When working towards an optimised Carotid stenting procedure does patient, procedural and pharmacological selection impact on outcome.

Carotid intervention for stroke prevention in the form of carotid artery stenting has been performed in clinical trials since the beginning of the 1980’s. Improvements in the operative technique and pharmacology used during the procedure have reduced complication rates since stenting began. Long term follow up of the Sheffield data set has shown that patient selection has the most impact on reducing adverse outcomes from the procedure.

Multivariable analysis of the Sheffield database detailed in this thesis has shown that retinal events have a lower risk of adverse outcomes than cerebral events, and clopidogrel use at the time of stenting prevents adverse events. Recurrent stenosis of more than 50% also increases risk for recurrent stroke in the long term and therefore warrants a long term surveillance programmes in stented patients. It was possible to show from the same analysis that stenting patients as a routine procedure prior to cardiac surgery had no immediate benefit in reducing operative stroke risk from the procedure.

The EPICAS study was developed from these initial observations to investigate the effects of variability in response to clopidogrel on outcomes. Using transcranial Doppler detected embolic events as a clinical endpoint for comparison with the clopidogrel dependant pathways of platelet activation the study hoped to show a direct effect of the degree of platelet inhibition on the number of emboli detected. This was not shown to be the case in the patients studied as part of this work. Patients classified as non responders to clopidogrel had no difference in emboli counts before and after the stenting procedure (p = 0.24). The results suggest that a variance in response to clopidogrel is unlikely to be clinically significant even in larger cohorts of patients.