The goal of this clinical trial is to investigate the impact of repetitive acute Cyclosporine A (CsA) bolus therapy in patients suffering from TTS with an elevated risk of impaired outcome. The main question it aims to answer is whether CsA reduces myocardial injury (primary outcome). Participants will receive CsA or placebo at baseline and every 12h in the first 24h after study inclusion. Researchers will compare CsA and the placebo group to see if a) myocardial injury is reduced, and b) ejection fraction is improved compared to baseline, as well as several other secondary endpoints over a one year follow-up.

Takotsubo syndrome (TTS) has been suggested to be caused by catecholamine excess with myocardial inflammation-enhanced cardiac injury. Substantial morbidity and mortality have repeatedly been reported, even though reduced ejection fraction frequently recovers spontaneously. So far there is no evidence-based treatment available. In a clinically relevant mouse model of catecholamine-driven TTS, cyclosporine A (CsA) bolus therapy markedly improves outcome, likely mediated via suppression of calcineurin-driven inflammation. The investigators have thus designed a pilot multicentre randomized controlled trial (RCT) to investigate the impact of repetitive CsA bolus therapy vs. placebo in acute TTS patients with an increased risk of intrahospital complications and a 32% estimated 5-year mortality. As primary outcome myocardial damage will be compared between groups via high-sensitive Troponin T plasma area under the curve (AUC). Recovery of cardiac function, the extent of myocardial oedema at 72h, length of hospital-stay, 30-day-, and 1-year composite clinical outcome as well as psychosocial and quality of life self-assessment will be secondary endpoints. The results of this trial may reveal CsA as a first pathophysiology-driven treatment option of TTS and enable a phase III follow-up trial with outcome parameters as primary endpoint.

Key inclusion criteria:

• Patients aged over 18
• Enrollment and first IMP administration within 24 hours after cardiac catheterization
• Regional Wall Motion Abnormality (WMA) consistent with TTS in angiography or echocardiography
• InterTAK prognostic score- or a GEIST Score ≥ 9 -
• Written informed consent

Key exclusion Criteria:

• Acute coronary syndrome (ACS) with significant coronary stenosis potentially associated with wall motion abnormalities (WMA) or percutaneous coronary intervention (PCI)
• Infection (defined as concomitant infection with a positive blood culture at the time of study inclusion)
• History of hypersensitivity to cyclosporine
• History of hypersensitivity to egg, peanut or soybean proteins
• History of chronic renal insufficiency (either creatinin clearance <30 ml/min/1.73m² or current medical care for severe renal insufficiency)
• History of liver insufficiency
• Uncontrolled hypertension at the time of screening for study inclusion (systolic blood pressure >180mmHg and/or diastolic blood pressure >110mmHg)
• Current medication with any compound containing Hypericum perforatum (St. John's worth) or Stiripentol or Aliskiren or Bosentan or Rosuvastatine (Rosuvastatine >5mg within 24h intake<48h before IMP administration)
• Female patients currently pregnant or women of childbearing age without negative pregnancy test or without effective contraception
• Any disorder associated with immunological dysfunction ≤6 months prior to presentation (autoimmune disease, known positive serology for HIV or hepatitis)
• Immunosuppressive, chemotherapeutical, or antibody treatment
• Participation in other clinical trials except for non interventional trials

Participants, investigators, care providers, and outcomes assessors are masked from study arm affiliation.