Formal methods based tools and techniques have been recognised to be a promising approach to support the process of verification and validation of a critical system in early stage of the development. Specially, medical devices are very prone to show an unexpected behavior of the system in operating due to stochastic nature of the system and when a system uses traditional methods for system testing. Device-related problems are responsible for a large number of serious injuries. FDA officials have found that many deaths and injuries related to the devices are caused by product design and engineering flaws. Cardiac pacemaker and implantable cardioverter-defibrillators (ICDs) are main critical medical devices, which require close-loop modeling (integration of system and environment modeling) for verification purpose to obtain a certificate from the certification bodies. No any technique is available to provide an environment modeling to verify the developed system model. This paper presents a methodology to model a biological system, like heart, for modeling a biological environment. The heart model is mainly based on electrocardiography analysis, which models the heart system at cellular level. Main objective of this methodology is to model the heart system and integrate with medical device model like cardiac pacemaker to specify a close-loop model. To build an environment model for a close-loop system is an open problem. Industries are striving for such kind of approach from long time to validate a system model under a virtual biological environment. Our approach involves the pragmatic combination of formal specification of a system and a biological environment to model a close-loop system to verify the correctness of a system and helps in quality improvement of the system.