The definition of arrhythmia is broader, as irregular heartbeats due to various causes can be called arrhythmia, while sinus arrhythmia refers only to arrhythmia due to sinus node causes. The concept of arrhythmia is broad and can include irregular heart rhythms caused by sinus arrhythmia, premature beats, unequal downbeat atrial tachycardia, atrial fibrillation, atrioventricular block, and so on. Sinus arrhythmia refers to an irregular heartbeat rhythm in which each beat of the heart is impulsed by pacing from the sinus node, the normal pacing point, but the interval between each beat is not exactly the same (a difference of >0.12). Sinus arrhythmia can be manifested in normal individuals, sinus arrest, sinus block, and sick sinus node syndrome. If you have an irregular heart rhythm, you should seek medical attention.