Sodium Restriction and Heart Failure Outcomes
What is the impact of sodium restriction on heart failure (HF) outcomes?
The study cohort was comprised of 902 New York Heart Association functional class II/III HF patients, enrolled in the multihospital HART (Heart Failure Adherence and Retention Trial) study. These patients were followed up for a median duration of 36 months (interquartile range, 27-36 months). The study investigators serially assessed sodium intake by a food frequency questionnaire. They classified patients into sodium restricted (<2500 mg/d) and unrestricted (≥2500 mg/d) groups based on the mean daily sodium intake prior to the first event of death or HF hospitalization. Study groups were propensity score matched according to possible confounders at baseline. The primary outcome was a composite of death or HF hospitalization. The secondary outcomes were cardiac death and HF hospitalization.
On analysis of the data, the study investigators found that sodium intake data were available for 833 subjects (145 sodium restricted, 688 sodium unrestricted), of whom 260 were propensity matched into sodium restricted (n = 130) and sodium unrestricted (n = 130) groups. They found that sodium restriction was associated with significantly higher risk of mortality or HF hospitalization (42.3% vs. 26.2%; hazard ratio [HR], 1.85; 95% confidence interval [CI], 1.21-2.84; p = 0.004), derived from an increase in the rate of HF hospitalization (32.3% vs. 20.0%; HR, 1.82; 95% CI, 1.11-2.96; p = 0.015) and a nonsignificant increase in the rate of cardiac mortality (HR, 1.62; 95% CI, 0.70-3.73; p = 0.257) and all-cause mortality (p = 0.074). Sodium-restricted patients were more frequently women and were more likely to have chronic kidney disease, prior stroke, been treated with a beta-blocker, and received higher doses of loop diuretic agents. Exploratory subgroup analyses suggested that sodium restriction was associated with increased risk of mortality or HF hospitalization in patients not receiving angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker (HR, 5.78; 95% CI, 1.93-17.27; p = 0.002).
The authors concluded that in symptomatic patients with chronic HF, sodium restriction may have a detrimental impact on outcome. They opined that a randomized clinical trial is needed to definitively address the role of sodium restriction in HF management.
This observational study is certainly hypothesis generating. More data are needed to determine whether salt intake has differential prognostic implications in those who ingest ‘excess’ dietary salt because of salt need as compared to those who do so simply because of preference. The excessive mortality in those restricting salt is concerning, and randomized clinical studies are urgently needed to determine the impact of dietary sodium restriction on HF outcomes. Also, data are needed to determine the impact of abrupt changes in salt intake as compared to gradual changes in salt ingestion.
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