What fat-soluble vitamin deficiency can cause electrocardiogram (EKG) abnormalities, such as QT prolongation, in a patient with a history of Small Intestine Bacterial Overgrowth (SIBO) or malabsorption, taking Ativan (lorazepam)?

Vitamin E Deficiency Causes EKG Abnormalities in SIBO Patients

Vitamin E deficiency is the fat-soluble vitamin most likely responsible for EKG abnormalities, particularly QT prolongation, in patients with SIBO-related malabsorption. 1

Why Vitamin E Specifically Affects Cardiac Conduction

Vitamin E deficiency causes peripheral neuropathy, ataxia, ophthalmoplegia, and myopathy—but critically, it also affects cardiac muscle function through oxidative damage to myocardial cells 1. The autonomic neuropathy associated with severe vitamin E deficiency can disrupt cardiac conduction pathways, leading to QT prolongation and other rhythm disturbances 1.

SIBO's Role in Fat-Soluble Vitamin Malabsorption

Bacterial overgrowth in the small intestine directly causes fat-soluble vitamin deficiencies through bile salt deconjugation and pancreatic enzyme degradation, resulting in steatorrhea and malnutrition 1. The mechanism is straightforward:

• Excessive bacteria in stagnant bowel loops deconjugate bile salts, making them less effective for fat emulsification 1
• Bacterial enzymes degrade pancreatic lipase, further impairing fat digestion 1
• Without proper fat absorption, fat-soluble vitamins (A, D, E, K) cannot be absorbed 1

Diagnostic Approach for Vitamin E Deficiency

Check serum vitamin E (alpha-tocopherol) levels immediately if your patient has unexplained anemia, neuropathy, or EKG abnormalities in the context of SIBO 1. The diagnostic workup should include:

• Serum alpha-tocopherol levels to confirm vitamin E deficiency 1
• Hydrogen and methane breath testing to confirm SIBO diagnosis 1
• Evaluation for steatorrhea and weight loss despite adequate caloric intake 1
• Complete fat-soluble vitamin panel: retinol (vitamin A), 25-hydroxyvitamin D, vitamin K1, and PIVKA-II 1

Why Other Fat-Soluble Vitamins Are Less Likely

While all fat-soluble vitamins are affected by SIBO, their clinical presentations differ:

• Vitamin A deficiency causes night blindness, xerophthalmia, and dry skin—not cardiac issues 2, 1
• Vitamin D deficiency increases fracture risk and causes bone pain, but does not directly affect cardiac conduction 1
• Vitamin K deficiency causes bleeding disorders with prolonged PT/INR and easy bruising, not EKG changes 1

Importantly, vitamin K can actually be manufactured by bacteria, making deficiency less common than other fat-soluble vitamins in SIBO 1.

Treatment Algorithm

Begin supplementation immediately while treating the underlying SIBO 1:

1. Start vitamin E supplementation at 100 IU daily using water-miscible forms for improved absorption 1
2. Treat SIBO with rifaximin 550 mg twice daily for 1-2 weeks to restore normal absorption 3
3. Monitor serum alpha-tocopherol levels every 6 months and adjust dosing based on laboratory results 2, 1
4. Add comprehensive fat-soluble vitamin supplementation: vitamin A (10,000 IU daily), vitamin D (3000 IU daily), and vitamin K (300 μg daily) 1

Critical Pitfall to Avoid

Do not use bile acid sequestrants (cholestyramine, colesevelam) to treat diarrhea in SIBO patients, as they will worsen fat-soluble vitamin deficiencies despite controlling symptoms 1. This is a common error that can perpetuate the malabsorption cycle even after SIBO treatment 1.

Lorazepam Consideration

While lorazepam itself does not cause vitamin deficiencies, it can mask neurological symptoms of vitamin E deficiency (such as peripheral neuropathy and ataxia), potentially delaying diagnosis 1. The sedative effects may also obscure early warning signs of worsening malnutrition 1.