Correspondence to: Prof. ZHONG Shi-long, Medical Research Center, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong 510080, China (Tel: 86-20-83827812 ext. 51157. Fax: 86-20-83769487. Email: zhongshilong@gmail.com)