TRACS-PRIME is a prospective, randomized, multicenter clinical trial evaluating whether transcatheter aortic valve implantation (TAVI) can be performed safely and effectively in selected hospitals without on-site cardiac surgery, when appropriate patient selection, experienced operators, advanced imaging, and established transfer pathways are available. The study will include patients with severe symptomatic aortic stenosis who have an indication for TAVI confirmed by a multidisciplinary Heart Team. Eligible patients will be randomized to undergo TAVI either in a center without on-site cardiac surgery or in a center with on-site cardiac surgery. All procedures will be performed according to current standards of care by experienced TAVI operators. The main purpose of the study is to determine whether TAVI performed in centers without on-site cardiac surgery is not inferior to TAVI performed in centers with on-site cardiac surgery with respect to clinical outcomes at 1 year. The primary clinical outcome includes death from any cause, stroke, or hospitalization related to the procedure or the implanted valve. The study will also assess safety outcomes, including valve-related death and major procedural or technical complications. Participants will be followed after hospital discharge to assess clinical events, safety, and longer-term outcomes. An independent committee blinded to treatment allocation will review clinical events, and an independent Data Safety Monitoring Board will monitor patient safety during the trial.

Severe symptomatic aortic stenosis is a common and clinically relevant condition in elderly and high-risk patients. Transcatheter aortic valve implantation (TAVI) is an established treatment option for patients with an appropriate indication after multidisciplinary Heart Team evaluation. As the number of patients eligible for TAVI continues to increase, access to timely treatment may be limited by the availability and capacity of hospitals with on-site cardiac surgery. Historically, TAVI has generally been performed in centers with on-site cardiac surgery because of the potential need for emergency surgical management of rare but severe procedural complications. However, advances in patient selection, pre-procedural imaging, device technology, procedural planning, and operator experience have reduced the frequency of complications requiring emergent cardiac surgery. These developments have raised the question of whether selected patients can safely undergo TAVI in appropriately organized centers without on-site cardiac surgery, provided that strict procedural safeguards are in place. The TRACS study was previously conducted as a pilot randomized clinical project to evaluate this strategy. That study supported the feasibility and safety of performing TAVI in selected centers without on-site cardiac surgery under a structured protocol, experienced operators, multidisciplinary patient selection, and predefined safety procedures. TRACS-PRIME is designed to extend this experience in a larger and more generalizable randomized trial. TRACS-PRIME is a prospective, randomized, multicenter, open-label trial with blinded adjudication of clinical outcomes. Patients with severe aortic stenosis and an indication for TAVI confirmed by a multidisciplinary Heart Team will be considered for enrollment. Before randomization, patients will undergo standard clinical, echocardiographic, laboratory, coronary, and computed tomography evaluation to confirm eligibility, assess procedural feasibility, and identify factors that may increase procedural risk. Eligible patients who provide written informed consent will be randomized to one of two treatment strategies. In the experimental strategy, TAVI will be performed in a participating center without on-site cardiac surgery. These centers must have experienced TAVI operators, advanced cardiac imaging, established collaboration with a referral cardiac surgery department, and predefined procedures for rapid transfer in case of complications. In the control strategy, TAVI will be performed in a center with on-site cardiac surgery. In both groups, the procedure will be performed according to current guidelines, local standards of care, and the judgment of experienced TAVI operators. The study is intended to evaluate whether TAVI performed in centers without on-site cardiac surgery is not inferior to TAVI performed in centers with on-site cardiac surgery in terms of clinical efficacy and safety at 1 year. Clinical events will be collected prospectively and adjudicated by an independent Clinical Events Committee blinded to treatment allocation. Patient safety and trial conduct will be monitored by an independent Data Safety Monitoring Board. After hospital discharge, participants will undergo structured clinical follow-up to assess clinical status, adverse events, hospitalizations, and other relevant outcomes. The overall aim of TRACS-PRIME is to determine whether a carefully controlled strategy of TAVI in selected centers without on-site cardiac surgery can preserve patient safety while potentially improving access to timely treatment for patients with severe aortic stenosis.

Inclusion criteria

1. Severe aortic stenosis
2. Indication to TAVI confirmed by the Heart Team

AND one of the following enrichment criteria:

1. Prohibitive operative risk
2. High surgical risk as defined as STS score >8%
3. Porcelain aorta or severely atherosclerotic aorta
4. Frailty/Reduced physical performance
5. Severe liver disease/cirrhosis
6. Hostile chest and/or internal mammalian artery or other critical conduit(s) crossing midline and/or adhering to the posterior table of the sternum
7. Severe pulmonary hypertension and/or severe right ventricular dysfunction
8. Age ≥85 years
9. Severe Chronic Obstructive Pulmonary Disease (COPD) The criteria listed above qualify the patient for eligibility in the study if present immediately after the heart team has indicated TAVI. However, this does not exclude patients without these criteria from entering the study if the heart team's evaluation still considers their risk/benefit profile appropriate for inclusion in the protocol.

Exclusion criteria

1. Unsuitable for transfemoral TAVI
2. Emergent TAVI
3. Non-cardiovascular comorbidity reducing life expectancy to <1 year
4. Any factor precluding 1-year follow-up
5. Refusal of informed consent

Individual participant data may be made available upon reasonable request after publication of the main study results. Requests will be reviewed by the Steering Committee and will be considered based on scientific merit, feasibility, participant privacy, and compliance with applicable ethical and regulatory requirements. Any data sharing will require appropriate approvals and a data use agreement.

The trial is open-label because the treatment setting cannot be concealed from participants, care providers, or investigators. Clinical outcomes are assessed by an independent Clinical Events Committee whose members are blinded to treatment allocation, participating center, and patient identifiers. Adjudication is performed according to predefined endpoint definitions.