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Background: Takotsubo syndrome (TS) is a life-threatening acute heart failure syndrome without any evidence-based treatment options. No treatment for TS has been examined in a randomized trial.

Study design and objectives: BROKEN-SWEDEHEART is a multicenter, randomized, open-label, registry-based 2 × 2 factorial clinical trial in patients with TS designed to test whether treatment with adenosine and dipyridamole accelerates cardiac recovery and improves clinical outcomes compared to standard care (study 1); and apixaban reduces the risk of thromboembolic events compared to no treatment with antithrombotic drugs (study 2). The trial will enroll 1,000 patients. Study 1 (adenosine hypothesis) will evaluate 2 coprimary end points: (1) wall motion score index at 48 to 96 hours (evaluated in the first 200 patients); and (2) the composite of death, cardiac arrest, need for mechanical assist device or heart failure hospitalization within 30 days or left ventricular ejection fraction <50% at 48 to 96 hours (evaluated in 1,000 patients). The primary end point in study 2 (apixaban hypothesis) is the composite of death or thromboembolic events within 30 days or the presence of intraventricular thrombus on echocardiography at 48 to 96 hours.

Conclusions: BROKEN-SWEDEHEART will be the first prospective randomized multicenter trial in patients with TS. It is designed as 2 parallel studies to evaluate whether adenosine accelerates cardiac recovery and improves cardiac function in the acute phase and the efficacy of anticoagulation therapy for preventing thromboembolic complications in TS. If either of its component studies is successful, the trial will provide the first evidence-based treatment recommendation in TS.

Clinical trials identifier: The trial has been approved by the Swedish Medicinal Product Agency and the Swedish Ethical Board and is registered at ClinicalTrials.gov (NCT04666454).