Dietary intervention for Heart Failure (DASH-DHF Trial)

Heart failure with preserved systolic function (HF-PSF, or 'diastolic heart failure') accounts for half of hospitalizations for heart failure in patients over the age of 65. Most HF-PSF patients have systemic hypertension (HTN), and characteristic HTN-induced cardiovascular changes contribute to HF-PSF. However, it is unclear why most patients with HTN never develop HF-PSF or which specific aspects of HTN predispose to HF-PSF. In the Dahl S rat, the primary animal model of HF-PSF, high dietary sodium intake suppresses the systemic renin-angiotensin-aldosterone system, but upregulates renal and cardiac renin-angiotensin-aldosterone system by inducing oxidative stress. In humans, the magnitude of blood pressure response to sodium ingestion and depletion can categorize subjects as "salt-resistant" and "salt-sensitive." Human salt sensitivity is associated with structural and loading conditions that increase the risk for HF-PSF, including HTN, ventricular hypertrophy and diastolic dysfunction, arterial stiffening, and increased plasma volume. High dietary sodium intake induces oxidative stress in salt-sensitive humans. In humans with HTN and normal ventricular systolic function that do not have heart failure, increased oxidative stress predicts impaired exercise capacity, ventricular hypertrophy, diastolic dysfunction, arterial stiffening, and vascular endothelial dysfunction. The investigators have proposed that "salt sensitivity" and the accompanying oxidative stress on the typical high-sodium Western diet may contribute to the initiation and progression of HF-PSF. In patients with HF-PSF, the investigators will relate dietary changes to biochemical and cardiovascular functional measures. The investigators will study subjects on ad-lib diet and and following three weeks of rigorous dietary modification with the Dietary Approaches to Stop Hypertension (DASH)/sodium-restricted diet (SRD). This diet is richer in natural antioxidants and lower in sodium than the usual American diet. The DASH/SRD is recommended to lower blood pressure in patients with HTN, and is particularly effective in elderly, obese, and salt-sensitive hypertensives. Dietary sodium restriction is recommended for all HF patients including those with HF-PSF. The investigators hypothesize that the DASH/SRD will have favorable effects on oxidative stress, ventricular and vascular function, and blood pressure control in patients with hypertensive HF-PSF.