Leads are designed for in vivo applications, however, for a definite period of time. In-vivo environment affects the mechanical behavior of implantable devices, therefore, there is a need to evaluate the residual properties of implantable leads used with pacemakers, defibrillator and neuro-stimulators. Silicone (MED-4719) lead is widely used in cardiac implantable electronic devices made by different manufacturers. . We collected 150 devices (with or without leads) from Anatomical Gift Program of the Wright State University. The objective of this study was to investigate the residual properties of Silicone (MED-4719) lead with different in vivo exposure time and compare the properties of a new, unused lead supplied by Medtronic for the purposes of this research. The tensile test was performed by applying specific load on the samples, percentage elongation at 5N and the corresponding displacement measured. Load to failure, percentage elongation, ultimate tensile strength, and modulus of elasticity were determined for each lead. Methods to collect and compile data were standardized, and statistical models were used to assess the sensitivity of measured parameters with in vivo performance. Load to failure, elongation to failure, ultimate tensile strength, and percentage elongation at 5N showed a significant decrease after 94 months (P = 0.0063), 8 months (P = 0.0136), 94 months (P = 0.0244) and 71 months (P-value = 0.0326) after implantation, respectively. On the other hand, modulus of elasticity was found proportional to the number of months device was exposed and showed significant increase after 71 months (P = 0.0446) of in-vivo environment.