Electrocardiogram monitoring is crucial for the prevention and treatment of cardiovascular diseases. In this paper, we developed a wearable device involving multiple leads that monitors cardiac electrical activity using very large-scale integration technology to facilitate long-term activity monitoring. In addition to using limb leads and augmented limb leads for monitoring heart activity, six unipolar chest leads were attached to six positive electrodes and placed on the surface of the chest to record electrical activity of different regions of the heart. The multiple leads lie perpendicular to the frontal plane and were integrated within a single circuit to reduce hardware costs and size of the device. The proposed architecture also allows users to switch between lossless and lossy compression to control the power consumption and bit compression ratio. The effectiveness of the proposed approach was verified by fabricating a chip using 0.18-μm CMOS technology. The proposed architecture core has an operating frequency of 41 MHz and a gate count of 4K.