GJA1 and myocardial ischemia: Serum samples are detected using kits according to instructions, including nitric oxide (NO) and endothelin-1 (ET-1); malondialdehyde (MDA), ELISA for superoxide dismutase (SOD), and vascular cell adhesion molecules (VCAM-1); western blot for detection of cardiac Cx43 protein expression; immunohistochemistry to detect Cx43 expression; and detection of myocardial ischemia.