Is Efficacy of PLAtelet Aggregation Inhibition by Ticagrelor Mediated P2Y12 Blockade Dependent Upon Endogenous Endothelial Nitric OXide?

Inclusion Criteria: * Age \> 18 years * Coronary artery disease deemed to require Percutaneous Coronary Intervention * Diabetics must be established on oral or subcutaneous therapy * Non diabetics must have HbA1c levels between 20-42 mmol/mol * Current smokers are those that have smoked greater than 100 cigarettes and currently smoke on a daily basis * Non smokers have not smoked for greater than 3 years (and not on nicotine replacement) * Healthy controls are non smokers without medical history and taking no regular medication Exclusion Criteria: * Contra-indication to dual antiplatelet therapy * Known bleeding disorders * Known malignant disease * Known myeloproliferative disease/malignant paraproteinaemia/heparin induced thrombocytopenia * Previous intracranial bleed * Already established on dual antiplatelet therapy * Known moderate-severe liver or splenic failure * Severe renal impairment * Major surgery due within one month of enrolment or before completion of measurements * Known allergy/intolerance to aspirin or ticagrelor * Reaction or side effect of aspirin or ticagrelor resulting in discontinuation prior to completion * Known allergy/intolerance to 3-hydroxy-3-methylglutaric acid Coenzyme A reductase inhibitor therapy (statins) * Concurrent use of high dose simvastatin/lovastatin (\>40mg daily) * Currently taking medication that will interact with platelet function ie NSAIDS, antibiotics or herbal remedies * Concurrent use of strong cytochrome P450 3A4 inhibitors eg. ketoconazole, clarithromycin, nefazodone, ritonavir, and atazanavir * Concurrent use of strong cytochrome P450 3A4 inducers e.g. rifampicin, dexamethasone, phenytoin, carbamazepine and phenobarbital * Known sick sinus syndrome, second or third degree AV block or bradycardia-related syncope without permanent pacemaker in situ * Known severe asthma/Chronic Obstructive Pulmonary Disease or worsening of dyspnoeic symptoms on ticagrelor * Known severe gout * Currently taking calcium channel antagonist * Currently taking long acting nitrate * Currently taking \>15mg/week of methotrexate * Women pregnant, breast feeding or of child bearing potential * Require anticoagulation on warfarin or Novel Oral AntiCoagulant * Platelet count \<150 x109/L or \>400 x109/L * Known blood bourne virus carrier * Unable to give informed consent * Involvement in a conflicting study * Non English speaker Withdrawal Criteria following initial recruitment due to not meeting inclusion or exclusion criteria * Develop significant bleeding complications of medication requiring discontinuation of antiplatelet therapy prior to completion of the study * Urgent surgery undertaken during the study resulting in discontinuation of antiplatelet therapy prior to completion of the study * React or develop side effects of aspirin or ticagrelor resulting in discontinuation prior to completion of the study * Commence medication that will interact with platelet function before completion of the study * Commence use of strong cytochrome P450 3A4 inhibitors before completion of the study * Commence use of strong cytochrome P450 3A4 inducers before completion of the study * Worsening of dyspnoea in subjects with mild/moderate asthma/Chronic Obstructive Pulmonary Disease resulting in discontinuation of ticagrelor prior to completion of the study * Platelet count on initial sampling \<150 x109/L or \>400 x109/L * Non diabetic patients HbA1c level \>42 mmol/mol * Noncompliance with medication * Subject wishes to no longer participate in the study (no reason or time period required)