Sinus arrhythmia is a common clinical condition. It is mainly seen in healthy infants and young children, with it being more common in children over three years of age and less common in infants and young children, and is seen when the heart rate is slow or can occur during sleep. The heart rate can become neat when it increases and when awake from exercise. If arrhythmia occurs, it can be treated with the following medications, such as digitalis, morphine, and beta blockers. It is also seen in patients with cardiac disease, usually with mild symptoms, especially in older children with palpitations and chest discomfort, and can be detected on auscultatory inquiry. It can be associated with the respiratory cycle, slowing down on expiration and speeding up on inspiration, and is often generally of no clinical significance. Treatment of sinus arrhythmia is generally not required for those without clinical symptoms, while those with symptoms require targeted treatment.