Effects of Dietary Sodium Restriction on Outcomes in HF
Effects of Dietary Sodium Restriction on Outcomes in HF
A pilot, open-label, blinded adjudicated end point, RCT was conducted to evaluate the efficacy of a low-sodium (65 mmol or 1500 mg daily) compared with a moderate-sodium (100 mmol or 2300 mg daily) diet on quality of life and BNP levels after 6 months of follow-up in ambulatory patients with chronic HF.
Patients were included if they were 18 years or older and willing/able to sign informed consent, with confirmed diagnosis of HF (both reduced and preserved systolic function), New York Heart Association (NYHA) classes II-III, and on optimally tolerated medical therapy according to Canadian Cardiovascular Society (CCS) guidelines. Patients were excluded if they had a serum sodium <130 mmol/L, glomerular filtration rate <20 mL/min, uncontrolled thyroid disorder, end-stage hepatic failure, a cardiac event within the prior month (implantation of a defibrillator or resynchronization pacemaker, a revascularization procedure or hospitalization due cardiovascular causes), uncontrolled atrial fibrillation (resting heart rate >90 beats/min), active malignancy with an expected life expectancy <2 years, or another comorbid condition or situation which, in the opinion of the investigator, could preclude compliance with the protocol. Patients were recruited from a specialty HF clinic, the Heart Function Clinic of the Mazankowski Alberta Heart Institute in Edmonton, Canada.
The study was approved by the Health Research Ethics Board of the University of Alberta, and all the patients provided written informed consent to participate in this study.
After providing written informed consent and having undergone baseline assessments, patients were randomly assigned by the research dietitian to either the low or moderate sodium group (randomization details provided as online Appendix Supplementary material). Dietary treatment was concealed from the clinician in charge of performing evaluations. Study data were collected and managed using REDCap electronic data capture tools.
The levels of sodium restriction were chosen to reflect clinical practice and guideline recommendations. Regardless of the level of sodium restriction (<2300 or <1500 mg/d), participants in both groups were prescribed a normocaloric diet with the following energy distribution as percentage of daily energy intake—carbohydrates, 50%-55%; protein, 15%-20%; fat, 25%-30%; and saturated fat, <7%—consistent with the guidelines for a cardiovascular healthy diet in order to standardize macronutrients intake between groups. Patients in both groups were encouraged to prefer homemade food and were provided with dietary recommendations (online Appendix Supplementary material) and a set of six daily sample menus according to their energy requirements, energy distribution, and targeted sodium intake.
Patients in both groups received conventional pharmacologic and nonpharmacologic treatment of HF, according to current CCS guidelines, and were asked to follow the recommendations for fluid restriction provided by the clinician as per clinical practice.
Dietary, clinical, biochemical, and quality of life evaluations were performed at baseline and repeated at 6 months. Dietary intake was evaluated by using a 3-day food record as described below. This evaluation was also repeated at 3 months to reinforce adherence to the dietary treatment. In addition, patients in both groups were contacted by telephone by the research dietitian every month to reinforce dietary compliance.
Dietary Intake. Patients were asked to complete a 3-day food record during the previous week to each clinical visit (baseline, 3 months, and 6 months), including 2 weekdays and 1 weekend day (details provided as online Appendix Supplementary material). Food record assessment of sodium intake has been validated against urinary sodium excretion in healthy individuals and in patients with hypertension. These 2 methods were also found to be correlated in patients with cardiac disease without HF (r = 0.624, P < .001) and in HF patients who were not taking a loop diuretic (r = 0.678, P < .001), but not in those who were taking loop diuretics (r = 0.132, P = .312), suggesting that the food record method is a more appropriate method for sodium intake assessment in HF patients on a diuretic therapy. The 3-day food record method has been previously used in populations with HF for assessing sodium and overall dietary intake
Clinical Data. Presence of symptoms and signs of HF and NYHA class (as well as comorbidities) were evaluated during the medical interview.
Biochemical. Nonfasting blood samples were collected to determine serum levels of electrolytes, albumin, creatinine, and hemoglobin, as well as plasma levels of BNP (Biosite assay; Alere, San Diego, California; measurable range 5.0–1300 ng/L).
Quality of Life. The Kansas City Cardiomyopathy Questionnaire (KCCQ) was used, with a higher score indicating better health-related quality of life. A difference of 5 points in the overall score is considered to be clinically meaningful.
Categorical variables are reported as percentages and continuous variables are presented as medians with 25th and 75th percentiles. χ Test was used to measure between-group differences for categorical variables, and Wilcoxon rank sum test was used for continuous variables. To test differences over time (within group), McNemar test was applied for categorical variables and Wilcoxon signed rank test was used for continuous variables.
Because of the significant reduction in sodium intake observed at follow-up in both the low and moderate-sodium diet groups, a post hoc analysis was performed to test the robustness of the association between a low sodium intake and improvement in BNP levels and quality of life. For this analysis, all patients were divided into 2 groups according to the dietary sodium intake achieved at the end of the follow-up (split at 1500 mg/d), regardless of randomized treatment group.
All statistical tests were 2 sided with a P value less than .05 considered as statistically significant. Statistical analyses were performed using SAS (version 9.3; Cary, NC).
The authors are solely responsible for the design and conduct of this study, all study analyses, the drafting and editing of the manuscript and its final contents.
