Moreover, we explore the predisposing factors to their associated cardiotoxicity along with an investigation of the QRS/QTc ratio as a potential biomarker for identifying patients at risk of ventricular arrhythmias, taking into consideration the impact of genetic variations and drug interactions, especially those involving the liver CYP2C19 metabolism. The gene discussed is CYP2C19; the disease is Ventricular arrhythmia.