Effects of the Dietary Approaches to Stop Hypertension(DASH) Sodium-restricted Diet in Diastolic Heart Failure

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.


Eligibility Criteria:
Inclusion Criteria:

* Satisfy European Society of Cardiology guidelines for the diagnosis of HF-PSF (Paulus WJ et al. Eur. Heart J. 2007;28:2539-2550).
* Framingham criteria for heart failure satisfied
* left ventricular ejection fraction ≥ 50% (contrast ventriculography, echocardiography, nuclear scintigraphy)
* Diastolic dysfunction on previous echocardiogram/catheterization or evidence of abnormal neurohormonal activation (B-type natriuretic peptide (BNP) ≥ 100 pg/ml) with supporting evidence (atrial fibrillation, left atrial enlargement, left ventricular hypertrophy)
* History of systemic hypertension
* Willing to adhere to provided diet

Exclusion Criteria:

* New York Heart Association Class IV heart failure symptoms
* Hospitalization for decompensated heart failure within past one month
* Uncontrolled hypertension (seated systolic blood pressure ≥ 180 or diastolic blood pressure ≥ 110) at rest, on current antihypertensive regimen
* Changes in medical regimen for heart disease or hypertension within past 1 month, including diuretic dose adjustment
* Primary exercise limitation due to severe pulmonary disease
* Poor echocardiographic windows
* Worse than moderate mitral or aortic stenosis or insufficiency.
* Serum potassium level \> 5.0 mmol/L at baseline or prior history of serum potassium level \> 6.0
* Serum calcium/phosphorus product \> 50 at baseline
* Severe renal insufficiency (current estimated glomerular filtration rate \< 30 ml/min)
* Severe anemia (hemoglobin \< 9 g/dL)
* Uncontrolled diabetes mellitus (hemoglobin A1c \> 9%)
* Non-hypertensive cause of HF-PSF, e.g. amyloidosis, sarcoidosis, constrictive pericardial syndromes
* Myocardial infarction or unstable angina, including new or worsening anginal syndrome, within the past three months
* Uncontrolled arrhythmia (including non rate-controlled atrial fibrillation)
* Terminal illness expected to result in death within six months or active solid-organ cancer
* Psychiatric disorder or dementia with potential to compromise dietary adherence