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Atrial FibrillationCLOT-LESSNCT07575867

CLOT-LESS - CLOsure Tailored: LEss Antithrombotic Strategy After LAAC for Stroke Prevention

An observational study of Atrial Fibrillation and Stroke Prevention in Patients With Atrial Fibrillation, run by National Medical Research Center for Therapy and Preventive Medicine at 1 site in Russia.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

This is a prospective, non-randomized, observational cohort study conducted at the FSBI "NMRC TPM" of the Ministry of Healthcare of the Russian Federation. Left atrial appendage closure (LAAC) has been shown to be non-inferior to oral anticoagulation for preventing cardioembolic events in patients with atrial… Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
Left Atrial Appendage Closure, Apixaban 2.5 mg BID and Standard-dose DOAC
How many people
464 participants
Where
1 siteRussia
Study dates
Apr 2026to Apr 2032
Phase
Observational
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Study population: The study population comprises adults with documented non-valvular atrial fibrillation who require stroke prevention therapy. Two distinct cohorts will be enrolled: Cohort 1 (LAAC group): Patients with non-valvular atrial fibrillation and elevated thromboembolic risk who have relative or absolute contraindications to long-term oral anticoagulation, history of bleeding complications on anticoagulation, or patient preference for a non-pharmacological stroke prevention strategy. These patients will undergo percutaneous left atrial appendage closure. Cohort 2 (Control group): Patients with non-valvular atrial fibrillation and elevated thromboembolic risk who are appropriate candidates for and willing to continue long-term standard-dose direct oral anticoagulant therapy. Both cohorts will be recruited from the same institution during the same time period to minimize selection bias related to temporal trends in clinical practice.

Who may be able to join

  • Age ≥18 years;
  • Documented nonvalvular AF (≥30 seconds on ECG within previous 12 months);
  • CHA2DS2-VASc score ≥3 for women and ≥2 for men;
  • Signed informed consent to participate in the study;

Who cannot join

  • Active indication for anticoagulation OTHER than atrial fibrillation at the time of enrollment and/or the predicted/unpredicted occurrence of such indications during the entire study period (e.g., mechanical valve, acute VTE, recent PE requiring >3 months anticoagulation);
  • Inability to tolerate at least 3 months of apixaban therapy (for LAAC arm);
  • Indications for antiplatelet therapy or therapy with P2Y12 inhibitors at the time of inclusion and/or the predicted/unpredicted occurrence of such indications during the entire study period;
  • The presence of mechanical prosthetic heart valves, mitral stenosis of severe or moderate degree;
  • Active DVT requiring anticoagulation;
  • Congenital or acquired haemostasis disorders, rheumatic heart disease or recurrent deep vein thrombosis;
Show all 24Show fewer
  • Left ventricular ejection fraction (LVEF) < 30%;
  • Glomerular filtration rate (GFR) < 30 ml/min (stage IV or V chronic kidney disease) or dialysis patient;
  • Severe liver failure, including cirrhosis and Child-Pugh Class C/D;
  • NYHA class IV congestive heart failure;
  • The patient had a myocardial infarction - MI with or without ST segment elevation (STEMI, NSTEMI) with or without intervention, within 30 days before LAAC;
  • The patient had a stroke (of any cause, ischemic or hemorrhagic) within 30 days before LAAC;
  • Intracardiac thrombus before LAAC;
  • Major bleeding according to BARC criteria (type 3 and higher) within 30 days before LAAC or before randomization;
  • Amyloid cardiomyopathy;
  • Platelet count < 100,000 x 109/l;
  • The patient participates in another study, with the exception of observational studies without therapeutic interventions;
  • Pregnant or breast-feeding patients, patients planning pregnancy during the study period;
  • The LAAC procedure was unsuccessful or interrupted for technical reasons;
  • PDL (peridevice leak) ≥ 3 mm;
  • Contraindications for one of the treatment regimens prescribed by the study protocol (including allergic reactions);
  • Planned cardiac or non-cardiac surgical procedure within 30 days before or 90 days after LAAC. Minor procedures not requiring discontinuation of antithrombotic therapy are permitted (e.g., cardioversion, catheter ablation, cataract surgery);
  • The patient has a heart tumor, active infection, signs of physiological tamponade;
  • The documented life expectancy of the patient is less than 12 months;

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Timofey Brontveyn, Medical doctor contact

+79150579995

tbrontveyn.md@gmail.com

Karapet Davtyan, Professor contact

+79037758779

kdavtyan@gnicpm.ru

Russia1 site, 1 recruiting

  • Federal State Budgetary Institution National Medical Research Center for Therapy and Preventive Medicine of the Ministry of Healthсare of the Russian Federation

