Advance care paramedics will be provided with 12-lead ECG monitors to help detect STEMI heart attacks.
The monitors are to be used before a patient arrives at hospital.
The device will let a paramedic know whether a specific type of heart attack, known as an ST-segment elevated myocardial infarction, or STEMI, is underway.
Such heart attacks are caused when coronary arteries are blocked. They require immediate treatment with drugs or surgery.
If the monitor indicates such a heart attack is occurring, the paramedic can notify the hospital so that staff can prepare appropriate medication or get ready to begin surgery.
Toronto EMS staff will begin to use the device immediately on patients who report chest pains.
Dr. Brian Schwartz, an emergency physician and director of the Sunnybrook-Osler Centre for Prehospital Care in Toronto, said the device would enable doctors to determine more quickly the best treatment for a patient.
Schwartz said it would save valuable time.
"By treating patients more quickly, we can reduce their chances of dying significantly, and we can save much more heart muscle so people can have a better quality of life," he said.
Toronto Emergency Medical Services said Wednesday that with early diagnosis and treatment of these specific types of heart attacks, mortality rates could decrease by 10 per cent.
It estimates that about 1,200 patients a year in the city suffer from such heart attacks.