What do my nuclear stress results mean

[SueMayer]

report says fixed medial & apical wall defect without significant reversibility

[djd1990]

It means that the middle portion and apex of the chamber walls (most likely of the left ventricle, although you didn't specify which chamber the report was referring to) responded abnormally to your stress test. The heart is ultimately a pump and the walls of each of the four chambers take on particular patterns of motion when they are functioning properly. For whatever reason there's some sort of abnormal motion and/or lack of blood flow along those portions of your LV walls. The "without significant reversibility" part means that it's not something that is temporary, such as post mild heart attack damage that might later heal. Instead, it could be something more "permanent" such as some sort of structural defect you were born with,a more severe heart attack that left permanent damage, or any other number of things. Obviously, you'll need to talk with your doctor about what exactly the defects are, as well as their underlying causes, and what approach to treatment/management they will pursue.