Cocaine use is a risk factor for myocardial infarction, coronary artery spasm, arrhythmia and ischemia (Devi and Chan 1999; Vongpatanasin et al. 1999), and the mechanisms linked to drug toxicity come from disturbances in OS biomarkers (higher MDA levels and SOD activity, lower glutathione level, impairment of catalase, and glutathione peroxidase activity in the myocardium (Devi and Chan 1999; Moritz et al. 2003a). The gene discussed is CAT; the disease is Arrhythmia.