[Evaluation of treatment adaptation for low response to ASA in vascular surgery]

A decreased antiplatelet prophylaxis (low response, LR/high on-treatment platelet reactivity, HPR) with acetylsalicylic acid (ASA) is associated with an increased risk of thromboembolic events. The prevalence of a LR is frequent with about 20% and a therapeutic regimen is not yet established. The aim of this prospective study was to evaluate the effectiveness of a therapeutic regimen for treatment adaptation when LR/HPR is detected in vascular surgery patients.

Overall, 36 patients under long-term antiplatelet treatment with 100 mg/day ASA and a detected ASA low response (ALR) were included in the study. In this patient group a modification of the prophylactic medication was carried out according to the established treatment plan and a control aggregometry was performed. The therapeutic regimen followed the test and treat principle. To evaluate the effect of ASA impedance, aggregometry with multiple electrodes was used (multiplate).

All 36 patients were successfully transferred to response status with the treatment scheme. In 32 (88.89%) patients an increased dose of 300 mg/day ASA was carried out and in 2 (5.56%) patients the medication was changed from ASA to clopidogrel. A further 2 (5.56%) patients were switched to oral anticoagulation with phenprocoumon, due to other indications. Bleeding complications or other side effects did not occur.

The chosen treatment regime for a low response proved to be effective and safe in vascular surgery patients. A guideline-compliant increase of the ASA dose from 100 mg to 300 mg/day predominantly led to an effective inhibition of platelet aggregation in the aggregometry.