The Aliev-Panfilov model is a simple model for signal propagation in cardiac tissue, and accounts for complex behavior such as how spiral waves break up and form elaborate patterns. Spiral waves can lead to life-threatening situations such as ventricular fibrillation. We discuss an implementation and underlying optimizations for the nVIDIA Tesla C1060 GPU as well as an implementation on multiple GPUs running under MPI. We achieve nearly perfect scaling on 4 GPUs, in single precision, running 58 times faster than a CPU-only implementation and 26 times faster in double precision.