    Moscow, 101990

    Timofey Brontveyn, Medical doctor, +79150579995, tbrontveyn.md@gmail.com

    Karapet Davtyan, Professor, +79037758779, kdavtyan@gnicpm.ru

    Recruiting

Other trials in Russia

About this study

This is a prospective, non-randomized, observational cohort study conducted at the FSBI "NMRC TPM" of the Ministry of Healthcare of the Russian Federation. Left atrial appendage closure (LAAC) has been shown to be non-inferior to oral anticoagulation for preventing cardioembolic events in patients with atrial fibrillation. However, the optimal post-procedural antithrombotic regimen following LAAC remains unclear, with no consensus on evidence-based therapy. Given current trends in cardiology favoring reduced-intensity antithrombotic strategies, this study aims to contribute to the evidence base by evaluating whether LAAC followed by reduced-dose apixaban (2.5 mg BID) for 3 months with subsequent complete withdrawal of antithrombotic therapy is superior to long-term standard-dose DOAC therapy in patients with non-valvular atrial fibrillation.

Read the detailed description

This is a prospective, non-randomized, observational cohort study enrolling patients with non-valvular atrial fibrillation (NVAF).

Participants will be assigned to one of two groups based on clinical indication. LAAC group: Patients with NVAF undergoing left atrial appendage closure (LAAC) who will receive reduced-dose apixaban (2.5 mg BID) for 3 months, followed by complete withdrawal of antithrombotic therapy. The criterion for anticoagulation discontinuation will be a satisfactory result on transesophageal echocardiography (TEE) or cardiac computed tomography (CT) at 3 months post-implantation, confirming adequate device sealing without significant peri-device leak or device-related thrombosis. Participants will undergo additional TEE or cardiac CT at 6 and 12 months after the procedure and will be followed up by telephone at 18, 24, 30, and 36 months after enrollment.

Control group: Patients with NVAF indicated for long-term oral anticoagulation will receive standard full-dose direct oral anticoagulant (DOAC) therapy. Participants in the control group will be followed up by telephone at 3, 6, 12, 18, 24, 30, and 36 months after enrollment.

Observation period: 36 months. Devices used for LAAC will include the Watchman FLX (Boston Scientific, St. Paul, Minnesota, USA) and the Amplatzer Amulet (Abbott, St. Paul, Minnesota, USA).

Primary endpoint: A composite of major bleeding (BARC type ≥3), all-cause mortality, ischemic stroke, systemic embolism, device-related thrombosis (DRT), and significant peri-device leak over 36 months of follow-up.

Secondary endpoints: Individual components of the primary composite endpoint over 36 months of follow-up.

Propensity score matching will be used to create balanced comparison groups for statistical analysis, adjusting for baseline differences between cohorts.

Being tested
Left Atrial Appendage Closure, Apixaban 2.5 mg BID, Standard-dose DOAC
Keywords
atrial fibrillation, left atrial appendage closure, anticoagulants, reduced dose apixaban
Medical subject headings
Atrial Fibrillation, Hemorrhage, Thromboembolism

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Left Atrial Appendage ClosureDevice

    Also called LAAC

    Percutaneous left atrial appendage closure using Watchman FLX (Boston Scientific) or Amplatzer Amulet (Abbott) devices

  • Apixaban 2.5 mg BIDDrug

    Reduced-dose apixaban 2.5 mg BID for 3 months post-LAAC, followed by complete withdrawal of antithrombotic therapy

  • Standard-dose DOACDrug

    Standard-dose DOAC therapy (e.g., apixaban 5 mg BID, rivaroxaban 20 mg daily, or other DOAC per physician discretion) continued for the duration of follow-up

Study groups in NCT07575867
Study groupRoleWhat they receive
LAAC with reduced-dose anticoagulationPatients undergoing left atrial appendage closure (LAAC) with Watchman FLX or Amplatzer Amulet devices, followed by reduced-dose apixaban (2.5 mg BID) for 3 months with subsequent complete withdrawal of antithrombotic therapy
Receives: Device: Left Atrial Appendage Closure; Drug: Apixaban 2.5 mg BID
Standard-dose DOACPatients receiving long-term standard-dose direct oral anticoagulant (DOAC) therapy per current guidelines
Receives: Drug: Standard-dose DOAC

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Composite of major adverse events

    Composite endpoint including: bleeding events (BARC type ≥3), all-cause death, ischemic stroke, systemic embolism, device-related thrombosis (DRT), and peri-device leak (>3 mm)

