Effect of fluid and dietary sodium restriction in the management of patients with heart failure and preserved ejection fraction: study protocol for a randomized controlled trial

Heart failure (HF) with preserved ejection fraction (HF-PEF), historically known as diastolic HF, is the clinical syndrome characterized by HF with normal or near-normal systolic function [1]. More recent epidemiological studies and registries have suggested that HF with reduced ejection fraction and HF-PEF are equally prevalent, with the latter accounting for 40 to 71% (mean approximately 50%) of cases [2, 3].

The etiology and epidemiology of HF-PEF appear to be distinct from those of HF with reduced ejection fraction. Women and older adults with comorbidities such as hypertension, diabetes, obesity, and coronary artery disease are more commonly affected [4‐8].

Despite the importance of HF-PEF, the pathophysiology and treatment of this phenotype of HF are still poorly understood. Thus far, the major clinical trials (I-Preserve, PEP-CHF, CHARM-Preserved, DIG-CHF and TOPCAT trial) [9‐13] have failed to demonstrate the efficacy of any specific treatment on mortality in these patients.

Currently, the mainstay of HF-PEF treatment is symptomatic care and management of comorbidities that predispose patients to this condition, including hypertension, diabetes, ischemia, and arrhythmias [14, 15], and include guidance on lifestyle modifications, such as restricted sodium and fluid intake [14, 15]. Sodium restriction is the self-care measure most commonly prescribed to patients with HF, as it appears to be effective in reducing congestion. However, the evidence base for this recommendation is scarce, and the few studies that have been conducted have yielded inconsistent findings [16‐25]. Research has focused on the physiological effects of intake of different amounts of sodium, and few have assessed morbidity and mortality outcomes [17‐25]. Except for an observational study by Lennie and colleagues [24] that compared number of hospital admissions and emergency department visits between patients with a sodium intake of >3 g/day versus <3 g/day, no studies have evaluated the effects of sodium restriction in patients with HF-PEF; therefore, its role in these patients remains unknown. Recently, however, Hummel and colleagues [26], investigating the effects of the sodium restricted DASH diet, showed an increased urinary aldosterone excretion during low-sodium diet in patients with HF-PEF.

In an attempt to bridge the knowledge gap in patients with decompensated HF-PEF, this trial seeks to compare the effect of a sodium- and fluid-restricted diet versus an unrestricted diet on weight loss, neurohormonal activation, and clinical stability at 7 days or at hospital discharge in patients admitted for decompensation of HF-PEF.

During protocol, patients will receive the standard hospital diet for both the control (normal diet) and intervention group (low-sodium diet), modified only in the amount of fluid offered to the intervention group. During the study, patients will be instructed to consume only foods and beverages offered by the hospital. The plate-waste method shall be used to measure sodium intake for 7 days or until hospital discharge, whichever comes first. A trained investigator will assess dietary intake twice daily: after lunch, for collection of information on intake during breakfast, morning snack, and lunch; and after dinner, for collection of information on intake during the afternoon snack, dinner, and supper. In addition, a visual scale (with values ranging from 0 to 10) will be used to verify the degree of thirst.

The trial is ongoing. Thirteen patients have completed the study protocol and additional patients are being recruited.