I have no norm. Heart risk factor but have had 2 scads causing mi. How does breath holding & straining incr the risk of another mi & what is mechanism?

SCAD? Sorry, i've been a cardiologist (in the usa) for 33 years, but i'm not familiar with the abbreviation "scads" - please clarify. Breath holding and straining are valsalva maneuvers which reduce venous return and cardiac output while raising BP and slowing hr - these should not cause mi. If they do, it would have occurred with your next bowel movement anyway.