Methods
Study Design
A pilot, open-label, blinded adjudicated end point, RCT was conducted to evaluate the efficacy of a low-sodium (65 mmol or 1500 mg daily) compared with a moderate-sodium (100 mmol or 2300 mg daily) diet on quality of life and BNP levels after 6 months of follow-up in ambulatory patients with chronic HF.
Patients were included if they were 18 years or older and willing/able to sign informed consent, with confirmed diagnosis of HF (both reduced and preserved systolic function), New York Heart Association (NYHA) classes II-III, and on optimally tolerated medical therapy according to Canadian Cardiovascular Society (CCS) guidelines. Patients were excluded if they had a serum sodium <130 mmol/L, glomerular filtration rate <20 mL/min, uncontrolled thyroid disorder, end-stage hepatic failure, a cardiac event within the prior month (implantation of a defibrillator or resynchronization pacemaker, a revascularization procedure or hospitalization due cardiovascular causes), uncontrolled atrial fibrillation (resting heart rate >90 beats/min), active malignancy with an expected life expectancy <2 years, or another comorbid condition or situation which, in the opinion of the investigator, could preclude compliance with the protocol. Patients were recruited from a specialty HF clinic, the Heart Function Clinic of the Mazankowski Alberta Heart Institute in Edmonton, Canada.
The study was approved by the Health Research Ethics Board of the University of Alberta, and all the patients provided written informed consent to participate in this study.
Randomization, Data Collection, and Treatment Allocation
After providing written informed consent and having undergone baseline assessments, patients were randomly assigned by the research dietitian to either the low or moderate sodium group (randomization details provided as online Appendix Supplementary material). Dietary treatment was concealed from the clinician in charge of performing evaluations. Study data were collected and managed using REDCap electronic data capture tools.
Dietary Intervention
The levels of sodium restriction were chosen to reflect clinical practice and guideline recommendations. Regardless of the level of sodium restriction (<2300 or <1500 mg/d), participants in both groups were prescribed a normocaloric diet with the following energy distribution as percentage of daily energy intake—carbohydrates, 50%-55%; protein, 15%-20%; fat, 25%-30%; and saturated fat, <7%—consistent with the guidelines for a cardiovascular healthy diet in order to standardize macronutrients intake between groups. Patients in both groups were encouraged to prefer homemade food and were provided with dietary recommendations (online Appendix Supplementary material) and a set of six daily sample menus according to their energy requirements, energy distribution, and targeted sodium intake.
Patients in both groups received conventional pharmacologic and nonpharmacologic treatment of HF, according to current CCS guidelines, and were asked to follow the recommendations for fluid restriction provided by the clinician as per clinical practice.
Assessments and Follow-up
Dietary, clinical, biochemical, and quality of life evaluations were performed at baseline and repeated at 6 months. Dietary intake was evaluated by using a 3-day food record as described below. This evaluation was also repeated at 3 months to reinforce adherence to the dietary treatment. In addition, patients in both groups were contacted by telephone by the research dietitian every month to reinforce dietary compliance.
Dietary Intake. Patients were asked to complete a 3-day food record during the previous week to each clinical visit (baseline, 3 months, and 6 months), including 2 weekdays and 1 weekend day (details provided as online Appendix Supplementary material). Food record assessment of sodium intake has been validated against urinary sodium excretion in healthy individuals and in patients with hypertension. These 2 methods were also found to be correlated in patients with cardiac disease without HF (r = 0.624, P < .001) and in HF patients who were not taking a loop diuretic (r = 0.678, P < .001), but not in those who were taking loop diuretics (r = 0.132, P = .312), suggesting that the food record method is a more appropriate method for sodium intake assessment in HF patients on a diuretic therapy. The 3-day food record method has been previously used in populations with HF for assessing sodium and overall dietary intake
Clinical Data. Presence of symptoms and signs of HF and NYHA class (as well as comorbidities) were evaluated during the medical interview.
Biochemical. Nonfasting blood samples were collected to determine serum levels of electrolytes, albumin, creatinine, and hemoglobin, as well as plasma levels of BNP (Biosite assay; Alere, San Diego, California; measurable range 5.0–1300 ng/L).
Quality of Life. The Kansas City Cardiomyopathy Questionnaire (KCCQ) was used, with a higher score indicating better health-related quality of life. A difference of 5 points in the overall score is considered to be clinically meaningful.
Statistical Analysis
Categorical variables are reported as percentages and continuous variables are presented as medians with 25th and 75th percentiles. χ Test was used to measure between-group differences for categorical variables, and Wilcoxon rank sum test was used for continuous variables. To test differences over time (within group), McNemar test was applied for categorical variables and Wilcoxon signed rank test was used for continuous variables.
Because of the significant reduction in sodium intake observed at follow-up in both the low and moderate-sodium diet groups, a post hoc analysis was performed to test the robustness of the association between a low sodium intake and improvement in BNP levels and quality of life. For this analysis, all patients were divided into 2 groups according to the dietary sodium intake achieved at the end of the follow-up (split at 1500 mg/d), regardless of randomized treatment group.
All statistical tests were 2 sided with a P value less than .05 considered as statistically significant. Statistical analyses were performed using SAS (version 9.3; Cary, NC).
The authors are solely responsible for the design and conduct of this study, all study analyses, the drafting and editing of the manuscript and its final contents.
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