Computer Simulations of Cardiac Electrophysiology John B. Pormann ∗ Craig S. Henriquez † John A. Board, Jr. ∗ Donald J. Rose ‡ David M. Harrild † Alexandra P. Henriquez § August 16, 2000 Abstract CardioWave is a modular system for simulating wavefront conduction in the heart. These simulations may be used to investigate the factors that generate and sustain life-threatening arrhythmias such as ventricular fibrillation. The user selects a set of modules which most closely reflects the simulation they are interested in and the simulator is built automatically. Thus, we do not present one monolithic simulator, but rather a simulator- generator which allows the researcher to make the trade-offs of complexity versus performance. The results presented here are from simulations run on an IBM SP parallel computer and a cluster of workstations. The performance numbers show excellent scalability up through 128 processors. With the larger memory of the parallel machines, we have been able to perform highly realistic simulations of the human atria. These simulations include realistic, 3-D geometries with inhomogeneity and anisotropy as well as highly complex membrane dynamics. 1 Introduction Cardiac arrythmias and fibrillation are a leading cause of death in the United States and abroad. Computer simulations are rapidly becoming a powerful tool for investigating the factors that cause and sustain these life-threatening conditions. However, the complexity of the human heart leads to tremendous complexity in the computer programs. For high accuracy, these simulations require spatial discretization down to the 10 micron level and time-step sizes at or below a microsecond. These factors in turn require the use of huge memories and very fast processors for the computer simulation to be at all practical. To further complicate matters, the real heart is not a simple geometry nor is it homogeneous. Both of these add to the memory and computational requirements of more realistic simulations. CardioWave is a simulation system for the flow of electrical current in the heart. It is mathemat- ically grounded in the Bidomain Equations which are a set of coupled partial differential equations comprising a reaction-diffusion system: * Department of Electrical and Computer Engineering, Duke University, Durham, NC † Department of Biomedical Engineering, Duke University, Durham, NC ‡ Department of Computer Science, Duke University, Durham, NC § North Carolina Supercomputing Center, Research Triangle Park, NC 0-7803-9802-5/2000/$10.00 c 2000 IEEE 1