Coronary arterial bypass graft surgery (CABG) is proven safe with improved survival and greater quality of life in patients with coronary arterial disease. Evidences on the cardiovascular and gas-exchanges responses during and right after early exercise-based rehabilitation of this patients are limited. Objective: The investigators aim to analyse breath-by-breath cardiopulmonary and metabolic responses during six-minute walk test (6MWT) and shuttle walk test (SWT) in patients with or without left ventricular dysfunction (LVD) after CABG. In addition, the investigators will investigate oxygen consumption and cardiopulmonary responses during the early exercise-based rehabilitation in the first days after surgery. Methods: According to the left ventricular ejection fraction (LVEF), subjects will be allocated into two groups: with LVD (LVEF < 45%) and without LVD (LVEF > 45%). Patients will be submitted to the 6MWT and SWT linked to portable spirometric-telemetric device before and 6 days after CABG. During the first days after surgery, patients will be evaluated about pulmonary function and respiratory strenght at rest and oxygen consumption during the portable cycle ergometer protocol. Clinical outcomes as time to hospital discharge, pulmonary complications and occurence of arrythmias will be assessed during inpatient time until hospital discharge. Incidence of mortality, hospital readmission and angina recurrence will be evaluated in a one-year follow up.