hf patients with lv systolic dysfunction of ischemic or non-ischemic origin and an lvef <40% using nuclear ventriculography or echocardiography within the last 6 months.

attempts should have been made at optimizing medical therapy and the participant should be stable on these medications for at least 3 months.

patients with a 25(oh)d level between 10-25 ng/ml

inability to give informed consent

patients with sarcoidosis or other granulomatous disease that can alter vitamin d metabolism

patients with primary valvular hf, hypertrophic cardiomyopathy, and drug-induced hf

renal dysfunction defined as serum creatinine > 2.5 mg/dl

pregnant women

patients <18 years of age

patients on vitamin d supplementation