What is an arrhythmia?
Simply refers to an irregular heart rhythm. That can even include a sinus arrhythmia, which is simply a pronounced variation in the heart rate with breathing, but we usually use it to describe pathological rhythms--potentially dangerous uncontrolled rhythms.
These may be fast or slow or markedly irregular, so this term is not nearly as useful as the specific diagnosis--e.g., afib, vtach or svt.
ABNORMAL HEART RHYTHMS