This article briefly describes the application of integrated circuits in the medical field, such as wearable and implantable medical devices. The article introduces the development process of integrated circuits used in cardiac pacemakers, explaining how it evolved from bipolar junction transistors integrated circuits in the past to today's complementary metal oxide semiconductor integrated circuits. The basic components of the pacemaker are described from a system level, including the signal amplifier, pulse generator, battery management system, and analog-to-digital converter. This allows for a clear presentation of the working process of the pacemaker. Furthermore, the article explains how analog integrated circuits and digital integrated circuits can be used together to achieve the goal of low power consumption of cardiac pacemakers at a circuit level, with reference to some cutting-edge scientific and technological achievements. The necessity and advantages of integrated circuits in medical applications are demonstrated, and the future development of integrated circuits in related aspects is forecasted based on the current development situation.