The Echo-AVCS Study is an investigator-initiated, prospective, multicenter observational study designed to derive and validate an artificial intelligence (AI)-based echocardiographic aortic valve calcium score (Echo-AVCS) for confirming severe aortic stenosis (AS). Transthoracic echocardiography (TTE) is the standard imaging modality for assessing AS severity; however, discrepancies between valve area and transvalvular gradient measurements may complicate diagnosis, particularly in low-flow or discordant AS presentations. Cardiac computed tomography (CT)-derived aortic valve calcium scoring is currently used to resolve diagnostic uncertainty, but it involves additional cost and radiation exposure. This study will enroll consecutive adult patients undergoing clinically indicated TTE and cardiac CT with calcium scoring performed within 3 months. Standardized echocardiographic images will be centrally analyzed using dedicated AI-based image segmentation and machine learning methods to quantify aortic valve calcification directly from TTE images. CT-derived aortic valve calcium score will serve as the reference standard. The primary objective is to derive and validate the Echo-AVCS score for identifying severe AS. Secondary objectives include determination of sex-specific diagnostic thresholds, correlation with CT calcium volume, association with symptoms and NYHA class, and evaluation of prognostic associations with aortic valve replacement, heart failure hospitalization, cardiovascular events, and mortality at 1-year follow-up.

Inclusion Criteria:

• Age > 18 years old
• Clinical indication for standard transthoracic echocardiography.
• Clinical indication for cardiac CT with available calcium score.
• 3-month time interval between transthoracic echocardiography and cardiac CT.
• Able to give informed consent.

Exclusion Criteria:

• Patients with inadequate transthoracic echocardiographic images.
• Poor quality cardiac CT, inadequate for standard calcium score assessment.
• Patients with known prior stents and/or coronary artery bypass grafts.
• Patients with known previous percutaneous or surgical aortic valve replacement.
• Patients with active or a history of endocarditis.
• Patients with congenital heart defects (other than isolated bicuspid aortic valve).

The Echo-CA score Study is an investigator-initiated, prospective, multicenter study of consecutive patients undergoing clinically indicated standard transthoracic echocardiography and cardiac CT with available calcium score performed within 3 months. The study population is expected to include approximately 50% patients with severe AS and 50% without severe AS, in order to ensure a balanced case-control distribution and optimize the precision of diagnostic performance estimates. All patients will be managed according to current standards of care. Clinical evaluation will include systematic collection of cardiovascular risk factors, comorbidities, medical therapy, and detailed symptom assessment (angina, syncope, dyspnea), as well as NYHA functional class. Each participant will undergo: i) comprehensive transthoracic echocardiography (TTE) performed according to current ESC Guideline; ii) cardiac CT with aortic valve calcium quantification, performed according to contemporary acquisiti