How can healthy people have cardiac arrests with no cause found ? causes great anxiety.

Most times a reason: Many times the patient reports no signs until the acute heart attack event. Many reasons are possible. It may be that the person did not realize that vague symptoms earlier may have been heart related. Other times, a blockage is not severe, but suddenly the cholesterol plaque is disrupted and a plaque goes from ~30% to 100% suddenly. Coronary calcium may be useful in some for info on their heart.