The identification of cardiac arrhythmias is a significant issue in modern healthcare and a major application for Artificial Intelligence (AI) systems based on artificial neural networks. This research introduces a real-time arrhythmia diagnosis system that uses a Spiking Neural Network (SNN) to classify heartbeats into five types of arrhythmias from a singlelead electrocardiogram (ECG) signal. The system is implemented on a custom SNN processor running on a low-power Lattice iCE40-UltraPlus FPGA. It was tested using the MIT-BIH dataset, and achieved accuracy results that are comparable to the most advanced SNN models, reaching 98.4% accuracy. The proposed modules take advantage of the energy efficiency of SNNs to reduce the average execution time to 4.32 ms and energy consumption to 50.98 uJ per classification.