Aortic stenosis (AS) is one of the most common valve diseases and is increasing worldwide due to an ageing population. Transcatheter Aortic Valve Replacement (TAVI) is a keyhole procedure that can be done through the groin to replace the narrowed aortic valve with a new valve, avoiding the need for cardiac surgery.Improved device design and greater operator experience has improved TAVI outcomes. It has become the standard treatment option in patients who are at high risk for cardiac surgery and is now being used increasingly in lower risk patients.~Cerebrovascular accidents in TAVI patients remain a significant risk with a reported 3 - 5 % risk. Furthermore, these patients have neurovascular injury that is not clinically identifiable. Covert brain injury has been identified to occur in many surgical and cardiovascular catheter-based interventions such as TAVI and can cause vascular brain injury (VBI).~TAVI valves are manufactured in room air conditions and retain air. Studies in TEVAR (Thoracic Endovascular Aortic Repair) stent grafts have shown release of air when they are deployed in the aorta. In vitro testing of TAVI valves has shown release of air when they are deployed.~Carbon-dioxide (CO2) is 1.5 times denser than air and can displace it. It is 25 times more soluble in blood than air and does not lead to bubble formation. Hence CO2 bubble are unlikely to result in significant damage. CO2 has been used in cardiac surgery with beneficial effects. It has shown to reduce peri-procedural cerebral air embolisation and post operative cognitive dysfunction.~This study aims to look at the neuroprotective benefits of flushing TAVI valves with CO2 and saline versus saline only by reducing air embolisation.~Patients undergoing TAVI will be approached to participate in this study. After consent is obtained, patients will undergo baseline MRI, neurological and neurocognitive testing pre-TAVI. Patient will be randomised to saline only or CO2 and saline flushing of their valves. During their TAVI procedure, they will have transcranial doppler (TCD) monitoring of their middle cerebral artery (MCA) bilaterally to record cerebral embolisation. Patients will also have biomarker testing pre-TAVI, post-TAVI and 24 hours following TAVI. They will have DW-MRI brain between day 1-7 following their TAVI to look for vascular brain injury. Thus MRI will be repeated at 6-months following their TAVI. Patients will also have neurological and neurocognitive testing during their inpatient admission, at 6-weeks and 6-months outpatients.
The study aims to evaluate the processes of a pilot single-centre randomised controlled trial (RCT) of carbon-dioxide flushing of transcatheter aortic valves (TAVI-CO2) versus standard saline flushing of valves (TAVI-S) and assess potential neuroprotection through a number of neurological endpoints for planning of a full-sized RCT