The P-R interval represents the atrioventricular conduction time on the electrocardiogram. The normal range is 120-200 ms, and a P-R interval of 118 ms is considered mildly shortened. Short P-R syndrome is mainly due to the presence of a congenital bypass, Jaim’s bypass, in which the impulse from the sinoatrial node bypasses the atrioventricular node through the bypass, resulting in a shortened P-R interval. It is the most common pathological type of preexcitation syndrome, and the main pathological significance is that it is prone to supraventricular tachycardia. For those who are usually asymptomatic, treatment is not necessary, and the specific situation depends on the presence or absence of preexcitation syndrome as the main cause of P-R interval shortening.