Electrocardiography / Humans / Blood Pressure / Female / Male / Risk factors / Clinical Sciences / Middle Aged / Coronary heart disease / Public health systems and services research / Risk Factors / Coronary artery bypass surgery / Exercise Test / Postoperative Period / Risk factors / Clinical Sciences / Middle Aged / Coronary heart disease / Public health systems and services research / Risk Factors / Coronary artery bypass surgery / Exercise Test / Postoperative Period