Updated May 2026 · ClinicalTrials.gov
The HALT Biomarker Study
Circulating Biomarkers of Hypo-Attenuated Leaflet Thickening After Transcatheter Aortic Valve Replacement
The HALT Biomarker Study (NCT04552275) is a Phase 1 interventional studying Aortic Stenosis and Hypo-attenuated Leaflet Thickening, sponsored by Massachusetts General Hospital. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.
About This Trial
The purpose of the HALT Biomarkers study are to identify a panel of circulating proteins that discriminates between patients with and without Hypo-Attenuated Leaflet Thickening (HALT) and can be used to supplement the diagnosis of HALT; to characterize changes in circulating proteins after treatment of HALT with systemic anticoagulation; and to identify circulating proteins that predict the occurrence of HALT. The study population will be adult patients undergoing transfemoral transcatheter aortic valve replacement (TAVR) for severe aortic stenosis (AS) or bioprosthetic valve degeneration. Enrollment will continue until 30 patients with HALT are identified for completion of phase 1. Based on a HALT incidence rate of 10%, we anticipate enrolling 300 patients. Patients are enrolled prior to undergoing transfemoral TAVR. Blood samples, clinical data and echocardiograms will be collected at the following timepoints: baseline (pre-TAVR, T0), post-TAVR (pre-discharge, T1), 30-day follow-up (window 3-9 weeks, T2), and 6-month follow-up (T3). Cardiac 4D CT will be performed at the 30-day follow-up visit to screen for the occurrence of HALT. Patients with HALT will be treated with systemic anticoagulation for 5-6 months, at which point a follow-up CT scan and blood sample will be obtained. Control subjects will also undergo a 6-month study visit with blood sample collection. The study will be conducted within two phases. Phase 1 will serve as a derivation / discovery study in which candidate protein biomarkers of HALT will be identified. Once this is successfully completed, a second cohort will be enrolled within phase 2. Phase 2 will be performed under the auspices a future contract or amendment and will seek to cross-validate the initial study findings.
What Stage of Research Is This?
Phase 1 trials test a new treatment for the first time in humans, focusing on safety, dosing, and how the body processes the drug. For Aortic Stenosis, a Phase 1 study typically enrolls a small number of participants — often healthy volunteers or patients who have exhausted standard treatment options. Phase 1 results determine whether a treatment moves into larger Phase 2 efficacy studies.
This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.
A target enrollment of 300 participants makes this a sizable late-stage trial. Studies in this range typically have enough power to detect clinically meaningful differences from a comparator and to characterize less-common side effects.
Who May Be Eligible (Plain English)
These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.
Original Eligibility Criteria
View original clinical language
Treatments Being Tested
Proteomics Analysis
Determine a panel of circulating proteins that discriminates between patients with and without Hypo-Attenuated Leaflet Thickening (HALT)
Locations (3)
Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.
How to Talk to Your Doctor About This Trial
Bring the printable summary of this trial — including the NCT ID (NCT04552275), the sponsor (Massachusetts General Hospital), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.
Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.
Authoritative Sources
The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.
Frequently Asked Questions
What is the NCT04552275 clinical trial studying?
The purpose of the HALT Biomarkers study are to identify a panel of circulating proteins that discriminates between patients with and without Hypo-Attenuated Leaflet Thickening (HALT) and can be used to supplement the diagnosis of HALT; to characterize changes in circulating proteins after treatment of HALT with systemic anticoagulation; and to identify circulating proteins that predict the occurrence of HALT. The study population will be adult patients undergoing transfemoral transcatheter aortic valve replacement (TAVR) for severe aortic stenosis (AS) or bioprosthetic valve degeneration. En… The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.
Who can participate in NCT04552275?
Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.
How do I contact the trial site for NCT04552275?
Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.
Is participating in a clinical trial safe?
Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.
Where can I verify the data on this page?
Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.
How This Page Is Built
Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.
Source: ClinicalTrials.gov API v2 record for NCT04552275. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT04552275. Data: ClinicalTrials.gov."
Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.
Last updated 2026-05-08 · Data from ClinicalTrials.gov.