Objective The aim of this study was to compare susceptibility differences in ventricular arrhythmias induced by programmed electrical stimulation between young and old mice

and to lay a foundation for subsequent research in this area. Methods C57BL/6J young mice （8~12 weeks old） and old mice （16+ months old） were included in this study. ECG and programmed electrical stimulation were used to observe the occurrence of ventricular tachycardia （VT）. Cardiac function indicators were detected by echocardiography

while membrane voltage and Ca2+ were also measured by optical mapping. Results Compared with young mice

old mice had a significantly prolonged R-R interval and increased occurrence rate of VT induced by electrical stimulation and ISO （P < 0.01）. Echocardiography results showed that compared with young mice

old mice had decreased ejection fraction （EF） and fractional shortening （FS） （P < 0.01）

but increased end-diastolic left ventricular posterior wall thickness （LVPWd） （P < 0.01）. Histomorphology results demonstrated that compared with young mice

old mice had an increased ratio of heart weight to tibia length

an enlarged cross-sectional area of cardiomyocytes

and an increased collagen volume（P < 0.001）. Optical mapping results showed that the action potential duration （APD） and Ca2+ transient duration （CaTD） of old mice were prolonged with statistically significant differences（P < 0.05）

and that old mice also exhibited obvious electrical reentrant under electrical stimulation and ISO stimulation

indicating that aging increased abnormal electrical conduction and susceptibility to arrhythmia. Conclusion Compared to young mice

aged mice exhibited morphological changes in cardiac tissue and a decline in cardiac function

particularly alterations in cardiac electrophysiology resulting from aging

which increased susceptibility to cardiac arrhythmias in aged mice.