POPular ACE TAVI (NCT05774691) is an investigator-initiated, multicenter, double-blind, placebo-controlled, randomized clinical trial. The trial tests the hypothesis that routine protamine administration reduces all-cause mortality or clinically relevant bleeding within 30 days after TAVI compared with selective protamine administration. A total of 1,000 patients will be randomized 1:1 to routine versus selective protamine administration and followed for 30 days ( Figure 1 ).

Flowchart POPular ACE TAVI trial. The activated clotting time is measured before sheath removal. Syringe A (containing either protamine or placebo, depending on randomization) is administered in all patients just before removal of the large-bore arterial sheath. If hemostasis is not achieved within 10 minutes after sheath removal, syringe B (containing either placebo or protamine) may be administered upon request of the operator. TAVI, transcatheter aortic valve implantation; PCI, percutaneous coronary intervention; VARC, Valve Academic Research Consortium.

Patients undergoing transfemoral TAVI, aged >18 years, and willing to provide written informed consent are eligible for enrollment. Key exclusion criteria are a documented protamine allergy or anaphylaxis, recent PCI (<3 months before TAVI), or planned arterial access via surgical cut-down. Patients are recruited at 6 sites in the Netherlands and Belgium. To maximize generalizability and to establish a “real-life” study population, all participating sites are strongly recommended to include patients on a consecutive basis. Recruitment started in November 2023 and will continue until 1000 patients have been randomized. The trial will conclude after completion of the 30‑day follow‑up for the last randomized patient. As of July 2025, 803 patients have been enrolled; completion is anticipated in December 2025.

After screening and enrollment, patients are randomized shortly before TAVI. Randomization is performed using the REDCap eCRF Randomization module. Patients are randomized in a 1:1 ratio, with variable block sizes, stratified by study site and concomitant antithrombotic therapy (single antiplatelet therapy vs. oral anticoagulation or dual antiplatelet therapy). Randomization is performed by an R&D staff member, who records the assignment in the drug accountability file. The study medication is prepared and verified by 2 catheterization laboratory staff members in line with the drug accountability file. They use 2 identical 10 mL syringes. Into 1 syringe, they draw up 10 mL of protamine sulfate (prepared by combining 2 5 mL ampules, 1,400 IU/mL). Into the other, they draw up 10 mL of NaCl 0.9% (placebo). Protamine sulfate and NaCl 0.9% have similar visual characteristics, making it impossible to distinguish between them. The staff members label the syringes “A” and “B” according to the randomization. In patients randomized to the routine protamine administration group, syringe A contains protamine and syringe B placebo. In the selective protamine group syringe A contains placebo and syringe B protamine. Syringe A is administered in all patients intravenously prior to removal of the large-bore arterial sheath. If hemostasis is not achieved within 10 minutes postsheath removal, syringe B may be administered upon request of the operator. In line with the recently published ACE-PROTAVI trial, we expect that syringe B is administered in about 5% in the routine protamine administration group and 15% in the selective protamine administration group. Protamine is administered at a 1:1 ratio (IU) in relation to the total dose of unfractionated heparin. In a recent observational study, complete heparin reversal (1:1) was associated with a significantly lower incidence of major bleeding after TAVI compared with partial reversal (1:0.5). The R&D staff member and 2 designated catheterization laboratory staff members are not allowed to share any information about the treatment assignment or syringe contents with anyone else, particularly not with the operator, the patient, other catheterization laboratory staff members, or study outcome assessors. The exact time of syringe A administration, sheath removal, hemostasis and syringe B (if administered), as well as the activated clotting time before sheath removal, are recorded per patient in dedicated case report forms. The activated clotting time is not used to guide the protamine dose (which is based on the amount of unfractionated heparin administered as described above).

The TAVI procedures are performed according to the local protocols of each participating study site, including choice of valve type, cerebral embolic protection, heparin dosing, and vascular closure strategy. Follow-up visits to assess clinical outcomes are performed at discharge and 30 days after TAVI, which may be conducted on site or by telephone.

The primary outcome is a composite of all-cause mortality and clinically relevant bleeding within 30 days after TAVI. Clinically relevant bleeding is defined as VARC-3 type 1-4 bleeding. Ranked secondary outcomes include clinically relevant bleeding (type 1-4); major, life-threatening, or fatal bleeding (type 2-4); major vascular complications; cardiovascular mortality; and all-cause mortality. Safety outcomes include anaphylaxis, as well as thromboembolic events, defined as the composite of myocardial infarction, ischemic stroke, transient ischemic attack, or noncerebral distal embolization. Furthermore, other outcomes are collected in line with the recommended outcomes according to the VARC-3 document. Except for anaphylaxis, which is defined according to the National Institute of Allergy and Infectious Diseases definition, all clinical outcomes are defined in accordance with the VARC-3 criteria. Bleeding events are also classified according to the Bleeding Academic Research Consortium (BARC) criteria. Other outcomes also include time to hemostasis, procedural hemostasis failure and delayed hemostasis failure. Time to hemostasis is defined as the elapsed time from sheath removal until achievement of arterial hemostasis. Procedural hemostasis failure is defined as either the inability to achieve hemostasis at the arteriotomy site within 20 minutes or the need for alternative treatment (e.g. fem-stop device, or adjunctive endovascular ballooning/stenting). Delayed hemostasis failure is defined as the occurrence of bleeding requiring prolonged manual compression or alternative interventions (new pressure bandage, fem-stop device, endovascular or surgical repair) after initial hemostasis was achieved and the patient is no longer in the catheterization laboratory. Full lists of outcomes are provided in Table 1 .

A blinded clinical endpoint committee (CEC) adjudicates all potential primary, secondary, safety, and other clinical outcomes. The CEC members consist of experienced clinicians with a track record in cardiovascular research. Anonymized source documentation is provided to the CEC, and adjudication is performed according to predefined definitions documented in the endpoint adjudication charter.

This investigator-initiated trial is funded by the St. Antonius Research Fund. There is no industry involvement in the trial. The study is conducted according to the principles of the Declaration of Helsinki, amended by the 64th WMA General Assembly, Fortaleza, Brazil, October 2013, and in accordance with the EU Clinical Trials Regulation and other guidelines, regulations, and acts. Ethics committees in each country and Institutional Review Boards at each participating site authorized the clinical trial protocol. Monitoring is performed according to Good Clinical Practice (GCP) guidelines under the direction of the Research and Development Academy of St. Antonius Hospital. An independent Data Safety Monitoring Board (DSMB) is established to perform safety surveillance on the accruing study data to safeguard the interests of the trial participants. The board discusses the study protocol and (interim) outcomes and provides recommendations to the investigators regarding the continuation of the trial. If the interim results are likely to convince a broad range of clinicians that 1 trial arm is clearly indicated or contraindicated, the DSMB provides advice on whether recruitment should be terminated. In addition, a yearly safety report is submitted to the accredited medical research ethics committees of the concerned Member States.