This study proposes to conduct the switch from ticagrelor to prasugrel in an organized stepwise manner, to allow for the evaluation of the relative efficacy of prasugrel versus ticagrelor using a stepped-wedge cluster randomized trial design.

The SWITCH SWEDEHEART trial is a prospective, multicenter, open-label, cross-sectional, stepped wedge cluster randomized clinical study, in which administrative regions in Sweden will constitute the clusters. Many administrative regions have already decided to switch from ticagrelor to prasugrel for the treatment of patients with ACS. The order in which the regions make the switch will be randomly assigned. At the start of the study, all regions will utilize and prescribe ticagrelor as the P2Y12 inhibitor drug of choice for patients with ACS. After 9 months, one cluster will switch from ticagrelor to prasugrel as the P2Y12 inhibitor of choice for patients with ACS. Every 9 months, an additional cluster will switch to prasugrel until all clusters have switched from ticagrelor to prasugrel. Study enrollment will be stop 9 months after the last cluster has switched to prasugrel. The study will be terminated when 1-year follow-up has been concluded for all patients.

All patients who are hospitalized due to acute coronary syndrome in any of the health care regions over the course of the study period will be included. All patients will be treated according to local treatment guidelines at the time of the index hospitalization (prasugrel or ticagrelor) for at least 12 months. Patients with relative or absolute contra-indications for the study drugs or patients experiencing side effects requiring treatment changes will be treated according to current guidelines at the discretion of the treating physician.

The patients will be identified via the Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDEHEART) registry. The events at 1 year will be identified and extracted from Patient registry (Socialstyrelsen), Population registry (Folkbokföringen), Causes of death registry (Socialstyrelsen). Compliance with the treatment after the transition from ticagrelor to prasugrel will be followed through Dispensed drug registry (Socialstyrelsen).

The primary analysis population will be patients undergoing percutaneous coronary intervention (PCI) due to ACS. The secondary analysis population will be all patients hospitalized with ACS.

Primary objective:

• To investigate the clinical efficacy of Prasugrel compared to Ticagrelor

Secondary objectives:

• To investigate the cost effectiveness of Prasugrel compared to Ticagrelor with respect to the 1-year outcomes.
• To investigate clinical safety of Prasugrel compared to Ticagrelor

Inclusion Criteria:

• Patients hospitalized for Acute coronary syndrome, as defined by the European Society of Cardiology, at any hospital participating in the study, and included in the SWEDEHEART registry during index hospitalization
• Age ≥ 18 years.