The Effects of Active VItamin D on Left Atrial Volume Index

Inclusion Criteria:

Sign informed consent.
Willing and able to adhere to all study-related procedures, including study medication regimen.
≥ 18 years old.
Previous clinical diagnosis of heart failure with preserved ejection fraction: NYHA Class II-IV.
Satisfy these echocardiographic criteria within the last year: Left ventricular ejection fraction ≥ 50%, cardiac magnetic resonance or ventriculogram; Left atrial size ≥ 4 cm in long axis or > 5.2 cm in four chamber length; Septal wall thickness > 1.2 cm (females) or 1.3 cm (males); Doppler evidence of moderate or severe diastolic dysfunction (≥ Grade II) by transmitral inflow, pulmonary venous flow, color M-mode and/or tissue Doppler (per European Society of Cardiology guidelines).
Experienced ≥ 1 of the following in last 12 months: Hospitalization for acute heart failure (primary diagnosis); Long term treatment with loop diuretic; Mean pulmonary capillary wedge pressure ≥ 16 mm Hg at catheterization for dyspnea; Left ventricular end diastolic pressure (LVEDP) ≥ 19 mm Hg at catheterization for dyspnea; Acute treatment with intravenous loop diuretic or hemofiltration.
On stable medical therapy in last 30 days before study entry (defined as no change in angiotensin converting enzyme inhibitors [ACEI], angiotensin receptor blockers, aldosterone inhibitors, beta-blockers or calcium channel blockers.
Satisfy these criteria at initial lab screening: Estimated glomerular filtration rate (eGFR) ≥ 30 ml/min; Corrected serum Ca 8.0-10.0 mg/dL (2.0-2.5 mmol/L); Phos ≤ 5.2 mg/dL (1.68 mmol/L); Serum albumin ≥ 3.0 g/dL (30 g/L);
Negative serum pregnancy test for females of childbearing potential (within 2 weeks of starting study treatment).
Women of childbearing potential must be practicing barrier/oral contraception during study-related treatment, or be surgically sterile or one year post-menopausal, be non-nursing and non-pregnant.

Exclusion Criteria:

Taking > 1,000 IU of vitamin D preparation daily within last 30 days.
Received activated vitamin D preparation including paricalcitol (Zemplar®), doxercalciferol (Hectorol®) or calcitriol (Rocalctrol®, Calcijex®) within last 90 days prior to study entry.
History of nephrolithiasis.
Poorly controlled hypertension (systolic blood pressure > 180 mmHg and/or diastolic blood pressure > 110 mmHg at Screening; confirmed by repeat).
Secondary hypertension (i.e. renal artery stenosis, primary aldosteronism or pheochromocytoma).
Severe hepatic impairment.
Use of known inhibitors (ie, ketoconazole) or inducers (ie, carbamazepine) of cytochrome P450 3A (CYP3A) within 2 weeks prior to taking study drug.
HIV positive.
Condition with prognosis < 1 year at study entry other than heart failure.
Significant valvular disease defined as moderate or severe aortic or mitral stenosis, mitral or aortic regurgitation.
Infiltrative cardiac disease (sarcoid, amyloid, hemochromatosis, lymphoma, etc.).
Arrhythmogenic right ventricular cardiomyopathy.
Active myocarditis.
Constrictive or restrictive pericarditis.
Acute coronary artery disease symptoms defined as emergency department visit or hospital admission with unstable angina, ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) within 90 days before study entry.
Poor echocardiographic windows.
Current active treatment in another investigational study or participation in another investigational study within 1 month before screening.
Active malignancies except in situ carcinoma of the cervix, localized squamous or basal cell carcinoma of skin.
Other serious concurrent or recent medical or psychiatric condition which, in Investigator's opinion, makes the patient unsuitable for participation.