Software is being used more frequently to control medical devices such as artificial heart or robotic surgery system. While much of software safety issues in such systems are similar to other safety-critical systems (e.g., nuclear power plants), domain-specific properties may warrant development of customized techniques to demonstrate fitness of the system on patients. In this paper, we report results of a preliminary analysis done on software controlling a Hybrid Ventricular Assist Device (H-VAD) developed by Korea Artificial Organ Centre (KAOC). It is a state-of-the-art artificial heart which completed animal testing phase. We performed software testing in in-vitro experiments and animal experiments. An abnormal behaviour, never detected during extensive in-vitro analysis and animal testing, was found.