Heart Failure is the most common cardiac disease worldwide; supraventricular arrhythmia the most common cardiac arrhythmia. The understanding of these diseases advances treatment options. Ablation therapy and atrial antitachycardial pacing are non-pharmacological options in the treatment of atrial fibrillation. Cardiac resynchronization therapy with biventricular pacing devices has been shown successful in patients with severe heart failure. However, an optimization or even individual therapy planning is not standard or not even carried out today. These non-pharmacological treatments can be investigated and optimized with the help of computer models of the heart. The simulation of atrial fibrillation with a realistic atrial anatomical model aims at explaining seemingly contradictory results from clinical studies. Different ablation strategies and pacing algorithms are then applied to terminate the arrhythmia in the virtual environment. Thus, a comparison of strategies can be carried out. With respect to cardiac resynchronization therapy, the computer model allows for automatic and non-invasive optimization of electrode positions and timing delays. With clinical validation, the presented computer models and methods have the potential to contribute to individualized therapy planning.