Fluctuating International Normalized Ratio in Patients Compliant on Warfarin: Could Gastroparesis Be the Cause?

Warfarin is the drug of choice to achieve therapeutic anticoagulation in patients with mechanical heart valves. Factors that interfere with the reliable absorption of warfarin may result in difficult to control international normalized ratio (INR) and can cause significant bleeding complications due to supra-therapeutic INR and thromboembolism from sub-therapeutic INR. The patient's non-compliance is an important factor leading to difficult to control INR but there are additional factors that should be considered in difficult cases when dietary and medication compliance are observed. Gastroparesis is one such predominant and overlooked factor. A 58-year-old African American female with a history of mechanical mitral valve who was on anticoagulation with warfarin was admitted multiple times, with frequent episodes of significant bleeding episodes and fluctuating INR between sub- and supra-therapeutic readings despite being on a relatively stable dose of Coumadin. She was eventually diagnosed with severe gastroparesis, which was the cause of her fluctuating INR. A case can be made to consider gastric motility testing in such patients, where achieving a therapeutic range for anticoagulation is difficult in the setting of medication and dietary compliance.