When the heart does not function properly, an artificial pacemaker is needed to correct the heart beat. However, more functionality at limited budget requires less power per function. Therefore, the power consumption of the pacemaker has to be reduced. The analog to digital converter in the pacemaker consumes the largest amount of power in the front-end, called the sense amplifier. Hence, an ultra low power ADC is . In this work, the IECG signal is filtered by band pass filter 50mHz-100Hz. Then, the signal output of the filter is converted to current by transconductance cell(Gm). The output of the Gm-cell is digitized by a Current Successive Approximation ADC. Circuit Simulation predict the overall system consumes the lowest power,416nW reported when compared with the state of the art.