Implantable cardiac pacemakers are equipped with batteries to provide power supply that have a limited lifetime. Battery-based implantable cardiac pacemakers need surgical intervention to replace batteries. This is an undesirable condition that can increase the risk of complications and costs for patients. To overcome the above shortcomings, a batteryless cardiac pacemaker is introduced, which harvests energy from the body temperature. In this article, a batteryless cardiac pacemaker is designed, which is powered by sustainable energy sources. Hence, thermoelectric generators (TEGs) are considered the sustainable renewable energy source that powers up cardiac pacemakers with effective reduction in dimension without limiting the capacity. Then, power electronic converters adapted with TEGs has enhanced the ability of controlling environmental conditions as well as maximizing energy harvesting. Therefore, a DC-DC converter is designed with TEG to solve environmental conditions issues of TEG. In this proposed methodology, a TEG with three different types of DC-DC converters is designed and validated to analyze the performance of converters such as boost converter, buck converter, and buckboost converter. The proposed design was analyzed based on a case example and simulated using Cadence Capture CIS. Finally, a prototype of our design was developed to evaluate the experimental outcome. Four modules are designed and validated: general pacemaker, TEG with pacemaker, TEG with boost converter, TEG with buck converter, and TEG with buck-boost List of Symbols and Abbreviations: ρ, density; Q, heat flux; Q, volumetric heat; C P , specific heat at consonant pressure; j !