This is a "before and after" observational study of a therapeutic strategy to treat patients with confirmed ST-segment myocardial infarction (STEMI) with remote ischemic conditioning (RIC) before undergoing primary percutaneous coronary intervention (PCI). RIC is the purposeful application of brief, intermittent cycles of limb occlusion by inflation/deflation of a pneumatic cuff. The autoRIC device is an automatic RIC delivery device (the autoRIC® Device; CellAegis Devices Inc, Toronto, ON) that has received clearance from Health Canada for this use under the direction of a health care professional. Paramedics in the Peel and Halton regional emergency services and the Emergency department (ED) staff of Brampton Civic Hospital and Mississauga Hospital will treat patients experiencing STEMI with autoRIC, and study data will be collected from existing patient records.

The 'before' group will include up to 900 patients who were treated before autoRIC implementation in the services and hospitals. These patients would have had a STEMI and undergone PCI, but did not receive the autoRIC device. The 'after' group will include up to 900 eligible patients who have had RIC treatment with the autoRIC device at the two participating sites following implementation in the services and hospitals.

The primary analyses will compare the short-term and long-term outcomes of eligible patients who have received completed primary PCI for STEMI in the time period before the implementation and following the implementation of this RIC strategy. In addition, a health economic analysis will be conducted to determine the cost-effectiveness of the therapeutic strategy to treat STEMI patients with RIC prior to PCI.

Inclusion Criteria:

• 18 years of age and older;
• patients diagnosed with STEMI in the prehospital environment by responding paramedics from Peel Regional Paramedic Services or Halton Emergency Medical Service and transported to the PCI laboratory of Brampton Civic Hospital or Trillium Health Partners;
• walk-in patients diagnosed with STEMI in the ED of either of these two facilities.

Exclusion Criteria:

• left-bundle branch block;
• Lymphedema on either arm
• PICC Line on either arm
• AV fistula or no palpable pulse on either arm;
• patient has a known bleeding disorder or known abnormality of blood flow to the left arm;
• patient has peripheral nerve injury, abnormal nerve supply, peripheral neuropathy or pre- existing traumatic injury to the limb to be treated (left-arm).