Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome in which blood flow to the heart muscle is reduced or interrupted. It predominantly affects women between 30 and 55 years of age and typically occurs in the absence of atherosclerosis. For many years, SCAD remained underdiagnosed and has only recently been more systematically recognised. The SCAD-ALIGN trial will be the first randomised study to systematically compare two antiplatelet treatment strategies in patients with SCAD.

SCAD is usually not associated with significant atherosclerosis or the classic vessel occlusion caused by a blood clot. Instead, bleeding occurs within the wall of a coronary artery, causing the vessel layers to separate and thereby impairing or completely obstructing blood flow. Patients develop symptoms of acute myocardial infarction, such as chest pain, shortness of breath, or nausea. A characteristic feature is that these symptoms often occur in individuals without a prior history or risk of heart disease.

Platelets play a crucial role in blood clotting but can also accumulate inside blood vessels and further impair flow. Antiplatelet medications are used to prevent this. In current clinical practice, SCAD patients are often treated according to general guidelines for acute coronary syndrome, which typically include two different antiplatelet therapies, a strategy developed and tested in older patients with proven atherosclerosis.

The SCAD-ALIGN trial is based on a fundamental difference between SCAD and classic heart attacks. In typical heart attacks, a blood clot usually blocks a vessel, and after the implantation of a vascular support device ("stent"), intensive antiplatelet therapy is used to prevent further clot formation. In SCAD, however, the underlying problem is a tear or bleeding within the vessel wall. In this situation, intensive antiplatelet therapy could delay the resolution of the bleeding or even worsen it, thereby adversely affecting the course of the disease. The study will therefore investigate whether a less intensive treatment strategy may be more beneficial in these patients.

The SCAD-ALIGN trial compares two treatment strategies: moderate antiplatelet therapy with a single medication for three months versus more intensive therapy with two agents for three months, followed by nine months of treatment with a single medication. The primary endpoint is a composite of recurrent myocardial ischemia, recurrent SCAD, myocardial infarction, the need for revascularization, and death.

The SCAD-ALIGN trial is part of the Multinational Clinical Trials Initiative of the Global Cardiovascular Research Funders Forum (GCRFF). The study is designed as an international, multicentre, randomised, open-label clinical trial. Because SCAD is a rare condition, close collaboration across national borders is essential. The results are expected to make an important contribution to the development of evidence-based treatment recommendations for SCAD, improve care and quality of life for patients worldwide.

Spontaneous Coronary Artery Dissection (SCAD) is an important cause of acute coronary syndromes (ACS), predominantly in younger women. Evidence to guide optimal antiplatelet therapy is limited. Although dual antiplatelet therapy (DAPT) is commonly prescribed, observational studies have linked DAPT to higher rates of adverse cardiovascular events in conservatively managed SCAD. The SCAD-ALIGN trial is an international, prospective, randomized, open-label, group-sequential adaptative, blinded endpoint-adjudicated with two-parallel groups, multicenter trial comparing an intensive APT strategy versus a moderate APT strategy in patients with ACS due to SCAD who are treated conservatively, i.e., without revascularization. The SCAD-ALIGN study will define the benefit-risk balance of these strategies, inform international guideline committees, and clarify optimal treatment strategies. To demonstrate the superiority of a moderate intensity APT strategy compared to an intensive treatment regimen in patients presenting with an ACS caused by SCAD with planned conservative management with regard to major adverse cardiovascular events (MACE), a composite endpoint consisting of all-cause mortali-ty, myocardial infarction, recurrent SCAD, unplanned coronary revascularization, ischemic stroke, or transient ischemic attack 12 months after randomization was chosen.

Inclusion Criteria:

1. Age ≥18 years.
2. Presentation with an Acute Coronary Syndrome.
3. Suspected SCAD on coronary angiography (determined by the local investigator).
4. Planned conservative treatment of SCAD.
5. Intensive as well as moderate treatment of SCAD is possible.
6. Ability to understand the patient information and to personally sign and date the informed consent to participate in the study, before completing any study-related procedures.
7. The patient is cooperative and available for the entire study.
8. Written and informed consent.
9. For women of childbearing potential: Patient is willing to use adequate contraceptive precautions during the study (until 12 Month FU)

Exclusion Criteria:

1. Hypersensitivity to the study medication.
2. Any indication for oral anticoagulation.
3. Any indication for APT (including thienopyridines, non-thienopyridines, ASA and other anti-thrombotic agents) other than SCAD.
4. Cardiogenic shock at the time of screening.
5. Coronary artery disease (CAD) requiring secondary preventive therapy with APT.
6. Life threatening bleeding (BARC type ≥3) at the time of screening.
7. Active bleeding, such as peptic ulcer, tumor bleeding or intracranial hemor-rhage at the time of screening.
8. History of major bleeding, BARC class ≥3 within 3 months before study in-clusion.
9. Known bleeding diathesis.
10. Known coagulopathy or refusal of blood transfusion.
11. Planned surgery or intervention at high bleeding risk during the study period.
12. Co-administration of contraindicated medications as follows: other P2Y12 inhibitors (prasugrel or ticagrelor); anticoagulants (warfarin, new oral antico-agulants, or chronic therapy with subcutaneous anticoagulants); cytochrome P450 2C19 inhibitors (fluoxetine, moclobemid or voriconazole); probenecid; high dose of methotrexate (≥15 mg/week); lithium.
13. Known pregnancy or lactation.
14. Current participation in another clinical trial with drugs or medicinal products.

to be determined as global study with various stakeholders and country-specific requirements.

A blinded Clinical Event Committee (CEC) will adjudicate all primary outcome and safety events.