention Trial demonstrate an increased risk for a composite outcome of death or hospitalization owing to HF (adjusted HR, 1.72; 95% CI, 1.12-2.65; P = .014) and hospitalization owing to HF (adjusted HR, 1.68; 95% CI, 1.02-2.75; P = .04) in patients whose sodium intake is < 2500 mg/d.
Evidence from several randomized controlled trials (RCTs) have shown mixed results as well. For example, our trial of 203 patients at a heart failure clinic in Mexico showed a trend toward fewer readmissions (11.1% vs 15.7%; P = .3) and higher 12-month survival (93.7% vs 88.1%; P = .2) in the group receiving dietary intervention with a targeted sodium intake < 2400 mg/d compared with the group receiving usual dietary recommendations for sodium restriction. In addition, our pilot study following 38 patients with HF suggested an improvement in quality of life (Kansas City Cardiomyopathy Questionnaire scores) and B-type natriuretic peptide levels in patients who achieved a sodium intake ≤ 1500 mg/d at 6 months; however, clinical outcomes were not assessed in these patients.
Conversely, a study by Parrinello and colleagues and two studies by Paterna and colleagues suggest a detrimental effect on clinical events of a low-sodium (1800 mg/d) vs a moderate-sodium diet (2800 mg/d) in combination with high-dose diuretics and strict fluid restriction. The inconsistencies in the evidence from these RCTs might be due, at least in part, to features of the study design (eg, they were underpowered, and co-interventions were inconsistent with clinical guidelines).
A recent systematic review of nine studies and 479 unique participants found limited evidence of clinical improvement in outpatients with HF who followed a reduced-sodium diet, and the findings were inconclusive for inpatients with HF. None of the studies included in the review provided sufficient data on clinical outcomes, such as cardiovascular-associated or all-cause mortality, cardiovascular-associated events, hospitalization, or length of hospital stay.
Following this, the PROHIBIT pilot study randomly assigned 27 patients with HF to receive daily meals containing 1500 mg or 3000 mg of sodium. After a 12-week follow-up, quality of life improved among patients in the 1500-mg arm but remained unchanged in patients in the 3000-mg arm. N-terminal pro-B–type natriuretic peptide levels were not affected in either group.
What We Need to Learn
Clearly, more research needs to be done in an effort to answer important questions about the role of sodium restriction in HF, such as:
Does sodium restriction have a greater or lesser effect on patients with chronic vs acute HF?
What is the real culprit affecting outcomes in HF—dietary sodium, fluid intake, or the broader diet composition?
If sodium restriction reduces adverse clinical outcomes in patients with HF, is it effective in reducing these outcomes for all types of HF, or only certain HF phenotypes or scenarios?
Meanwhile, on the basis of the available evidence, relevance of fluid balance in HF, and potential contribution of dietary sodium consumption to fluid overload, we consider it reasonable to moderately restrict the sodium intake of patients with HF (particularly those who are symptomatic), to between 2000 mg/d and 3000 mg/d. One ongoing trial, SODIUM-HF, is assessing the efficacy of a low-sodium diet (< 1500 mg/d) on clinical outcomes compared with usual care in patients with HF. Results of this pragmatic trial will provide additional information on the effects of significantly restricting sodium intake and will help guide future recommendations.
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Cite this: Sodium Restriction in Heart Failure: What We Do and Don't Know - Medscape - Aug 06, 2020.
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