Sinus arrhythmia is a normal physiological phenomenon in the human body, a natural change where the heart rate varies with breathing. This type of sinus arrhythmia is not a disease. On the other hand, arrhythmias generally refer to conditions like premature heartbeats, bradycardia, tachycardia, and atrial fibrillation, collectively indicating diseases. Arrhythmias are generally pathological phenomena. Furthermore, sinus arrhythmia does not cause symptoms, whereas arrhythmias can lead to symptoms such as palpitations, chest tightness, dizziness, and difficulty breathing. In severe cases, arrhythmias may cause blurred vision and fainting.