2.1 Study subjects
Patient enrollment criteria: age ≥18 years old; diagnosed with severe calcific AS by echocardiography with a maximum aortic jet velocity >4.0 m/s and mean gradient >40 mm Hg, or continuity equation valve area <1.0 cm2, or valve area indexed for body surface area (BSA) <0.6 cm2/m2;12considered for a biological aortic valve. Exclusion criteria included planned and unplanned concomitant procedure, history of previous cardiac surgery, thoracic deformity, porcelain ascending aorta, and high surgical risk if patient’s Society of Thoracic Surgeons (STS) score was higher than 8%.