Sodium Lowering Vascular Effects Trial

Study Overview
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Brief Summary
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The proposed mechanistic trial will test the effect of dietary sodium reduction on cardiac and vascular structure and function in those with elevated blood pressure or hypertension. Findings from this study will fill the knowledge gap on the underlying mechanisms of dietary sodium intake on cardiovascular disease risk in addition to blood pressure and could provide further evidence on sodium reduction for the prevention of cardiovascular disease.

Detailed Description
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High dietary sodium intake increases risk of cardiovascular disease (CVD) independent of established risk factors, including blood pressure (BP). Non-BP mediated mechanisms underlying the increased risk of CVD associated with dietary sodium intake are not well understood, but observational studies suggest direct target organ damage in the heart and vasculature might play an important role. Little evidence exists from randomized controlled trials (RCTs) on target organ effects of dietary sodium reduction, and the National Academy of Medicine has recommended future research to test the effects of different sodium intake levels on endothelial and vascular function in order to to better characterize the relationship between sodium intake and chronic disease. The overall objective of the proposed mechanistic trial is to test the effect of dietary sodium reduction on cardiac and vascular structure and function. Specifically, the proposed trial will test whether dietary sodium reduction (targeting a dietary sodium intake of <2,300 mg/day) will improve left ventricular mass index (LVMI), left ventricular global longitudinal strain (LVGLS), carotid-femoral pulse wave velocity (cfPWV), and flow-mediated dilation (FMD) compared to usual intake. Additionally, we will test whether this effect is independent from BP reduction. We will recruit 256 people with elevated BP or hypertension from the greater New Orleans area and randomly assign them to a dietitian-led behavioral intervention aimed at decreasing dietary sodium intake to <2,300 mg/day for 12 months or to a usual diet. Study outcomes, including cardiac magnetic resonance imaging (CMR)-determined LVMI and LVGLS, cfPWV, and FMD, will be measured at baseline, 6-month, and 12-month clinic visits using standardized protocols with stringent quality control. These outcomes are validated biomarkers for target organ damage and predict the risk of clinical CVD events. In primary analyses, the effect of sodium reduction on each subclinical CVD endpoint will be compared between the sodium reduction and usual diet groups according to the intention-to-treat principle without adjusting for covariates. In secondary analyses, changes in ambulatory and clinical BP will be adjusted to assess the BP-independent effect of dietary sodium reduction on each subclinical CVD endpoint. The proposed trial has 85% statistical power to detect a clinically significant difference in changes of the four co-primary outcomes (10 g/m2 in LVMI, 1.3% in LVGLS, 0.9 m/s in cfPWV, and 1.1% in FMD) over 12 months between the two groups at a 2-sided significance level of 0.0125 (0.05/4). Findings from this trial will fill the knowledge gap of the underlying mechanisms of dietary sodium intake on CVD risk and provide further evidence on sodium reduction for CVD prevention.

Official Title
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A Mechanistic Trial of Dietary Sodium Reduction on Vascular Structure and Function

Conditions
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Endothelial Dysfunction, Vascular Stiffness, Left Ventricular Hypertrophy, Left Ventricular Dysfunction

Intervention / Treatment
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* Behavioral: Sodium Reduction Intervention


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men or women aged ≥40 years. Individuals <40 years are at a low risk for clinical and subclinical CVD Elevated BP or hypertension (systolic BP ≥120 mmHg and diastolic BP ≥80 mmHg with or without use of antihypertensive medications) Exclusion Criteria: Glomerular filtration rate (eGFR) <30 or end-stage renal disease (kidney transplant or chronic dialysis) History of cardiovascular disease Shift worker or regularly work at night Cancer requiring chemotherapy or radiation treatment in the previous two years Current pregnancy or breastfeeding or plans to become pregnant during the study Consumption of ≥21 alcoholic drinks/week Current participation in another lifestyle intervention or drug trial Current residence or planned residence that makes it difficult to meet trial requirements Other concerns regarding ability to meet trial requirements (at the discretion of the study coordinator)

Ages Eligible for Study
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Minimum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Eligible participants will be randomized 1:1 into the dietitian-led behavioral intervention and usual diet.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: sodium reduction intervention<br>The sodium reduction intervention is a dietician-led behavioral intervention consisting of two phases, first a 3-month intensive intervention phase, followed by a 9-month maintenance phase. The overall goal of the intervention is to reduce sodium intake to <2,300 mg per day based on the most recent guideline from the National Academies of Medicine. Both phases will include individual and group behavioral modification counseling designed to facilitate a reduction in dietary sodium intake. | Behavioral: Sodium Reduction Intervention<br>* The sodium reduction intervention is a dietician-led behavioral intervention consisting of two phases, first a 3-month intensive intervention phase, followed by a 9-month maintenance phase. The overall goal of the intervention is to reduce sodium intake to <2,300 mg per day based on the most recent guideline from the National Academies of Medicine. Both phases will include individual and group behavioral modification counseling designed to facilitate a reduction in dietary sodium intake.<br>|
| No Intervention: Usual Diet<br>Participants randomized to the usual diet group will receive standard care from their providers with no study intervention. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Left Ventricular Global Longitudinal Strain (LVGLS) from baseline to 12 months | Cardiac magnetic resonance imaging will be used to determine LVGLS. | 12 months | 
| Change in Left Ventricular Mass Index (LVMI) from baseline to 12 months | Cardiac magnetic resonance imaging will be used to determine left ventricular mass (LVM). LVM will be indexed to body surface area. | 12 months | 
| Change in Pulse Wave Velocity (PWV) from baseline to 12 months | A carotid tonometer will be used to measure carotid-femoral PWV. | 12 months | 
| Change in Flow-Mediated Dilation (FMD) from baseline to 12 months | Endothelial-dependent FMD will be quantified using high resolution ultrasound. | 12 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Left Ventricular Volumes | Cardiac magnetic resonance imaging will be used to determine left ventricular volumes. | Baseline, 6 months, and 12 months | 
| Left Atrial Maximum and Minimum Volume | Cardiac magnetic resonance imaging will be used to determine left atrial maximum and minimum volumes. | Baseline, 6 months, and 12 months | 
| Left Atrial Ejection Fraction | Cardiac magnetic resonance imaging will be used to determine left atrial ejection fraction. | Baseline, 6 months, and 12 months | 
| Left Atrial Global Strain | Cardiac magnetic resonance imaging will be used to determine left atrial global strain. | Baseline, 6 months, and 12 months | 
| Aortic Pulse Wave Velocity | Cardiac magnetic resonance imaging will be used to determine aortic pulse wave velocity. | Baseline, 6 months, and 12 months |