Working Hypothesis: a treatment with thiamine improves functional status and heart function of patients with congestive heart failure when on a diuretic treatment.

In the treatment of congestive heart failure, diuretic drugs have become a firm cornerstone of therapy. Up to 50% of patients with congestive heart failure in industrialized nations will undergo long-term diuretic treatment. Diuretic therapy is associated with a loss of water soluble vitamins, including vitamin B1 (thiamine). Electrolyte dysbalance, a major side effect of diuretic therapy, has been extensively studied. In sharp contrast, only few data are available about the effects of vitamin loss and in particular of thiamine in this setting. Available data suggest that a diuretic treatment is associated with an increased risk for thiamine deficiency. Thiamine plays a crucial role for normal cardiac function, since severe thiamine deficiency leads to congestive heart failure (wet beriberi). Consequently, patients undergoing diuretic treatment might have compromised heart function. Supplementation of thiamine has been reported to improve cardiac function in patients with congestive heart failure on long-term treatment with diuretic drugs. However, no efforts have been made to confirm those preliminary observations by a placebo-controlled, double-blind study.

Inclusion Criteria:

• Patients with stable congestive heart failure on a prescription for diuretic drugs

Exclusion Criteria:

• Acute heart failure
• Foreseeable need for further changes in medication
• Current medication containing vitamins
• Patients with a creatinine above 250 μmol/l