Additional Study Information: Aortic stenosis (AS) or narrowing of the arteries remains one of the most common valvular diseases in the Western population requiring intervention. The deterioration of the aortic valve is more common in the older population and usually along with coronary artery disease (CAD) requires the need for treatment. This is a study that is collecting safety and effectiveness data in a high or extreme surgical risk patient population with symptomatic, severe native AS and who meet eligibility criteria for implantation of the PorticoNG valve. The Portico NG Valve (along with the delivery and loading system) is indicated for transcatheter delivery in patients with symptomatic severe aortic stenosis who are considered high or extreme surgical risk. Subjects participating in the clinical study will be followed for a total of 5 years with data collected at screening, baseline, procedure, prior to hospital discharge, and follow-up at 30 days, 12 months, and annually thereafter up to 5 years. The expected duration of enrollment is 12 months, and the total duration of the clinical study is expected to be 6.5 years.