    Measured: 36 months from enrollment

Secondary outcomes (6)

  1. Major bleeding events

    Incidence of bleeding events classified as BARC type 3 or higher

    Measured: 36 months from enrollment

  2. All-cause mortality

    Incidence of death from any cause

    Measured: 36 months from enrollment

  3. Ischemic stroke

    Incidence of ischemic cerebrovascular events confirmed by imaging

    Measured: 36 months from enrollment

  4. Systemic embolism

    Incidence of systemic embolic events excluding stroke

    Measured: 36 months from enrollment

  5. Device-related thrombosis

    Incidence of thrombus formation on the LAAC device detected by imaging (LAAC group only)

    Measured: 36 months from enrollment

  6. Peri-device leak

    Incidence of peri-device leak >3 mm detected by transesophageal echocardiography or cardiac CT (LAAC group only)

    Measured: 36 months from enrollment

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted8 May 2026
  2. Study startApr 2026 (estimated)
  3. Primary completionApr 2032 (estimated)
  4. Study completionApr 2032 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Observational
Observational model
Cohort
Time perspective
Prospective
Enrolment
464 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07575867
Sponsor's protocol ID
03-03/26
Acronym
CLOT-LESS
Status last verified
May 2026
First submitted
4 May 2026
Last updated
8 May 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No

Publications

  • Potpara T, Grygier M, Hausler KG, Nielsen-Kudsk JE, Berti S, Genovesi S, Marijon E, Boveda S, Tzikas A, Boriani G, Boersma LVA, Tondo C, De Potter T, Lip GYH, Schnabel RB, Bauersachs R, Senzolo M, Basile C, Bianchi S, Osmancik P, Schmidt B, Landmesser U, Dohner W, Hindricks G, Kovac J, Camm AJ. Practical guide on left atrial appendage closure for the non-implanting physician: an international consensus paper. Europace. 2024 Mar 30;26(4):euae035. doi: 10.1093/europace/euae035.

    PubMed 38291925

  • Continisio S, Montonati C, Angelini F, Bocchino PP, Carbonaro C, Giacobbe F, Dusi V, De Filippo O, Ielasi A, Giannino G, Boldi E, Fabris T, D'Ascenzo F, De Ferrari GM, Tarantini G. Single versus dual antiplatelet therapy following percutaneous left atrial appendage closure-A systematic review and meta-analysis. Eur J Clin Invest. 2024 Aug;54(8):e14209. doi: 10.1111/eci.14209. Epub 2024 Apr 10.

    PubMed 38597271

  • Kramer A, Korsholm K, Nielsen-Kudsk JE. Single antiplatelet therapy following Amplatzer left atrial appendage occlusion. EuroIntervention. 2024 Mar 4;20(5):e301-e311. doi: 10.4244/EIJ-D-23-00684.

    PubMed 38436367

  • Li X, Jin Q, Yao Y, Zhang X, Lv Q. Clinical Effectiveness and Safety Comparison between Reduced Rivaroxaban Dose and Dual Antiplatelet Therapy for Nonvalvular Atrial Fibrillation Patients Following Percutaneous Left Atrial Appendage Closure: A Prospective Observational Study. Rev Cardiovasc Med. 2023 Nov 27;24(11):335. doi: 10.31083/j.rcm2411335. eCollection 2023 Nov.

    PubMed 39076450

  • Cepas-Guillen PL, Flores-Umanzor E, Regueiro A, Brugaletta S, Ibanez C, Sanchis L, Sitges M, Rodes-Cabau J, Sabate M, Freixa X. Low Dose of Direct Oral Anticoagulants after Left Atrial Appendage Occlusion. J Cardiovasc Dev Dis. 2021 Oct 28;8(11):142. doi: 10.3390/jcdd8110142.

    PubMed 34821695

  • Faroux L, Cruz-Gonzalez I, Arzamendi D, Freixa X, Nombela-Franco L, Peral V, Caneiro-Queija B, Mangieri A, Trejo-Velasco B, Asmarats L, Regueiro A, McInerney A, Mas-Llado C, Estevez-Loureiro R, Laricchia A, O'Hara G, Rodes-Cabau J. Short-term direct oral anticoagulation or dual antiplatelet therapy following left atrial appendage closure in patients with relative contraindications to chronic anticoagulation therapy. Int J Cardiol. 2021 Jun 15;333:77-82. doi: 10.1016/j.ijcard.2021.02.054. Epub 2021 Feb 27.

