On the other hand, the expression levels of genes regulating abnormal alternative vascularization, such as hypoxia-inducible factor-1A (HIF1A) and High-Temperature Requirement A Serine Peptidase 1 (HTRA1) were significantly increased in degenerated AF grade IV and V (Fig. 3a). The gene discussed is HTRA1; the disease is atrial fibrillation.