Scientists have developed a new 3D virtual heart tool to help doctors determine the risk of sudden cardiac death from life-threatening arrhythmias. The tool uses patient-specific MRI scans to create digital replicas of the heart and simulate the electrical processes to predict arrhythmic events more accurately than existing methods. This non-invasive assessment could help identify which patients truly need invasive and costly defibrillator implants and prevent unnecessary procedures for those not at high risk.