A new approach for designing power-efficient wireless ECG sensors based on level-crossing sampling and linear interpolation is presented in this paper. With the adoption of level-crossing sampling at sensor nodes, significant sampling rate reduction is achievable which lowers the power consumption of wireless transmitters. At sensor gateways, linear interpolation is applied to convert the non-uniform samples into uniform format to enable conventional uniform DSP. A linear interpolator for such a system is demonstrated using a 0.35μm CMOS process, which consumes 12.08μW under a 3.3-V supply.