Correlation of Abnormal Response to Acetylsalicylic Acid and the Phenomenon of Carotid Artery Restenosis

The purpose of carotid endarterectomy and long-term administration of acetylsalicylic acid to a group of patients suffering from carotid arteries stenosis is to reduce the risk of ischemic stroke of the central nervous system. However, the long-term effects of the treatment process are adversely impacted by the phenomenon of re-stenosis of the unclogged artery (carotid artery restenosis), as well as the widely discussed in literature lack of a proper response to the antiplatelet effect of acetylsalicylic acid (i.e. aspirin resistance). The authors of this study have attempted to investigate the correlation of both pathologies. The study was conducted in the years 2011-2013 at the Vascular Surgery and Angiology Clinic in Warsaw (at the Centrum Medyczne Kształcenia Podyplomowego, Medical Postgraduate Training Centre). Qualified for the study were 181 patients, with the mean age of 68 years, of whom 70% were male and whose average body weight was that of 76 kg (167.2 lbs); the patients were administered 75 mg/day of Acetylsalicylic Acid (ASA). Control group was formed from 36 patients. Restenosis was defined as a reduction in vessel diameter by a minimum of 50% (75% of the surface area), as confirmed by a Doppler Duplex ultrasound examination where the peak systolic velocity (Vmax) >125 cm/sec or peak systolic ratio (ICA/CCA) >2. Platelet reactivity was measured using the method of impedance aggregometry (Multiplate Dynabyte, Munich Germany). The average observation period was 18 months since the time of the operation. Parameters characterizing the study group were described using the standard statistical tools: average values and standard deviation, medians, and quarters or frequency tables. The relationships between selected pairs of variables were examined respectively by using the chi square or Student's t-test, with possible amendments to unequal variances. With the help of multivariate logistic regression models, a study was performed on the effect of some factors on the likelihood of resistance to antiplatelet effects of aspirin. The models take into account the following factors: blood biochemical parameters, co-morbidities, use of other drugs. Using stepwise elimination, some statistically significant variables selected were at 0.05, wherein it is assumed that the model preserves variables for which the test does not exceed the level of 0.1. The predictive value of the models was evaluated using the ROC curve graph. The area under the curve shows the predictive value of the model: the area can take values from the interval (0.1); the closer to 1.0 the greater the predictive value. Statistical significance was set at 0.05. All the performed tests were two-tailed. Calculations were performed using Stata 7.0. No statistical significance between the abnormal response to acetylsalicylic acid and restenosis was evidenced. Out of 14 (8%) patients within correct reactions to ASA only one (7%) was distinguished as showing signs of carotid restenosis. However, among the 167 (92%) ASA-responsive patients, the group suffering from restenosis consisted of 20 (12%) patients. The level of aggregation rate did not vary significantly between the two groups. The lack of inadequate response to the antiplatelet effect of acetylsalicylic acid is a complex phenomenon which has not been fully investigated. The phenomenon of inadequate response to acetylsalicylic acid has no impact on the development of carotid restenosis. Lewszuk A* and Madycki G Department of Vascular Surgery, Bielanski Hospital Warsaw, Poland