Life-threatening ventricular tachycardias (heart palpitations), which often develop after a heart attack in the scar tissue replacing dead heart muscle, alongside viable tissue, are typically treated with medication or, if necessary, ablation. These methods have been successfully applied for many years. However, in patients who have undergone prior cardiac surgeries such as coronary bypass or valve replacement, or when the arrhythmia originates from the outer surface of the heart, reaching and treating the source of the arrhythmia can become difficult or even impossible. The treatment of these hard-to-reach arrhythmia source regions by targeting them with a special, computer-guided radiotherapy method is called 3D stereotactic radiotherapy.