3. Measurement of serum biomarkers Venous blood samples will be obtained before CMR study. Serum will be isolated within 30 min of phlebotomy and stored at -80°C prior to simultaneous analysis of biomarkers of collagen metabolism. Serum carboxy-terminal propeptide of procollagen type I (PICP) concentration will be determined by sandwich enzyme immunosorbent assay using the METRA EIA kit (Quidel, San Diego, California, USA), and carboxy-terminal telopeptide of collagen type I (CITP) will be determined using a commercial radioimmunoassay (Orion Diagnostica, Espoo, Finland).15 The PICP:CITP ratio was considered an index of the degree of coupling between the synthesis and degradation of collagen type I.15 Serum levels of MMP-9 and TIMP-1 will be analyzed using commercially available 2-site sandwich enzyme-linked immunosorbent assay (Quantikine R&D Systems, Minneapolis, Minnesota, USA).16 The sera of all subjects will be sent to the measurement of plasma BNP levels utilizing the Biosite Triage BNP test (Biosite, San Diego, Calif).