What happens if your posterior descending arterial branch of the right coronary artery diffuse proximal 60 to 80%?

Depends: Many people walk around with significant blockages without knowledge or harm. If the person described has angina or evidence of ischemia on testing, a percutaneous intervention should be considered. Otherwise, forget it - but treat the underlying arteriosclerosis: statin, aspirin, Mediterranean Diet, exercise, ideal body weight, no smoking, good BP control.