How could ischemia be prevented?

Several ways. Cardiac ischemia can be prevented either by improving the supply of blood to the heart, or reducing the demand for blood by the heart. The supply can be increased by bypass surgery, angioplasty, stents, and some medications. The demand can be reduced by restricting the activity of the patient, controlling arrhythmias, and medications such as beta blockers.
In general. Avoid atherosclerosis no smoking excellent diet bmi. Weight at recommended for height regular exercize.