Who can have cardioversion?

Almost anyone. If there is any compromise in bp, consciousness, breathing, anyone can be cardioverted. If more chronic, then making sure there is a low probability of a clot inside the heart (that could be disrupted and cause an embolic event), sorting the need for prophylactic blood thinning to avoid a clot, making sure the atria (upper heart chambers) are not too large (reduced success) help select patients.
See below . Somebody who has a fib-flutter , svt , or ventricular tachycardia!