**2.1.1 The nature course of ARVD**

According to the shear stress rule, ostial and proximal lesions are mostly encountered and 20%-50% of cases are bilateral sites in ARVD (Safian & Textor, 2001). A significant progression of ARVD was observed in 11.1% of 14,152 subjects with high cardiovascular risks within a 2.6-year period in an angiographic study (Crowley et al, 1995) and in 35%-51% from 3 to 5 years in a doplex unltrasonography study (Caps et al, 1998). From these reports, the predictors to disease progression include old age, female gender, hypertension, diabetes and the presence of significant coronary artery disease or peripheral vascular disease in which the odds ratios range from 1.2 to 2.1. On the other hand, patients with ARVD are associated with approximately 2-times risk of the occurrence of adverse coronary events and mortality as compared to those without ARVD in a long-term follow-up (Conlon et al, 2001; Edwards et al, 2005).
