How do i tell kids grandma has arrhythmia? what do they need to know?

How old are they: You could start by telling them grandma's heart is having a hiccup. If they are older try and describe the abnormality in terms that are easy to understand without going into too much details. If grandma's arrhythmia is potentially life threatening they should know that she is very sick.

Arrhythmia: I wouldn't try too hard to explain arrhythmias to little kids. I'd just tell them grandma has a heart problem. Plenty of adults don't understand what we're talking about in this area.