Thiamine supplementation in symptomatic chronic heart failure: a randomized, double-blind, placebo-controlled, cross-over pilot study.

Background: Diuretic treatment for heart failure may lead to an increased urinary thiamine excretion and in long-term thiamine deficiency, which may further compromise cardiac function. This study evaluated the effect of high dose thiamine supplementation in heart failure patients.
Methods: Nine patients with diuretic treatment for symptomatic chronic heart failure and a left ventricular ejection fraction (LVEF) <40% were randomly assigned to receive thiamine (300 mg/day) or placebo for 28 days. After a wash-out of 6 weeks, the patients crossed-over to a second treatment period. The primary outcome was a change in LVEF.
Results: Mean age was 56.7 ± 9.2 years (range 44.9-75.4 years). Baseline LVEF was similar for both treatment groups (29.5% in the thiamine group and 29.5% in the placebo group, P = 0.911). After 28 days of thiamine treatment, the LVEF increased to 32.8% which was significantly (P = 0.024) different from the LVEF in the placebo group (28.8%). This corresponds to a treatment effect for LVEF of 3.9% in absolute terms.
Conclusions: This study suggests that thiamine supplementation has beneficial effects on cardiac function in patients with diuretic drugs for symptomatic chronic heart failure. Subclinical thiamine deficiency is probably an underestimated issue in these outpatients.