Inclusion Criteria:  severe aortic stenosis, life expectancy >1 year, patient candidate to percutaneous transfemoral aortic valve implantation after formal indication of our "Heart Team".  Exclusion Criteria:  clinical history of lung cancer or lung surgery, fibrothorax and pneumothorax, pulmonary fibrosis, patients undergoing urgent aortic valvuloplasty, patients admitted for cardiogenic shock, recent (within 1 month) pneumonia or ARDS (Acute Respiratory Distress Syndrome), lack of will to participate, more than moderate aortic regurgitation, valve-in-valve procedures, transapical and transaortic TAVR.