Avr Thrombosis OutcoMe Study

Inclusion Criteria: 1. Male and female patients aged 18 years or over. 2. Patients diagnosed with aortic valve disease, undergoing surgical or transcatheter AVR and free of exclusion criteria below. 3. The patient is willing and able to understand the Patient Information Sheet and provide informed consent. 4. The patient agrees to comply with the study protocol, including phlebotomy and imaging as required at pre-specified time points. Exclusion Criteria: 1. Inability to provide valid informed consent. 2. Male and female patients aged \< 18 years of age. 3. The patient has, in the opinion of the investigator, significant neurological, hepatic, renal, endocrine, cardiovascular, gastrointestinal, pulmonary, haemorrhagic, metabolic or other disease likely to confound the study requirements or analyses. 4. The patient has a history of substance abuse or demonstrates signs or clinical features of active substance abuse or active psychiatric disease that may result in non-compliance with visits or inability to obtain venous access. 5. Alcohol consumption above recommended safe levels (i.e. more than 14 units per week owing to the potential effects of high alcohol levels on platelet reactivity). 6. Any illness deemed significant by the investigator during the four (4) weeks preceding the screening period of the study such as sepsis. 7. Any major bleeding diathesis or blood dyscrasia (platelets \< 70 x 109/l, Hb \< 8 g/dl, INR \> 1.4, APTT \> x 2 UNL, leucocyte count \< 3.5 x 109/l, neutrophil count \< 1 x 109/l). 8. Currently enrolled in an investigational device or drug trial. 9. Active or disseminated malignancy at the time of recruitment. Additionally, for those patients taking part in the additional 4D CT angiography substudy: 10. Any contraindications to CT angiography: renal failure (Cr\>250 μmol/L or eGFR\<30 mL/min) due to the additional risk of contrast medium nephrotoxicity; or allergy to iodine. 11. Women of childbearing age who have not had a hysterectomy and/or who may be breastfeeding.