    PubMed 33647365

  • Bergmann MW, Betts TR, Sievert H, Schmidt B, Pokushalov E, Kische S, Schmitz T, Meincke F, Stein KM, Boersma LVA, Ince H. Safety and efficacy of early anticoagulation drug regimens after WATCHMAN left atrial appendage closure: three-month data from the EWOLUTION prospective, multicentre, monitored international WATCHMAN LAA closure registry. EuroIntervention. 2017 Sep 20;13(7):877-884. doi: 10.4244/EIJ-D-17-00042.

    PubMed 28606886

  • Freixa X, Cruz-Gonzalez I, Cepas-Guillen P, Millan X, Antunez-Muinos P, Flores-Umanzor E, Asmarats L, Regueiro A, Lopez-Tejero S, Li CP, Sanchis L, Rodes-Cabau J, Arzamendi D. Low-Dose Direct Oral Anticoagulation vs Dual Antiplatelet Therapy After Left Atrial Appendage Occlusion: The ADALA Randomized Clinical Trial. JAMA Cardiol. 2024 Oct 1;9(10):922-926. doi: 10.1001/jamacardio.2024.2335.

    PubMed 39110427

  • Vignali L, Gurgoglione FL, Barocelli F, Cattabiani MA, Solinas E, Maini A, Tadonio I, Benatti G, Pela G, Coli S, Ardissino D, Niccoli G. Looking for optimal antithrombotic strategy after transcatheter left atrial appendage occlusion: a real-world comparison of different antiplatelet regimens. Int J Cardiol. 2023 Jan 15;371:92-99. doi: 10.1016/j.ijcard.2022.09.066. Epub 2022 Sep 29.

    PubMed 36181948

  • Zhou Q, Liu X, Gu ZC, Yang X, Huang XH, Wu YZ, Tao YY, Wei M. Short-term antiplatelet versus anticoagulant therapy after left atrial appendage closure: a systematic review and meta-analysis. J Thromb Thrombolysis. 2024 Feb;57(2):194-203. doi: 10.1007/s11239-023-02919-2. Epub 2024 Jan 5.

    PubMed 38180590

  • Wazni OM, Saliba WI, Nair DG, Marijon E, Schmidt B, Hounshell T, Ebelt H, Skurk C, Oza S, Patel C, Kanagasundram A, Sadhu A, Sundaram S, Osorio J, Mark G, Gupta M, DeLurgio DB, Olson J, Nielsen-Kudsk JE, Boersma LVA, Healey JS, Phillips KP, Asch FM, Wolski K, Roy K, Christen T, Sutton BS, Stein KM, Reddy VY; OPTION Trial Investigators. Left Atrial Appendage Closure after Ablation for Atrial Fibrillation. N Engl J Med. 2025 Apr 3;392(13):1277-1287. doi: 10.1056/NEJMoa2408308. Epub 2024 Nov 16.

    PubMed 39555822

  • Raffo C, Greco A, Capodanno D. Antithrombotic therapy after left atrial appendage occlusion. Expert Rev Cardiovasc Ther. 2025 Apr;23(4):141-152. doi: 10.1080/14779072.2025.2486154. Epub 2025 Apr 3.

    PubMed 40151884

  • Osmancik P, Herman D, Neuzil P, Hala P, Taborsky M, Kala P, Poloczek M, Stasek J, Haman L, Branny M, Chovancik J, Cervinka P, Holy J, Kovarnik T, Zemanek D, Havranek S, Vancura V, Peichl P, Tousek P, Lekesova V, Jarkovsky J, Novackova M, Benesova K, Widimsky P, Reddy VY; PRAGUE-17 Trial Investigators. 4-Year Outcomes After Left Atrial Appendage Closure Versus Nonwarfarin Oral Anticoagulation for Atrial Fibrillation. J Am Coll Cardiol. 2022 Jan 4;79(1):1-14. doi: 10.1016/j.jacc.2021.10.023. Epub 2021 Nov 5.

    PubMed 34748929

Questions about this trial

What is this clinical trial studying?

An observational study of Atrial Fibrillation and Stroke Prevention in Patients With Atrial Fibrillation, run by National Medical Research Center for Therapy and Preventive Medicine at 1 site in Russia.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 4 inclusion and 24 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 8 May 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Russia. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Timofey Brontveyn, Medical doctor (+79150579995, tbrontveyn.md@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Composite of major adverse events (time frame: 36 months from enrollment). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07575867, which also lists 13 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 May 2026; AzTrials last refreshed its copy on 26 Oct 2026.

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