Plasma Vitamin K1 Levels in Italian Patients Receiving Oral Anticoagulant Therapy for Mechanical Heart Prosthesis: A Case–Control Study

Background Oral anticoagulant therapy (OAT) with a vitamin K antagonist (VKA) is the choice of treatment for preventing thromboembolism in patients with mechanical heart valve prosthesis (MHP). The percentage of time in the therapeutic range (TTR%) expresses the OAT quality. We planned a case-control study in order to determine vitamin K1 plasmatic concentrations in MHP patients and to correlate these with TTR%. Materials and Methods Of 756 MHP patients receiving OAT, 125 patients (61 younger than 65 years, and 64 older than 65 years) and 120 healthy blood donors, matched for sex and age, were enrolled in the study. All subjects completed a living questionnaire regarding diet, and underwent blood collection. Vegetable and fruit intake was categorized as optimal or suboptimal, and the high-performance liquid chromatography method was used to determine vitamin K1 levels. Results Neither the patients nor controls had been taking vitamin supplements prior to the start of the study. The median vitamin K1 level was 290 pg/L in 72 controls with optimal intake, and 274 pg/L in 48 controls with suboptimal intake, while the median vitamin K1 level in MHP patients with optimal intake was 409 pg/L, significantly higher (p < 0.001) than the 133.5 pg/L in patients with suboptimal intake. Vitamin K1 concentration in MHP patients appears to be linked to an agerelated threshold: in patients younger than 65 years of age, the median vitamin K1 level was 431 pg/L, significantly higher (p < 0.05) than the 290 pg/L in patients older than 65 years of age. No clear relation was found between vitamin K1 levels and TTR% (Pearson = 0.14). However, patients with vitamin K1 > 160 pg/L showed a TTR% > 60 %. Among patients younger than 65 years, subjects with vitamin K1 > 160 pg/L showed a median TTR of 66 %, this being significantly higher (p < 0.001) than the 46 % level shown by patients with vitamin K1 > 160 pg/L. Conclusions Vitamin K1 concentrations in MHP patients seem to be related to both diet and age. © Springer International Publishing Switzerland 2016