The heart may be described as the engine room of all mammals. It is responsible for pumping of blood to every part of the body. Digested food nutrient, oxygen and blood are transported to all parts of the body through the a network of veins in a process known as the circulatory system. This transportation is initiated by the heart pumping blood into the system. Therefore the heart is a very important organ of the body and should be cared for. Medically, the wellness of the heart can be determined by the electrical potential it produces. This electrical potential is called electrocardiogram (ECG). ECG may be affected by unwanted signals that may be recorded in the process of recording the signal. One of those unwanted signals is the power line interference (PLI). This paper proposes and demonstrates the removal 0.1mV 50Hz PLI from a contaminated single cycle ECG signal using a Parzen windowed Finite Impulse Response (FIR) filter.