Aortic stenosis (AS) is a common valvular heart disease whose prevalence increases markedly with age-approximately 2-4% in individuals aged 65 years and older, and up to 3.4% for severe AS in those over 75. Degenerative calcific AS predominates in high-income countries, whereas rheumatic disease remains a major cause in low-income regions. With global population aging, the disease burden of AS continues to rise.

Transcatheter aortic valve replacement (TAVR/TAVI), owing to its minimally invasive nature, has become an important treatment option for severe AS and selected aortic regurgitation patients, expanding from high-surgical-risk populations to those at intermediate and low risk. In recent years, the number of TAVR procedures in many regions has surpassed or approached that of surgical aortic valve replacement, and major clinical guidelines have elevated TAVR to a recommended standard therapy.

Conventional TAVR relies on combined fluoroscopic and echocardiographic guidance. However, perioperative complications remain frequent in elderly and high-risk patients, particularly acute kidney injury (AKI), which significantly increases short- and long-term mortality. Contrast exposure during the procedure is a major contributor to AKI; thus, clinical practice increasingly favors strategies that minimize contrast use, such as low-dose and low-kV imaging. Elevated contrast concentration in the renal tubules increases viscosity, prolongs renal exposure, and can lead to tubular injury and renal dysfunction. Continuous radiation exposure during vascular access, device positioning, valve deployment, and post-release assessment also poses safety concerns for both patients and medical staff.

Echocardiography-only guidance for TAVR has therefore emerged as an attractive alternative, with the potential to replace fluoroscopy and contrast for anatomical visualization and device positioning, thereby reducing radiation exposure and contrast-related kidney injury. However, no prospective randomized study has directly compared echocardiography-only guidance with conventional fluoroscopy-plus-echocardiography guidance, and current evidence remains preliminary.

To address this gap, a randomized controlled trial was designed to evaluate whether echocardiography-only guidance is non-inferior to combined fluoroscopic and echocardiographic guidance in terms of device success, while also assessing the safety, efficacy, and clinical feasibility of both approaches.

Inclusion Criteria:

• 1. Patients aged 70 years or older with obvious clinical symptoms or a left ventricular ejection fraction less than 50% due to severe aortic valve stenosis (aortic valve orifice area < 1.0 cm² or peak velocity ≥ 4.0 m/s or mean transvalvular pressure ≥ 40 mmHg); or patients with obvious clinical symptoms of low blood flow and low pressure difference aortic valve stenosis (effective aortic valve orifice area < 1.0 cm², mean transvalvular pressure difference < 40 mmHg, left ventricular ejection fraction < 50%, stroke volume index < 35 ml/m², and diagnosed as true severe aortic valve stenosis by dobutamine stress test);
• 2. Patients aged 65 years ≤ age < 70 years with severe aortic stenosis who have surgical contraindications or high risks, or have other risk factors such as post-chest radiotherapy, liver failure, diffuse severe aortic calcification, extreme weakness, etc., or patients refuse to undergo routine open-chest surgery;
• 3. The patient's anatomical structure is suitable for TAVR and can tolerate transesophageal ultrasound;
• 4. The patient has signed the informed consent form and is willing to participate in this study.

Exclusion Criteria:

• 1. Imaging (ultrasound and/or CT and/or MRI) confirmed a lesion, thrombus or calculus in the left ventricle;
• 2. Severe obstruction of the left ventricular outflow tract;
• 3. Severe right ventricular dysfunction;
• 4. Acute myocardial infarction within 30 days before the procedure;
• 5. Active endocarditis history within 180 days before the procedure;
• 6. Inappropriate aortic root anatomy (such as combined aortic dissection, excessive aortic annulus, risk of coronary artery occlusion, etc.);
• 7. Severe calcification and distortion of the surgical approach;
• 8. Left ventricular ejection fraction less than 20%;
• 9. Other cardiac diseases that require concurrent treatment (such as severe mitral regurgitation, atrial fibrillation, etc.);
• 10. History of stroke or transient ischemic attack within 90 days before the procedure;
• 11. Liver cirrhosis or active liver disease;
• 12. Renal insufficiency (creatinine clearance rate < 30 mL/min) and/or undergoing renal replacement therapy;
• 13. Unable to tolerate anticoagulation therapy during or after the procedure;
• 14. Participating in other drug or device research;
• 15. Any emergency or surgical operation within 30 days before the procedure;
• 16. Other severe comorbidities, even if the valve stenosis is corrected, the expected life expectancy is less than 1 year;
• 17. Other conditions deemed unsuitable for TAVR surgery by the cardiac team.