We have previously found thiamine (vitamin B₁) deficiency in patients with congestive heart failure (CHF) who had received long-term furosemide therapy. In the present study, we assessed the effect of thiamine repletion on thiamine status, functional capacity, and left ventricular ejection fraction (LVEF) in patients with moderate to severe CHF who had received furosemide in closes of 80 mg/d or more for at least 3 months.

Thirty patients were randomized to 1 week of double-blind inpatient therapy with either IV thiamine 200 mg/d or placebo (n = 15 each). All previous drugs were continued. Following discharge, all 30 patients received oral thiamine 200 mg/d as outpatients for 6 weeks. Thiamine status was determined by the erythrocyte thiamine-pyrophosphate effect (TPPE). LVEF was determined by echocardiography.

TPPE, diuresis, and LVEF were unchanged with IV placebo. After IV thiamine, TPPE decreased (11.7% ± 6.5% to 5.4% ± 3.2%; P <0.01). LVEF increased (0.28 ± 0.11 to 0.32 ± 0.09; P <0.05), as did diuresis (1,731 ± 800 mL/d to 2,389 ± 752 mL/d; P <0.02), and sodium excretion (84 ± 52 mEq/d to 116 ± 83 mEq/d, P <0.05). In the 27 patients completing the full 7-week intervention, LVEF rose by 22% (0.27 ± 0.10 to 0.33 ± 0.11, P <0.01).

Thiamine repletion can improve left ventricular function and biochemical evidence of thiamine deficiency in some patients with moderate-to-severe CHF who are receiving long-term furosemide therapy.